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Home My WebLink AboutCT 2019-0001; LA COSTA VILLAS NORTH; PRELIMINARY GEOTECHNICAL INVESTIGATION UPDATE; 2019-01-02--------- ---------- ---- ------ ---- P~l,-.,e}( ~ "--./ Geotechnical Investigation Update Proposed La Costa Villas North Condominium Project 400 Gibraltar Street Carlsbad, California January 2, 2019 Prepared For: Mr. Far Shaba 30051 Corte Tolano Temecula, California 92591 Prepared By: §.M§ Geotechnical Solutions, Inc. 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010 Project No. GI-18-12-158 RECEIVED JAN 1 8 2019 CITY OF CARLSBAD PLANNING DIVISION - ----- • ------------- --- .. -- -- • -- Project No. GI-18-12-158 January 2, 2019 Mr. Far Shaba 30051 Corte Tolano Temecula, California 92591 §.ff§ GEOTECHNICAL SOLUTIONS, INC. Consulting Geotechnical Engineers & Geologists 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010 Office: 760-602-7815 smsgeosol.inc@gmail.com GEOTECHNICAL INVESTIGATION UPDATE, PROPOSED LA COSTA VILLAS NORTH CONDOMINIUM PROJECT, 400 GIBRALTAR STREET, CARLSBAD, CALIFORNIA Pursuant to your request, 6116 Geotechnical Solutions, Inc. has completed the attached Geotechnical Investigation Update report for the proposed nine-unit, three-story condominium development project at the above-referenced property. The following report summarizes the results of our research and review of the project pertinent documents and previous geotechnical reports, current shallow sampling and additional laboratory testing, and provides updated, revised or amended conclusions and recommendations for the proposed development based on the most current plans, applicable codes and engineering standards, as understood. From a geotechnical engineering standpoint, it is our opinion that the project property remains suitable for the proposed multi-unit, multi-story condominium development, provided the recommendations presented in this report are incorporated into the design and reconstruction of the project. If you have any questions or need clarification, please do not hesitate to contact this office. Reference to our Project No. GI-18-12-158 will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you . 6116 Geotechnical Solutions, Inc. --_) ----------------------------.. --------- TABLE OF CONTENTS INTRODUCTION ... . SITE DESCRIPTION .............. . PROPOSED DEVELOPMENT .............. . PAGE . 1 .. 2 ... 3 I. II. III. IV. V. REGIONAL GEOLOGY ......................... 4 GEOTECHNICAL CONDITIONS ....... . ........................ 4 A. Subsurface Conditions ................................ . . ..... 4 ....... 5 VI. VII. VIII. IX. X. XI. B. Groundwater and Surface Drainage C. Slope Stability .................. . D. Faults/Seismicity •................ E. Site Classification for Seismic Design F. Seismic Ground Motion Values G. Geologic Hazards ............ . H. Laboratory Tests and Test Results SITE CORROSION ASSESSMENT STORMWATERBMPs CONCLUSIONS •.••................ RECOMMENDATIONS .... A. B. C. D. E. Grading and Earthworks .........•.....•.. Foundations and Floor Slabs .....•........ Soil Design Parameters Exterior Concrete Slabs / Flatworks Permeable Interlocking Concrete Pavers (PICP) F. General Recommendations ••...•........•...• GEOTECHNICAL ENGINEER OF RECORD (GER) LIMITATIONS Regional Index Map Site Map ....... . Geotechnical Map Geologic Map .... Geologic Cross-Sections ........ . Fault-Epicenter Map Typical BMP Swale ...... . Typical Bio-Retention Detail Typical Retaining Wall Back Drainage Typical Isolation Joints and Re-Entrant Corner Reinforcement Typical Permeable Interlocking Concrete Paver (PICP) Detail Typical Pipes Through or Trench Adjacent to Foundations APPENDICES • 5 . ..... 7 ...... 9 ... 9 ...... 9 10 12 13 14 17 17 . ......... 28 . .... 35 ....... 37 ..... 38 ............... 39 . ................. 41 •• 42 FIGURES .. 1 ...... 2 . ... 3 ... 4 • 5 .6 . . 7 .. 8 .. 9 10 11 12 ... • • - .. ------------ ------------------- I. GEOTECHNICAL INVESTIGATION UPDATE PROPOSED LA COSTA VILLAS NORTH CONDOMINIUM PROJECT 400 GIBRALTAR STREET CARLSBAD, CALIFORNIA INTRODUCTION The project site evaluated in this update geotechnical effort is an existing graded pad located on the east side of Gibraltar Street near the Jerez Court intersection. The site is generally north of La Costa A venue within the La Costa neighborhood of the City of Carlsbad. The project property is also known as Lot 400 of La Costa South Unit No. 5. The approximate site location is shown on a Regional Index Map attached to this report as Figure 1. A Google Image depicting general site conditions prior to the more recent development of the southern adjacent neighboring property, is reproduced herein as a Site Map, Figure 2. The approximate site coordinates are 33.0859°N latitude and -117.2475°W longitude. Grading works and level building pad development for Lot 400 was apparently carried out in a mass operation with the adjacent lots (vacant Lot 399 to the east and recently developed Lot 401 to the west) presumably in early 1970s. Records of engineering observations and compaction testing services during the original pad development are unavailable. However, the project Lot 400 property was originally studied with the adjacent neighboring Lots 399 and 401 with respect to surface and subsurface geotechnical conditions in connection with earlier multi-family development schemes which were to occupy all three lots. The following pertinent soils and geotechnical investigation reports are available: A. "Addendum Geotechnical Plan Review Update, Proposed La Costa Villas Development, Gibraltar Street At Jerez Court, Carlsbad, California," prepared by S.MS Geotechnical Solutions, Inc., Project No. GI-9-14-18, dated September 9, 2014. B. "Second Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi- Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by Allied Earth Technology, Project No. 13-1147Hl, dated June 5, 2014. C. "Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by Allied Earth Technology, Project No. 13-1147Hl, dated October 10, 2013. D. "Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad," prepared by Vinje & Middleton Engineering, Inc., Job #04-287-P, dated July 7, 2004. E. "Preliminary Soil And Geotechnical Investigation, Graded Hillside Property, Gibraltar Street Near Jerez Court, La Costa Area Of Carlsbad, San Diego County, California," prepared by MV Engineering, Inc., Job #1017-91, dated February 20, 1991. ---------------------------------- -- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page2 The referenced reports were reviewed as a part of this effort and copies are attached herein as Appendices A through E, respectively. Pertinent geotechnical parameters including subsurface exploration data, laboratory testing and engineering analysis ware incorporated into the conclusions and recommendations provided in the following sections, as appropriate and where applicable. A Site Plan-Building Pads, depicting the planned most current development concept, was provided to us and was used as a base map for the preparation of the attached Geotechnical Map, Figure 3. Associated preliminary architectural site development concept plans were also provided to us and were reviewed as a part of this update study. The purpose of this effort was to evaluate the existing site-specific geotechnical conditions present at Lot 400, and update the referenced reports (References A through E) for compatibility with the proposed new development plan (Figure 3). Our work in connection with this effort included geologic mapping of the existing surfaces exposures, and the excavations of two shallow hand dug test pits at selected site locations with sampling of representative onsite near surface soils for added pertinent laboratory testing. Revised and/ or amended conclusions and recommendations consistent with the present site conditions, attached development plan (Figure 3), current applicable codes and engineering standards are also provided in the following sections, and will supplement or superseded those given in the referenced reports, where specifically indicated. II. SITE DESCRIPTION Based on our recent site visit, with the exception of southern slope, Lot 400 appears to remain substantially unchanged from those conditions generally described in referenced reports. Existing site conditions are depicted on the enclosed Site Map, Figure 2. Overall, Lot 400 consists of an existing nearly level graded building pad surrounded with perimeter graded slopes. Access to the site is via Gibraltar Street which borders the property to the north. A graded slope ranging to 12 feet in a maximum vertical height descends at 1.5: 1 gradients from the northern and eastern perimeters to the lower Gibraltar Street grades and adjacent vacant lot (Lot 399) pad levels below respectively. A nearly 10 feet high roughly 1: 1 gradient graded slope ascends from the western pad perimeter to a recent condominium development (Lot 401) above. A large graded slope, with a drainage terrace/bench approximately in the lower 1/a of the slope and a concrete lined drainage ditch roughly above the slope mid-height, ascends nearly 70 vertical feet at approximately 1.5: 1 to locally steeper gradients from the southern building pad perimeter to the developed residential lots above. Overall site drainage generally appears poor with surface runoff sheetflowing in locally uncontrolled and concentrated conditions, draining from higher elevations toward lower ground in the northern and eastern perimeter. This is evidenced by severe erosional and slumping failures impacting the southern slope above the drainage terrace/bench. The concrete drainage ditch above the southern drainage terrace/bench also appears to have experienced overflow and local failures additionally contributing to the indicated southern slope face erosional features and shallow slump failures. • • -• --------------------.. .. ---- • - --- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page3 Elsewhere, northern and eastern slope faces are also impacted by erosion and local slumping as a result of poor drainage and lack of proper slope cover and continuous maintenance. III. PROPOSED DEVELOPMENT Current site development schemes are now different from those considered as a basis of the prior geotechnical studies (see referenced). As shown on Figure 3, project plans now depict Lot 400 will be individually developed similar to the adjacent Lot 401 for supporting a condominium development. Two three-story buildings (two stories above a two-car garage level) will comprise the planned condominium units, designated as Units 1 through 9. Units 1 through 4 will comprise the building occupying eastern property margins, while Units 5 through 9 will be located in a building planned along the western property margin, with a shared central driveway serving all units. Significant ground modifications or the creation of large new graded embankments is not planned in connection with the planned site development, as currently proposed. The project development is mainly cut grading operations with minor filling. Based on current plans, earthwork quantity estimates are on the order of 1170 CY of cut, 331 CY of fill and 839 CY of export. The majority of site earthworks are expected to consist of remedial grading and slope repair operations. New modest to relatively large excavations and construction of perimeter site transition and building basement type retaining walls, on the order of 10 feet high maximum, are incorporated into the designs for establishing final level building pad surfaces and achieving finish design grades. Site transition retaining walls to the south and west will be developed into the base of the adjacent graded slope, and will require slightly larger (considering the wall foundation excavations) temporary vertical backcut excavations removing the existing toe support. The remaining portions of the adjacent slopes above the new southern and western transition retaining walls will then be contour graded to construct a maximum 2:1 slope gradients. Slope face re-contour grading will mostly remove the existing drainage terrace/bench in the southern slope. However, a new terrace retaining wall, supporting a concrete lined drainage ditch with an inlet box at the eastern end, is proposed along the top of re-contoured slope areas for providing surface drainage improvements . Associated improvements include underground utilities, permeable shared central access driveway and a stormwater BMP concrete or masonry box at the northeast comer. Based on the project plans, project development will construct three-story condominium buildings with a lower driveway grade garage level and two-stories above. There will be no subterranean structures or below grade basement floor levels. Building construction is expected to consist of conventional wood frame with exterior stucco structures supported on stiff concrete grade beam footings and thick slab-on-grade floor foundations, post-tensioned or mat slab foundation support. - • • • .. ------ ------------ ---- ------ Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page4 IV . REGIONAL GEOLOGY The community of La Costa is situated at the western margin of the Peninsular Ranges Geomorphic Province of southern California. This geomorphic province encompasses an area that extends for approximately 790 miles, from the Transverse Ranges and the Los Angeles Basin to the tip of Baja California, and varies in width from 30 to 100 miles. In general, the Peninsular Ranges consist of rugged mountains underlain by Mesozoic era (67 to 245 million years old) metamorphic and crystalline rocks to the east and a dissected coastal plain underlain by Cenozoic era (up to 67 million years old) sediments. The mountain ranges of this geomorphic province are generally northwest-trending and separated by subparallel fault zones, and are largely composed of granitic and related rocks and smaller amounts of metamorphic rocks. The coastal portions of this geomorphic province in the San Diego region are typically comprised of marine and non-marine sedimentary rocks that have been deposited within a northwest-trending basin known as the San Diego Embayment. The Peninsular Ranges are bounded on the east by the Salton Trough and on the north by the Los Angeles Basin, and extends westward into the Pacific Ocean where its highest peaks are exposed at Catalina, Santa Barbara, San Clemente, and San Nicholas Islands. The Peninsular Ranges are traversed by several major active faults. Right-lateral, strike-slip movement is the major tectonic activity associated with faults in the regional tectonic framework. Earthquakes along these faults have the potential for generating strong seismic ground motions in the region. The seismic event most likely to affect the project site would be a major earthquake on the Rose Canyon Fault. The Rose Canyon Fault is a complex zone of strike-slip, oblique, reverse, and normal faults that extend onshore from La Jolla Cove south to San Diego Bay, and is capable of generating a magnitude-7.2 earthquake. A site specific Geologic Map of the project and surrounding areas is attached with this report as Figure 4. V. GEOTECHNICAL CONDITIONS In general, geotechnical conditions at the project property remain largely the same as reported in detail in the referenced reports (see Appendices A through E). The following are recognized: A. Subsurface Conditions: Subsurface conditions at Lot 400 were chiefly evaluated by excavation of exploratory test trenches completed in support of the original site study performed by the prior consultant (MV Engineering, Reference E) in 1991. Approximate locations of the exploratory test trenches pertinent to Lot 400 (Test Pit 4, 5 and 7) are transferred and shown on the Geotechnical Map, Figure 3. The general subsurface geologic conditions, based on the approximated existing topography and our interpolation of anticipated proposed grades, are depicted on Geologic Cross-Sections X-X' and Y-Y' enclosed as Figure 5. Logs of the test trenches are attached to the enclosed Appendix E as Plates 5, 6 and 7. ---• ---------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page5 Based on our review of the referenced reports ( see attached appendices), Lot 400 is a cut-fill daylight transition lot underlain by undocumented fills (Uat) and local topsoil (Qs) over Terrace Deposits (Qt) in the western portion of the property, siltstone/sandstone rocks (Eocene Age Santiago Formational-Tsa) in the southern portion, and undocumented fills (Uat) over Terrace Deposits (Qt) over the Santiago Formation {Tsa) in the northern and eastern portions. The approximate cut-fill transition line is mapped on the enclosed Figure 3. The western nearly 1: 1 gradient embankment is mostly a fill slope, while the eastern roughly 1.5: 1 gradient embankment includes a fill-over-cut slope. The rear 1.5: 1 graded embankment to the south is largely a cut slope underlain by Santiago Formational rocks {Td). Site existing undocumented fills are reported to reach 4 feet thick maximum underlain by approximately 2 feet thick layer of topsoil over Terrace Deposits of a variable thickness atop formational units. Project surficial undocumented fills, topsoil, and the upper exposures of the highly weathered formational rocks are loose to soft and compressible deposits, not suitable for structural support and should be regraded as specified in the following sections (also see references). Below the upper highly weathered zones, the underlying dense Terrace Deposits (Qt) and Santiago Formation {Tsa) are considered adequately suitable for support of new fills, structures and improvements. Site soils also range to medium expansive. B. Groundwater and Surface Drainage: Subsurface groundwater is not reported at the project property and is not expected to impact site remedial grading efforts or the future performance of the developed site. However, existing overall side drainage is considered poor, as noted by the erosional features throughout the perimeter slopes including slumping failures impacting the lower portions of the southern graded slope. Site and slope drainage control facilities and improvements shall be required and should be designed and implemented as a part of the project development, as shown on the approved civil/drainage improvement plans. The proper control and disposal of site storm water and slope face run-off and are considered the most geotechnical concerns in continued stability and performance of the new condominium development and perimeter graded slopes. Ponding of water over the pad surface and concentrated flow over the perimeter slopes shall not be allowed. C. Slope Stability: Overall, large deep seated gross geologic slope instability was not reported in the referenced reports ( see Appendices A through E), nor was observed during our recent site geologic mapping. However, the following conditions were noted: ----- ----- ----- ------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page6 1. The 1.5:1 gradient descending graded slopes ranging to 12 feet in maximum vertical height around the northern and eastern perimeters have experienced severe surficial erosion and local failures. Slope repairs and mitigation will be required as a part of the project remedial grading efforts as specified in the following sections. For this purpose, a remedial grading encroachment permit will be required should be obtained from the adjacent property owner to the east (Lot 399). 2. The nearly 10 feet high, roughly 1: 1 gradient graded slope along the western pad perimeter ( below Lot 401) is underlain by loose spill-over fills with local construction debris inclusions. Majority of the western slope will be removed and replaced with transition retaining walls as part of pad development. Temporary wall backcut excavation will expose loose undocumented fill materials and shall require temporary shoring procedures for the protection of the upper property line retaining wall and adjacent condominium development, as specified below. As an option, limited "slot- cutting" temporary wall backcut excavation and transition wall construction procedure at alternating units may be used, if determined feasible and approved in the field by the project geotechnical consultant. Remedial grading will be required for the upper remaining potions of the slope during re-contour grading and establishing maximum 2: 1 slope ratios, as specified in the following sections. 3. Large massive and gross deep-seated instability impacting the southern perimeter-graded slope is not reported, nor currently in evidence. However, the lower portions of the southern slope, below the concrete drainage ditch, and above and below the drainage terrace/bench have experienced modest to major shallow slumping and sloughing failures, suggesting more significant features are presently impacting the slope areas from those previously reported in the referenced documents. The noted features, manifesting in topographic impressions (see Figure 2), include local failure scarps that likely resulted from uncontrolled and concentrated slope drainage conditions. Evidence of prior repair attempts by construction of short keystone type failure-retainment walls below the concrete drainage ditch are apparent, and slope faces above the concrete ditch are locally irregular and eroded. Based on our geologic mapping of the existing exposures shallow failures and slumping within the lower slope sections are estimated to be on the order of 5 feet thick. Construction of transition walls is also planned at the base of the southern slope as shown on the enclosed Figure 3. Associated temporary wall backcut excavations will mostly expose shallow slump deposits and failure scarps. Shallow temporary backcut excavations less than 5 feet high may be developed at 1: 1 maximum gradients, unless otherwise directed in the field. However, shoring support shall be required for larger excavations and vertical backcuts to avoid instability and major slope failures, as specified below. Remedial grading efforts consisting of removals and recompaction of the shallow slump debris and failure scarps in the impacted areas will also be required for the upper remaining portions of the slope during re-contour grading and establishing maximum 2:1 slope gradients. Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 7 I The approximate erosional features, shallow failures and slumping areas impacting the project perimeter slopes are also mapped on the enclosed Figures 2 and 3. D. Faults/Seismicity Based on a review of published geologic maps, faults or significant shear zones are not indicated on or in close proximity to the project site. As with most areas in California, the San Diego region lies within a seismically active zone; however, coastal areas of the county are characterized by low levels of seismic activity relative to inland areas to the east. During a 40-year period (1934-1974), 37 earthquakes were recorded in San Diego coastal areas by the California Institute of Technology. None of the recorded events exceeded a Richter magnitude of 3. 7, nor did any of the earthquakes generate more than modest ground shaking, and did not produce significant damages. Most of the recorded events occurred along various offshore faults which characteristically generate modest earthquakes. Historically, the most significant earthquake events which affected local areas originated along well known, distant fault zones to the east and the Coronado Bank Fault to the west. Based upon available seismic data, compiled from California Earthquake Catalogs, the most significant historical event in the area of the study site occurred in 1800 at an estimated distance of 6. 7 miles from the project area. This event, which is thought to have occurred along an offshore fault, reached an estimated magnitude of 6.5 with an estimated bedrock acceleration value of 0.188g at the project site. The following list represents the most significant faults that commonly impact the region. Estimated ground acceleration data compiled from Digitized California Faults (Computer Program EQF AULT VERSION 3.00 updated) typically associated with each fault is also tabulated. TABLE 1 I I MAXIMUM I FAULT.ZONE DISTANCE FROM SITE PROBABLE ACCELERATION (R.H.} Rose Canyon Fault 6.3 miles 0.225g Newport-Inglewood Fault 11.6 miles 0.171g Elsinore-Julian Fault 24.2 miles 0.176g Coronado Bank Fault 21.3 miles 0.220g The locations of significant faults and earthquake events relative to the study site are depicted on a Fault -Epicenter Map attached to this report as Figure 6. ------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page8 Recently, the number of seismic events that affect the region appears to have somewhat heightened. Nearly 40 earthquakes of magnitude 3.5 or higher have been recorded in coastal regions between January 1984 and August 1986. Most of the earthquakes are thought to have been generated along offshore faults. For the most part, the recorded events remain as moderate shocks which typically resulted in low levels of ground shaking to local areas. A notable exception to this pattern was recorded on July 13, 1986. An earthquake of magnitude 5.3 shook county coastal areas with moderate to locally heavy ground shaking. This resulted in $700,000 in damages, one death, and injuries to 30 people. The quake occurred along an offshore fault located nearly 30 miles southwest of Oceanside. A series of notable events shook county areas with a (maximum) magnitude 7.4 shock in the early morning of June 28, 1992. These quakes originated along related segments of the San Andreas Fault, approximately 90 miles to the north. Locally high levels of ground shaking over an extended period of time resulted; however, significant damages to local structures were not reported. The increase in earthquake frequency in the region remains a subject of speculation among geologists; however, based upon empirical information and the recorded seismic history of county areas, the 1986 and 1992 events are thought to represent the highest levels of ground shaking that can be expected at the study site as a result of seismic activity. In recent years, the Rose Canyon Fault has received added attention from geologists. The fault is a significant structural feature in metropolitan San Diego that includes a series of parallel breaks trending southward from La Jolla Cove through San Diego Bay toward the Mexican border. Test trenching along the fault in Rose Canyon indicated that at that location the fault was last active 6,000 to 9,000 years ago. More recent work suggests that segments of the fault are younger having been last active 1,000 -2,000 years ago. Consequently, the fault has been classified as active and included within an Alquist-Priolo Special Studies Zone established by the State of California. Furthermore, a more recent study concluded that the coastal region of San Diego may experience earthquakes up to magnitudes 7.3 and 7.4 (Sahakian et al, 2017). This study used the N ewport-Ingelwood/Rose Canyon fault offshore. An earthquake of this magnitude has likely not occurred in the last 100,000 years, according to the data. Fault zones tabulated in the preceding table are considered most likely to impact the region of the study site during the lifetime of the project. The faults are periodically active and capable of generating moderate to locally high levels of ground shaking at the site. Ground separation as a result of seismic activity is not expected at the property. ---------------------------.. ---------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad E. Site Classification for Seismic Desi2n January 2, 2019 Page9 Site soils are classified based on the upper 100 feet maximum of site profile. Site Classes A and B shall not be assigned to a site, if there is more than 10 feet of soil ( or fill) between the top of the underlying rock surface and bottom of the foundation. Site Classes A and B are most commonly supported by shear wave velocity determination (us, ft/s). Site Class F, which may require a site response analysis, consists of liquefiable or collapsible soils and highly sensitive clays soil profile. Site Classes C, D, and E soils may specifically be classified from subsurface explorations and using an average Standard Penetration Resistance (N) method for soil layers based on Section 20.4.2 of ASCE 7-10. Site Classification is then established based on Table 20.3-1 of ASCE 7-10. In the absence of sufficient or specific site data, appropriate soil properties are permitted to be estimated by the project geotechnical consultant based on known geotechnical conditions, and Site Class D is typically used conservatively as a default, unless otherwise noted. F. Seismic Ground Motion Values Seismic ground motion values were evaluated as part of this investigation in accordance with Chapter 16, Section 1613 of the 2016 California Building Code (CBC) and ASCE 7-10 Standard using the web-based United States Geological Survey (USGS) ground motion calculator. Generated results including the Mapped (Ss, S1), Risk-Targeted Maximum Considered Earthquake (MCER) adjusted for Site Class effects (SMs, SM1) and Design (S0s, Sm) Spectral Acceleration Parameters as well as Site Coefficients (Fa, Fv} for short periods (0.20 second) and I-second period, Site Class, Design and Risk-Targeted Maximum Considered Earthquake (MCER) Response Spectrum, Mapped Maximum Considered Geometric Mean (MCEa) Peak Ground Acceleration adjusted for Site Class effects (PGAM) and Seismic Design Category based on Risk Category and the severity of the design earthquake ground motion at the site are summarized in the enclosed Appendix F. G. Geolo2ic Hazards Geologic hazards are not presently indicated at the project site. The noted adverse shallow erosional and slumping features impacting the site perimeter slopes should be mitigated and surficial slope stability reestablished by new toe retaining walls and reconstruction of the impacted slopes to 2:1 maximum gradients, as recommended in this report. The most significant geologic hazards at the property will be those associated with ground shaking in the event of a major seismic event. Liquefaction or related ground rupture failures are not anticipated. Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad H. Laboratory Tests and Test Results January 2, 2019 Page 10 Additional shallow soil sampling and laboratory testing were performed in the support of this update study. The test results, supplemented by the pertinent available testing performed by the previous consultants are presented below. Based upon the available test pits and field exposures and referenced documents site soils have been grouped into the following soil types: TABLE 2 SoUTvoe Descrlotion I Light brown clayey sand/sandy clay 2 Light colored silty sand 3 Tan brown silty sand 4 Dark brown siltv to sandv clav The following tests were conducted in support of this investigation, supplemented by the pertinent available prior testing: 1. Maximum Dry Density and Optimum Moisture Content: The maximum dry density and optimum moisture content ofrepresentative samples of onsite soils were evaluated in accordance with ASTM D1557. The results are presented in Table 4. TABLE3 Location Soll Type/ MaximumDry Optimum Moisture Descrlotlon Density (T m-ncn Content (c.>opt-o/e) Pad Grade Light brown to tan color silty sandy/sandy clay 115 15 Reference E 2 115.7 15 Reference E 4 114.5 16 2. Expansion Index Test: Expansion index (EI) tests were performed on representative samples of onsite soils in accordance with the ASTM D4829. The test results are presented in Table 4. Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad TABLE4 January 2, 2019 Page 11 Sample Molded Degree of Final Initial Dry Meuured EI (a) Saturation (a) Density 50% Location (%) (o/e) c•.1.> (PCF) EI Satuntion Pad Grade 14 54 26 98.3 62 66 Pad Grade 14 51 28 96.2 79 80 Reference E 19 -29 --46 Reference E 13 -34 --98 ( w) = moisture content in percent. El50 = Elmeas -(50 -Smeas) ((65 + Elmeas) + (220 -Smeas)) Expansion Index (El) Expansion Potential 0 -20 Very Low 21 -50 Low 51 -90 Medium 91 -130 High ) 130 Very High 3. Direct Shear Test: Direct shear tests were performed on representative samples of onsite soils in substantial accordance with ASTM D3080. The prepared specimens were soaked overnight, loaded with normal loads of 1, 2, and 4 kips per square foot respectively, and sheared to failure in an undrained condition. The test result is presented in Table 5. TABLES Sample Sample Unit Angle of Apparent Weight Int. Frie. Cohesion Location Condition a'w-pcn (~Dee.) (c-nsf\ Pad Grade Remolded to 90% of Y m @ % wopt 119.4 26 150 Reference E Remolded 119 34 146 4. pH and Resistivity Test: pH and resistivity of a representative sample of onsite soils was evaluated using "Method for Estimating the Service Life of Steel Culverts" in accordance with the California Test Method (CTM) 643. The test result is tabulated in Table 6. Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 12 TABLE6 S le Location Minimum Resistivi Pad Grade 870 8.1 5. Sulfate Test: A sulfate test was performed on a representative sample of onsite soils in accordance with the California Test Method (CTM) 417. The test result is presented in Table 7. TABLE? Sample Location Sample Description Amount of Water Soluble Sulfate In Soil (o/e by Weh!ht) Pad Grade Light color silty sandy/sandy clay 0.005 6. Chloride Test: A chloride test was performed on a representative sample of onsite soils in accordance with the California Test Method (CTM) 422. The test result is presented in Table 8. TABLES Sample Location Soil Type Amount of Water Soluble Chloride In Soil (•;. bv Weil!ht) Pad Grade Light color silty sandy/sandy clay 0.003 VI. SITE CORROSION ASSESSMENT A site is considered to be corrosive to foundation elements, walls and drainage structures if one or more of the following conditions exist: * Sulfate concentration is greater than or equal to 2000 ppm (0.2 percent by weight). * Chloride concentration is greater than or equal to 500 ppm (0.05 percent by weight). * pH is less than 5.5. For structural elements, the minimum resistivity of soil (or water) indicates the relative quantity of soluble salts present in the soil ( or water). In general, a minimum resistivity value for soil ( or water) less than 1000 ohm-cm indicates the presence of high quantities of soluble salts and a higher propensity for corrosion. Appropriate corrosion mitigation measures for corrosive conditions should be selected depending on the service environment, amount of aggressive ion salts ( chloride or sulfate), pH levels and the desired service life of the structure. Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 13 Results oflimited laboratory tests performed on selected representatives of site samples indicate that the minimum resistivity is less than 1000 ohm-cm suggesting a potential for presence of high quantities of soluble salts. However, test results further indicated that pH levels are greater than 5.5, sulfate concentrations are less than 2000 ppm and chloride concentration levels are less than 500 ppm. Based on the results of the available limited corrosion analyses, the project site may be considered non-corrosive. Based upon the result of the tested soil sample, the amount of water soluble sulfate (SO4) was found to be 0.005 percent by weight which is considered negligible according to ACI 318 (SO Exposure Class with Not Applicable severity). Water soluble chloride (CL) was found 0.003 percent by weight, and the project property is not located within 1000 feet of salt or brackish water. Consequently, exposures to chloride may also be considered negligible (CO Exposure Class with Not Applicable severity). As a minimum, concrete consisting of Portland cement Type II with minimum 28 days compressive strength (f c) of 2500 psi and maximum 0.50 water-cement ratio is typically considered adequate for SO and CO Class exposures, unless otherwise specified, or noted on the project plans. Table 9 below is appropriate based on the pH-Resistivity test results, and adequate protective measures should be considered for all buried metal pipes, conduits, improvements and structures, as necessary and appropriate. TABLE9 Design Soll Type Gauge 16 14 12 10 8 Pad Grade Years to Perforation of Metal Culverts 29 38 52 66 81 VII .. STORMWATERBMPs Stormwater BMP facilities, if required or considered in connection with the project development, should be designed and constructed considering the site indicated geotechnical conditions. The implemented management and water treatment control practices shall have no short and long term impacts on the new building pad and improvement surfaces, fills and backfills, structures, and onsite and nearby offsite improvements. Testing for site infiltration feasibility condition was not a part of this study. However, based on the geotechnical data collected during this work, underlying soil profiles at the site include plastic clayey materials which may be characterized as Group D hydrologic classification (based on San Diego Hydrology Manual classification) with "No Infiltration" feasibility. Consequently, bio- retention/detention system consisting of a suitably sized excavated basin( s) with specially engineered sand filter media and a perforated underdrain pipe(s) surrounded with ¾-inch crushed rocks, and provided with impervious liner (minimum 30-mil HDPE Geomembrane) on sides and bottom may ---• -• --- ------------------- ------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 14 be considered. Captured water should be filtered and slowly discharge via a storm drain pipe to an approved storm drain facility. Schematic concepts of a Typical BMP Swale and a Typical Bio- Retention Detail are attached herein as Figures 7 and 8. Actual designs for the project BMP facilities should be provided by the responsible design consultant. The bio-retention/detention basin(s) should be properly sized for adequate storage capacity with filtrations completed not more than 72 hours and vegetation carefully managed to prevent creating mosquito and other vector habitats. Additional and more specific recommendations should be provided by the project geotechnical consultant at the final plans review phase, if necessary. VIII. CONCLUSIONS Based on our review of the attached reports (Appendices A through E) and current site geologic mapping, development of Lot 400 as currently planned for a 9-unit, 3-story condominium project, is substantially feasible from a geotechnical viewpoint. Geotechnical conditions reported in the referenced reports generally remain unchanged, except for the noted surficial slumping on the southerly ascending slope. All conclusions provided in the referenced reports remain valid and should be considered in the final designs except where specifically superseded or amended below. The following are appropriate: A. Landslides, faults or significant shear zones are not present at the project property and are not considered a geotechnical factor for future site development. The study site is not located near or within the Alquist -Priolo earthquake fault zone established by the State of California. Liquefaction, seismically induced settlements and soil collapse, will also not be a major concern in the development of the project property provided our remedial grading and foundation recommendations are followed. B. Existing terrain at the property is generally characterized by relatively level graded pad surrounded with graded slopes. Significant grade modifications or the creation of large graded slopes are also not planned in connection with the proposed development. However, transition retaining walls are planned constructed into the base of the southern and western ascending graded slopes, and near the top of the eastern perimeter descending slope to enlarge the building pad and achieve final design grades. Minor slope contour grading above the toe retaining walls along the southern and western perimeter are also proposed for reestablishing final slope grades and achieve maximum 2: 1 slope gradients. C. Large deep-seated gross geologic slope instability was not reported in the referenced reports, nor was observed during our recent site geologic mapping. However, project existing perimeter slopes are over-steepened embankments, impacted by modest to sever erosion and slump failures, as discussed herein. Current grading codes and ordinance require maximum 2: 1 slope ratios, unless otherwise specifically approved. Surficial stability of the impacted -- • ---.. - ------------------ ---------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 15 perimeter slopes and development of temporary wall backcut excavations into the erosional and slump failure deposits are the most significant geotechnical concerns in developing the project property. D. Slope repairs and mitigation consisting of remedial grading of the eastern slope and upper portions of the western slope behind the new transition retaining, and the lower impacted portions of the southern slope shall be required as a part of the project remedial grading efforts, as specified in the following sections. Remedial slope grading shall effectively remove all existing loose to soft soils and eroded and slump debris, with new fills/wall backfill properly benched and keyed into the unaffected slope as necessary and appropriate. All regraded and reconstructed portions of the project slopes shall be programmed for 2:1 maximum gradients. E. Temporary backcut excavations for perimeter transition retaining walls to the west will expose loose fills in an over-steepened (1: 1) slope conditions while the backcut for the southern toe retaining wall will predominantly expose irregular and over-steepened shallow to modest slump deposits and failure scarps. Wall backcut exposures will consist of marginally stable to unstable deposits and are expected to perform poorly in temporary vertical excavations. Large vertical wall backcut excavations at the base of the southern slope can also impact the overall slope gross stability with consequential affects on the upper offsite development at the top, and shall be avoided. Recommendations for temporary excavations, wall backcut development and shoring support are provided in the following sections. Stability of offsite portions of the rear slope is beyond the scope of the effort. F. The project property is a cut-fill transition pad generally underlain by undocumented fills/topsoils over Terrace Deposits over formational rocks units in the eastern, western and northern portions, and formational rocks units in the southern portions as approximately mapped on the attached Figure 3. The existing undocumented fills, as reported in the reference documents, are 4 feet thick in maximum thickness with the underlying topsoil layer, where it occurs nearly 2 feet thick. Site existing undocumented fill/topsoils and upper weathered formational rock exposures, where they occur in the cut areas, are soft and compressible deposits not suitable for structural support. These deposits should be stripped (removed) to the underlying suitable firm formational units, as approved in the field, and placed back as properly compacted fills in accordance with the recommendations of this report. Approximate stripping depths are provided in the following sections. The remedial grading recommendations provided herein will also eliminate the existing cut-fill transition providing a uniform bearing soil conditions throughout the building surfaces. G. Stripping and recompaction remedial grading work will be required under all proposed new structures and site and improvements, as specified herein. There shall be at least 24 inches of new well-compacted fills below bottom of the deepest footing(s), unless otherwise approved. This requirement also applies to the planned eastern retaining wall. -------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 16 H. Earth materials generated from site excavations, stripping, and removals will chiefly consist of poor to marginal quality, plastic and moisture sensitive silty to clay soils. The generated silty to clayey soils may be considered for reuse as project new compacted fills, provided they are properly processed, adequately moisture conditioned and manufactured into a suitable mixture, as specified in the following sections. However, plastic silty to clay soils are typically difficult to process and added mixing, moisture conditioning, blending and compaction efforts should be expected during the project grading and earthworks utilizing suitable construction equipments. Plastic silty to clayey soils are not suitable for wall and trench backfills and good quality sandy granular soils should be used for this purpose. I. Expansive soils are considered the second most geotechnical concern at the project site. Based upon our field observations and results of available laboratory testing, final bearing soils may be anticipated to consist of plastic clay to sandy silty clay (CH/CL) deposits ranging to high expansion potential (based on ASTM D4829 classification). Actual classification and expansion characteristics of the finish grade soil mix can only be provided in the final as-graded compaction report based upon proper testing of foundation bearing soils when rough finish grades are achieved. J. Potentially expansive bearing and subgrade soils will require special mitigation designs per Section 1808.6 of California Building Code (CBC). Typical mitigation design methods consist of pre-saturation of subgrade soils as well as deeper grade beam type footings and thicker slab-on-grade floor foundations, post-tensioned or mat slab foundations, as specified in the following sections. Other mitigation method(s) to alleviate adverse effects of expansive soils such as over-excavating the expansive bearing soils a minimum depth of 4 feet and reconstruction to rough finish pad grades with good quality non-expansive, sandy granular (D.G.) import soils, and foundation alternative(s) such as deep caissons and structural floor slabs are also available and can be provided upon request. The choice of a specific mitigation method and foundation support system will depend on the expected future performance of the planned new buildings and site improvements, economic feasibility and ease of construction. K. Project new fills and backfills should be clean deposits free of trash, debris, organic matter and deleterious materials as outlined in the following sections. Site new fills and backfills should be properly processed, throughly mixed, placed in thin lifts horizontal lifts and mechanically compacted as specified in the following sections. L. Groundwater is not reported at the project property, however existing overall side surface drainage is considered poor, as evidenced by the erosional and slump failure features affecting the perimeter slopes throughout. Uncontrolled runoff and concentrated flow over the slope faces and graded surfaces shall not be allowed. The southern slope drainage shall be improved as part of the project development by regrading/re-contouring efforts and installing appropriate drainage control facilities, as shown on the project civil/drainage improvement plans. ---- -----------------------------.. --- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 17 IX. The proper control of site surface drainage is considered a critical factor in continued stability and performance of the new condominium development and perimeter graded slopes. Ponding of water over the pad surface shall not be allowed. Site transition retaining walls should be provided with a subsurface back drainage and concrete line surface drainage ditches behind the wall. M. Added care will be required to avoid any damages to the existing nearby on and off site structures and improvements due to site excavations, remedial earthwork grading and construction works. Adjacent public and private properties and right-of-ways should also be properly protected as necessary and appropriate. Permission to perform off-site or near property line grading works shall also be obtained from neighboring property owner(s) and public agencies as necessary and appropriate. N. Soil collapse and post construction settlements are not expected to be a major geotechnical concern provided our remedial grading and foundation recommendations are followed. Post construction settlements are expected to be less than approximately I-inch and should occur below the heaviest loaded footing(s). The magnitude of post construction differential settlements, as expressed in terms of angular distortion, is not anticipated to exceed ½-inch in a distance between similarly loaded adjacent structural elements (spread pad or column footings) or a maximum distance of 20 feet ( continuous footings), whichever applicable. 0. Foundations and improvement edges, where they near or at the top of descending slopes, shall be adequately setback or deepened to provide a minimum horizontal distance from the bottom outside edge of the foundation/improvement deepened edge to the slope face (daylight), as specified in the following sections. RECOMMENDATIONS Recommendations provided in the referenced preliminary and updated soils and geotechnical investigation reports (Appendices A through E) remain valid and should be incorporated into the final designs and implemented during the construction phase except where specifically superseded or amended below. Added or modified recommendations consistent with the project new development plans and current applicable codes and engineering standards are also provided, as necessary and applicable. A. Gradin& and Earthworks Modest remedial grading efforts and slope stabilization earthworks are anticipated in order to achieve final design grades, establish safe and stable perimeter slopes and construct level pad surfaces for the support of planned future buildings, structures and improvements. All excavations, grading, earthworks, construction and bearing soil preparations shall be ------------------------------ ------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 18 completed in accordance with Chapter 18 (Soils and Foundations) and Appendix "J" (Grading) of the 2016 California Building Code (CBC), the Standard Specifications for Public Works Construction, City of Carlsbad Grading Ordinances, the requirements of the governing agencies and following sections, wherever appropriate and as applicable: 1. Existing Underground Utilities and Buried Structures: All existing underground waterlines, sewer lines, pipes, storm drains, utilities, tanks, structures and improvements at or nearby the project site should be thoroughly potholed, identified and marked prior to the initiation of the actual grading and earthworks. Specific geotechnical engineering recommendations may be required based on the actual field locations and invert elevations, backfill conditions and proposed grades in the event of a grading conflict. Utility lines may need to be temporarily redirected, if necessary, prior to earthwork operations and reinstalled upon completion of earthwork operations. Alternatively, permanent relocations may be appropriate as shown on the approved plans. Abandoned irrigation lines, pipes and conduits should be properly removed, capped or sealed off to prevent any potential for future water infiltrations into the foundation bearing and subgrade soils. Voids created by the removals of the abandoned underground pipes, tanks and structures should be properly backfilled with compacted fills in accordance with the requirements of this report. 2. Clearing and Grubbing: Remove all existing surface and subsurface structures, tanks, vaults, pipes, old foundations and slabs, improvements, vegetation, roots, stumps, large boulders, and all other unsuitable materials and deleterious matter from all areas proposed for new fills, improvements, and structures plus a minimum of five horizontal feet outside the perimeter, where possible and as approved in the field. All debris generated from the site clearing, trash, debris and vegetation removals should also be properly disposed off from the site. Trash, vegetation and debris generated from the site clearing and grubbing shall not be allowed to occur or contaminate new site fills and backfills. The prepared grounds should be observed and approved by the project geotechnical consultant or his designated field representative prior to grading and earthworks. --------------------... ----------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 19 3. Stripping and Removals: Uniform and stable bearing soil conditions shall be constructed under all planned new buildings, structures and improvements. For this purpose, stripping (removal) and recompaction of site all existing undocumented fills, topsoils and highly weathered soft and compressible Terrace Deposits/formational rocks to the minimum specified depths will be required. Stripping and remedial grading should extend a minimum of 5 horizontal feet outside the perimeter envelop of new fills, embankments, building and site improvements, where possible and as directed in the field. Stripping depths shall encompass the entire building pad and be extended to the underlying adequately dense to firm Terrace Deposits or Formation rocks suitable for receiving new fills and backfills, as approved in the field. Actual stripping depths should be established in the field by the project geotechnical consultant or his designated field representative. However, based on our review of the referenced reports and available exploratory test trenches, stripping depths are anticipated to be on the order of 4 to 5 feet below the existing ground surfaces (BGS), or 2 feet below the bottom of deepest footing(s), whichever is more. Locally, specially in the areas of the existing undocumented fills, deeper removals should be anticipated. All existing undocumented fills and topsoils, where they are encountered, shall be entirely removed and recompacted as a part of the project remedial grading operations . Exploratory test pits excavated in connection with our study at the indicated locations (see Figure 3) were backfilled with loose and uncompacted deposits. The loose/uncompacted exploratory trench backfill soils shall also be re-excavated and placed back as properly compacted fills in accordance with the requirements of this report. Bottom of all removals should be additionally prepared, ripped and recompacted to a minimum depth of 6 inches, as a part of initial fill lift placement, as directed in the field. The exposed stripping, removals and over-excavation bottoms should be observed and dense to firm Terrace Deposit/Formational Rock exposures approved by the project geotechnical consultant or his designated field representative prior to fill or backfill placement. 4. Northern and Eastern Perimeter Slopes: At least the upper 4 to 5 feet of the northern and eastern perimeter existing 1.5:1 gradients graded slopes will be removed and reconstructed as a part of the building pad remedial grading efforts. For this purpose, permission to grade on the neighboring property to the east (Lot 399) should be obtained from the respective owner(s). -------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 20 Permission to perform offsite grading to the east will also allow remedial grading repairs and stabilization of the remainder portions of the slopes by removals of existing severe erosion and local failures. For this purpose all slope eroded and failure areas shall be removed to expose dense to firm unaffected formational materials. A minimum of one and one-half equipment width (not less than 12 feet minimum) keyway should then be established at the base of the removals, and slope reconstructed by developing level back benches into the hillside and placing well compacted fills against the toe keyway and back benches. The bottom of base keyway shall be heeled back a minimum of 5 percent into the slope, and observed and approved by the project geotechnical engineer. Reconstructed slopes should be compacted to 90 percent minimum of the laboratory standard out to the slope face and neatly blended into the surrounding areas to provide a smooth transition. Over-building and cutting back to the compacted core, or backrolling at a maximum 4-foot vertical increments and "track-walking" at the completion of grading is recommended for site fill slope construction. Geotechnical engineering observations and testing will be necessary to confirm adequate compaction levels within the fill slope face. The regraded and reconstructed slope, portions there of, are recommended for 2:1 maximum gradients. However, steeper 1.5:1 gradients are also permitted provided the stability of reconstructed slopes is enhanced by providing earth reinforcement Geo grid consisting ofTensar UX-1400 ( or similar) placed within the compacted fills at maximum 3 feet vertical increments. In order to additionally enhance surficial stability, it is recommended to provide a synthetic slope face reinforcement mat (such as a Landlock TRM or similar products) to adequately retain and aid in establishing the slope face plant protection. In case permission to perform off site grading could not be obtained, the northern perimeter slope shall be repaired as specified, while concrete caissons or pile type foundation support will be necessary for the planned retaining wall at eastern property line, and provide retainment for the recommended remedial grading stripping and recompaction works elsewhere. Concrete caissons or pile type retainment structures/wall foundation support are typically more closely spaced and adequately extended to penetrate the upper loose to soft fills and weathered formational rocks embedded into the dense to form units below. Specific recommendations will be provided at the final plan review phase, if it becomes necessary. 5. Western Perimeter Slope: The majority of the western property margin nearly 10 feet high, roughly 1: 1 gradient graded slope ( below Lot 401) will be removed and replaced with transition retaining walls as part of pad development. The over-steepened slope is generally underlain by loose spill-over fills with local construction debris inclusions, and is expected to be unstable or perform poorly in temporary vertical wall backcut ----------- ------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 21 excavation. Temporary shoring procedures shall be required for development the planned wall backcut exactions and protection of the upper adjacent property line retaining wall and condominium development. Upon completion of the shoring support, the remainder portions of the slope above the new transition retaining wall(s) currently underlain by loose spill-over fills with trash debris should be removed by developing level benches into the slope and reconstructed at 2: 1 maximum gradients with clean well- compacted fills free of trash and construction debris. The new fills shall be compacted (minimum 90 percent) out to the slope face. Specific temporary shoring designs should be provided by the project design-build contractor. Typical shoring support consists of a series of drilled reinforced cast-in-place (CIP) concrete piles adequately extended below the specified remedial grading stripping depths (minimum 5 feet) reinforced with a steel cage or "W-shape" soldier beam, and provided with wood lagging during excavations spinning between the soldier piles. The following goetechnical design parameters specific to the temporary shoring system are also appropriate: * Design point of fixity should be considered 12 inches below the recommended remedial grading stripping and removal depths (minimum 6 feet BGS). * Shoring wall CIP piles should be at least 18 inches in diameter and have a minimum of 9 feet embedment below the point of fixity, as specified herein. Maximum pile spacing should not exceed 9 feet maximum, nor be less than 2.5 times the pile diameter, center to center. * A net allowable pile capacity of 150 psf per pile surface area per unit length may be used for pile designs based on skin friction, for the portion embedded into competent undisturbed formational rocks below the point of fixity (the weight of the pile may be assumed to be supported by end bearing). The net allowable pile capacity increase should be limited to a maximum of depth of 20 times pile diameter. * A design shoring passive resistance of 300 psf/ft may be considered for the portion of the pile below the point of fixity embedded into the underlying undisturbed formational rocks. The indicated design passive resistance may be increased for each additional foot of depth to a maximum of 15 times of the designated value ( 4500 pounds per square feet maximum). * Design maximum shoring pile deflection should be limited to 1-inch, unless otherwise noted or approved. ------- ---------------- ---- ------ Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page22 * A design apparent lateral static soil pressure of 35 pcf (EFP) may be considered for the temporary shoring pile designs. Additional surcharge loading due to nearby foundations, embankments and improvements shall be considered by the project design consultant as necessary and appropriate. * Design apparent coefficient of friction for pile design (portion embedded below point of fixity) = 0.31. * All pile shafts should be thoroughly cleaned to the satisfaction of the project geotechnical engineer using a "clean out bucket." Free fall of concrete in the drill shafts shall not be allowed. Concrete can be placed only upon the approval of the geotechnical engineer using the "tremie" techniques. * All drilled shafts shall be plumb. Drill shafts which are more than 1 percent of their height maximum out-of-plumb shall be rejected and required to be re-drilled. * Use a minimum 3500 psi (f'c) concrete for temporary CIP concrete shoring pile designs, unless otherwise noted. * A set of shoring plans should be provided to us for review. Additional recommendations will be given at that time if necessary. * All shoring pile shafts should be observed and approved by the project geotechnical consultant prior to the placement of steel cage/beam and pouring the concrete. As an option, limited "slot-cutting" temporary wall backcut excavation and transition wall construction procedure at alternating units (Units 5, 7 and 9 in one phase and Units 8 and 6 in a subsequent phase) may be used, if determined feasible, cost effective and approved in the field by the project geotechnical consultant. For this purpose, an initial slot-cut may be developed at one bay section, but not longer 10 feet in maximum lineal feet for geologic mapping and stability evaluations by the project geotechnical consultant. Limited slot-cutting construction procedures may then be implemented based upon an evaluation of the developed exposure and as approved by the project geotechnical consultant. Developing additional exposures and further geologic evaluations may also be necessary prior to allowing slot-cutting construction procedures as directed in the field and should be anticipated. 6. Southern Perimeter Slope: Excavations, remedial grading efforts, and construction of transition walls, are also planned at the base of the southern slope as shown on the project plans. Planned excavations, remedial grading stripping works and temporary wall backcut excavations will mostly remove the slope toe support and expose shallow ------------- ------------------------ Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page23 slough/slump deposits and failure scarps. Slough/slump deposits are estimated to be a minimum of 5 feet thick within the lower slope sections and areas of the existing failed drainage terrace/bench. Slumping/sloughing debris and soil erosions are expected to unstable and perform poorly in temporary vertical excavations and wall backcut development, and require special grading and construction procedures. All shallow failures, erosions and sloughing features currently impacting the entire slope within the property limits shall be removed and repaired by developing adequate base keyways and level back benches into the unaffected hillside, and proper slope drainage reestablished, as part of the project development procedures. The following are appropriate: * All slope erosional, slumping and sloughing failures within the property limits shall be removed to expose dense to firm unaffected formational materials. Adequate base keyways, not less than 8 feet in width, should then be established at the base of the repair areas, and impacted portions of slope reconstructed to pre-failure conditions. Slope repairs and reconstruction work should be carried out by placing pre moisture- conditioned compacted fills in thin horizontal limits against the base keyway and subsequent level back benches developed into the hillside as the backfilling progresses. The bottom of base keyway shall be heeled back a minimum of 5 percent into the slope. The base keyways and subsequent back benches should be observed and approved by the project geotechnical engineer. Reconstructed slopes should be compacted to minimum 90 percent of the laboratory standard out to the slope face and neatly blended into the surrounding areas to provide a smooth transition. Over- building and cutting back to the compacted core, or backrolling at a maximum 4-foot vertical increments and "track-walking" at the completion of grading is recommended for site fill slope construction. Geotechnical engineering observations and testing will be necessary to confirm adequate compaction levels within the fill slope face. * The stability of slope repairs reconstructed to match the surrounding 1.5: 1 gradients maximum should be enhanced by providing earth reinforcement Geogrid consisting ofTensar UX-1400 ( or similar) placed within the compacted fills at maximum 3 feet vertical increments. Additional surficial and slope face stability should also be provided by synthetic slope face reinforcement mat such as a Landlock TRM or similar products for adequately retaining and aiding in establishing the slope face plant protection. * The southern slope is generally expected to perform poorly in the temporary vertical excavations and wall backcuts planned at the base of the slope, and temporary shoring procedures shall be considered for this purpose. In general, smaller temporary excavations and wall backcut development less than 5 feet high may be developed at 1: 1 maximum gradients, unless otherwise directed in the field. The remaining temporary slope wedge should then be adequately benched out and new fill/backfill tied into the slope as the backfilling progresses. ----.. ---- ---------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 24 Temporary shoring support shall be required for larger exposures, and all vertical excavations and wall backcuts to avoid instability and major slope failures. Temporary shoring requirements will remain the same as recommended for the western perimeter, except a design apparent lateral static soil pressure of 52 pcf (EFP) should be considered for the southern perimeter temporary shoring designs. * Regrading/re-contouring of the slope is also proposed behind the planned new southern retaining walls for establishing maximum 2: 1 slope gradients and achieving design drainage patterns, as shown on the project plans. Requirements for slope regrading/re-contouring will remain the same as recommended for slope repairs and reconstruction works, and should include properly benching and keying the new fills into the unaffected and stable hillside as specified. 7. Soil Properties, Fill/Backtlll Materials, Shrinkage and Select Grading: Soils generated from the site stripping, removals and over-excavations will predominantly consist of poor to marginal quality plastic and moisture sensitive silty to clayey deposits. Plastic and moisture sensitive silty to clayey soils typically require additional processing, mixing and moisture conditioning efforts in order to manufacture a uniform homogeneous mixture suitable for reuse as new site fills. Generated soil deposits may be considered for reused as site new fills provided they are adequately prepared and properly processed to the satisfaction of the project geotechnical consultant. Placing the well-manufactured and moisture conditioned fills in thin lifts with adequate compactive efforts using heavy construction equipment suitable to the site plastic and moisture sensitive soil properties should also be considered for achieving the minimum specified compaction levels. Plastic expansive silty to clayey soils will also have detrimental effects on the site structures and improvements, if appropriate mitigation measures are not incorporated into the project designs and construction. Additionally, plastic silty to clayey soils are not considered suitable for wall and trench backfills and good quality sandy granular (D.G.) import soils should be considered for this purpose. As an alternative, site poor to marginal quality expansive soils may be removed from the building pad areas and exported from the site, and the upper 4 feet below rough finish pad grades ( or 24 inches below the deepest footing, whichever is more) capped with good quality sandy granular (D.G.) import soils. -------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page25 Onsite undocumented fills/topsoils and weathered formational rocks may be expected to shrink nearly 10 percent to 15 percent, on volume basis, when compacted (minimum 90%) as specified herein. Import soils, where used as wall and trench backfills and if considered to cap the building and improvement surfaces, should be good quality sandy granular non-corrosive deposits (SM/SW) with very low expansion potential (100 percent passing 1-inch sieve, more than 50 percent passing #4 sieve and less than 18 percent passing #200 sieve with expansion index less than 20). Import soils should be observed, sampled and tested as necessary, and approved by the project geotechnical engineer prior to delivery to the site. Import soils should also meet or exceed engineering characteristic and soil design parameters as specified in the following sections. 8. Fill/Backfill Materials Spreading and Compaction: Uniform bearing soil conditions should be constructed at the site by the project remedial grading operations. There should be at least 24 inches of well-compacted fills under the bottom of deepest footing(s). New fills and backfills should be adequately processed, thoroughly mixed, moisture conditioned to approximately 3 percent to5 percent above the optimum moisture levels, or as directed in the field, placed in thin (6 to 8 inches maximum) uniform horizontal lifts and mechanically compacted with heavy construction equipment to a minimum of 90 percent of the corresponding laboratory maximum dry density per AS TM D 1557, unless otherwise specified. Sandy granular import soils, where used, should be moisture conditioned to approximately 2 percent above the optimum moisture levels and compacted as specified. The upper 12 inches of subgrade soils (including trench backfills) under the asphalt concrete pavement base layers should be compacted to minimum 95 percent compaction levels. 9. Retaining Wall Back Drainage System: A well-constructed back drainage system should be provided behind all project site and building basement type retaining walls. Retaining wall back drainage system should consist of a minimum 4-inch diameter, Schedule 40 (SDR 35) perforated pipe surrounded with a minimum of 1 ½ cubic feet per foot of ¾-crushed rocks ( 12 inches wide by 18 inches deep) installed at the depths of the wall foundation level and wrapped in filter fabric (Mirafi 140-N). If Caltrans Class 2 permeable aggregate is used in lieu of the crushed rocks, the filter fabric can be deleted. The wall back drain should be installed at suitable elevations to allow for adequate fall via a non-perforated solid pipe (Schedule 40 or SDR 35) to an approved outlet. Protect pipe outlets as appropriate. All wall back drain pipes and outlets should be shown on the final approved plans. A retaining wall back drain system schematic is depicted on the enclosed Typical Retaining Wall Back Drainage detail, Figure 9. Provide appropriate waterproofing where applicable as indicated on the project pertinent construction plans. --- ---------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 26 10. Surface Drainage and Erosion Control: Critical elements to the continued stability of the graded building pad, perimeter graded slopes and improvement surfaces are an adequate stormwater and surface drainage control, and protection of the slope faces. Surface and storm water shall not be allowed to occur in concentrated conditions, flow over the top of retaining walls, impact graded surfaces or the developed construction and improvement sites. This can most effectively be achieved by appropriate vegetation cover and the installation of the following systems: * The rear slope drainage will be modified by excavations into and partial removals and lower drainage terrace/bench as shown on the project plans. New drainage facilities, structures and improvements should be provided for the rear slope to reestablishing adequate slope drainage and present erosion, as necessary and appropriate. * Slope face surface run-off should be collected in suitable drainage facilities and directed to a selected location in a controlled manner. Saturation of the new regraded slope faces and surrounding embankments will cause surficial slumping and shall not be allowed. * Concrete-lined drainage swales should be constructed behind the planned toe retaining walls with an added wall free board height for disallowing debris flow over top of walls, as appropriate. * Building pad and improvement surface run-off should be collected and directed away from the planned buildings and site improvements to a selected location in a controlled manner. Area drains should be installed. * The finished slopes should be planted soon after completion of grading, as specified on the project plans prepared by the landscape architect. Additional slope face stability should be provided by synthetic slope face reinforcement (Landlock TRM or similar) as specified herein. Unprotected slope faces will be subject to severe erosion and should not be allowed. Over-watering of the slope faces should not be allowed. Only the amount of water to sustain vegetation should be provided. Planting large trees behind the site retaining walls should also be avoided. * Temporary erosion control facilities and silt fences should be installed during the construction phase periods and until landscaping is fully established as indicated and specified on the approved project grading/erosion plans. -.. ------------------------------------ Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page27 11. Engineering Observations and Testing: All grading and earthwork operations including excavations, shoring, stripping and removals, suitability of earth deposits used as new compacted fills and backfills, import soils and compaction procedures should be continuously observed and tested by the project geotechnical consultant and presented in the final daily reports. The nature of finished bearing and subgrade soils should be confirmed at the completion of grading. Geotechnical engineering observations should include but are not limited to the following: * Initial observation -After clearing limits have been staked but before remedial grading starts. * Keyway/benches, stripping, bottom over-excavation observation -After dense and competent formational rocks are exposed and prepared to receive fill or backfill but before fill or backfill is placed. * Shoring, temporary wall backcut, trenching and excavation observations -After the excavation is started but before the vertical height of excavation is more than 5 feet. Local and Cal-OSHA safety requirements for open excavations apply. * Fill/backfill observation -After the fill/backfill placement is started but before the vertical height of fill/backfill exceeds 2 feet. A minimum of one test shall be required for each 100 lineal feet maximum in every 2 feet vertical gain with the exception of wall backfills where a minimum of one test shall be required for each 30 lineal feet maximum. Onsite plastic and moisture sensitive silty to clayey soils are not suitable for wall backfills. Wall backfills should consist of sandy granular (SM/SW) type import soils and mechanically compacted to a minimum of90 percent compaction levels unless otherwise specified or directed in the field. Finish rough and final pad grade tests shall be required regardless of fill thickness. * Foundation trench and subgrade soils observation -After the foundation trench excavations and prior to the placement of steel reinforcing for proper moisture and specified compaction levels. * Geotechnical foundation/slab steel observation -After the steel placement 1s completed but before the scheduled concrete pour. * Underground utility, plumbing and storm drain trench observation -After the trench excavations but before placement of pipe bedding or installation of the underground facilities. Local and Cal-OSHA safety requirements for open excavations apply. ... -.. -- ------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 28 Observations and testing of pipe bedding may also be required by the project geotechnical engineer. * Underground utility, plumbing and storm drain trench backfill observation -After the backfill placement is started above the pipe zone but before the vertical height of backfill exceeds 2 feet. Testing of the backfill within the pipe zone may also be required by the governing agencies. Pipe bedding and backfill materials shall conform to the governing agencies' requirements if applicable, and project soils report. Onsite plastic and moisture sensitive silty to clayey soils are not suitable for trench backfills. All trench backfills should consist of good quality sandy granular (SM/SW) type import soils and mechanically compacted to a minimum of90 percent compaction levels unless otherwise specified. Plumbing trenches more than 12 inches deep maximum under the floor slabs should also be mechanically compacted and tested for a minimum of 90 percent compaction levels. Flooding or jetting techniques as a means of compaction method should not be allowed. * Paving and improvements aggregate base and subgrade observation -Prior to the placement of the base layer or asphalt/concrete/PICP improvement surfaces for proper moisture and specified compaction levels. B. Foundations and Floor Slabs The proposed three-story condominium buildings may be supported on stiff concrete grade beam type footings and thick slab-on-grade floor foundations, post-tensioned or mat slab foundations consistent the anticipated plastic clay to sandy silty clay (CH/CL) deposits ranging to high expansion potential (based on ASTM D4829 classification). Other alternatives including utilizing more conventional foundation system used in conjunction with capping the building pad with at least 4 feet of very low to non-expansive sandy granular D.G. type import soils, as specified in this report, are also available. The choice of appropriate alternative, however, will depend on acceptable levels of future building and improvement performance, economic feasibility and ease of construction. Recommendations for stiff concrete grade beam type footings and thick slab-on-grade floor foundation, post-tensioned and mat slab foundations consistent with the engineering properties of the onsite soils are provided in the following sections. Pertinent recommendations for other alternative mitigation methods and foundation support system can be provided by this office upon request. Added or modified recommendations may also be necessary and should be given at the time of foundation plan review phase. All foundations and floor slab recommendations should be further confirmed and / or revised as necessary at the completion of rough grading based on the actual expansion characteristics of the final foundation bearing and sub grade soils. - ------------------------------------ Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 29 1. Stiff Grade Beam Footings and Thick Floor Slab Foundations: The following recommendations and geotechnical mitigation are appropriate for grade beam type footings and thick slab-on-grade floor foundations consistent with the onsite expansive foundation bearing and subgrade soils: * The new building may be supported on a system of perimeter and interior continuous grade beam type footings and interconnected spread pad footings. Perimeter and interior continuous grade beam footings should be sized at least 18 inches wide and 24 inches deep. Interior and exterior spread pad footings, if any, should be at least 30 inches square and 18 inches deep and structurally tied to the continuous grade beam footings with interconnecting grade beams. Interconnecting grade beams should be a minimum of 12 inches wide by 18 inches deep. Footing depths are measured from the lowest adjacent ground surface, not including the sand/gravel layer beneath floor slabs. Exterior continuous grade beam footings should enclose the entire building perimeter. Flagpole footings also need to be tied together, if the footing depth is less than 6 feet below rough finish grade. * Continuous interior and exterior grade beam footings should be reinforced with a minimum of four #5 reinforcing bars. Place two2-#5 bars 3 inches above the bottom of the footing and 2-#5 bars 3 inches below the top of the footing. Interconnecting grade beams should be reinforced with 2-#4 bars top and bottom and #3 ties at 24 inches on center maximum. Reinforcement details for spread pad footings should be provided by the project architect/structural engineer. * The slab sub grade and foundation bearing soils should not be allowed to dry prior to pouring the concrete or additional ground preparations, moisture re-conditioning and pre-saturation will be necessary as directed in the field. The required moisture content of the bearing soils is approximately 3 percent to 5 percent over the optimum moisture content to the depth of 24 inches below slab sub grade. Attempts should be made to maintain as-graded moisture contents in order to preclude the need for pre- saturation of the sub grade and bearing soils. * In the case of pre-saturation of the slab subgrade and/or non-monolithic pour (two- pour) system, dowel the slab to the footings using #4 reinforcing bars spaced 15 inches on center extending at least 20 inches into the footing and 20 inches into the slab. The dowels should be placed mid-height in the slab. Alternate the dowels each way for all interior footings. * After the footings are dug and cleaned, place the reinforcing steel and dowels and pour the footings. This office should be notified to observe the foundation trenches and reinforcing prior to pouring concrete. -- ----------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page30 * Once the concrete for the footings has cured and underground utilities tested, place 4 inches of %-inch rock over the slab subgrade. Flood with water to the top of the %-inch rock, and allow the slab subgrade to soak until moisture testing indicates that the required moisture content is present. After the slab subgrade soils have soaked, notify this office and schedule for appropriate moisture testing. * When the required moisture content has been achieved, place a well-performing moisture barrier/vapor retardant (minimum 15-mil Stego) over the %-inch rock, and place 2 inches of clean sand (SE 30 or greater) on top of the plastic. If sufficient moisture is present, flooding/presaturation will not be required. The dowels may be deleted, slab underlayment may consist of 2 inches of clean sand over a well performing moisture barrier/vapor retardant (minimum 15-mil Stego) over 2 inches of clean sand, and the footings and slab may be poured monolithically. Alternatively, a 4-inch thick base of compacted ½-inch clean aggregate provided with the vapor barrier (minimum 15-mil Stego) in direct contact with (beneath) the concrete may also be considered provided a concrete mix which can address bleeding, shrinkage and curling is used. This office should be notified to observe the sand, slab thickness, and reinforcing prior to concrete pour. * All interior slabs should be a minimum 5 inches in thickness, reinforced with #4 reinforcing bars spaced 15 inches on center each way, placed near the slab mid- height. * Interior slabs should be provided with "softcut" contraction/control joints consisting of saw cuts spaced 10 feet on center maximum each way. Cut as soon as the slab will support the weight of the saw, and operate without disturbing the final finish which is normally within two hours after final finish at each control joint location or 150 psi to 800 psi. The softcuts should be a minimum of I-inch in depth, but should not exceed 1 ¼-inch deep maximum. Anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. A void wheeled equipment across cuts for at least 24 hours. Provide re-entrant corner (270 degrees corners) reinforcement for all interior slabs consisting of minimum two, 10 feet long #3 bars at 12 inches on center with the first bar placed 3 inches from the re-entrant corner. Re-entrant corners will depend on slab geometry and/or interior column locations. The enclosed Figure 10 may be used as a general guideline. -------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 31 * Footings located on or adjacent to the top of descending slopes shall be adequately setback or extended to a sufficient depth(s) to provide a minimum clear distance of 7 feet or % of the slope height, whichever is more, horizontal distance from the bottom outside edge of the footing to the slope face. Concrete flatwork, paving surfaces and site improvements placed near the top of descending slopes should also be provided with a thickened edge to satisfy this requirement, unless otherwise specified or noted. * Foundation depths adjacent to pervious (permeable) paves shall also satisfy requirements of the Permeable Interlocking Concrete Pavers (PICP) section of this report (foundations extended a minimum of2 feet below the bottom of the pavement section). * Foundation trenches and slab sub grade soils should be observed and tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant prior to the placement of concrete. 2. Post-Tensioned Slab Foundations: The following post-tensioned slab foundations are consistent with the onsite expansive ( expansion index ranging to 98) foundation bearing soils and site specific geotechnical conditions. Additional recommendations may also be required and should be given at the plan review phase. All design recommendations should be further confirmed and/or revised at the completion ofrough grading based on the as-graded site geotechnical conditions, and presented in the final as-graded compaction report: * The proposed new condominium buildings may be supported on post-tensioned slab foundations with perimeter edge grade beams. Post-tensioned slab foundation designs should be completed by the project structural engineer or design/build contractor. The following soil design parameters are appropriate: The post-tensioned foundation designs should consider slabs with stiffening beams (ribbed foundation). In the case of a uniform slab thickness foundation, the design shall satisfy all requirements of the design procedure for ribbed foundations. The fully conformant ribbed foundations may then be converted to an equivalent uniform thickness foundation. In this case, however, perimeter edge beams shall be required as specified here. All designs shall conform to the latest addition of the California Building Code (CBC), specifications of the Post-Tensioning Institute (PTI), local standards, and the specifications given in this report. -------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 32 Remedial grading, foundation bearing soils preparations, specified moisture contents and minimum compaction levels remain the same as specified and should be confirmed by the project geotechnical engineer prior to trenching and actual construction. A well-performing vapor barrier/moisture retardant (minimum 15-mil ·stego) should be placed mid-height in 4 inches of good quality well-graded clean sand over the finish sub grade soils. Alternatively, a 4-inch thick base of½ inch clean aggregate and a vapor barrier (minimum 15-mil Stego) in direct contact with concrete, and a concrete mix design, which will address bleeding, shrinkage and curling (ACI 302.2R-06) may also be considered per California Green Building Standards Code (4.505.2). At the completion of ground and subgrade preparation as specified, and approval of the project geotechnical engineer, the post-tensioned slab foundations should be constructed as detailed on the structural/construction drawings. Based on our experience on similar projects, available laboratory testing and analysis of the test results, the following soil design parameters are appropriate: • Design predominant clay mineral type ............... Montmorillonite. • Design percent of clay in soil ........................... 60 percent. • Design effective plasticity index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50. • Design depth to constant soil suction . . . . . . . . . . . . . . . . . . . . . . . . 7 feet. • Design constant soil suction ............................... Pf 3.6. • Design velocity of moisture flow ................... 0.70 inch/month. • Thomwaite Moisture Index for edge lift . . . . . . . . . . . . . . . . . . . . . . . . . 0. • Thomwaite Moisture Index for center lift . . . . . . . . . . . . . . . . . . . . . . -20. • Design edge moisture variation distance for center lift (em) ..... 8.5 feet. • Design edge moisture variation distance for edge lift (em) ...... 4.0 feet. • Design differential swell occurring at the perimeter of slab for center lift condition (Ym) . . . . . . . . . . . . . . . . . . . . . . . . . 0.66 inches. • Design differential swell occurring at the perimeter of slab for edge lift condition (Ym) . . . . . . . . . . . . . . . . . . . . . . . . . . 1.70 inches. • Design soil subgrade modulus (K.) ........................ 100 pci. • Design net allowable bearing pressure for post-tensioned slab foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000 psf. .. -------------------------- ---- ---- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad Notes: January 2, 2019 Page33 Design internal net allowable foundation pressure within the perimeter of the post- tensioned slab foundations should be considered 1000 psf for a minimum embedment depth of 12 inches, and may be increased 20 percent for each additional foot of embedment only or a portion thereof to a maximum of3500 psf. The net allowable foundation pressure provided herein for post-tensioned foundations applies to dead plus live loads and may be increased by one-third for wind and seismic loading. Provide a minimum 15 inches wide by 18 inches deep perimeter edge beam. Perimeter edge beam embedment depth is measured from the lowest adjacent ground surface, not including the sand/gravel beneath the slabs. Perimeter edge grade beams should also enclose the entire building circumference and reinforced with at least 2- #5 continuous bar near the bottom. Provide adequate interior stiffening ribs as necessary. Interior pad footings, if any, should be an integral part of the post-tension slab foundations. Actual dimensions and reinforcement per structural designs. Post-tension slabs should not be less than 5½ inches thick minimum. Use a minimum r c=3500 psi concrete. We recommend considering pre-tensioning in order to preclude early concrete shrinkage cracking. 3. Mat Slab Foundations: Mat slab type foundation support consistent with the onsite potentially expansive foundation bearing and subgrade soils ranging to high expansion potential may also be considered for the support of the planned new condominium buildings. Remedial grading and foundation bearing soils preparation, specified moisture contents and minimum compaction levels remain the same as specified and should be confirmed by the project geotechnical engineer prior to actual trenching and foundation construction. The following geotechnical design parameters are appropriate: * The mat slab foundations should be underlain by 4 inches of clean sand (SE 30 or greater) which is provided with a well performing moisture barrier/vapor retardant (minimum 15-mil Stego) placed mid-height in the sand. Alternatively, a 4-inch thick base of compacted ½-inch clean aggregate provided with the vapor barrier (minimum 15-mil Stego) in direct contact with (beneath) the concrete may also be considered provided a concrete mix which can address bleeding, shrinkage and curling is used. * The design of mat slab foundations should incorporate a vertical modulus of subgrade reaction (K.), which is a unit value for a 1-foot square footing, and should be reduced in accordance with the following equation when used with the design of larger foundations: ----------------------------.. ----- --- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad KR= K. ((B+ 1) + 2B)**2 KR = Reduced Subgrade Modulus K. = Unit Subgrade Modulus B = Foundation Width (in feet) January 2, 2019 Page34 A unit sub grade modulus (K.) of 85 pci should be considered for the mat foundation design, unless otherwise noted or specified. * Design allowable differential settlements (deflections) on either direction shall be less than I-inch maximum. * Actual thickness and reinforcement for the mat foundation support should be provided by the project structural engineer. However, as a minimum, a uniform thickness concrete mat slab foundation (UTF) at least 15 inches thick, reinforced with minimum of two layers of mesh reinforcement, consisting of minimum #5 bars at 12 inches on centers maximum each way, one mesh layer placed near the top and one mesh layer placed near the bottom, should be considered. * The minimum mat slab foundation thickness, as specified herein, is an actual embedment measured below the lowest adjacent ground level. A minimum of 15 inches wide by 18 inches thick perimeter edge grade beam reinforced with at least 2- #5 bars near the top and 2-#5 bars near bottom also acting as a cut-off moisture barrier will be required, unless otherwise noted or determined by the project structural engineer. * Non-UTF mat slab foundations, if considered, should be at least 12 inches thick (actual embedment below adjacent grade) reinforced with minimum double mat of #5 bars at 12 inches on centers, each way top and bottom, with perimeter and interior stiffening beams. Actual mat and stiffening beams, per the structural engineer designs, however, the perimeter and interior stiffening beams should be a minimum of 15 inches wide by 18 inches deep reinforced with at least 2-#5 bars near the top and 2-#5 bars near the bottom . * A design net allowable foundation pressure 1000 psf for a minimum embedment depth of 12 inches should be considered in mat foundation design for minimum 90 percent compacted fill bearing soils, placed in accordance with the requirements of this report. The designated mat slab foundation bearing value may be increased 20 percent for each additional foot of embedment only or a portion thereof to a maximum of 3500 psf. The net allowable foundation pressure provided herein also applies to dead plus live loads and may be increased by one-third for wind and seismic loading. .. ----------------------- -- ------- - Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 35 * Foundation excavations and slab subgrade soils should be observed and tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant prior to the placement of steel reinforcement or concrete pour. C. Soil DesiKn Parameters The following soil design parameters are based upon tested representative samples of onsite earth deposits and our experience with similar earth materials in the vicinity of the project site. All parameters should be re-evaluated when the characteristics of the final as-graded soils have been specifically evaluated: 1. Design soil unit weight = 119 pcf. 2. Design angle of internal friction of soil = 26 degrees. 3. Design active soil pressure for retaining structures = 46 pcf (EFP), level backfill, cantilever, unrestrained walls. 4. Design active soil pressure for retaining structures = 70 pcf (EFP), 2: 1 sloping backfill, cantilever, unrestrained walls. 5. Design at-rest soil pressure for retaining structures = 67 pcf (EFP), non-yielding, restrained walls. 6. Design soil passive resistance for retaining structures = 300 pcf (EFP), level ground surface on the toe side (soil mass on the toe side extends a minimum of 10 feet or 3 times the height of the surface generating passive resistance). 7. Design coefficient of friction for concrete on soils = 0.31. 8. Net allowable foundation pressure (continuos strip/grade beam and spread pad type foundations) for onsite compacted fills (minimum 12 inches wide footings with at least 12 inches embedment into approved bearing soils)= 1500 ps£ 9. Allowable lateral bearing pressure ( all structures except retaining walls) for onsite compacted fill = 100 psf/ft. Notes: * In case of terraced retaining walls, upper wall foundation pressures should not be allowed to surcharge the lower retaining walls, unless otherwise considered in the designs. For this purpose, the upper wall should be adequately set back from the top of the lower wall a minimum clear distance equal to the height of the lower wall. Alternatively, upper wall foundation should be adequately depended so that the lower wall is above a projected imaginary plane having a downward slope of 1-unit vertical to 2-units horizontal (50 percent) from a line 9 inches above the bottom edge of the upper wall footing. A combination of setback and deepened foundations may also be considered. The passive resistance of the upper terraced walls should also be considered as an additional active pressure for the lower wall, where applicable. Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 36 * An additional seismic force due to seismic increments of earth pressure should also be considered in the retaining walls designs, if appropriate and where applicable. A seismic lateral inverted triangular earth pressure of 18 pcf (EFP), acting at 0.6H (His the retained height) above the base of the wall should be considered. Alternatively, seismic loading based on Mononobe-Okake (M-O) coefficients may be considered for seismic force due to seismic increments of earth pressure. The following relationships and design values are appropriate: TABLE 10 Wall Total Seismic Lateral KA Ko Kh KAE KOE T Condition Lateral Pressure Pressure (pct) Unrestrained PAE=PA + PAE ~p AE=%Kh TH2 0.39 -0.15 0.54 -119 Restrained POE=PO + POE ~POE=KbTH2 -0.56 0.15 -0.71 119 * Use a minimum safety factor of 1.5 for wall over-turning and sliding stability. However, because large movements must take place before maximum passive resistance can be developed, a minimum safety factor of 2 may be considered for sliding stability particularly where sensitive structures and improvements are planned near or on top of retaining walls. * When combining passive pressure and frictional resistance, the passive component should be reduced by one-third. The upper 6 inches of ground surfaces should not be included in the design for passive soil resistance, unless otherwise noted or specified. * The net allowable foundation pressure provided herein was evaluated based on minimum 12 inches wide by 12 inches deep footings. The designated value may be increased by 20 percent for each additional foot of depth, and 10 percent for each additional foot of width to a maximum of3500 psf. The net allowable foundation pressure provided herein also applies to dead plus live loads and may be increased by one-third for wind and seismic loading. * A design net allowable foundation pressure of 2500 psf for a minimum 12 inches wide by 12 inches deep footings may be considered by implementing the following bearing soil improvement procedure: Over-excavate foundation trenches to a minimum depth of 2 feet, and neatly place a layer of TerraGrid RX-1200 (or greater) earth reinforcement geogrid over the prepared bottom of over-excavation. Bottom of foundation trench over-excavation shall be observed and approved by the geotechnical engineer prior to installing the geogrid. ---------------- ------------------ - Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 37 Reconstruct the trench to the bottom of foundation level by backfilling over the earth reinforcement geogrid with minimum 95 percent compacted Caltrans Class 2 aggregate base materials. In this case, the designated bearing value may also be increased by 20 percent for each additional foot of depth, and 20 percent for each additional foot of width to a maximum of5500 psf. The net allowable foundation pressure provided herein also applies to dead plus live loads and may be increased by one-third for wind and seismic loading. * The lateral bearing earth pressures may be increased by the amount of designated value for each additional foot of depth to a maximum 1500 pounds per square foot. D. Exterior Concrete Slabs / Flatworks 1. All exterior slabs (sidewalks, patios, etc.) supported on potentially expansive subgrade soils should be a minimum of 4 inches in thickness, reinforced with #3 bars at 16 inches on centers in both directions placed mid-height in the slab. Subgrade soils underneath the exterior slabs should be moisture conditioned and compacted to minimum 90 percent compaction levels at the time of fine grading and before placing the slab reinforcement. In order to enhance performance of exterior slabs and flatworks supported on expansive and moisture sensitive subgrade soils, a minimum 8 inches wide by 8 inches deep thickened edge reinforced with a minimum of 1-#4 continuous bar near the bottom should be considered along the slab perimeter. Tying the slab panels to adjacent curbs, where they occur, with #3 bars at 16 inches on centers, may also be considered. 2. Reinforcements lying on subgrade will be ineffective and shortly corrode due to lack of adequate concrete cover. Reinforcing bars should be correctly placed extending through the construction joints tying the slab panels. In construction practices where the reinforcements are discontinued or cut at the construction joints, slab panels should be tied together with minimum 18 inches long #3 dowels at 16 inches on centers placed mid-height in the slab (9 inches on either side of the joint). 3. Provide ''tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not to exceed 12 feet maximum) each way. The larger dimension of any panel shall not exceed 125 percent of the smaller dimension. Tool or cut as soon as slab will support weight, and can be operated without disturbing the final finish which is normally within two hours after final finish at each control joint location or 150 psi to 800 psi. Tool or softcuts should be a minimum of ¾-inch but should not exceed 1-inch deep maximum. In case of softcut joints, anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. A void wheeled equipment across cuts for at least 24 hours. ----------------.. ----------- --------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 38 Joints shall intersect free-edges at a 90 degree angle and shall extend straight for a minimum of 1 ½ feet from the edge. The minimum angle between any two intersecting joints shall be 80 degrees. Align joints of adjacent panels. Also, align joints in attached curbs with joints in slab panels. Provide adequate curing using approved methods (curing compound maximum coverage rate= 200 sq. ft./gal.). 4. All exterior slab designs should be confirmed in the final as-graded compaction report. 5. Subgrade soils should be tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant prior to the placement of concrete. E. Permeable Interlocking Concrete Pavers (PICP): Project development proposes Permeable Interlocking Concrete Pavers (PICP) for the central access driveway as a part of the project stormwater quality treatment BMPs. The proposed PICP driveway, is generally considered feasible from a geotechnical viewpoint. However, the following recommendations are appropriate and should be considered in the final designs and implemented during the construction phase, where appropriate. 1. Project stormwater BMP permeable interlocking pavers should consist of a self- contained system disallowing saturation of adjacent foundation bearing soils, graded embankments, wall backfills and site improvement subgrade. In general, PICP pavements finish subgrade should be sloped away at a minimum 2 percent onto a minimum 12 inches wide by 12 inches deep collector trench near the center of the driveway and provided with a 4-inch diameter (Sch. 40 or SDR 35) underdrain pipe surrounded with ¾-inch crushed rocks. A conceptual detail is shown in the enclosed Typical Permeable Paver Detail, Figure 11. The perforated underdrain pipe should discharge collected water into an appropriate storm drainage facility. Perimeter deepened foundations, cut off walls and curb restraints should be provided, and bottom and sides of the system lined with an impervious liner (minimum 30-mil HOPE or PVC geomembrane ), as shown. 2. Building foundation adjacent to PICP pavements should be deepened to a minimum depth of 2 feet below the bottom of the pavement section (impervious liner). Additional mitigation measures such as construction of a minimum 8 inches wide, three-sack concrete cutoff walls may also be necessary. More specific recommendations should be provided by the project geotechnical consultant at the final plan review phase. 3. PICP pavement structural section should consist of traffic grade (31/a-inch), PICP over a minimum of2 inches of ASTM No. 8 bedding course/choke stone over a minimum 12 inches of ASTM No. 57 stone base course (reservoir layer) over a minimum of 12 inches of95 percent compacted sub grade (per ASTM D 1557). Bedding course/choke stone and Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 39 base course stone should also be well compacted, consolidated and interlocked (avoid crushing the underdrain pipes) with heavy construction equipments. ASTM No. 8, No. 9 or No. 89 should be used for joint materials depending on the joint size and per manufacturer recommendations. Gradation requirements for ASTM No. 57, No. 8, No. 89 and No. 9 are as follows: TABLE 11 Sieve Percent Passine: Size No.57 No.8 No.89 No.9 1½" 100 1" 95 to 100 ½" 25 to 60 100 100 3/a" 85 to 100 90 to 100 100 No.4 0 to 10 10 to 30 20 to 55 85 to 100 No. 8 0 to 5 0 to 10 5 to 30 10 to 40 No. 16 0 to 5 0 to 10 0 to 10 No. 50 0 to 5 0 to 5 F. General Recommendations 1. The minimum foundation design and steel reinforcement provided herein are based on soil characteristics and are not intended to be in lieu of reinforcement necessary for structural considerations. 2. Adequate staking and grading control is a critical factor in properly completing the recommended remedial and site grading operations. Grading control and staking should be provided by the project grading contractor or surveyor/civil engineer, and is beyond the geotechnical engineering services. Staking should apply the required setbacks shown on the approved plans and conform to setback requirements established by the governing agencies and applicable codes for off-site private and public properties and property lines, utility easements, right-of-ways, nearby structures and improvements, leach fields and septic systems, and graded embankments. Inadequate staking and/or lack of grading control may result in illegal encroachments or unnecessary additional grading which will increase construction costs. -------------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 40 3. Open or backfilled trenches parallel with a footing shall not be below a projected plane having a downward slope of 1-unit vertical to 2 units horizontal (50 percent) from a line 9 inches above the bottom edge of the footing, and not closer than 18 inches from the face of such footing. Enclosed Figure 12 may be used as a general guideline. 4. Where pipes cross under-footings, the footings shall be specially designed. Pipe sleeves shall be provided where pipes cross through footings or footing walls, and sleeve clearances shall provide for possible footing settlement, but not less than 1-inch all around the pipe. A schematic detail entailed Pipes Through or Below Foundation is included on the enclosed Figure 12. 5. Expansive clayey soils should not be used for backfilling of any retaining structure. All retaining walls should be provided with a 1: 1 wedge of granular, compacted backfill measured from the base of the wall footing to the finished surface and a well-constructed back drain system as specified (Figure 9). Planting large trees behind site retaining walls should be avoided. 6. All underground utility and plumbing trenches should be mechanically compacted to a minimum of 95 percent of the maximum dry density of the soil unless otherwise specified or required by the governing agencies. Care should be taken not to crush the utilities or pipes during the compaction of the soil. Very low expansive, granular import backfill soils should be used. Trench backfill materials and compaction beneath pavements within the public right-of-way shall conform to the requirements of governing agencies. 7. Onsite soils include expansive and moisture sensitive silty to clayey soils ranging to high expansive. These deposits can experience movements and undergo volume changes upon wetting and drying, detrimental to the supporting structures and improvements. Maintaining a uniform as-graded soil moisture during the post construction periods is essential in the future performance and stability of site structures and improvements. Excessive irrigation resulting in wet soil conditions should be avoided. Surface water should not be allowed to infiltrate into the underlying bearing and subgrade soils. 8. Site drainage over the finished pad surfaces should flow away from structures in a positive manner. Care should be taken during the construction, improvements, and fine grading phases not to disrupt the designed drainage patterns. Rooflines of the buildings should be provided with roof gutters. Roof water should be collected and directed away from the buildings and structures to a suitable location. -- ----------------------------------- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 41 X. 9. Final plans should reflect preliminary recommendations given in this report. Final foundations and grading plans may also be reviewed by the project geotechnical consultant for conformance with the requirements of the geotechnical investigation report outlined herein. More specific recommendations may be necessary and should be given when final grading and architectural/structural drawings are available. 10. All foundation trenches should be observed to ensure adequate footing embedment and confirm competent bearing soils. Foundation and slab reinforcements should also be observed and approved by the project geotechnical consultant. 11. The amount of shrinkage and related cracks that occur in the concrete slab-on-grades, flatworks and driveways depend on many factors, the most important of which is the amount of water in the concrete mix. The purpose of the slab reinforcement is to keep normal concrete shrinkage cracks closed tightly. The amount of concrete shrinkage can be minimized by reducing the amount of water in the mix. To keep shrinkage to a minimum the following should be considered: * Use the stiffest mix that can be handled and consolidated satisfactorily. * Use the largest maximum size of aggregate that is practical. For example, concrete made with %-inch maximum size aggregate usually requires about 40-lbs. more (nearly 5-gal.) water per cubic yard than concrete with 1-inch aggregate. * Cure the concrete as long as practical. The amount of slab reinforcement provided for conventional slab-on-grade construction considers that good quality concrete materials, proportioning, craftsmanship, and control tests where appropriate and applicable are provided. 12. A preconstruction meeting between representatives of this office, the property owner or planner, city inspector as well as the grading contractor/builder is recommended in order to discuss grading and construction details associated with site development. GEOTECHNICAL ENGINEER OF RECORD (GER} §HI§ Geotechnical Solutions, Inc. is the geotechnical engineer of record (GER) for providing a specific scope of work or professional service under a contractual agreement unless it is terminated or canceled by either the client or our firm. In the event a new geotechnical consultant or soils engineering firm is hired to provide added engineering services, professional consultations, engineering observations and compaction testing, SMS Geotechnical Solutions, Inc. will no longer be the geotechnical engineer of the record. Project transfer should be completed in accordance with the California Geotechnical Engineering Association (CGEA) Recommended Practice for Transfer of Jobs Between Consultants. - ---------------------------.. -------• Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page42 The new geotechnical consultant or soils engineering firm should review all previous geotechnical documents, conduct an independent study, and provide appropriate confirmations, revisions or design modifications to his own satisfaction. The new geotechnical consultant or soils engineering firm should also notify in writing 6616 Geotechnical Solutions, Inc. and submit proper notification to the City of Carlsbad for the assumption of responsibility in accordance with the applicable codes and standards (1997 UBC Section 3317.8). XI. LIMITATIONS The conclusions and recommendations provided herein have been based on all available data obtained from the review of pertinent geotechnical reports and documents, available project development plans, current site observations and geologic mapping of site surface conditions, additional shallow sampling and laboratory testing, and our experience with the soils and bedrock materials located in the general site areas. Of necessity we must assume a certain degree of continuity between available exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be verified during the grading operation. In the event discrepancies are noted, we should be contacted immediately so that an observation can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/ developer to ensure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of 6616 Geotechnical Solutions, Inc., shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our observation or control. The property owner( s) should be aware that the development of cracks in all concrete surfaces such as floor slabs and exterior stucco are associated with normal concrete shrinkage during the curing process. These features depend chiefly upon the condition of concrete and weather conditions at the time of construction and do not reflect detrimental ground movement. Hairline stucco cracks will often develop at window/door corners, and floor surface cracks up to 1/s-inch wide in 20 feet may develop as a result of normal concrete shrinkage (according to the American Concrete Institute). This report is issued with the understanding that the owner or his representative is responsible for ensuring that the information and recommendations are provided to the project architect/structural engineer so that they can be incorporated into the plans. Necessary steps shall be taken to ensure that the project general contractor and subcontractors carry out such recommendations during construction. --------------------------.. ----- ----- Geotechnical Investigation Update, Proposed La Costa Villas North Condominium Project, 400 Gibraltar Street, Carlsbad January 2, 2019 Page 43 The project geotechnical engineer should be provided the opportunity for a general review of the projects final design plans and specifications in order to ensure that the recommendations provided in this report are properly interpreted and implemented. The project geotechnical engineer should also be provided the opportunity to field verify the foundations prior to placing concrete. If the project soil engineer is not provided the opportunity of making these reviews, he can assume no responsibility for misinterpretation of his recommendations. This report should be considered valid for a period of one year and is subject to review by our firm following that time. In case of plan revisions including changes in the final pad size, graded embankments, actual building and improvement locations, lines and grades, and final elevations, this report should be reviewed and updated by this office for review comments and additional recommendations based on the plan changes, as appropriate. N•N Geotechnical Solutions, Inc., warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. Once again, should any questions arise concerning this report, please do not hesitate to contact this office. Reference to our Project No. GI-18-12-158 will help to expedite our response to your inquiries. We appreciate this opportunity to be of service to you. ~=-'="'~ ~~~ . ~~t& N•N Geotechnical Solutions, Inc. No. 2885 ~d~ Steven J. Melzer CEG#2362 Distribution: Addressee (3, e-mail) MBM Development, Majid Mortazavi ( e-mail) ACE Engineering, Mike Massodnia ( e-mail) CCH Design Group, Charles Heiney ( e-mail) §.M§ GEOTECHNICAL SOLUTIONS, INC. -------------------------------------- REFERENCES -Annual Book of ASTM Standards, Section 4 -Construction, Volume 04.08: Soil and Rock (I); D420 -D5876, 2016. -Annual Book of ASTM Standards, Section 4-Construction, Volume 04.09: Soil and Rock (11); D5877 -Latest, 2016. -Highway Design Manual, Caltrans. Fifth Edition. Corrosion Guidelines, Caltrans, Version 1.0, September 2003. -California Building Code (CBC), California Code of Regulations Title 24, Part 2, Volumes 1 & 2, 2016, International Code Council. -"The Green Book" Standard Specifications For Public Works Construction, Public Works Standards, Inc., BNi Building News, 2015 Edition. -California Geological Survey, 2008 (Revised), Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117 A, 108p. -California Department of Conservation, Division of Mines and Geology (California Geological Survey), 1986 (revised), Guidelines for Preparing Engineering Geology Reports: DMG Note 44. -California Department of Conservation, Division of Mines and Geology (California Geological Survey), 1986 (revised), Guidelines to Geologic and Seismic Reports: DMG Note 42. -EQFAULT, Ver. 3.00, 1997, Deterministic Estimation of Peak Acceleration from Digitized Faults, Computer Program, T. Blake Computer Services and Software. -EQSEARCH, Ver 3.00, 1997, Estimation of Peak Acceleration from California Earthquake Catalogs, Computer Program, T. Blake Computer Services and Software. -Tan S.S. and Kennedy, M.P., 1996, Geologic Maps of the Northwestern Part of San Diego County, California, Plate(s) 1 and 2, Open File-Report 96-02, California Division of Mines and Geology, 1 :24,000. -"Proceeding of The NCEER Workshop on Evaluation of Liquefaction Resistance Soils," Edited by T. Leslie Youd and Izzat M. Idriss, Technical Report NCEER-97-0022, Dated December 31, 1997. -"Recommended Procedures For Implementation of DMG Special Publication 117 Guidelines For Analyzing and Mitigation Liquefaction In California," Southern California Earthquake Center; USC, March 1999. .. ------------------------ - - ------- REFERENCES (continued) "Soil Mechanics," Naval Facilities Engineering Command, DM 7.01. "Foundations & Earth Structures," Naval Facilities Engineering Command, DM 7.02. "Introduction to Geotechnical Engineering, Robert D. Holtz, William D. Kovacs. "Introductory Soil Mechanics and Foundations: Geotechnical Engineering," George F. Sowers, Fourth Edition. "Foundation Analysis and Design," Joseph E. Bowels. Caterpillar Performance Handbook, Edition 29, 1998. Jennings, C. W., 1994, Fault Activity Map of California and Adjacent Areas, California Division of Mines and Geology, Geologic Data Map Series, No. 6. Kennedy, M.P., 1977, Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, California, Special Report 131, California Division of Mines and Geology, Plate 1 (East/West), 12p. Kennedy, M.P. and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area, California: California Division of Mines and Geology Bulletin 200, 56p. Kennedy, M.P. and Tan, S.S., 1977, Geology of National City, Imperial Beach and Otay Mesa Quadrangles, Southern San Diego Metropolitan Area, California, Map Sheet 24, California Division of Mines and Geology, 1 :24,000. Kennedy, M.P., Tan, S.S., Chapman, R.H., and Chase, G.W., 1975, Character and Recency of Faulting, San Diego Metropolitan Areas, California: Special Report 123, 33p. "An Engineering Manual For Slope Stability Studies," J.M. Duncan, A.L. Buchignani and Marius De Wet, Virginia Polytechnic Institute and State University, March 1987. "Procedure To Evaluate Earthquake-Induced Settlements In Dry Sandy Soils," Daniel Pradel, ASCE Journal OfGeotechnical & Geoenvironmental Engineering, Volume 124, #4, 1998. "Minimum Design Loads For Buildings and Other Structures," ASCE 7-10, American Society of Civil Engineers (ASCE). "Seismic Constraints on The Architecture of The Newport-Ingelwood/Rose Canyon Fault: Implications For The Length And Magnitude of Future Earthquakes," Sahakian, V., Bormann, J.,Driscoll, N.,Harding,A. Kent, G. Wesnousky, S. (2017),AGU. doi:10.1002/2016JB 013467. z z 0 ..... ID ID ID 0 l"i 117.26667° W TOPO! map printed on 12/10/18 from •sanDlego.tpo" and "Untitled.tpg" 117.25000° W WGS84 117.23333° W fYl F""~H l:<"'--.""'~n----....,,_--a---,..--., Job Site Coordinates : Lat. 33.0859°. Lon. 117.2475° 117.26667° W !i---=~!!11!!!!!!!11==?-llllill:=::::11-111!===---==~HU -..Jl'O FUT --J m --!000'" 117.25000° W WGS84 117.23333° W Primed from TOPO• Ct999 WildJIO\\-w Productions ( ... .,..w.topo.com) z 0 § ..., l"i fYl z 0 fYl fYl fYl CX) 0 l"i fYl z 0 ..... ID :g 0 l"i fYl UJ a: ~ a: ; <( a: co [ GEOTECHNICAL MAP] BfDROOIIIISL~ ,, 8EOROOMS I.E\IEI. UNIT#4 109-60 UNIT#8 MAIN lMNGLEVB.. 100".liDlW -. "' • "-OS: " MAIN LIVIN~ LEVEi.. ~~ lfr='-11r=~F"'===~l,=-,J==--·=~0~...,,,·-=~-d; -------------~--- UNIT#4 . I BEOROOMS l£VS. UNIT#2 INIIN LIVING LEVB. .BEDROOMS LEVEL ,, ""'IN LIVINGLEVEL GISRALTAR S1REET 60.ot/ RIGHT OF' WAY . alaOROOMS LEVEL UNIT#8 MAIN LIVING L!:VEL 8EOROOMS LEVEL ,, UNIT/17 • MAIN LMNG l.EVEL • i) 'ii PROJECT I Ja.oo''---_ -_:_-_-_+:_-_-_-:--Jo.oo·-----i , · p:.l -·-I '"'"-t~t-7 / EXJSTING °"' j ! . s l "·' I .,.,-/:XISTING SLOPE: )f-1 __, ---' J,--SLOPE VARI£$ /. 7 :::rl.---£ _:= --:::_-,. --_j7= -iT I' , VARJ£S .,, EXISTING__/J E .:::: I ---\::::: :=:I ~ \.,EXISTING -.. SIDEWALK S/DEW/lK " EXISTING EXISTING.../ E)(JST/NG EXISTING CURE/ &< GUTTE:R AC AC CURB &< GUTT£/? TYPICAL SECTION ND SCALE ~ EXISTING STREET SECTION ,., GIBRALTAR STREET ---------- PREUM!INARY EARTH QUANTITIES 109.60 CUT: 1170 Cr FILL: R!EJ<1t;DIAL R&R: """""'"'T· ""'"''"" . 331 Cr 65 CY 839 Cf f UTit.mES WATER: DEMAND: IRRIGATION: SEWER: CARLSBAD MUNICIPAL WATER DISTRICT AVG. 2000 Gf>M WATER li)EMAND PEAK 63 GPD LEUCADIA WASl'E, WATER DISTRICT AVG.$ E9U'$ ($EE AVAilABILTY LETTER DATED 12/26/2013 FIRE PROTECTION:CA'i'Uil\l'AD Affls: DEPARTMENT FIRE FLOW DEM:4:NID · 300@ GPM ~fH lJN!!'.LW:'!i]..LJi~\tEE!llMLSPRINKLERS ON EACl:LLEVEL. ASINGLE-STAFION-'-- SMO.l<!E ~Cl'@R 0'-/!I. !M.OI LEVEL AND IN SLEEPING ROOMS. ALL ~FUGE W:J:,LL l!fE Pil'-CilliED lJP AT CURBSIDE ELEMENTRY SCHOOL El!5r.: ENCINITAS UNION SCHOOL HIGH SCHOOL DIST.: SAN DIEGUITO UNION HIGH SCHOOL TELEPMONE: PACIFIC BELL STORM WATER: F'-RIVATE SAN DLl~GO GA£ & E~CTRIC: CANNOT BE PLOTTED ACCURATLY FROM SAID INSTERMEl'!JT. M!.t!MENT PER DOC. 74-281428, SIX FEET OR MORE 1 WIDTH IMzING TH~ FEIIT MleASURE-0 AT RIGHT ANGLES, ON EACH AND EVERY ELECTRJiC A:ND GAS UTILITY FACILITY INSTALLED WITHIN THE PROPERTY ON OR li½l!:.f'Omf DK:. 26, 1:~73 +/-(FROM EXIST UTIUTIES SHOWN ONSITE NO WEMENl'S W@lJLD AFriECT THIS PARCEL . AVERAGE: DAillLY l'~FIC: 1,4 I l i AUTOMATIC F]l'li!l: $PM~b~ $¥$"liEM: -AN AUTOMATIC FIRE SPRINKL,... 4 'STEM $MALL IBBNSTALLl!lli!l /¥i, Pl1:R N.F.P.A. 13 OR 13D, WHICHEVER IS._ "/9_ :ABLE THE MOIIT ClJ~~Ni'IEt>mON SHALL BE USED AND THE CITY OF G.~ BADL,,.~~.--;Hl:b POLIOE:$. [)lffMLD §PRJNKLER PLANS SALL BE SUBMI I I ED ro THE Fl E f>R:EVENTI0N EllJ~IJ Rl~ APPROVAL PRIOR TO PERMIT ISSUANCE. _,.-- k d===:-:=~~r~-•~~-~F~m I 92..l:5 ~'St *-' r. ,--½lr.':1'~~-=-::....i'k.J~c...-~-I ---~ -a-r I d----+--el-.5-0 -+-l's 1' RETAINUNQ \l,':O,LL PEFi' ~LAl'f --~-~------n,,, + 1ERRACE WALLS IJSE . f4 6Afi$ TC:,P l.ND son~.I RETAINING WALL PER PLAN Y' CI.EARA>ICE FRO>! SOTTOM, 1,5• CLEARANCE 1.j•. FACE Of WALL o:i,,a 4~ INTO RETAINING VIALL.$ FOR WEIR A~O ORIFICE SEE !€TAIL S-B TYPICALBIORETENTIONSECTION SITE PLAN - 1" = 10"-0" TP-5 jll//71 X X' 6=-=- GEOTECH.lVICAL LEGEND Approximate Location of Test Pit (MV Eng. 1991) Geologic Cross-Section I) ev Appmrimatc Locanon of Erosion/Slump Failure -----_ / Approximate Geologic Contact Tsa Santiago Fonnational Rock Vaf/QtlTsa Undocumented Fill Over Terrace Deposits Over- Santiago Formational Rock roject No. GJ-18-12-158 BUILDl1NG PADS I "' • • Tsa GARAGE 544 s.t SIDEWALi( ~ Ill 68°33'47" E 64.93' Tsa GARAGE 455 s.f. F.F.G.::.8'!.!ll ,,,,,1:e,.<11 2 GARAGE 455 s.f. F ..F.G. = 81.23 FAD:aJ.73 ENffiY FFMf6 HALL 274s.f. -----------r ---- I I I I I I I .. I I I I I I I I I PROJECT NO. Gl-18-12-158, REPORT DATED JANUARY 2019 Tsa. 1 GARAGE 460 s.f. F.F.G.=W£ PAD:00.06 t/Tsa I I I I I I I I I I I I I • ----.. (: . 'T I l I 8 GARAGE F.F.G.•122.1 PAD:81.73 \ 7 GARAGE \ \ , __ _ --~ -\ \ \ \ 6 -GARAGE F.F.G.::ao.as PAD:80.39 5 ,-eaosrnNG RE'TAJN:NG WAl.l. f,.TF'.L,PER.LOT401. GARAGE F.F.Gs&ll2 PA0:79.72 -~ ~ --· ....... .. ING: RETAINING WAU. f\T P,L, PE-'-: I..Or-401. 100 PR.DlECT: LACOSTA VILLAS LOT 400 GIBRALTAR STREET CARLSBAD,CA CAA.WING lln.E:: TITLE/DATA SHEET PLAN CHE(l{: [> REVJSIONS: PROJECT INFORMATION: OFFICE PROJECT NO.: CCHDG 006·13 REV!Bo\'EO BY: DRAWN BY: CCH SCALE: NOTTO SCALE DATE: A1.00 SHEETNO. · FIGURE 3 .. CU'PBD CLBANOUT M•T PIPE· : HOPE OR PK; GCOMEJIJRANE THIO<NfSS AT LEAST JOMII. Project No: Gl-18-12-1 58 J" WIN/MUN (TYP AGGRf:GA TE 8£l.OW UNOERDRAJH TO A\00 Ct.OCQNG Typical Bio-Retention Detail Schematic & Conceptual Only No-Scale 18" HOP£ STORM DRAIN RISER W/A TRIUM VARIES ,;,~ DE~;· ·,.s~ :_:__;/. SOIL Fil. TER MIX -! " PERFORA 'TF:D PIPE SLOPED AT 0.5% IN¾" AGGREGATE BAS£ GRA "fl. BE:D. CONN£CTfD TO STORM DRAIN. 6.ll§GEOTECHNICAL SOLUTIONS. INC. 0-MODIFic.A.TION OLOVFICBAT !JIADB ELEVATION HOPE OR PVC GEOMEMBRAHE THfCKNCSS AT LEAST JOI.Ill OUTZ£T PIPE Figure: 8 SPECIFICATIONS FOR CALTRANS CLASS 2 PERMEABLE MATERIAL (68-1 .025) U.S. STANDARD SIEVE SIZE 1• 3/◄ 3/8 No. 4 No. 8 No.30 No. 50 No. 200 %PASSING 100 90-100 -40-100. 25--40 18-33 5.15 0-7 0-3 SAND EQUIVALENT > 75 FILTER MATERIAL, 3/-4' • I~' CRUSHED ROCKS (WRAPPED IN FILTER FABRIC OR CAL TRANS CLASS 2 PERMfASlf MATERIALS (SEE SPECIFICATIONS) WATERPROOFING (iYP) FINISH GRADE CONCRETE-LINED DRAINAGE DITCH FILTER MATERJAL, 3/-4' · lf CRUSHED ROCKS (WRAPPED IN FILTER FABRIC OR CALTRANS CLASS 2 PERMEABLE MATERlALS (SEE SPECIFICATIONS) PROPOSED GRADE !NOSCALE! CONSTRUCTION SPECIFICATIONS: I NO SCALE I GROUND SURFACE APPROVED FILTER FABRIC (MIRAFI 1 .CON) 12" OVERlAP, TVP. -4' NC PERFORATED PIPE MIN. (SCH .CO OR SDR35) MIN. 1 /2% FALL TO APPROVED OUTLET (SEE REPOR'T) NATURAL OR GRADED SLOPE TEMPORARY 1 : 1 CUT SLOPE PROPERLY COMPACTED (MIN. 90%) BACKFILLED GROUND "'----BENCH AND TIGHTLY KEY INTO TEMPORARY • z GOw --w !:!l., BACKCUT AS BACKFILLING PROGRESSES APPROVED FILTER FABRIC (MIRAFI l ◄ON) 12' OVERLAP, TVP. .__ _____ ◄' PVC PERFORATED PIPE MIN. (SCH -40 OR SDR35) MIN. 112% FALL TO APPROVED OUTLET (SEE REPORT) 1. Provide granular, non-expansive backfill soil in 1 :1 gradient wedge behind wall. Compact backfill to minimum 90% of laboratory standard. 2. Backdrain should consist of 4" diameter PVC pipe (Schedule 40 or equivalent) with perforations down. Drain to suitable at minimum½%. Provide¾" -1-½" crushed rocks filter materials wrapped in fabric (Mirafi 140N or equivalent). Delete filter fabric wrap if Caltrans Class 2 permeable material is used. Compact Class 2 permeable material to minimum 90% of laboratory standard. 3. Seal back of wall with approved waterproofing in accordance with architect's specifications. 4. Provide positive drainage to disallow ponding of water above wall. Drainage to flow away from wall at minimum 2%. Provide concrete-lined drainage ditch for slope toe retaining walls. 5. Use 1-½ cubic feet per foot with granular backfill soil and 4 cubic feet per foot if expansive backfill is used. SMS GEOTECHNICAL SOLUTIONS. INC. TYPICAL RETAINING WALL Consulting Geotechnlcal Engineers & Geologists BACK DRAINAGE 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010760-602-7815 PROJECT NO. FIGURE NO. smsgeosol.inc@gmail.com Gl-18-12-158 9 (a) RE-ENTRANT CORNER REINFORCEMENT NO. 3 BARS PLACED MID-HEIGHT IN SLAB ISOLATION JOINTS CONTRACTION JOINTS (c) NO SCALE NOTES: ( 6) RE-ENTRANT CORNER CRACK 1. Isolation joints around the columns should be either circular as shown in (a) or diamond shaped as shown in (b). If no isolation joints are used around columns, or if the corners of the isolation joints do not meet the contraction joints, radial cracking as shown in (c) may occur (reference ACI). 2. In order to control cracking at the re-entrant corners(+ /-270 degree corners), provide reinforcement as shown in (c). 3. Re-entrant corner reinforcement shown herein is provided as a general guideline only and is subject to verification and changes by the project architect and / or structural engineer based upon slab geometry, location, and other engineering and construction factors. TYPICAL ISOLATION JOINTS AND SMS GEOTECHNICAL SOLUTIONS1 INC. RE-ENTRANT CORNER Consulting Geotechnical Engineers & Geologists REINFORCEMENT 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010 760-602-7815 PROJECT NO. FIGURE NO. smsgeosol.inc@gmail.com Gl-18-12-158 10 • Project No: Gl-1 8-1 2-158 Typical Permeable Interlocking Concrete Paver (PICP) Detail Schematic & Conceptual Only No-Scale NO. 8 AGGRfGA TES IN OPENINGS PER MANUF'ACnJR£R SPECS. PERMEABLE PA \£RS (TRAmc RA TED) Schematic And Conceptual On1v· No-Scale (Also See Report) N•6GEOTECHNICAL SOLUTIONS, INC. 3-1/8,. THICK CONCRETr PAVfRS, TRAFF'IC LOADING 6,. CONCRETE fDGF RESTRAIN l\) - Figure: 11 Typical Pipes Through or Trench Adjacent to Foundations SPREADFTG .• CONT. FTG.., OR GRADE~ Schematic, No-Scale LOCATE TRENCH SO ---, TWtT FOOTINGS ARE NOT UNDERMINED .... 8ACKFIU. TRENCH PER GEOTECHMCAl REPORT NOTES: 1. DO NOT PUCE SLEEVES OR CONDUIT IN ISOlATED SPREAD FOOTINGS· A AROUND OR BB.OW MSE FOOTINGS. 2. Sl.EEVES ARE NOT TO~ n<ROOGH C0NTIHUOUS FOOTWGS q'-....,. .... . 2 . . . ,·. ..... OR GRADE 8£AMS UM.ESS SHOWN O'TIERWtSE · WHERE S!.EEVES ME PERMITTED, SEE SEE SECTION eaow NOEXCAVAltoNALlOWED ' BELOW THIS LINE SW~GMOE A ELEVA TIQN A-A CONT. FOMNG ORGIWJE'~ • • • £.(I •.• ----PLACEfflSCONCRETE BEFORE FOOffiG ABOVE SEE NOTE2 affl.FOOTWG ORGRADE~ ~ •• <1 •• Pipes Throu&h or Below Foundation Project No: Gl-18-12-158 6.116GEOTECHNICAL SOLUTIONS, INC. 5931 Sea Lion Place, Suite 109 Carlsbad, California 92010 Figure: 12 .. .. ,. .. .. .. .. .. C APPENDIX A C C C C C C C C C C C C C C -------------------------------------- Project No. GI-9-14-18 September 9, 2014 ACE Engineering Mr. Mike Massoclnia SMS GEOTECHNICAL SOLUTIONS, INC. Consulting Geotechnical Engineers & Geologists Value Engineering 1645 S. Rancho Santa Fe Road, Suite 208, San Marcos, California 92078 Office: 760-761-0799 Cell: 760-331-8738 smsgeoso/. inc@gmail.com 1645 South Rancho Santa Fe Road, Suite 208 San Marcos, California 92078 Addendum Geotechnical Plan Review Update, Proposed La Costa Villas Development, Gibraltar Street At Jerez Court, Carlsbad, California Pursuant to your request, SMS Geotechnical Solutions, Inc. has completed the following Addendum Geotechnical Plan Review Update report for the proposed La Costa Villas development at the above- referenced property. This letter also serves as our verification that SMS Geotechnical Solutions, Inc, is now retained as the Geotechnical Engineer of Record (GER) for the above-referenced project. The undersigned has prior work history on the project while employed at Vinje & Middleton Engineering, Inc. in 2004, as noted in the references below. The project property is also designated as Lots 399,400 and 401 of La Costa South Unit No. 5. The approximate site coordinates are 33.086°N latitude and -1 l 7.2475°W longitude. Project development Plans are available and were reviewed as a part of this effort. Surface and subsurface geotechnical conditions at the project property were previously studied by prior consultants who issued the following technical reports outlining their findings and recommendations: 1. "Second Update of Preliminary geotechnical Investigation Update Report, Proposed Multi- UnitAttached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by Allied Earth Technology, Project No. 13-1147Hl, dated June 5, 2014. 2. "Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by Allied Earth Technology, Project No. 13-l 147Hl, dated October 10, 2013. 3. "Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad," prepared by Vinje & Middleton Engineering, Inc., Job #04-287-P, dated July 7, 2004. This report was completed under the engineering supervision of the undersigned while employed at the Vinje & Middleton Engineering, Inc. -------------------------------------- ACE Engineering Mr. Mike Massodnia September 9, 2014 Pagel 4. "Preliminary Soil and Geotechnical Investigation, Graded Hillside Property, Gibraltar Street Near Jerez Court, La Costa Area of Carlsbad, San Diego County, California," Prepared by MV Engineering, Inc., Job #1017-91, dated February 20, 1991. The referenced reports were reviewed in connection with this effort and copies can be provided upon request. Based on the project available plans and reports, Lot 399 is a cut lot underlain mostly by Terrace Deposits, while Lots 400 and 401 are transition lots with filled ground in the northern frontage areas and fonnational bedrock cut surfaces in the southern rear areas. The purpose of this transmittal was to review the referenced reports and confirm compatibility of the project most current Grading Plans with the site indicated geotechnical conditions. Revised and/or amended recommendations consistent with the attached plans, current applicable codes and engineering standards are also provided in the following sections, and will supplement or superseded those given in the referenced reports. Based on our review of the referenced reports and project grading plans, development of the project properties for multi-unit attached residential dwelling purposes, substantially as proposed, is feasible from a geotechnical viewpoint. Geotechnical conditions reported in the referenced reports remain unchanged. All conclusions and recommendations provided in the referenced reports also remain valid and should be incorporated into the final designs and implemented during the construction phase except where specifically superseded or amended below. 1. Based on our review of the project plans, the southern perimeter site retaining walls are on the order of 6 feet high maximum, while north-south running site retaining walls separating individual pads along the east and west sides are minor features less than 3 feet high maximum. Building basement type retaining walls, parallel and adjacent to the site perimeter retaining walls, are on the order of 10 feet high maximum, will replace slope conditions and enlarge terraced pads upon construction, where they occur. 2. Adequate setback or deepened foundations shall be required for all foundations constructed on or near the top of descending slopes to maintain minimum horizontal distances to daylight or adjacent slope face, as specified. There should be a minimum of7 feet or one-third of the slope height, whichever is more, horizontal setback from the bottom outside edge of the footing to daylight. The temporary transition slopes will be removed and replaced with building basement type retaining walls during the course of project development. The recommended foundation setback requirement will also provide for a safe future temporary wall backcut excavation, necessary for the adjacent lower building wall construction. -------------------------------------- ACE Engineering Mr. Mike Massodnia September 9, 2014 Page3 3 Based on our review of the project plans, the upper site retaining walls (3 feet high maximum) appear to maintain adequate set backs with sufficient embedment depths avoiding surcharging of the lower building basement type retaining walls. In general, a downward projected 1: 1 line from edge of the upper wall foundations should not intercept the lower building basement type wall. 4. The following soil design parameters are based on the available strength tests completed by others on representative samples of onsite earth deposits and our review of referenced reports: * Design active soil pressure for retaining structures = 35 pcf (EFP), level backfill, cantilever, unrestrained walls. * Design active soil pressure for retaining structures = 50 pcf (EFP), 2: 1 sloping backfill, cantilever, unrestrained walls. * Design at-rest soil pressure for retaining structures = 53 pcf (EFP), non-yielding, restrained walls. * Design passive soil resistance for retaining structures= 350 pcf (EFP), level surface at the toe, compacted fills, soil mass extends 10 feet or 3 times the height of the surface generating passive resistance. * Design passive soil pressure for retaining structures = 420 pcf (EFP), level surface at the toe, competent undisturbed bedrock, soil mass extends 10 feet or 3 times the height of the surface generating passive resistance. * Design coefficient of friction for concrete on compacted fills= 0.35. * Design coefficient of friction for concrete on competent undisturbed bedrock= 0.40. * Net allowable foundation pressure (minimum 12 inches wide embedded at least 12 inches into compacted fills) = 1500 psf. • Net allowable foundation pressure (minimum 12 inches embedded at least 12 inches into underlying competent undisturbed bedrock) = 2000 psf. Notes: -An additional seismic force due to seismic increment of earth pressure should also be considered in the project wall designs for building walls with greater than 6-feet soil differential on each side or retaining walls 12 feet or taller, as appropriate. A seismic lateral inverted triangular earth pressure of 24 pcf (EFP) acting at 0.6H (His the retained height) above the base of the wall should be considered, where applicable. The seismic lateral earth pressure should be considered in addition to the specified static earth and surcharge (due to nearby foundation) pressures. -When combining passive pressure and frictional resistance, the passive component should be reduced by one-third. -------- ------------------------------ ACE Engineering Mr. Mike Massodnia September 9, 2014 Page4 -The net allowable foundation pressure provided herein, was determined for footings having a minimum width of 12 inches embedded at least 12 inches into the underlying compacted fills or competent undisturbed bedrock, as approved in the field. The indicated value may be increased by 20% for each additional foot of depth and l 0% for each additional foot of width to a maximum of 3500 psffor compacted fills and 4500 psffor undisturbed competent bedrock, if needed. The allowable foundation pressures provided herein also apply to dead plus live loads and may be increased by one-third for wind and seismic loading. LIMITATIONS The conclusions and recommendations provided herein have been based on all available data obtained from the review of pertinent geotechnical documents as well as our experience with the soils and bedrock materials located in the general site areas. Of necessity we must assume a certain degree of continuity between available exploratory excavations and/ornatural exposures reported bu previous consultants. It is necessary, therefore, that all observations, conclusions, and recommendations are verified during the grading operation. In the event discrepancies are noted, we should be contacted immediately so that an inspection can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to ensure that these recommendations are carried out in the field. It is almost impossible to predict with certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm of SMS Geotechnical Solutions, Inc., shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our inspection or control. The property owner( s) should be aware that the development of cracks in all concrete surfaces such as floor slabs and exterior stucco is associated with normal concrete shrinkage during the curing process. These features depend chiefly upon the condition of concrete and weather conditions at the time of construction and do not reflect detrimental ground movement. Hairline stucco cracks will often develop at window/door comers, and floor surface cracks up to ¼-inch wide in 20 feet may - develop as a result of normal concrete shrinkage (according to the American Concrete Institute). GEOLOGIC MAP * Scale I :33,333 Geologic Units: GNV B B 0 0 [E] Young alluvial flood-plain deposits (Holocene and late Pleistocene) Old alluvial flood-plain deposits, undivided (late to middle Pleistocene) Delmar Formation (middle Eocene) Santiago Formation (middle Eocene) Metasedimentary and metavolcanic rocks , undivided (Mesozoic) Exerpt From the Geologic Map of the Oceanside 30' x 60' Quadrangle, California Michael P. Kennedy and Siang S. Tan 2007. Figure 4 I I 100 80 60 I I I I I I I I I I I I fP T------------=r 1-----------------------------X. (J I --1 1 --1 EXISTING 80 60 I PROPOSED WALL • 1 --I _ 7 WALL PROPOSED T ,-PROPOSED • I UNIT #2 I J UNIT #7 :-------1 i----------l r~.-I •• -'~SEDGRAD~~-1_ ·JI.-:::- -~---? -· UNDOCUMltNTEDFIL1 L[u~r· . • ,:-· , , ·.' ? --• ? .• · I 1_.,;.-- • . _,-,-,, I l . 'TERRACE DEPOSIT [Qt] . . TOPSOIL {Qs} ••.-~.-·. ----' . 'I~-----=--------- . . --------------'-. ~--FORMATION_Ah_ ROCK {Tsa) ___ -=r=_-,-' ---------1..--= ft: I SLUMP FAILURE • FORMATIONAL ROCK (Tsa) SCALE: I" = 20' PROPOSED GRADE (APPROX.) ----- 100 80 60 FIGURE 5 Gl-18-12-158 t I 60 "I • • .... , ' f , ,,.,., .. , . .. ,•·· ,. •• ·, •• • 1 .. ·· .. FAULT-EPICENTER MAP SAN DIEGO COUNTY REG ION • -.. --♦--- •: ~ ·. "'.·· .-.. __ . ~-. _ __.---- -~ -·-~ ·~ Indicated Earthquake Events Through A 200 Year Period Map is reproduced from California Division of Mines and Geology, "Epicenters of/ and Areas Damaged by M ~ 5 California Earthquakes, 1800-1999" . F igure 6 Typical BMP Swale TURF REINF<RCEIIENT MAT IF APPIJCABt.E i-----------PER PLAN ----~----t 18" 1111 ll'ERJEJaE ~<>-FABRr F Rf(XJRf[) BY StlS £JIClllIR. • ENCIN£ER£D sat LA'ifR 9IIJ.l l£ 1/MUJ 6• DEEP SAIIJY LOAM .SY.I IIX tf7H NO IDiE THAN 5% tlAY C<llTENT. TIC 1B SHAU C(J(TAII 50-60X ~ 20-JOX ctJl'OST fR IWiDlfXlJ WLOI, ANO 2<f-JOZ Tr1'StM.. ---- SMS Geotechnical Solutions, Inc. 5931 Sea Lion Place, Suite 109 Carlsbad, CA 92010 NPTH _[ PCRPLAN 6. MIN. £JQEfRf/) Sl1L 'S£E NOTf EELOW 10• 1111. Fl TfR IEDIA: ~~~~~~~~:._-J PART QENi WASIEO SANO TO 1 PART Jft• Qi'A~ ~~~~-2• -J/8• Q?A~ ~' 6• -J/4. CRIJSH[I) ROCK · 4• PfRF<RA 1fD SBRMI PIPE SUK AT 1X /Iii. AMJ CflKCT TO (11-S11f FWIVA TE ORA/NA~ SYSTEII Figure 7 ------------ ---- -------------------- ACE Engineering Mr. Mike Massodnia September 9, 2014 Page5 This report is issued with the understanding that the ov.11er or his representative is responsible for ensuring that the information and recommendations are provided to the project architect/structural engineer so that they can be incorporated into the plans. Necessary steps shall be taken to ensure that the project general contractor and subcontractors carry out such recommendations during construction. The project geotechnical engineer should be provided the opportunity for a general review of the projects final design plans and specifications in order to ensure that the recommendations provided in this report are properly interpreted and implemented. The project geotechnical engineer should also be provided the opportunity to field verify the foundations prior to placing concrete. If the project soil engineer is not provided the opportunity of making these reviews, he can assume no responsibility for misinterpretation of his recommendations. This report should be considered valid for a period of one year and is subject to review by our firm following that time. In case of plan revisions including changes in the final pad size, graded embankments, actual building and improvement locations, lines and grades, and final elevations, this report should be reviewed and updated by this office for review comments and additional recommendations based on the plan changes, as appropriate. We appreciate this opportunity to be of service to you. If you have any questions or need clarification, please do not hesitate to contact the undersigned. Reference to our Project No. GI-9- 14-18 will help to expedite our response to your inquiries. SMS Geotechnical Solutions, Inc. Distribution: Addressee (2, e-mail MBM Development, Mr. vi (2, e-mail) ANP Engineering, Mr. Pirouz Etemad SMS GEOTECHNICAL SOLUTIONS, INC Consulting Geotechnical Engineers & Geologists VALUE ENGINEERING c· C C C C APPENDIXB [· C C C [ [ [ [ [ [ [ [ C C ---- --------------------------------- ALLIED EARTH TECHNOLOGY 7915 SIL VER TON A VENUE, SUITE 317 SAN DIEGO, CALIFORNIA 92 I 26 PH (858) 586-1665 FAX (858) 586-1660 (619) 447-4747 ROBERT CHAN, P.E. June 5, 2014 Ace Civil Engineering 7668 El Camino Real #104-463 Carlsbad, CA. 92009 Attn: Subject: Mr. Mike Massoodnia Project No. 13-1147Hl Second Update of "Preliminary G~otechnical Investigation Update Report" Proposed Multi-Unit Attached Dwellings Gibraltar Street at Jerez Court La Costa, California Dear Mr. Massoodnia : In accordance with your request, we have performed geotechnical engineering services for subject property, more specifically referred to as being Lot Nos. 399 to 401, inclusive, La Costa South Unit No. 5, in the City of La Costa, State of California. The purpose of our work is to prepare an update report with current geotechnical recommendations for the site development as presently proposed. The scope of our work includes two visits to the site, and a review of the following plans and documents: --------- - ------------------------- Project No. 13-l 147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 2 "Preliminary Soil and Geotechnical Investigation, Graded Hillside Project, Gibraltar Street near Jerez Court, La Costa area of Carlsbad, San Diego County, California" prepared by MV Engineering, Inc. (Their Job #1017-91, dated February 20, 1991.) "Preliminary Geotechnical Investigation Update Report -Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad" prepared by MV Engineering, Inc. (Their Job #04-287-P, dated July 7, 2004). "Update of Preliminary Geotechnical Investigation Update Report - Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad" prepared by Allied Earth Technology, dated October 10, 2013. "Site Grading Plan for La Costa Villas" prepared by ACE Civil Engineering of Carlsbad, dated May 27, 2014. PROPOSED DEVELOPMENT It is our t.q1derstanding that the site is to be developed to receive 26 townhomes units. Nine units each will be constructed on Lot Nos. 399 and 400; and eight units on Lot No. 401. The proposed structures will consist of two stories above a two-car garage, and will be of wood-frame/stucco and slab-on-grade construction. FIELD INSPECTION Inspections of the property on September 24, October 7, 2013, and May 23,2014, indicate that the site was found to be generally of the same condition when rough grading was completed in the early part of 1970, with the following exception : A high combined cut/fill slope on the order of70 feet in maximum was observed along the rear, south end of the property, ascending to the residential lots to the south. .. -.. ... .. .. .. ... 111 411 .. .. ... "" ... ... -.. - .. .. - ... .. .... .. .. Project No. 13-l 147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 3 This combined cut/fill slope has a slope ratio of 1 ½: I (horizontal : vertical), with tvm drainage ditches at mid-height . This combined cut/fill slope has been in existence since the early I 970's. The upper portions of this slope, which are within the properties to south, are well maintained and in good condition. The lower portions of the existing high cut/fill slope, which are within subject property has suffered some erosion and sloughing, due to lack of maintenance over the decades. The erosion and sloughing were caused by overflow of surface runoff from the drainage ditches on the slope, which were had been filled with debris and vegetation through the decades . A review of the subdivision grading plan indicates that Lot 399 consists of all cut or natural soils. Lot 400 is a "transition lot", with a maximum of 3 feet of fill soils along the front portion of the site. Lot 401 is also a "transition lot", with a maximum of 7 feet of fill soils along the front of the property . The fi.11 soils encountered on the property site were derived locally, and consist of a mixture of light brown/light gray/dark brown sandy clay, clayey sands and silty sands. These soils possess low to high expansion potential (Expansion Index of 46 and 98) . SlTE GEOLOGY Reviews of California DMG open-file report 96-02 and CGS geologic map of the Oceanside quadrangle indicate that the property is underlain by two formations : the . • .. .. .. .. - -.. -.. - -... .. ----- • .. • .. ... .. ... Project No, 13-1147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 4 Santiago Formation, and Quaternary terrace deposits per the Department of Mine and Geology report, or Quaternary Old alluvium, per the California Geologic Survey map. Both types of Quaternary units are mapped equivalently. As described in open-file report 96-02, the Santiago Formation is middle Eocene in age (approximately 49 to 45 million years old). It consists primarily of fine to medium-grained sandstone interbedded with siltstone and claystone, and localized coarse-grained sandstone and conglomerate. Bedding attitudes in the Santiago Formation generally dips westward 5 degrees. The terrace/alluvium deposits are younger, late to middle Pleistocene (approximately L8 to 1 million years old). They are reddish brown, poorly bedded and poorly to moderately indurated sandstone, siltstone and conglomerate . G,EOLOGIC HAZARDS Earthquake Fault Rupture Hazard San Diego's tectonic setting includes north and northwest striking fault zones, the most prominent and active of which is the Rose Canyon Fault Zone. Other fault zones lie in eastern and northern San Diego County., Fault rupture hazard would affect a property if an active fault trace or traces traverse the property. The subject property lies approximately 7 miles east of the offshore Newport-Inglewood Rose Canyon fault zone and 20 miles east of the offshore Coronado Banks fault zone. The property is approximately 28 miles west of the ' -------------------------------------- ProjectNo. 13-1147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 5 Elsinore fault :wne, 57 miles west of the San Jacinto fault zone, and 82 miles west of the San Andreas fault zone. The property is outside any State and City designated fault and fault hazard zones and is therefore not subject to a special fault investigation. The Rose Canyon Fault Zone is capable of generating a 6.9 magtnitude earthquake. Even though direct ground rupture from faulting directly underneath the subject property is unlikely, the property will be subjected to considerable ground acceleration and shaking from an earthquake event along the nearby faults. The intensity of ground shaking is dependent on distance from faults, earthquake magnitude and duration, and seismic characteristics of foundation soils and bedrock. Soil Liquefaction . It is our opinion that due to the relatively high density of the competent natural and compacted fill soils (after remedial grading recommended herein) prevalent at the site; the lack of near-surface groundwater and the grain size characteristics of the in-situ soils, the risk for seismically induced soil liquefaction is very low. FINDINGS, CONCLUSIONS AND RECOMMENDATIONS In general, we concur and agree with the findings, conclusions and recommen- dations presented in the above-mentioned Report and Update, and said findings, conclusions and recommendations are still valid and applicable for the proposed site development. • .. .. • ... .. .. ... .. .. -.. .. - ..., --.. - ---.. --.. --.. Project No. 13-l 147H1 Ace Civil Engineering Gibraltar Street 06/05/14 Page 6 The following addendum recommendations are made, however, as supplement to the recommendations presented in the subject Report and Update. If there are discrepancies, the addendum recommendations herein will prevail. Expansiveness of On-site Near Surface Soils 1. Some of the near-surface soils encountered on the site possess high expansion potential (Expansion Index = 98) . Earthwork 2. The current grading plans for the project were reviewed. The three building 3, 4. pads will remain in their current elevations. Prior to commencement of grading, it is recommended that the site be cleared and grubbed, and all debris and vegetation disposed of offsite. It is recommended that existing fill soils along the front of Lot Nos. 400 and 40 t be removed. Maximum depths of fill on these lots are on the order of 3 to 7 feet. The bottom of the over-excavation should be inspected by our firm, and scarified to a depth of 12 inches. The removed soils should then be properly moistened, and uniformly recompacted to at least 90 percent of maximum dry density in accordance with A.S.T.M. D1557, until finished grade is achieved .. For Lot No. 401, it is recommended that the upper soils below finished grade be scarified to a depth of 12 inches, properly moistened and uniformly to at least 90 percent of maximum dry density in accordance with ASTM DI557. All footings .. .. .. • " .. • ,. .. .. -.. ----... • ... .. ... .. -.. .. -- Project No. 13-l 147Hl Ace Ci vii Engineering Gibraltar Street 06/05/14 Page 7 5 . 6. are to be extended into the underlying competent formation soils or bedrock . Since the maximum depth of fill soils on Lot No. 400 is only 3 feet, and extends over a relatively small area, it is recommended that the footings of the proposed structure be extended through the compacted fill soils at least} 2 inches into the underlying competent formational soils. The upper, surface and near-surface soils on the building pads had been subjected to weathering for decades. It is recommended that the natural soils on Lot Nos . 399 and 400 be scarified to a depth of 12 inches, properly moistened and uniformly compacted to at least 90 percent of maximum dry density, in order to provide adequate support to the concrete slab of the proposed structures. Repair of Surficial Slope Failure 7. It is recommended that the soils loosened by the erosion and sloughing of the 8 . 9. existing slope be removed. The building pads along the toe of the existing slope will be widened, excavating and removing the loosened soils. A retaining wall will also be constructed along the bottom of the existing slope . As the repair work progresses up the existing slope, benches will have to be provided. The interval and width of the benches required will be determined by our field personnel during the remedial grading . The surface of the slope should be properly compacted with a sheepsfoot roller. • .. • • .. .. .. .. -• -.. - .. ... -... .. ... -... - - .. • .. ... .. .. • Project No. 13-l 147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 8 In order to further minimize the potential for future surficial slumping, it is recommended that the slope be planted with deep rooted ground cover and shrubs at 1 0 feet on center . Foundation and Slab 10. It is recommended that a safe allowable soil bearing value of 1,500 pounds per 11. square foot be used in the design and checking of continuous or spread footings that are a minimum of 15 and 24 inches in minimum horizontal dimension, respectively, and are embedded at least 24 inches into the competent natural or compacted filled ground . The above safe allowable soil bearing value may be further increased by one third when considering wind and/or seismic forces . 12. The concrete slab for the proposed structures should be at least 4 ½ inches net in thickness, and be reinforced with a minimum of #3 re bars at 18 inches on center in both directions, placed at mid-height of concrete slab. The concrete slab should be underlain by 4 inches of clean sand and a vapor barrier in moisture sensitive areas . 13. The continuous footings should be reinforced with a minimum of 4 #5 rebars; two rebars located near the top, and the other two rebars near the bottom of the footings. Isolated pier footings should be reinforced with 2 #5 rebars in both ... 41 • .. .. ... - .. .. .. .. • -----.. ... -.. - - .. - - Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 9 14. 15 . 16 . directions, placed near the bottom of the footings. Please note that the above slab and foundation reinforcements are based on soil characteristics only, and should be superceded by the requirements of the project architect or structural engineer. It is recommended that the moisture content of the subgrade soils beneath the proposed structures be maintained at approximately 120% of optimum moisture content. However, no flooding of the foundation soils is permitted immediately prior to the placement of concrete . It is recommerided that the foundation for the proposed structure be setback at least 7 feet back from the top of the fill slope. Foundations placed closer to the top of the slope than 7 feet should be deepened such that the outer edge of the footing along the bottom is at least 7 feet back from the face of slope at that level. For footings subject to lateral forces, such as those of a retaining wall, the above setback should be increased to 10 feet. It is further recommended that the foundation trench excavations be inspected by our firm prior to the placement of concrete. Any loose and/or unsuitable soils encountered should be removed and/or replaced under our direction. Retaining Wall Design 17. It is recommended that retaining walls be designed to withstand the pressure exerted by equivalent fluid weights given on the following page : .. .. - .. ... ... ., • .. • .., -.. - -..., ... .. -... -.... • .. .. Project No. 13-1147Hl Backfill Surface (horizontal : vertical) Level 2 : ] 1 ½: 1 Ace Civil Engineering Gibraltar Street 06/05/14 Equivalent Fluid Pressure (pct) 35 50 58 Page 10 The above values assume that the retaining walls are unrestrained from movement, and have a granular backfill. For retaining walls restrained from movement at the top, such as basement retaining walls, an uniform horizontal pressure of 7H (where His the height of the retaining wall in feet) should be applied in addition to the active pressures recommended above. 18. All retaining walls should be supplied with a backfill drainage system adequate to prevent the buildup of hydrostatic pressure. The subdrain should consist of one- inch gravel and a perforated pipe near the bottom of the retaining wall. The wiath of this subdrain should be at least 12 inches, and extend at least 2/3 height of the retaining wall. The subdrain should be enclosed in a geotextile fabric such as Mirafi 140N or equal. Seismic Earth Pressure 19. Seismic earth pressures can be taken as an inverted triangular distribution with a maximum pressure at the top equal to 15H pounds per square foot (with H being the height of the retained earth in feet. This pressure is in addition to the static design wall load. The allowable passive pressure and bearing capacity can be • • .. -... -... -- .. ... ---... - -------- .. ---... - Project No. 13-1147H1 Ace Civil Engineering Gibraltar Street 06/05/14 Page 11 increased by 1 /3 in determining the stability of the wall. A factor-of-safety of 1.2 can be used in determining the stability of the retaining wall under seismic conditions . Lateral Loading 20. To resist lateral loads, it is recommended that the pressure exerted by an 21. 22. equivalent fluid weight of 350 pcf be used for footings or shear keys poured neat against competent natural or compacted fill soils. The upper 12 inches of material in areas not protected by floor slabs or pavements should not be included in the design for passive resistance. This value assumes that the horizontal distance of the soil mass extends at least IO feet or three times the height of the surface generating the passive pressure, whichever is greater. A coefficient of sliding friction of 0.35 may be used for cast-in-place concrete on competent natural or compacted fill soils. Footings can be designed to resist lateral loads by using a combination of sliding friction and passive resistance. The coefficient of friction should be applied to dead load forces only. All backfill soils behind the retaining wall should consist of soils having low expansion potential (Expansion Index < 50), and be compacted at least 90 percent ofmaximwn dry density . Seismic Coefficients 23. The seismic design factors were determined in accordance with the 20 IO .. .. .. - ◄ .. • .., .. .. .... .. - .. -... - -.. -.. .. • Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 12 California Building Code, and presented below : Site Coordinates : Latitude = 33.0860 Longitude = 117.2475 Site Class: = D Site Coefficient Fa = 1.040 Site Coefficient Fv = 1.565 Spectral Response Acceleration At Short Periods Ss = 1.153 Spectral Response Acceleration At I-second Period SJ 0.435 Sms = FaSs = 1.200 Sm1 = FvSl = 0.681 Sds = 2/3*Sms = 0.800 Sdl = 2/3*Sml = 0.454 Preliminary Structural Pavement Section Design 23. For preliminary design purposes, it is recommended that a structural pavement 24. 25. section of 3 inches of asphaltic concrete over 6 inches of Class II base material over compacted subgrade be used. The upper 8 inches of subgrade and base material should be compacted to at least 95 percent of maximum dry density. For PCC pavement sections, it is recommended that the pavement section be 5 ½ inches in thickness, and be reinforced with #3 rebars at 18 inches on center in both directions, placed at mid-height of concrete slab. Control joints at 12-foot intervals should also be provided . I • • .. -.. .. .. - .. .. .. --------.. ... -.. .. -.. .. Project No. 13-114 7H l Utility Trench Backfill Ace Civil Engineering Gibraltar Street 06/05/14 Page 13 26. It is recommended that any backfill soils placed in utility trenches located within 5 feet of any improvements and deeper than 12 inches, or backfill placed in any trench located 5 feet out or more from a building and deeper than 5 feet, be compacted to at least 90 percent of maximum dry density. Surface Drainage and Lot Maintenance 27. Adequate drainage control and proper maintenance of all drainage facilities are imperative to minimize infiltration of surface water into the underlying soil mass in order to reduce settlement potential and to minimize erosion. The building pad should have drainage swales which direct storm and excess irrigation water away from the structure and into the street gutters or other drainage facilities. No surface runoff should be allowed to pond adjacent to the foundation of structures. Concrete Flatwork 28. It is recommended that concrete flatwork be 3 ½ inches in thickness and reinforced with 6 x6-10/10 welded wire fabric placed at mid-height of slab. One- inch expansion joints should be provided at 15-foot intervals; with ¼ inch weakened plane contraction joints at 5-foot intervals. LIMITATIONS The opinions and recommendations presented in this report are based upon surficial observations and logical projections inferred from observed conditions and the assumption that the soil conditions do not deviate appreciably from those encountered. Should conditions vary from those presented herein be encountered during the developmental construction phase, this firm should be notified immediately so that a qualified soil engineer can inspect the site conditions and evaluate the potential effects and present recommendations. .. .. .. .. .. .. .. .. - -... - ---... -.. • .. --- - -- Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street 06/05/14 Page 14 This report has been prepared in accordance with generally accepted standards of geotechnical engineering practice at the time of its preparation. No other warranties, expressed or implied, are made as to the professional consultation and recommendations contained herein. This report is provided for the exclusive use of the client or his authorj~ed-~ . ---, ',,·' ·"' •' \ _, ., ,,.< ) Respectfully subJ;11fu-/d, /' 1 ALLIED ~AR.)1f TECHNgJ..doY ' / .,,.✓ / ...... , ___..,,.,,, f ROBERT C AN, P.E. /1 \, // ( N.o. 0..00,06 __ '. l;i:}') 12131' /';:) --APPENDIXC -----------------.. ----• --• -- -.. ------------------------------------ ALLIED EARTH TECHNOLOGY ROBERT CHAN, P.E. 7915 SILVERTON AVENUE, SUITE317 SAN DIEGO, CALIFORNIA 92126 PH. (858) 586-1665 FAX (858) 586-1660 (619) 447-4747 UPDATEOF "PRELIMINARY GEOTECIINICAL INVESTIGATION UPDATE REPORT PROPOSED MULTI-UNIT A'IT ACHED DWELLINGS GIBRALTAR STREET AT JEREZ COURT LA COSTA, CALIFORNIA FOR ACECMLENGINEERING PROJECT NO. 13-1147Hl OCTOBER 10, 2013 -------------------------------------- ALLIED EARIB TECHNOLOGY 7915 SILVERTON A VENUE, SUITE 317 SAN DIEGO, CALIFORNIA 92126 PH. (858) 586-1665 FAX (858) 586-1660 (619) 447-4747 ROBERT CHAN, P .E. October 10, 2013 Ace Civil Engineering 7668 El Camino Real #104-463 Carlsbad, CA. 92009 Attn: Subject: Mr. Mike Massoodnia ProjectNo. 13-1147Hl Update of"Preliminary Geotechnical Investigation Update Report" Proposed Multi-Unit Attached Dwellings Gibraltar Street at Jerez Court La Costa, California Dear Mr. Massoodnia : In accordance with your request, we have perfonned geotechnical engineering services for subject property, more specifically referred to as being Lot Nos. 399 to 401, inclusive, La Costa South Unit No. 5, in the City of La Costa, State of California. The purpose of our work is to prepare an update report with cwrent geotecbnical recommendations for the site development as presently proposed. The scope of our work includes two visits to the site, and a review of the following plans and docwnents: ------------- ------------------------ ProjectNo. 13-1147H1 Ace Civil Engineering Gibraltar Street 10/10/13 Page2 "Preliminary Soil and Geotechnical Investigation, Graded Hillside Project, Gibraltar Street near Jerez Court, La Costa area of Carlsbad, San Diego County, California" prepared by MV Engineering, Inc. (Their Job #1017-91, dated February 20, 1991.) "Preliminary Geotechnical Investigation Update Report -Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad" prepared by MV Engineering, Inc. (Their Job #04-287-P, dated July 7, 2004). "Preliminary Site and Building Plans for La Costa Villas" prepared by Lance Drew Dickes, Architecture & Garden Design, dated February 11, 2013. ''Grading Plans for La Costa South Unit No. 5, Sheet 3 of 5 sheets" prepared by Rick Engineering (City of La Costa Grading Permit No. L-5548). PROPOSEDDEVEWPMENT It is our understanding that the site is to be developed to receive 24 townhomes. The proposed structures will consist of two stories above a two-car garage, and will be of wood-frame/stucco and slab-on-grade construction. FIELD INSPECTION Inspections of the property on September 24 and October 7, 2013, indicate that the site was found to be generally of the same condition when rough grading was completed in the early part of 1970, with the following exception : A high combined cut/fill slope on the order of70 feet in maximum was observed along the rear, south end of the property, ascending to the residential lots to the south. This combined cut/fill slope bas a slope ratio of 1 ½ : I (horimntal : vertical), with two ---- -----------------.. --------------- Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street drainage ditches at mid-height. 10/10/13 Page3 This combined cut/fill slope has been in existence since the earlyl970's. The upper portions of this slope, which are within the properties to south, are well maintained and in good condition. The lower portions of the existing high cut/fill slope , which are within subject property has suffered some erosion and sloughing, due to lack of maintenance over the decades. The erosion and sloughing were caused by overflow of surface nm.off from the drainage ditches on the slope, which were had been filled with debris and vegetation through the decades. A review of the subdivision grading plan indicates that Lot 399 consists of all cut or natural soils. Lot 400 is a ''transition lot'', with a maximum of 3 feet of fill soils along the front portion of the site. Lot 401 is also a "transition lot"', with a maximum of 7 feet of fill soils along the front of the property. The fill soils encountered on the property site were derived locally, and consist of a mixture oflight brown/light gray/dark brown sandy clay, clayey sands and silty sands. These soils possess low to high expansion potential (Expansion Index of 46 and 98). SITE GEOLOGY Reviews of California DMG open-file report 96-02 and COS geologic map of the Oceanside quadrangle indicate that the property is underlain by two formations : the -----------.. - ------------------------ Project No. 13-l l 47Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page4 Santiago Formation, and Quaternary terrace deposits per the Department of Mine and Geology report, or Quaternary Old alluvium, per the California Geologic Survey map. Both types of Quaternary units are mapped equivalently. As described in open-file report 96-02, the Santiago Fonnation is middle Eocene in age (approximately 49 to 45 million years old). It consists primarily of fine to medium-grained sandstone interbedded with siltstone and claystone, and localized coarse-grained sandstone and conglomerate. Bedding attitudes in the Santiago Formation generally dips westward 5 degrees. The terrace/alluvium deposits are younger, late to middle Pleistocene (approximately 1.8 to 1 million years old). They are reddish brown, poorly bedded and poorly to moderately indurated sandstone, siltstone and conglomerate. GEOLOGIC HAZARDS Earthquake Fault Rupture Hazard San Diego's tectonic setting includes north and northwest striking fault z.ones, the most prominent and active of which is the Rose Canyon Fault Zone. Other fault zones lie in eastern and northern San Diego County. Fault rupture hazard would affect a property if an active fault trace or traces traverse the property. The subject property lies approximately 7 miles east of the offshore Newport-Inglewood Rose Canyon fault zone and 20 miles east of the offshore Coronado Banlcs fault zone. The property is approximately 28 miles west of the ------------- ------------------------ Project No. 13-l 147Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page 5 Elsinore fault zone, 57 miles west of the San Jacinto fault zone, and 82 miles west of the San Andreas fault zone. The property is outside any State and City designated fault and fault hazard zones and is therefore not subject to a special fault investigation. The Rose Canyon Fault Zone is capable of generating a 6.9 magtnitude earthquake. Even though direct ground rupture from faulting directly underneath the subject property is unlikely, the property will be subjected to considerable ground acceleration and shaking from an earthquake event along the nearby faults. The intensity of ground shaking is dependent on distance from faults, earthquake magnitude and duration, and seismic characteristics offowdation soils and bedrock. Soil Liquefaction It is our opinion that due to the relatively high density of the competent natural and compacted fill soils (after remedial grading recommended herein) prevalent at the site; the lack ofnear-surface groundwater and the grain size characteristics of the in-situ soils, the risk for seismically induced soil liquefaction is very low. FINDINGS, CONCLUSIONS AND RECOMMENDATIONS In general, we concur and agree with the findings, conclusions and recommen- dations presented in the above-mentioned Report and Update, and said findings, conclusions and recommendations are still valid and applicable for the proposed site development. ----------------------.. --------------- Project No. 13-1147HI Ace Civil Engineering Gibraltar Street 10/10/13 Page6 The following addendum recommendations are made, however, as supplement to the recommendations presented in the subject Report and Update. If there are discrepancies, the addendum recommendations herein will prevail. Expansiveness of On-site Near Surface Soils l. Some of the near-surface soils encountered on the site possess high expansion potential (Expansion Index = 98). Earthwork 2. No cUJTent site development plans are available at this time. However, it is our 3, understanding that the three building pads will remain in their current elevations. Prior to commencement of grading, it is recommended that the site be cleared and grubbed, and all debris and vegetation disposed of offsite. It is recommended that existing fill soils along the front of Lot Nos. 400 and 401 be removed. Maximum depths of fill on these lots are on the order of3 to 7 feet. The bottom of the over-excavation should be inspected by our finn, and scarified to a depth of 12 inches. The removed soils should then be properly moistened, and uniformly recompacted to at least 90 percent of maximum dry density in accordance with A.S.T.M. D1557, until :finished grade is achieved .. 4. For Lot No.401, it is recommended that the natural soils be over-excavated to a depth of 3 feet ( or I 2 inches below the bottom of the deepest footings), and uniformly compacted to at least 90 percent of maximwn dzy density. -- ----------------------------------- Project No. 13-l 147Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page7 5. Since the maximum depth of fill soils on Lot No. 400 is only 3 feet, and extends over a relatively small area, it is recommended that the footings of the proposed structure be extended through the compacted fill soils at leastl2 inches into the underlying competent formational soils. 6. The upper, surface and near-surface soils on the building pads had been subjected to weathering for decades. It is recommended that the natural soils on Lot Nos. 399 and 400 be scarified to a depth of 12 inches, properly moistened and unifonnly compacted to at least 90 percent of maximum dry density, in order to provide adequate support to the concrete slab of the proposed structures. Repair of Surficial Slone Failure 7. It is recommended that the soils loosened by the erosion and sloughing of the existing slope be removed. Beginning along the bottom of the existing slope, the loosened soils should be removed, and the bottom of the excavation inspected and approved by our finn. A new keyway should be excavated along the bottom of the slope, and the soils properly moistened, and uniformly compacted in lifts on the order of 6 to 8 inches. 8. As the repair work progresses up the existing slope, benches will have to be provided. The interval and width of the benches required will be determined by our field personnel during the remedial grading. -------------------------------------- Project No. 13-1147HI Ace Civil Engineering Gibraltar Street 10/10/13 Page8 9. The surface of the slope should be properly compacted with a sheepsfoot roller. In order to further minimize the potential for future surficial slumping, it is recommended that the slope be planted with deep rooted ground cover and shrubs at 10 feet on center. Foundation and Slab 10. It is recommended that a safe allowable soil bearing value of 1,500 pounds per square foot be used in the design and checking of continuous or spread footings that are a minimum of 15 and 24 inches in minimum horizontal dimension, respectively, and are embedded at least 24 inches into the competent natural or compacted filled ground. 11. The above safe allowable soil bearing value may be further increased by one third when considering wind and/or seismic forces. 12. 13. 1he concrete slab for the proposed structures should be at least 4 ½ inches net in thickness, and be reinforced with a minimum of #3 re bars at 18 inches on center in both directions, placed at mid-height of concrete slab. The concrete slab should be underlain by 4 inches of clean sand and a vapor barrier in moisture sensitive areas. The continuous footings should be reinforced with a minimum of 4 #S rebars; two rebars located near the top, and the other two rebars near the bottom of the footings. Isolated pier footings should be reinforced with 2 #5 rebars in both -------------------------------------- ProjectNo. 13-1147Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page9 directions, placed near the bottom of the footings. Please note that the above slab and foundation reinforcements are based on soil characteristics only, and should be superceded by the requirements of the project architect or structural engineer. 14. It is recommended that the moisture content of the subgrade soils beneath the proposed structures be maintained at approximately 120¾ of optimum moisture content. However, no flooding of the foundation soils is permitted immediately prior to the placement of concrete. 15. It is recommended that the foundation for the proposed structure be setback at least 7 feet back from the top of the fill slope. Foundations placed closer to the top of the slope than 7 feet should be deepened such that the outer edge of the footing along the bottom is at least 7 feet back from the face of slope at that level. For footings subject to lateral forces, such as those of a retaining wall, the above setback should be increased to 10 feet. 16. It is further recommended that the foundation trench excavations be inspected by our firm prior to the placement of concrete. Any loose and/or unsuitable soils encountered should be removed and/or replaced under our direction. Retainin1 Wall Design 17. It is recommended that retaining walls be designed to withstand the pressure exerted by equivalent fluid weights given on the following page : -------------------------------------- Project No. 13-1147Hl Backfill Surface (horizontal : vertical) Level 2: 1 I½: 1 Ace Civil Engineering Gibraltar Street 10/10/13 Equivalent Fluid Pressure (pcf) 35 50 58 Page 10 The above values assume that the retaining walls are unrestrained from movement, and have a granular backfill. For retaining walls restrained from movement at the top, such as basement retaining walls, an uniform horizontal pressure of 7H (where His the height of the retaining wall in feet) should be applied in addition to the active pressures recommended above. 18. All retaining walls should be supplied with a backfill drainage system adequate to prevent the buildup of hydrostatic pressure. The subdrain should consist of one-- inch gravel and a perforated pipe near the bottom of the retaining wall. The width of this subdrain should be at least 12 inches, and extend at least 2/3 height of the retaining wall. The subdrain should be enclosed in a geotextile fabric such as Mirafi 140N or equal. Seismic Earth Pressure 19. Seismic earth pressures can be taken as an inverted triangular distribution with a maximum pressure at the top equal to 15H pounds per square i>ot (with H being the height of the retained earth in feet. This pressure is in addition to the static design wall load. The allowable passive pressure and bearing capacity can be -- -----------------.. ----------------- Project No. 13-l 147Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page 11 increased by 1/3 in determining the stability of the wall. A factor-of-safety of 1.2 can be used in determining the stability of the retaining wall under seismic conditions. Lateral Loading 20. To resist lateral loads, it is recommended that the pressure exerted by an equivalent fluid weight of 350 pcf be used for footings or shear keys poured neat against competent natural or compacted fill soils. The upper 12 inches of material in areas not protected by floor slabs or pavements should not be included in the design for passive resistance. This value assumes that the horizontal distance of the soil mass extends at least l 0 feet or three times the height of the surface generating the passive pressure, whichever is greater. 21. A coefficient of sliding friction of0.35 may be used for cast-in-place concrete on competent natural or compacted fill soils. Footings can be designed to resist lateral loads by using a combination of sliding friction and passive resistance. The coefficient of friction should be applied to dead load forces only . 22. All backfill soils behind the retaining wall should consist of soils having low expansion potential (Expansion Index < 50), and be compacted at least 90 percent of maximum dry density. Seismic Coefficients 23. The seismic design factors were determined in accordance with the 2010 -------------------------------------- Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street 10/10/l3 California Building Code, and presented below : Site Coordinates : Latitude Longitude Site Class: Site Coefficient Fa Site Coefficient Fv Spectral Response Acceleration At Short Periods Ss Spectral Response Acceleration At I-second Period SI Sms FaSs Sml FvSl Sds 2/3•Sms Sdl 2/3*Sml 33.0860 117.2475 D 1.040 1.565 1.153 0.435 I.200 0.681 0.800 0.454 Preliminary Structural Pavement Section Design Page 12 23. For preliminary design purposes, it is recommended that a structural pavement section of 3 inches of asphaltic concrete over 6 inches of Class II base material over compacted subgrade be used. 24. The upper 8 inches of subgrade and base material should be compacted to at least 95 percent of maximum dry density. 25. For PCC pavement sections, it is recommended that the pavement section be 5 ½ inches in thickness, and be reinforced with #3 rebars at 18 inches on center in both directions, pJaced at mid-height of concrete slab. Control joints at 12-foot intervals should also be provided. ----------------------------------------- Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page 13 Utility Trench Bacld"dl 26. It is recommended that any backfill soils placed in utility trenches located within S feet of any improvements and deeper than 12 inches, or backfill placed in any trench located 5 feet out or more from a building and deeper than 5 feet, be compacted to at least 90 pem:nt of maximum dry density. Surface Drainage and Lot Maintenance 27. Adequate drainage control and proper maintenance of all drainage facilities are imperative to minimize infiltration of surface water into the 1D1derlying soil mass in order to reduce settlement potential and to minimize erosion. The building pad should have drainage swales which direct storm and excess irrigation water away from the structure and into the street gutters or other drainage facilities. No surface runoff should be allowed to pond adjacent to the foundation of structures. Concrete Flatwork 28. It is recommended that concrete flatwork be 3 ½ inches in thickness and reinforced with 6 x6-l 0/10 welded wire fabric placed at mid-height of slab. One- inch expansionjoints should be provided at IS-foot intervals; with¼ inch weakened plane con~onjoints at 5-foot intervals. LIMITATIONS The opinions and recommendations presented in this report are based upon surficial observations and logical projections inferred from observed conditions and the assumption that the soil conditions do not deviate appreciably from those encountered. Should conditions vary from those presented herein be encountered during the developmental construction phase, this firm should be notified immediately so that a qualified soil engineer can inspect the site conditions and evaluate the potential effects and present recommendations. -- ----------------------------------- Project No. 13-1147Hl Ace Civil Engineering Gibraltar Street 10/10/13 Page 14 This report has been prepared in accordance with generally accepted standards of geotechnical engineering practice at the time of its preparation. No other warranties, expressed or implied, are made as to the professional consultation and recommendations contained herein. This report is provided for the exclusive use of the client or bis authoriz.ed agent Respectfully submitted, ALLIED EARTII TECHNOLOGY ROBERT CHAN, P.E. E E t C [ APPENDIXD [ [ [ [ [ [ C £ C C C [ [ [ .. • : 1 : '.] : ~1 • r-·, . ' : ~ : . l -~J .. - - -j - -.J .. .. J --J -_ _, -I --1 - Preliminary Geotechnical Investigation Updaje Report Proposed Multi-Unit Attached Dwellings Glbralter Street at Jerez Court La c°'ll lt ·to PY July 7, 2004: . Prepared For: , · MR. ALVIN WASHINGTON 6479 Paseo Cerro Carlsbad, California 92009. Prepared. By: VINJE & MIDDLETON ENGINEERING, INC. 2450 Vtm,yard Avenue, su1t,.102 . Escondido, CaUfornla 92029 Job #04-287-P .. 7 ' : :l ~ VINIE & MIDDLETON ENGINEERING, INC. --7 --l : n : :-i :a : ~l -] --u - -] - - - -.J -._j -.J --J - Job #04••287 -P July 7, 2004 Mr. Alvin Washington 6479 PaE;eo Cerro Carlsbad, California 92009 2450Vine~td Avtnut Escondido, California 92029-1229 Phone (760) 743-1214 · Fax (760) 739-0343 . PRELIIVUNA.RY GEOTECHNICAL INVESTIGATION UPDATE REPORT, PROPOSEb MULTI- UNIT ATTACHED DWELLINGS, GIBRALTER STREET, JEREZ COURT, LA COSTA, . CAR~sa,~o, CALIFORNIA ' . Pursuant to your request, Vinje and Middletor:i Engineering, Inc., has completed the Preliminary Geotechnical Investigation Report for the subject site. The following update report summarizes results of our research and review of pertinent geotechniical reports and documents, · current field reconnaissance, and provides conclusioins and recommendations for the prop~sed development as understood. From a geotechnical engineering standpoint, it Is our opinion that the site is suitable for the support· of planned multi•uni_t development and associated improvements provided the recomme11dations presented in. this report are Incorporated into the design and construction of the project. The concliusions and recommendations provided in this study are consistent with the site geotechni,~I conditions and are Intended to aid In preparation of final development plans and allow more accurate estimates of development costs. If you havEt any questions or need clarification, please do not hesitate to contact this office. Referencei to our Job #04-287-P will help to expedite our response to your inquiries. We apprei::iate this opportunity to be of service to you. VINJE &"MIDDLETON ENGINEERING, INC. ~ Dennis Middleton CEG#980 DM~t r -.. , -l -:-I --~-, --:1 --~ I --··1 --] --:-1 --] --'.-1 --., --·_, --.J --I --_I - -_J - -_I -I -J --- TABLE OF CONTENTS PAGE NO. I. INTFIODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . 1 II. PROPOSED DEVELOPMENT . .. • .. . . . . . . .. . • .. .. • • . .. • • . . • • .. . • • . . . 1 Ill. COJ\ICLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 IV. RECqMMENDATIONS ...... • ....................................... 2 A. Remedial Grading and Earthworks ..•••• : . • . . . • . • . . . . . . • • • . . . • . • . • 2 B. Foundations and Slab~on-Grade Floors . • . • . . . . . • • • • • • . . . . • • . • • • • . . 8 C. Exterior CQncrete / Flatwork ••..••••.•••..•••..•••..•.•..••.••. • • . 10 . P, Soll Design Parameters . . . • • . • . . . . . . . . . . . . . . • • . . . . . . . • • . . . . . . . . 11 E. Asphalt and PCC Pavement Design •.•• ~ . . . . • . . • . . • • • • • . • . . . • . • • • 12 F. Gieneral Recommendations . ! •• , • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 13 VIII. LIMITATIONS ..... ~ .......................... ~ .................. 16 PLATE NO. Region~I Index Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 1 Site Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • . . . . . . . . . . . . . . . . 2 Retainin1J Wall Drain Detail ••••••••.••.••••.••••.•.••••.. ~ .••.••. ; . • • • • 3 Isolation Joints and Re-entrant Corner Reinforcement . . . • • . . • • . . . . • . . . . • . . 4 Prellmlmlry Soll and Geotechnical Investigation Report Graded Hillside Project, Gibraltar Street, near Jerez Court La Costa, Carlsbad, San Diego County APPENDIX A -·-1 -f -C ] --·1 --1 --: f --'J --] --] --J --J --] --.·1 --J --1 --J --J -I -J -I -J --- PROPOSED MUL Tl-UNIT ATTACHED RESIDENTIAL DWELLINGS GIBRAL TER STREET, JEREZ COURT LA COSTA, CALIFORNIA I. JlillRODUCTION The pu1rpose · of this report is to update our "Preliminary Soil and Geotechnical lnvestlgc1tion, Graded Hillside Project, Gibraltar Street, ·Jerez Court, La Costa, San Diego County, California.'' dated February 20, 1991. Our efforts in this regard Included a detailed · review olf the referenced report and most recent plans in addition to a site visit conducted by our Engineering Geologist. The study property le>cation is shown on a Regional Index Map enc:losed with this report as Plate 1. The referenced report has been reviewed in connecti-on ·with this work and a copy of the report is included as Appendix A II. eacieoseo· DEVELOPMENT The scope of the planned new development ls comparable to the proposed development addressEld in the referenced Geotechnical Investigation. Current plans submitted to us depict mu"i:-unit attached residential dwellings, extensive retaining walls, and associated improvements. A copy of the most current Site Plan is enclosed herein as Plate 2. Ill. ~CLUSION!p The site remains substantially ·unchanged from the original geotechnical investigation and subsequEmt ~ferenced report Based on our review of drawings made available to us, and from a geotechnical engineering point of view, the proposed development is in substantial compliance with the referenced report. The conclusions ~nd recommendations put forth in that report remain valid and :should be implemented during the construction phase except where superceded in the following sections. The following comments are also appropriate and should be considered and/or i~corporated into the final plans whe~ appropriate and applicable: * All grading should be conducted per the referenced Geotechnical lnve~tigation. The Geotechnical Investigation report should be considered as a part of the project foundation plans. V1NJE & MIDDI.ETON ENGINEERING, INC. • 2450Vineyard Avenue• Escondido, California 92029-1229 • Phone (760) 743-1214 : ·-1 : •01 : -1 -J - -J - -.l -~ j - -_J -- -.J - -.J - -1 --1 - -1 - PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRALTER STREET, JEREZ COURT, LA COSTA PAGE 2 JULY7, 2004 * All grading operatiQns including removals, suitability of earth deposits used as compacted fill, and compaction pro9edures should be continuously inspected a_nd b~sted by the project geotechnical consultant and presented in the final as-graded compaction report. The natu~e of f!nished subgrade soils should also be confirmed in the final compaction report at the completion of grading. * Final foundation plans may also be r~viewed by the project geotechnical consultant for conformance with the requirements of the referenced geotechnical investigation mport. More specific. recommendations may be necessary and should be given when final grading and archib~ctural/structural drawings are available. IV. BEQDMMENDATIONS The following recommendations are consistent with the indicated geotechnical conditions . at the prciject site and should be reflected on the final plans and implemented during the . construction phase. All following recommendations, where applicable, supercede ·those put forth in the previous report. Added or modified recommendations may also be appropriate and can be provided at the ·plan review phase when final plans are available: A. &amedial Grading and Earthworks c,ut-fill and remedial grading techniques should be used in order to achieve final dusign grades and improve soil conditions beneath the new structures and improvements. All ground preparations and project_ construction should be ccimpleted in accordance with the Appendix Chapter 33 of the Uniform Building Code, City of Carlsbad Grading Ordinances, the Standard Specifications for Public Works Construction, and the. requirements of the following sections: 1. Clearing and Grubbing: Existing vegetation, deleterious materials and debris should be removed from areas to receive new ·fills, structures, and improvements plus 1 O feet where possible, or as directed in the field. The prepared ground should be inspected and approved by the project geotechnical engineer; or his designated field representative prior to remedial grading work. Abandoned pipes and utility lines should be properly removed and replaced, or plugged as approved in the field. Voids created by removals of the abandoned underground pipes and structures should be properly backfilled in accordance with the requirements of this report. VINJE & MIDDLETON ENGINEERING, INC. • 2450\lineyard Annut • Escondido, California 92029-1229 • Phone (760) 743-1214 --, I -:r l .. -r-l --~J --:·1 --.. l --] --~I --'] --:.1 ----I --J --. l -t -_ l --------- PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL TER STREET, JEREZ COURT, LA COSTA PAGE 3 JULY7, 2004 2:. Non-uniform Bearing Soil Transitioning: Non-uniform ground transition from excavated cut to placed fill should not be permitted underneath the proposed structures and improvements. Building foundations; floor slabs, improvements, and retaining wall foundations should be supported entirely on compacted fills or founded eritir~ly on competent undisturbed cut ground. Transition pads will require special treatment. The cut portion of the cut-fill pads .plus 10 feet · should. be undercut to a sufficient depth to provide fqr a minimum of 3 feet of compacted fill mat below rough finish grades or at least 12 .inches of compacted fill beneath the deepest footing whichever is more. In· the roadways,. driv~way, · parking and on-grade slabs/Improvement transition areas there should be ·a minimum of 12 inches of compacted soils below rough finish subgrade. · 3. FIii Materials ·and Compaction: Soils generated from on-site ·removals and over-excavations will predominantly consist of po·or to marginal quality plastic, moisture sensitive olay--:rich deposits. Plastic clayey soils typicaJly require additional processing, mixing and moisture conditioning efforts in order to manufacture a uniform -homogeneous mixture suitable for reuse as new compacted fills. Project fill soils should be clean deposits free of roots, stumps, vegetation, deleterlom~ matter, trash, and unsuitable materials as approved by t~e projec~ geotechnical consultant. · Uniform bearing soil conditions should be constructed at the site by the reme~ial grading and earthwork operations. Site soils should be adequately processed, thoroughly -mixed, moisture conditioned to 3% to 5% above the optimum moisture levels or as directed in the field,· p_laced in thin uniform horizontal lifts and mechanically compacted to a minimum of 90% of the- corresponding laboratory maximum dry density per ASTM Dw1557, unless otherwise specified. · Fill soils placed within areas subject to potential flood inundation . should be mechanically compacted to a minimum of 90% of the laboratory maximum dry density (AStM D-1557). Slope protection and erosion control facilities should be installed as shown on the approved civil d~awings. 4. Capping and Select Grading: Final bearing and subgrade soil mixture at the completion of remedial grading is anticipated to consist of moisture sensitive potentially expansive deposits with detrimental affects which will require geotechnical and structural mitigation designs as provided in the following sections. Select grading and capping of the site may also be considered which will allow more conventional foundations/slab and paving designs. In this case, VINJE & MIDClLETON ENGINEERING, INC. • 2450Vineyard Avenue• Escondido, California 92029-1229 • Phone (760) 743-1214 -------------------------------------- · 1 . I :·, "'I r. :-, r-1 ] -1 I 'I ,_ :-, ''] l :1 J J ..1 J l I I I J PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL~rER STREET, JEREZ COURT, LA COSTA PAGE 4 JULY 7, 2004 the upper 3 feet in the building envelope plus 10 feet, and upper 1 ½ feet in the paving and improvement c;lreas plus 3 feet should be capped wi~h non- expansive to very low expansive sandy granular import soils (expansion index less-than 21) comp~cted as specified herein. Import sandy soils should also be considered for the project wall backfills. Import soils should be inspected, tested as necessary and approved by the project geotechnical consultant prior to the delivery to the site. In the even·t only the building envelope plus 1 O feet is capped with non- expansive to very low expansive sandy import soils within the upper 3 feet, a subsurface drainage system consisting of a minimum .2 feet deep by 2 feet wide trench with 4 i11ches di.ameter perforated pipe (SDR 35) .surrounded with ¾-inch crushed rocks and wrapped in filter fabric (Mitafi 140 N) installed below the capping soils. will be required as directed in the field. 5. Permanent Graded Slopes: Project graded slopes should be programmed for 2: 1 gradients maximum. Graded fill slopes constructed at 2: 1 gradients will be grossly stable with respect to deep seated and surficial failures for the· anticipated design maximum vertical heights. Graded cut slopes should be reconstructed as stabilization fill slopes to develop stable ·embankments, or retaining walls may be constructed at the toe of the graded cut slope for additional support. All fill slopes shall be provided with a lower keyway. The ~eyway for the building pad fill slopes should maintain a minimum depth of 1 o feet into the competent bedrock units with a minimum width of 20 feet as approved by the project geotechnical engineer or his designated representative. The keyway should expose competent bedrock units throughout with the bottom heeled back a minimum of 2% into the natural hillside, and inspected an_d approved by the project geotechnical' engineer. Additional level benches should be constructed into the .natural hillside as the fill slope construction progresses. Initial keyway _development into the competent and stable formational units should be inspected and approved by the project engineering geologist prior to any fill placement. Locally deeper keyway depths should be anticipated. The keyway for the driveway fill slopes should maintain a minimum depth of 3 feet into the firm native ground with a minimum width of 12 feet as approved by the project geotechnlcal engineer or his designated representative. Bottom of keyway stabilization by placing Geogrid earth reinforcement may also be necessary and should be anticipated. VJNJE & MmCrJ,ETON ENGINEERING, INC. • 2450\line}•atd AYtnue • Escondido, California 92029-1229 • Phone (760) 743-1214 --:·-, --.. l ----, -·1 --. I --·-1 ---, --] --I --J ----· ! ... -j --l --l --I -I -J --I _J --- PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL liER STREET, JEREZ COURT, LA COSTA PAGE 5 JULY7, 2004 Fill slopes should also be compacted to 90% {minimum) of the laboratory standard out to the slope face. Over-building ~nd cutting back to the compacted core, or backrolling at a minimum of 3 feet vertical increments and "track-walking" at the pompletion of grading is recommended for site fill slope construction. Geotechnical engineering inspections and testing will be necessary to confirm adequate compaction levels within the fill slope face: a~ Temporary Construction Slopes: Unsupported temporary construction -slopes necessary during the removals, over-excavations and wall construction$ within the project existing fills, topsoil, terrace deposits, highly weathered and friable formational units should be laid ~ack at 1 :1 or flatter gradients as directed in the field. · Elsewhere, temporary slopes less than 1 O feet high · maximum develpped within the on-si~e competent formational units niay be constructed at near vertical within the .lower 3 feet and laid back at ½:1 gradients within the upper. portions. Trenching within the site upper soils or . weathered friable formational units may be laid back at· ~:1 gradients or_ provided with temporary shoring support. The new fill wall backfill should be tightly keyed-in and benched into the temporary slopes as the filling/backfilling progresses. Temporary shoring support will also be required for all vertical trenches greater than 3 feet unless otherwise approved by the project geotechnical consultant. Any continuous shoring technique which can ailow safe and stable excavations may be· considered provided it is approved by the owner or his designated project consultants. Minor sloughing of the temporary slope face may occur requiring maintenance or cleanup. All temporary construction slopes require continuous geotechnical inspections during the grading and wall construction operations. Additional recommendations including revised slope gradients, setbacks and the need for additional shoring support should be given at that time as neces·sary. The project contractor shall also obtain appropriate permits, as needed, and conform to Cal-Osha and local governing agencies requirements for trenching/open excavations and safety of the workmen during construction. 7. Wall Back Drainage System: All site retaining wall_s should be provided with an adequate back drainage system. The wall back drain system should consist of a minimum 18 inches wide trench excavated to the depths of the wall foundation level. A minimum 4-inch diameter, Schedule 40 (SDR 35) perforated pipe surrounded .with a minimum of 2.25 cubic feet per foot of ¾- crushed rocks wrapped in filter fabric (Mirafi 140 N), or Caltrans Class 2 permeable-aggregate should be used. The perforated drain pipe should be VJNJE & MIDDLETON ENGINEER.ING, INC. • 2450Vinryard A\'tnue • Escondido, California 92029-1229 • Phone (760) 743-1214 --------: -] : -1 : ] -1 --'] ----- 1 ] -I -J - - -J --- -1 - -_l - -1 --- PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL.TER STREET, JEREZ COURT, LA COSTA PAGE 6 JULY 7, 2004 installed at suitable elevations to allow for adequate fall via a non-perforated solid pipe to an approved outlet. Filter fabric can be eliminated if Class 2 permeable material ls used. A typical wall back drain system is depicted on the enclosed Plate 3. Appropriate waterproofing should be provided behind the walls. Protect pipe outlet as necessary. 8. Surface Drainage and Erosion Control:· A critical element to the continued stability of the graded building pads i·s an adequate surface and storm water drainage control, and the installation of drainage control facilities. This can most effectively be achieved by appropriate vegetation cover and the installation of the following systems: * Periods of prolonged rains can result in flowing surface water-within the swale area of .the study site. Storm water and .erosion control facilities should be installed per approved plans. * .Drainage swales should be provided at the top and toe of the graded slopes per project civil engineer design. · * Building pad surface run-off should be coll_ected and directed away from the planned buildings and improvements to a selected location in a controlled manner. Area drairis should be installed. * The finished slope should be planted soon after complet1o·n of grading. Unprotected slope faces will be subject to severe erosion and should not be allowed. Over-watering of the slope faces should also not be allowed. Only the amount of water to· sustain vegetation should be p_rovided. * Temporary erosion control facilities and si!t fencfjs should be installed during the construction phase periods and until landscaping is fully established as indicated and specified on the approved project grading/erosion plans. 9. Engineering Inspections: All grading operations including removals, suitability of earth deposits used as compacted filis, and compaction procedures ~hould be eontinuously inspected and tested by the project geotechnical consultant and presented in the final as-graded compaction report. The nature of finished subgrade soils should also be confirmed in the final compaction report at the completion of remedial grading. Geotechnical engineering inspections shall include but not limited to the foUowing: VINJE & MIDDLETON ENGJNEERJNG,-INc. • 2450Vineyard Avenue• Escondido, California 92029-1229 • Phone (760) 743-1214 --,-l -~l --"'} --:-'J --·1 --,-l --] --: } --··1 --_j --] .. -J --J --_j --J - -_J --1 -_J --j - PRELIMINARY GEOTECHNICAL UPDA re REPORT GJBRALTER STREET, JEREZ COURT, LA COSTA PAGE 7 JULY7, 2004 * Initial Inspection -After the grading/brushing limits have been staked but before grading/brushing starts. · * . Bottom of over-excavation inspection -After the natural ground or competent formational rock is exposed and prepared to receive fill but before fill is placed. * Excavation inspection -After the excavation is started but before the vertical depth of excavation is more than 5 feet. Local and Cal-Osha safety . requiremen~s for open excavations apply. * Fill/backfill inspection -After the fill/backfill placement is started but before · the vertical height of fill/backfill exceeds 2 feet. A minimum of one test shall be required for each 100 lineal feet maximum with the exception of wall backfills where a minimum of one test shall be required for each 25 lineal feet maximum. Wall backfills shall also be mechanically cQmpacted to at least 90% compaction levels unless otherwise specified. Finish rough and final pad grade tests shall be required regardless of fill thickness. * Foundation trench inspection -After the foundation trench excavations but · before steel placement. * Foundation bearing/slab subgrade soils inspection -Prior to the placement of concrete for proper ·moisture and specified compaction levels. · * Foundation/slab steel inspection -After steel placement is completed but before the scheduled concrete pour. * Subdrain/waH back drain inspection -After the trench excavations but during the actual placement. All material shall conform to the project material specifications and approved by the project soils engineer. * Uflderground utility/plumbing trench inspection -After the trench excavation, but before placement of bedding or installation of th~ underground facilities. Local and Cal-Osha safety requirements for open excavations apply. Inspection of pipe bedding may also be required by the project geotechnlcal engineer. " Underground utility/plumbing trench backfill inspection -After the backfill placement is started above the pipe zone but before the vertical height of backfill exceeds 2 feet. Testing of the backfill within the pip~ zone may also be required by the governing agencies. Pipe bedding and backfill materials VINJE & MrDDLETON ENGINEERJNG, INC, • 2450\fineyard Avenue• Escondido, California 92029-1229 • Phone (760) 743-1214 -:-1 --·_1 --' } --] --~-, --~-) --] --] --] --:-] •---J --_J --J --..1 --J· --J -_j --.J -_ _J - PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL.TER STREET, JEREZ COURT, LA COSTA PAGE 8 JULY 7, 2004 shall conform to the governing agencies requirements and project .soils report if applicable. All trench backfills shall be mechanically compacted to a minimum of 90% compaction levels unless otherwise specified. Plumbing trenches over 12 inches deep maximum under the interior floor slabs should also be mechanically compacted and · tested for a minimum of 90% compaction levels. * Pavement/improvements subgrade and ba$egrade inspections -Prior to the placement of concrete or asphalt for proper moisture and specified compaction levels. B. f oundatlons and· Slab-on-Grade Floors The following recommendations and geotechnical mitigation are consistent with clay to sandy silty clay (CH/CL), medium to high expansion potential (expansion index less than 131) foundation bearing soil anticipated at finish grade levels. Added or modified recommendations may also be necessary and should be given at the time of the foundation plan review phase. All foundations and fl_oor slab reicommendations should be further confirmed and/or revised as necessary at the cc,mpletion of rough grading based on the actual expansion characteristics of the foundation bearing and subgrade ~olls. In the event capping of the building·pad with non-expansive to very expansive import soils are considered, this office should bu notified fo provide appropriate revised foundations/slab recommendations: 1. Continuous interior and exterior foundations shollld be sized at least 15 inches wide and 24 inches -deep for single-story and two-story structures. Exterior spread pad footings, if any, should be at least 30 inches square and 18 inches deep and structurally tied to the perimeter strip footings with tie beams at feast in one direction. Tie beams should be at. least 12 inches wide by 12 inches deep. Footing .depths are measured from the lowest adjacent ground surface, not including the sand/gravel beneath floor slabs. . Exterior continuous footings should enclose ·the entire building perimeter. Flagpole footings_ also need to be tied together if the footing depth is less than 4 feet below the rough finish grades. 2. Continuous interi"or and exterior foundations should be reinforced with a minimum of four-#5 reinforcing bars. Place 2-#5 bars 3 inches above the bottom of the footing and 2-#5 bars 3 inches below the top of the footing. Tie beams should also be reinforced with 2-#4 bars top and bottom and #3 ties at , V1NJE & MIDDLETON ENGINEERING, INC. • 2450Vineyard Avenue• Escondido, California 92029-1229 • Phone (760) 743-1214 -------------------------------------- :-1 · .. I ] r•1 :] ] ] [] 1 :J ~ j ,.,, J · 1 J _J .J . . l J 1 PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL TER STREET, JEREZ COURT, LA COSTA PAGE 9 JULY 7, 2004 24 inches on center maximum. Reinforcement details for spread pad footings should be provided by the project architecVstructural engineer. 3. The slab subgrade and foundation bearing sqils should not be allowed to dry prior to pouring the concrete or additional ground preparations, moisture re- conditioning, and pre.;saturation will be necessary as directed in the field. The required moisture content of the bearing soils is apprQxim~tely 3% to 5% over the optimum moisture content to t~e depth of 24 inches pelow slab subgrade. Attempts should be made to maintain as-graded moisture contents in ·order. to preclude the -need· for pre-saturation· of the subgrade and bearing soils. 4. In the case of pre-saturation of the slab subgrade and/or non-monolithic pour (two-pour) system, dowel the slab to the footings using #4 reinforcing bars spac~d 18 Inches on center and extending at least 20 inches into the footing and·20 inches into slab. The dowels should be placed mid-height in the slab. Alternate the dowels each way for all interior footings. 5. After the footings are dug and cleaned, place the reinforcing steel and dowels, and pour the footings. 6. This office should be notified to inspect the foundation trenches and reinforcing prior to pouring the concrete. · · 7. Once the concrete for the footings has cured and underground utilities tested, place 4 inches of 3/e-incfl rock over the slab subgrade. Flood wi~h water to the top of the %-inch rock, and all9w the slab subgrade to soak until moisture testing indicates that the required moisture content is present. After the slab subgrade soils have soaked, notify this office and schedule for appropriate moisture testing. · · 8. When the required moisture coment has been achieved, place a 10-mil plastic moisture barrier over the %-inch rock, and place 2 inches of clean sand (SE 30 or greater) on top of the plastic. If sufficient moisture is present, flooding/pre-saturation will not be required. The dowels may be deleted, and slab underlayment may consist of 2 inches of clean sand over a 6 mil-plastic moisture barrier over 2 inches of clean sand, and the footings and slab may be poured monolithically . VJNJE & MJDDLHON IiNGJNEERJNG, INC. • 2450Vine}'ard Avenue• Escondido, California 92029-1229 • Phone (7~0) 743-1214 I= --·1· --~l ---1 ---1 --] --·1 --J --J -.. . .,. -.. -J --, .. -J --J --_J --J --J --.J - -.J --. J - PRELIMIINARY GEOTECHNICAL UPDATE REPORT GIBRAL'fER STREET, JEREZ COURT, LA COSTA PAGE 10 JULY7, 2004 This office should be notified to inspect the sand, slab thickness, and reinforcing pr.ior to the concrete pour. 9. All interior slabs should be a minimum of 5 inches in thickness reinforced with #4 reinforcing bars spaced 18 inches on center each way, placed 1 ½ inches below the _top of the slab. · 10. Interior slabs · should be. provided with "softcut" contraction/control joints consisting of sawcuts spaced 10 feet on center maximu·m each way. Cut as soon as the slab will support the weight of ·the ~aw, and operate without · disturbing the final finish which is normally within 2 hours after final finish at each control joint location gr 150 psi to 800 psi. The softclits should be a . minimum of ¾-inch in depth but should not exceed 1-inch deep maximum. Anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipment across cuts for at least 24 hours . 11 . Provide re-entrant corner reinforcement for all interior slabs. Re-entrant corners will depend on slab geometry andfor interior column locations. Plate 4 may be used as a general guideline. · 12. Foundation trenches and slab subgrade soils should be inspected and tested for proper moisture and specified compaction levels and approved by the project, geotechnical consultant prior to the placement of concrete . C. .Exterior Concrete I Flatwork 1. · All exterior slabs (walkways, patios) should be a minimum of 4 inches in thickness, reinforceq with. #3 b~us at 18 inches on centers in both directions placed 1 ½ inches below the top of slab. Use 6 inches of 90% compacted clean sand beneath all exterior slabs. 2. Provide 11tool joint" or "softcut" contraction/control Joints sp·aced 10 feet on center (not to exceed 12 feet maximum) each way. Tool or cut as soon as the slab will support weight and can be operated without disturbing the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi. Tool or softcuts should be a minimum of ¾-inch but should not exceed 1-inch deep maximum. In case of softcut joints, anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24 hours. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Vine)"ard A,·enue • Escondido, California 92029-1229 • Phone (760) 743-1214 --r l --r·1 --·--i --~-1 -:--, --r-l -,_ -] --~-, -I• -'f --' .I ---_-, --! I _J --J --J ---l --..1 --- ' -1 •• J --- PRELINIINARY GEOTECHNICAL UPDATE REPORT GJBRAL.TER STREET, JEREZ COURT, LA COSTA PAGE 11 JULY 7, 2004 ~t It is recommended to provide a minimum of 8 inches wide by 12 inches deep thickened edge reinforced with a minim.um of 1-#4 continuous bar near the bottom along the free-ends of all exterior slabs and flatworks supported on moisture sensitive expansive soils. 4. All exterior slab designs should be confirmed in the final as-graded compaction report. Ei. Subgrade soils should be tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant prior to the placement of concrete. o. ~ioH Design Parameters · The following soil design parameters are based on tested representative samples of on-site selected sandy materials. Potentially expansive plastic clayey soils . should not be used for wall bacldill soils. All parameters should be re-evaluated when the characteristics of the final soils have been specifically determined: "' Design wet density of soil = 119.0 pcf. * Design angle of Internal friction of soil = 34 degrees. · * Design active soil pressure.for retain.ing structures = 34 pcf (EFP). level backfill, cantilever, unrestrained walls. · * Design at-rest soil pressure for_ retaining structu(es = 53 pcf (EFP), . non- yielding, restrained walls. · "' D~sign passive soil pressure for retaining structures = 421 pcf (EFP). level surface at the toe. * Design coefficient of friction for concrete on soil= 0.35. * N_et allowable foundation pressure for certified compacted fill = 1500 psf (minimum 1 s·-inch wide by 24-inch deep footings). · * Allowable lateral bearing pressure (all structures except retaining walls) for certified compacted fills = 100 psf/ft. Ne>tes: * Good quality sandy import soils may be considered for. site wall backfill purposes which will improve the above specified design parameters. Import soils for wall backfill will require additional laboratory testing. "' Use a minimum safety factor of 1.5 for wall over-turning and sliding stability. However, because large movements must take place before maximum passive resistance can be developed, a minimum safety factor of 2 may be considered VrNJE & MIDDl~ETON ENGrNEERrNG, INC. • 2450Vineyard Avtnue • Escondido, California 92029-1229 • Phone (760) 743-1214 . -,-=-------__ , ~ ..... ~ ~--••~' --~l --~ I PRELIMINARY GEOTECHNICAL UPDATE REPORT PAGE 12 GIBRAL TER STREET1 JEREZ COURT, LA COSTA JULY 7, 2004 ---1 for sliding stability particularly where sensitive structures and improvements are --1 planned near or on top of retaining walls. -* When combining passive pressure and frictional resistance the passive ---, component should be reduced by one-third. -* The net allowabl~ bearing pressure provided herein was determined for -] footings having a minimum width of 15 inches and depth of 24 inches. The -indicated value may be·increa~ed by 20% for each additional foot of depth and 5% for each additional foot of width to a maximum of 3500 psf. The allowable -J foundation pressures provided herein also apply to dead plus live loads and -may be increased by one-third for wind and seismic loading. J * The lateral bearing earth pressure may be increased by the amount of --. designated value for each additional foot of depth to a maximum of 1500 pounds per square foot. . -.. , ' E. ~sphalt and ecc Pavement Design --'·1 Spec_ific pavement designs ~an best be provided at the completion of rough grading based on R-value tests of the actual finish subgrade soils; however, the -following structural sections may be considered for cost estimating purposes only -·J (not for construction): -1. A minimum section of 3 inches asphalt on 6 inches Caltrans Class 2 aggregate -j base may be considered for on-site asphalt paving surfaces not within the public or private street right-of -way. - _J Base materials should be compacted to a mm1mum of 95% of the ~ -corresponding maximum dry density (ASTM D-1557). Subgrade soils beneath -the asphalt paving surfaces should also be compaqted to a minimum of 95% -_I of the corresponding maximum dry density within the upper 12 inches. -2. Residential PCC driveway and parking areas not within the public or private -J street right-of-way supported on medium to high expansive subgrade soils, should be a minimum of 5½ inches in thickness, reinforced with #3 reinforcing -bars at 18 inches on centers each way placed 2 inches below the top of slab. -J Subgrade soils beneath the PCC parking and driveway should be compacted to a minimum of 90% of the corresponqing maximum dry density within the -upper 6 inches. Use a minimum 560-C-3250 concrete per Standard -l Specifications for Public Works Construction (Green Book) standards. -I -_j --J VINJE &,MIDDI-ETON ENGINEERING, INC, • 2450Vinc)'ard Avenue• Escondido, California 92029-1229 • Phonr (760) 743-1214 - --~l --:-, -~I ---1 ---_ l --· 1. ---· 1 --] --J --__J ---I --_J --J ---I --.1 --J - -.I -! i _, J - .. f - PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL TER STREET, JEREZ COURT, LA COSTA PAGE 13 JULY 7, 2004 In order to enhance performance of PCC pavements supported on expansive subgrade soils, a minimum 8 inches wide by 12 inches deep thickened edge reinforced with a minimum of 1-#4 continuous bar placed near the bottom should be considered along the outside edges. Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not to exceed 15-feet maximum) each way. Tool or cut as soon as the slab will support weight and can be operated without disturblr-g the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi. Tool or softcuts should be a minimum of 1-inch but should not excee·o 1 ¼-inches deep maximum. In case of softcutjoints, anti- ravel skid plates should.be used and replaced with each blade to avoid spalfing and raveling. Avoid wheeled equipments across cuts for at least 24-hours. 3. Subgrade and basegrade soils should· be tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant just prior to the placement of the base or asphalt/PCC finish surface. 4.. Base section and subgrade preparations per structural section design will be requfred for all surfaces subject to traffic Including roadways, travelways, drive lanes, driveway approaches and ribbon (cross) gutters. Driveway ·approaches within the public right-of-way should have 12 Inches subgrade compacted to a minimum of 95% compaction levels and provided with a 95% compacted Class 2 base section per the structural section design. In the case of expansive subgrade soils, provide-6 inches of Class 2 base under curb and gutters and 4 inches of Class 2 base (or 6 inches of Class Ill) under sidewalks. Base layer under curb and gutters should be compacted to a minimum of 95%, while subgrade soils under curb and gutters; and base and subgrade under sidewalks should be compacted to a · mihi111um of 90% compaction levels. F. ~meral Recommendations 1. The minimum foundation design and steel reinforcement provided herein are based on soil characteristics and are not intended to be in lieu of reinforcement necessary for structural considerations. All recommendations should be further evaluated based on final as-graded geotechnical conditions and confirmed by · the project architect/structural engineer. VJNJE & MIDDLETON ENGINEERING, INC. • 2450\fineyacd Avenue• Escondido, California 92029-1229 • Phone (760) 743-1214 --'·., --~ I PRELIMINARY GEOTECHN~CAL UPDATE REPORT PAGE 14 GIBRAL TER STREET, JEREZ COURT, LA COSTA JULY 7, 2004 --rl ,., Adequate staking and grading control is a critical factor in properly completing ~ .. -the recommended remedial and site grading operations. Grading control and --i staking should be provided by the project grading' contractor, or surveyor/civil engineer, and is beyond the geotechnical engineering services. Inadequate -"I staking -and/or lack of grading control may result in unnecessary additional -grading which will increase construction costs. --I 3. Footings located on or adjacent to the top of slopes should be extended to a -. sufficient depth to provide a minimum horizontal distance of 1 O feet or one-third of the slope height; whichever is greater (need not exceed 40-feet maximum) -J between the bottom outside edge of the footing and face of slope. This -requirement applies to all improvements, and structures including fences, posts, poois, spas, etc. Concrete and AC improvements should be provided with a -. I thicken~d edge to satisfy this requirement. -4. Expansive clayey soils should not be used for backfilling of any retaining -I structure. All retaining walls should be provided with a 1: 1 wedge of granular, -compacted backfill measured from the base of the wall footing to the finished surface, -. I 5 .. All underground utifity and plumbing trenches should be mechanically -compacted to a minimum of 90% of the maximum dry density of the soil unless -., otherwise specified. Care should be taken not to crush the utilities or pipes I during ttie compaction of th_e soil. Non-expansive, granular backfill soils should -. be used. -6. On-site soils are potentially expansive moisture sensitive clayey deposits which -will undergo continued swelling and shrinkage upon wetting and drying. r---.I Maintaining a uniform as-graded soil m_oisture during the post construction periods is es~entlal In the future performance of site structures and -improvements. In no case should water be allowed to pond or accumulate -J adjacent to the improvements and structures·. -7. Site drainage over the finished pad surfaces should flow away from structures -J onto the street in a positive manner. Care should be taken during the construction, improvements, and fine grading phases not to disrupt ,he -designed drainage patterns. Roof lines of the buildings should be provided with -.I roof gutters. Roof water should be collected and directed away from the buildings and structures to a suitable location. · Consideration should be given -to adequately damp-proof/waterproof the basement walls/foundations and -provide the planter areas adjacent to the foundations with an impermeable liner and a subdrainage system. ----V1NJE & MIDDLETON ENGTNEERING, INC.• 2450Vim:yard Avenue• Escondido, California 92029-1229 • Phont (760) 743-1214 - --r ·:i --r-, -!l --, · 1 --:-1 -.. ] --] --'."f -.. J --j --J ---I --J --J --.J --] --.1 -.. J -_J - PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRALTER STREET, JEREZ COURT, LA COSTA PAGE 15 JULY 7, 2004 8. Based upon the result of the tested soil sample, the amount of water soluble sulfate (SO4) was found to be 0.021 percent by weight which is considered negligible according to the California Building Code Table No. 19-A-4. Portland cement Type I or II may be used. 9. Final plans should reflect preliminary recommendations given in this report. Final foundations and grading plans should also be reviewed by the project geotechnical consultant for conformance with the requirements of the · geotechnical investigation report outlined herein. More specific recommendations may be necessary and should be given when final grading and architectural/structural drawings are available. 10. All foundatlon trenches should be inspected to ensure adequate fo9ting embedment and confirm competent bearing soils._ Foundation and slab - reinforcements should also ~e inspected and approved by the project geotechnical consultant. 11. The amount of-shrinkage a-nd related cracks that occur in the concrete slab-on- grades, flatworks and driveways depend on many factors, the most important of which is the amount of water in the concrete mix. The purpose of the slab reinforcement is to keep normal concrete shrinkage crack~ closed tightly. The amount of concrete shrinkage can be minimized by reducing the amount of water in the mix. To keep shrinkage to a minimum the following should be considered: · * Use the stiffest mix that can be handled and consolidated satisfactorily. * Use the largest maximum size of aggregate that is practical. For example, concrete made with %-in9h maximum size aggregate usually requires about 40 lbs more (nearly 5-gal.) water per cubic yard than concrete with 1-inch aggregate. · * Cure the concrete as long as practical. The amount of slab reinforcement provided for conventional slab-on-grade construction considers that good quality concrete materials, proportioning, craftsmanship, and control tests where appropriate and applicable are provided. 12. A preconstruction meeting between representatives of this office, the property owner or planner, city inspector and the grading contractor/builder is recommended in order to discuss grading/construction details associated with the site development. .. YINJE & MtoDI.ETON ENGINEERING, INC. • 2450\lineyard A\'enue •Escondido.California 92029-1229 • Phone (760) 74J-IZl4 .. --·-1 i --,., --. -, -:-1 --:J --· 1 --.] --. l --. I --.. j ---i --I --_J ------j --I --I _} --- PRELIMINARY GEOTECHNICAL UPDATE REPORT GIBRAL.TER STREET,JEREZ COURT, LA COSTA VIII. Lll\~IJAIIONS PAGE 16 JULY 7, 2004 The com:lusions and recommendations provided herein have been based on all available data obtained from site observations, research and review of pertinent geot~chnical reports and plans, subsurface exploratory excavations, as well as our experience with the soils and formational materials located in the general area. The materials encountered on the project site and utilized in laboratory testing are believed representative of the total area; however, earth m~terials may vary in characteristics between excavations. Of neqessity we must assume a certain degree of continuity between exploratory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, arid recommendations be verified during th~ grading-operation. In the event discrepancies are noted, we should be contacted immediately so that an inspection can· be made and additional recommendations issued if required . The recommendations made in this _report are applicable to the site at the time this report was prepared. It is the responsibility of the owner/developer to ensure that these recommEmdations are carried out In the field. It is almost impossible to predict with · . certainty the future performance of a property. The future behavior of the site is also dependent on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The firm ,of VINJE & MIDDLETON ENGINEERING, INC., shall not be held responsible. for changes to the physical conditions of the property such as addition of fill soils, added cut slopes, or changing drainage patterns which occur without our Inspection or control. The property owner(s) should be aware of the development of cracks in all concrete surfaces ::;uch as floor slabs and exterior stucco associated with normal concret~ ~hrinkage i'- during thE~ curing process. These features depend chiefly upon the condition of concrete and weather conditions at ~he time of construction and do· not reflect detrimental ground movem_ent. Hairline stucco cracks will often develop at window/door corners, and floor surface cracks up to 1/e-inch wide in 20 feet may _develop as a result of normal concr~te shrinkage: (according to the American Concrete lnstltute).This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made· to yo_ur tentative development plan, especially with respect to, the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. Vlnje & Middleton Engineering, Inc., warrant$ that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. VJNJE & MJDC>LETON ENGINEERING, INC. • 2450Vineyard A\'enue • Escondido, California 92029-1229 • Phone (760) 743-1214 · -··1 -] --·1 --·1 --l ---1 --] --J --] --J --_j --] --.J --J --J --I --j --j --j --l - PRELIMIINARY GEOTECHNICAL UPDATE REPORT GIBRAL'TER STREET, JEREZ COURT, LA COSTA PAGE 17 JULY7, 2004 Once again, should any questions arise concerning ttiis report, please do not hesitate to contact this office; Reference to our Job #04-287-P will help to expedite our response to your inquiries. We appr•9ciate this opportunity to be of service to you. VINJE & MIDDLETON ENGINEERING, INC. ~ Dennis Middleton . CEG#980 s~~~§: RG#6953 DM/SMSS/SJM~t Distributic>n; Addressee (5) c:ljl/myfiles/u11dales.04/04-287-P VINJE & MIDl)LETON-ENGINEERING, INC. • 2450Vineyard Avemtt • Escondido, California 92029-1229 • Phont (760) 743-1214 7 7 J J J J J J _j 1 _J .J .J .. ; / 1 f \ e 2002 D•Lorm•. Topo USA C>. Data copyright of content owner. www.delorme.com ~- Scale 't : 26,000 .... 111 c:11 2000 ft i:..~ !ll ii , .. !i"' I" ! .. ... .,. .,. "'" r] L. ] J _ I J J :J -j ' _l j Waterproofing RETAINING WALL DRAIN DETAIL Typical -no scale . .,.,, Pertoiroted drain · Filter Material. Crushed rock (wrapped in filter _fabric) or Class 2 Permeable Material (see specifications below) · Competent,· approved soils o_r bedrock CONSTRUCTION SPECIFICATIONS: 1. Provide g1ranular, nQn-expansive backfdl soil In 1 :1 gradient Wedge behind wall. Compact backfill to minimum 90% of laboratory standard. · 2. Provide back drainage for wall to prevent build-up of hydrostatic pressures. Use drainage openings along base of wall or back drain system as outlined below. 3. Backdraln should consist of 4" diameter PVC pipe (Schedule 40 or equtvalent) with perforations down. Drain to suitable outlet· at minimum 1 %. Provide¾" -1 ½" crushed gravel filter wrappe~ In filter fabric (Mlrafi 140N or eq1,1lvalent). Delete filter fabric wrap i_f C:altrans Class 2 permeable material Is used. Compact Class 2 .material to minimum 90% of laboratory standard. 4. Seal baclc of wall with waterproofing in accordance with architect's specifications. 5. Provide p ositlve drainage to disallow ponding of water above wall. Lined drainage ditch to minimum 2% flow away from wall Is recommended. " Use 1 ½ cubic foot per foot with granular backfill soil and 4 cubic foot per foot if expansive backfill soll is used. VINJE & MIDDLETON ENGINEERING, INC~ PLATE 3 _] J J -l .J .I _J J NOTES: ISOLATION JOINTS AND RE-ENTRANT CORNER REINFORCEMENT Typical -no scale (a) ISQLATION JOINTS CONTRACTION JOINT~ RE-ENTRANT CORNER--.... REINFORCEMENT NO. 4 BARS PLACED 1. 5" BEL.OW TOP OF SLAB (c) ·. . . (b) RE-ENTRANT CORNER CRACK 1. Isolation joints around the columns should be either circular as shown in (a) or diamond shaped as shown In (b). If no Isolation joint$ are used around columns, or If the corners of the Isolation Joints do not meet the contraction joints, radial cracking as shown in {c)may occur (reference ACI). 2. In order to control cracking at the re-entrant corners (±270° cor_ners), provide· reinforcement as shown in (c). 3. Re-entra1nt corner reinforcement shown herein is provided as a general guideline only and is subject to verification and changes by the project architect and/or structural engineer based upon slab geometry, location, and other engineerirfg and constructlon factors . VINJE & IYIIDDLETON ENGINEERING, INC. PLATE 4 • • • .. Ill Ill Ill &. C APPENDIXE C C C C C C C C C C C C C C -... , ----, --J --:·1 --.. ] --] --] --J --] --J --] --J --J --.J --_} -_J -I -j -i I -j : _I - MV ENGINEERING, INC. 2450 Vineyard Ave., Suite 102 Escondido, CA 92029-1229 619/743-1214 Fax: 739-0343 Job #1Cl17-91 Februa1·y 20, 1991 Mr. Hos:sein Zomorrodi Zomorrqdi Engineering 5983 Ci.rrus Street San Die1go, California 92110 Prelimi.nary Soil and Geoteohnioal :Investigation, Graded Hillside Property, Gibraltar street Near Jerez court, La Costa Area of Carlsbad, San Diego county, ca1itorni1 PUrsuan.t to your request, MV Engineering, Inc. has completed the attached investigation of soils and geotechnical conditions at the subject site. The fc,llowing report summarizes the results of our field investigation, laboratory analyses, and conclusions, and provides recommendations for the site development as understood. From a geotechnical engineering standpoint, it is our opinion that the site is suitable for the proposed development provided the recommendations presented in this report are incorporated into the design and construction of the project. Thank you for choosing MV Engineering, Inc. If you have any questions concerning this report, please do not hesitate to call us. Reference to our Job 1#1017-91 will expedite our response to your in,quiries. we appr,eciate this MV ENGJ:l~BERING, INC. Ralph M .. Vinje GE #863 RMV/kmh to you. -. I -I --TABLE OF CONTENTS --, -Page --l -I. INTRODUCTION. . . . . • . . . . . . . . 1 II. SITE DESCRIPTION/BACKGROUND • . . • • . 1 -l -J:II. PROPOSED DEVELOPMENT. . . . • . . . . . 1 IV. SITE INVESTIGATION. . • • . . . • • • . 2 -l v. GEOTECHNICAL CONDITIONS • . • . . • . . 2 A. Earth Materials. . . . . . . • . . • 2 --j - 1. Fill (af) . . . . • . . • • . • • 2 2. Terrace Deposit (Qt). . • • • • • 2 3. Bedrock (Td). . • . . • • • . • . 2 -1 B. Laboratory Testing/Results . . . . • 3 --_'I 1. Maximum Dry Density and Optimum Moisture Content. . • • . 3 2. In-Place Dry Density and -Moisture content. . . . . . • . • 3 -j 3. Expansion Index Test. • . . . . • 4 4. Direct Shear Test • . . . • . . • 4 --1 c. Geologic Structure • . . . . • . . • 4 D. Seismicity . . . . • • . . . . . . . 4 E. Slo~e Stability. . . . • . • • . . • 5 --I VI. CONCLUSIONS/RECOMMENDATIONS . . . . . . 5 A. Grading. • • • . • . . • . . • . . • 6 B. Foundations. • . . . . . • • . • . . 6 --J c. Interior Slabs . . . • • • • . • . . 7 "" D. Exterior Slabs • . • . • . • • • • . 8 E. Retaining Walls. • • • . . • • . . . 8 -F. Design . • • • . • • • • • . . . . . 9 G. Drainage/Erosion Control . • • . . . 9 -H. Pavement • • . . . . . . • . . . . . 10 --.I I. Utility Trench Backfi+l• . • . . . • 10 J. Plan Review. • • • • . . . . . . • . 10 K. Geotechnical and Construction Inspections. . . . . . . . . . . . . 10 -L. Preconstruction Conference . . . . . 11 -VJ:I. LIMITATIONS • . . . . • • . • . . • • . 11 ---(continued) ---- -~----~, ---I --·-, --l -------.. --I ... -l ----l -J --j --I --l --i I ----1 -- ______..,_ .. , Table •::>f Contents/Page 2 APPENDIXES Ali?PENDIX 11A11 -SUBSURFACE INVESTIGATION . . . . . . . . . . . . Plate l 2 Geotechnical Map .••• Geologic Cross Sections. Test Pit Logs (including Key) . • • • 3-7 Isolation Joints and Re-Entrant Corner Reinforcement •••••••• a Typical Wall Drainage Detail •••• 9 APPENDIX 11B11 -SPECIFICATIONS FOR CONSTRUCTION OF CONTROLLED FILLS, AND UNIFIED SOIL CLASSIFICATION --l ---·1 --l --·1 --I --I ---, ----I ---l -J --f --1 --I ------f -_j - I. ~tODUCTIQN PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION GRADED HILLSIDE PROJECT GIBRALTAR STREET NEAR JEREZ COURT LA COSTA AREA OF CARLSBAD SAN DIEGO COUNTY, CALIFORNIA The st\:tdy property consists of three vacant graded sites along the north Elide of Gibraltar Street in La Costa. The site location is depicte1d on the Vicinity Map included on the Geotechnical Map attacheid with this transmittal as Plate 1. We undtarstand that the property is presently planned to support several attached dwelling units in separate buildings as shown on Plate l.. The purpose of this study was to determine geotechnical conditi.ons in the planned construction areas and their influence on the planned improvements. II. SI1rE DESCRIPTION/BACKGROUND The stu.dy site is located within graded hillside terrain north of and below La Costa Avenue. Access onto the property is provided by Gibraltar Street which defines the north property boundary. Tpe site consists of three level pad surfaces which are surrounded by graded slopes. Rear areas are terminated by a large cut slope which flScends as much as 70 feet onto off site terrain above. smaller side and front slopes define each of the three pads as shown 1::m Plate 1. Slope gradients are 1\: 1 (horizontal to vertical). Surface areas are bare or support a light cover of native grass. Site dJ:-ainage sheet flows over surface areas toward Gibraltar Street. Some erosion of front slopes has occurred as a result of concentrated run-off. Technic,al records for the grading are unavailable. Aerial photo- graphs ,:md topographic maps of the area indicate that site grading took pl,ace between 1960 and 1977. III. ~)POSED DEVELOPMENT Detailed development plans for the project are presently unavailable. However, we understand that the site is planned to support attached dwelling units as shown on Plate 1. Construction will be conventional wood-frame and stucco supported by eontinuous foundations. Slab-on-grade floors are planned for lower units. -------------------------j ----l J -) I -J ------- 1 l I I I I PRELIMI:~ARY SOIL AND GEOTECHNICAL INVESTIGATION GIBRALT:!'\R STREET r LA COSTA AREA OF CARLSBAD PAGE 2 FEBRUARY 20, 1991 Planned grades (shown on Plate l) indicate modest cut/fill grading to esta.blish new, level building surfaces. A maximum cut of 12 feet and a maximum fill of seven feet is planned. Retaining walls a:c-e proposed throughout as shown. :IV. SITleJ INVESTIGATION Geotechlllical conditions at the site were determined chiefly by field ma.pping of available surface exposures and the excavation o~ seven e>cploratory trenches dug with a tractor-mounted backhoe. The trencheis were logged by our project geologist who retained represei,tative soil/rock samples for laboratory testing. Rasul ts of the testing are tabulated in a following section. Geologic cross s.ections and logs of the test trenches are attached as Plates :a through 7 ( including the Key) • V. ~~CHNICAL CONDITIONS A. Earth Materials -The following earth materials were encountered at the project and will affect site development: 1. Fill (af) -Fill soils occur at the project, particularly bE~neath front areas of the graded parcels. The fill consists chiefly of locally derived sands and silts with included rock fragments. The fill generally occurs in a loose condition. 2. Turrace Deposit (Qt) -Natural Terrace Deposit soils underlie the front portion of the project. These are dark colored clay-silt deposits which mantled lower hillside terrain along the southern margin of San Marcos Creek. Deposits at the site occur in a soft to stiff condition. 3. Beidrock (Td) -Formational sedimentary rocks underlie rear areas of the property including the large ascending slope. The rocks consist of interbedded sandstone and siltstone units which are widely exposed in local hillside terrain to the south. on-site exposures occur in a firm to locally hard cc,ndi tion. Detalls of the earth materials underlying the project are included on the enclosed logs (Plates 4 through 7) • The apprc,ximate distribution of major earth materials is depicted on Plate 1 and on the Geologic cross Sections enclosed as Plate 2. -.. -I --: I -----_, ---··1 --I --I --j --t --1 --I --J -I -j --J --1 -I -I --I --J -~----,, PRELIMJ:NARY SOIL AND GEOTECHNICAL INVESTIGATION PAGE 3 GIBRAL'l1AR STREET, LA COSTA AREA OF CARLSBAD FEBRUARY 20, 1991 B. ~►ratory Testing/Results -Excavations of on-site earth depc►sits will result in soils which have been grouped into the following soil types: s0,il/Rook Type 1 2 3 4 SOIL TYPES Soil Desorigtion light brown clayey sand/ sandy clay light colored silty sand tan to brown silty sand dark brown silty to sandy clay The following tests were conducted in support of this study: 1, Maximum Dry Density and Optimum Moisture Content -The maximum dry density and optimum moisture content of selected soil types were determined in accordance with ASTM D-1557- 78. The results are tabulated below. optimum Test Soil Maximum Dry Moisture Location ~ Density Cgofl I content (%} TP 1@5 1 2 115.7 15.3 TP 2@2 1 4 114.5 15,6 TP = Test Pit These results may be used during the grading where aJPplicable. 2. J:i11-Plaae Dry Density and Moisture content -In-place .dry d(msities and moisture content of representative chunk soil samples were determined using the water displacement method. R1~sul ts are presented below. Test Soil Dry Density Field Moisture Location ~ Cpof) (%) TP 1@5 1 2 133.8 7.2 TP 1@8 1 2 101.1 17.3 TP 1@8 1 2 108.4 17.0 TP 1@10 1 3 129.8 12.0 TP 1@13 1 3 110.1 17.0 .. ---- ---- l .I -·1 ----------1 --1 --l -_J -l -1 :1 :.1 ·1 -·· - PRELIMJCNARY SOIL AND GBOTECHNICAL INVESTIGATION GIBRAL~~AR STREET, LA COSTA AREA OF CARLSBAD PAGE 4 FEBRUARY 20, 1991 3. l~xpansion Index Test -The potential for on-site soils to change in volume in response to moisture fluctuations was determined by expansion index tests. The tests were performed in accordance with the Uniform Building Code Standard Procedure 29-2. Results are presented below. Remolded saturated Sample Moisture Moisture Expansion Location Content (%) content (%) Index TP 1@8 1 19.3 29.3 46 TP 2@2 1 12.8 33.6 98 4. D1ireot Shear Test -A direct shear test was performed on a representative site soil sample for strength parameters in the lateral load and bearing capacity calculations. Three soil specimens were prepared by molding them in 2%-inch diameter, 1-inch high rings to 90% of the corresponding maximum dry density and optimum moisture content and soaked overnight. The specimens were loaded with normal loads of 1, 2, and 4 KSF respectively and sheared to failure in an undrained shear. The results are presented below. Location TP 1@5 1 Soil ~ 2 wet Density (pen 119.0 Angle of Int. Frio. c6 (degree> 34 Apparent Cohesion o, (psf) 146 c. Geolc)gio Structure -Bedding conditions within on-site bedrock are poorly developed. However, noted exposures indicate nearly flat··lying conditions throughout. Faults or significant shear zones are not in evidence at the projE~ct site. D. Seis11lioity -As with most areas of California, the San Diego region lies within a seismically active zone. However, coastal areae, of the county are characterized by low levels of seismic activity relative to inland areas to the east. During a 40-year pericid {1934-1974), 37 earthquakes were recorded in San Diego coastal areas by the California Institute of Technology. None of the recorded events exceeded a Richter magnitude of 3.7 nor did cmy of the earthquakes generate more than modest ground shaking or significant damages. Most of the recorded events occurred along various offshore faults which characteristically generate modest earthquakes. -. ·1 l -.1 -·1 ----l --------. I --I --l --------J ---i -I J ------- _.......__., ___ PRELIMINARY SOIL ANO GEOTECHNICAL INVESTIGATION GIBRAL't'AR STREE'l', LA COSTA AREA OF CARLSBAD PAGE 5 FEBRUARY 20. 1991 Hist.orically, the most significant earthquake events which affect local areas originate along well known, distant fault zone.a to the east. Less significant events have been recorded alon.g off shore faults to the west. The following list represents the most significant active fault which typically impact the region. Fault zone Distant from Site Elsinore Fault 28 miles San Jacinto Fault 57 miles San Andreas Fault 82 miles Coronado Bank Fault 20 miles More recently, the number of seismic events which affect the region appears to have heightened somewhat. Nearly 40 earthquakes of magnitu.de 3. 5 or higher have been recorded in coastal regions between, January, 1984 and August, 1986. Most of the earthquakes are thought to have been generated along offshore faults. For the most part, the recorded events remain moderate shocks which typically resulted in low levels of ground shaking to local areas. A notable exception to this pattern was recorded on July 13, 1986. An earthquake of magnitude 5. 3 shook North coast coastal areas resulting in $400,000 in damages and injuries to 30 people. The quake e>ccurred along an offshore fault located nearly 30 miles southwest of Oceanside. The event resulted in moderate to locally high lEivels of ground shaking in areas of the study site. The increase in earthquake frequency in the region remains a subject of spec::ulation among geologists. However, the 1986 event is thought to represent the highest levels of ground shaking which can be expe,cted at the study site as a result of seismic activity. Ground separation during expected earthquake events is not antici- pated at the study site. E. Slope stability -Existing site slopes do not evidence geologic instability. Underlying bedrock units are flat-lying, sedi- mentary rocks which are expected to perform well in modest slopes planned for redevelopment. The stability of off-site slopes is beyond the scope of this transmittal. VI. CON1CLUSIONS/RECOMMENDATIONS Based upon the foregoing investigation, development of the study property for residential purposes is feasible from a geotechnical viewpoi:rit. The property is underlain by old fill and Terrace Deposit soils which, in their present condition, have a potential -------------------------------------- I . } · 1 · 1 I .l . ) l J l j J l ) I l .l I .I- PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION iIBRALTAR STRBE~. LA COSTA AREA OF CARLSBAD PAGE 6 FEBRUARY 20, 1991 for detrimental soil movement. Loose, compressible soils, as well as exp,~nsi ve soils, are present at the site. Consequently, regrading of near-surface soils is recommended in order to create safe and stable building surfaces. Recommendations given below are consistent with site geotechnical conditions and should be incor- porated into finalized plans. A. Grading: 1. Grading operations at the property should generally be conducted in accordance with the enclosed "Specifications for Construction of Controlled Fills" attached with this report as Appendix "B" • 2. J?•rior to grading, site vegetation and other deleterious d.ebris should be removed from the property • 3. N'ear surface soils should be excavated to grade elevations d.epicted on Plate l. The indicated removal depths apply to t.he existing plans and the finished elevations given on J?'late 1. Changes in the plans will likely require 1:r1odifications in the removal elevations given herein. 4. A.fter completion of the indicated remoyals, planned grades e,hould be achieved by on-site soils as properly compacted f'ill. The fill should be brought to optimum moisture levels a.nd mechanically compacted in thin, horizontal lifts to a 1r1inimum 90% of the laboratory maximum density value. 5. C1n-site soils may be re-used in compacted fill. However, d:ark colored Terrace Deposit soils represent the most expan- s,ive deposits at the site. Consideration should be given to placing these deposits within the deeper fills as a means of 1t1inimizing the expansive potential of finish grade soils. I:" B • .l.2ID).dations -At the completion of rough grading, this office should confirm by testing the actual expansion potential of finish grade soils so that more specific foundation/s1ab reco,mmendations can be provided. However, based upon site soil characteristics, it is assumed that expansive soils will be expo,sed at finish grade. Consequently, the following founda- tion/slab-recommendations are provided for preliminary design and estimating purposes. 1. F'oundations should be founded a minimum depth of 24· inches below the lowest adjacent grade (not including sand/gravel under the slab). Footings should maintain a minimum width of 12 inches. Isolated square footings are not recommended. -, I ·1 -_:f --I --J --1 --I -I --J --j --l ------1 --.l ----------- PRELIMIN~RY SOIL AND GEOTECHNICAL INVESTIGATION GIBRALTAR STREET, LA COSTA AREA OF CARLSBAD PAGE 7 FEBRUARY 20, 1991 2. Foundations should be reinforced with four #4 bars, two placed three inches below the top and two bars placed three inches above the bottom of the footing. 3. Dowel the slab to the footings using #4 reinforcing bars spaced 18 inches on center extending 20 inches into the footing and slab. The dowels should be placed mid-height in. the slab. Alternate the dowels each way for all interior fo,otings. 4. Af'ter the footings are dug and cleaned, place the reinforcing st.eel and dowels and pour the footings. s. 'l'llLis office must be notified to inspect the footings and re,inforoing prior to pouring oonorete. c. interior Slabs: 1. All utility trenches under slabs in expansive soils should bEl backfilled with sand (S. E. 30 or greater) and flooded with WcLter to achieve compaction. 2. Once the concrete for the footings has cured and underground utilities tested, place four inches of pea gravel (\-inch rock) over the slab subgrade. Flood with water to the top 01: the pea gravel, and allow the slab subgrade to soak for approximately seven to 10 days. The required moisture content of the slab subgrade soils is 3S.~ to 5% over the optimum moisture content at a depth of 24 inches below slab subgrade. After the slab subgracSe soils have soaked, notify this office and schedule appropriate m<>isture testing. .... N<>TEs If sufficient moisture is present, flooding will not b«, required. The dowels may be deleted, and th_e footings and sJLab may be poured monoli thioally. 3. When the required moisture content has been achieved, place a 10-mil plastic moisture barrier over the 3/8-inch rock and place two inches of clean sand (SE 30 or greater) on top of the plastic. 4. U::;e #3 reinforcing rods spaced 18 inches on center each way placed one and one-half inches below the top of the slab. All slabs should be a minimum of five inches in thickness. - --I :~1 : J :1 --, -- :·1 -1 - -·1 --J --J - -j --1 --J - -1 ------- PRELIMIN;lRY SOIL AND GEOTEOHNICAL INVESTIGATION GIBRAL'l'A1R STREET, LA COSTA AREA OF CARLSBAD PAGE 8 FEBRUARY 20, 1921 5. Th.is office must be notified to inspect the sand, slab thickness, and reinforcing prior to concrete pour. 6. Pr,ovide contraction joints consisting of sawcuts spaced 12 fe-et on center each way within 72 hours of concrete pour for all interior slabs. The sawcuts must be a minimum of one- half inch in depth and must not exceed three-quarter inch in depth or the reinforcing may be damaged. D. Exterior Blabs (patios, walkways, and driveways> -All exterior slabs (walkways, patios, etc.) must be a minimum of four inches in thickness reinforced with 6X6/lOxlO welded wire mesh placed one and one-half inches below the top of the slab. Driveways must be a minimum of five inches in thickness and reinforced with #3 reinforcing bars spaced 18 inches on center each way placed one and one-half inches below the top of the slab. Use six inches of clean sand (SE 30 or greater) beneath all slabs. Provide contraction joints consisting of sawcuts spaced six feet on center each way within 72 hours of concrete pour. The depths of the sawcuts should be as described in interior slab rein- forcing, item (6) above. Special attention should be given to any "re-entrant" corners and curing practices (during and after concrete pour) to limit crack.ing. Construction recommendations are given on the enclosed Plate 8. The concrete reinforcement recommendations provided herein should not be considered to preclude the development of shrin.kage related cracks, etc. ; rather, these recommendations are i.ntended to minimize this potential. If shrinkage cracks do deivelop, as is expected from concrete, reinforcements tend to limit the propagation of these features. These recommenda- tions are believed to be reasonable and in keeping with the local standards of construction practice. Footing and slab designs provided herein are based upon soil characteristics only and should not supersede more restrictive requirements set forth by the architect or the structural engi111eer. Please note that minimum requirements set forth by the respective government agencies may also supersede the recon~endations provided in this report. E. Retaining Walls 1. E:>1:pansive clayey soils should not be used for backfilling of a111y retaining structure. All retaining walls, including those planned to surround the interior gymnasium, should be -. I --: l --: l --. I --;·-1 ---.. I -: l --: ] --: ] --I --) --.J --. J --.'J --.J --.J --_J -l j -J --- PRELIMJ:NARY SOIL AND GEOTECHNICAL INVESTIGATION GIBRAL'l1AR STREET r LA COSTA AREA OF CARLSBAD PAGE 9 FEBRUARY 20, 1991 provided with a 1: 1 wedge of granular, compacted backfill measured from the base of the wall footing upward to the f'inished surface. Retaining walls should be provided with a. backdrainage as outlined on the enclosed Plate 9. 2. I,ateral active pressures for sandy soils with a minimum friction angle of 30 degrees and assumed drained backfill c:onditions are provided below. These values may be used for p,reliminary design estimates only and are to be re-evaluated when the characteristics Qf the backfill soils have been d.etermined. Revised recommendations should be anticipated. F'assive resistance is also provided. .1\.ctive Pressure = 53 pcf equivalent fluid pressure, canti- lever, unrestrained walls with 2:1 backfill surface. A.ctive Pressure • 34 pcf equivalent fluid pressure, canti- lever, unrestrained walls with level backfill surface. At Rest Pressure= 53 pcf equivalent fluid pressure, re- strained walls. *Passive Pressure= 421 pcf equivalent fluid pressure, level surface condition. *Note: Because large movements must take place before maximum passive resistance can be developed, the earth pressures given for passive conditions should be reduced by a safety factor of two. 3. A coefficient of friction of o. 35 may be considered for concrete on soils. This value is to be verified at the completion of grading when the properties of the subgrade soils are specifically known. ~ ' F. Desi,i;m -Based upon the nature of on-site soils and the fore1:1oing recommendations, an allowable bearing value of 1900 pounds per square foot for a 12-inch wide by 24-inch deep footing may be utilized for design purposes. This value applies to d,ead plus live loads and may be increased by one-third for wind and seismic loading. G. Draii:iage/Erosion control 1. E:,cessive moisture can adversely impact the stability of h:lllside properties. Consequently, finished grades should pl~ovide positive drainage away from structures and site slopes. Ponding of surface waters should not be allowed at -• I -I --1 :-1 :··1 :· 1 :·1 -· 1 -· I ·1 :,_ : :1 -} --I ----J --. ] --J --_j ------- PRELIM:I~rARY SOIL AND GEOTECHNICAL INVESTIGATION GIBRALTJ,R STREET r _LA COSTA AREA OF CARLSBAD PAGE 10 FEBRUARY 20, 1991 the site. construction soils should be dispersed in a proper ma,nner that will not interfere with positive drainage flow. 2. cc,nsideration should be given to providing a suitable plant g:i:'.owth upon the graded cut slopes around the north perimeter of the property as a means of controlling surface erosion. Pl.ants should be broad-leafed, deep-rooted types which ruguire minimum irrigation as recommended by the project lemdscaper. overwatering of on-site vegetation should be avoided. Only the amount of irrigation necessary to sustain plant growth should be provided. 3. Buck-drainage should be provided behind all retaining walls at the project in accordance with the attached Plate 9. H. Paver~ -AC pavement surfaces should only be placed atop granular, non-expansive subgrade soils which have been compacted to 951 of the laboratory standard in the upper 12 inches. Spec:Lf ic pavement designs can best be provided at the completion of r<>ugh grading based upon R-value tests of the actual soils. Howe~rer, for prelim,1-nary design purposes, a section of two-inch AC over five inches of compacted Class II base may be utilized for preliminary design purposes. Post grading tests should be conducted to verify this design. I. Util;lty Trench Backfill -All underground utility trenches should be compacted to a minimum of 90% of the maximum dry denslty of the soil unless otherwise specified by the respective agenc:::ies. Care should be taken not to crush the utilities or pipe1; during the compaction of the soil. Non-expansive, !"" granular backfill soils should be used. J. Plan Review -Final grading and foundation plans should incor- porate recommendations provided in this transmittal and be revicawed and approved by this office. If the final development plan:; significantly change, or if they were not available at the time of this investigation, further investigation and subsoil stud;{ may be required and should be anticipated. K. Geot•~ohnioal and construction Inspections -Grading operations should be continuously inspected by the project geotechnical consultant. Testing of fill will assist the contractor to achi•ave proper moisture and compaction levels. Particular atteJiltion should be given to removal oper~tions and drainage installation. - - --1 --l :1 : ·1 :1 : l -l --I --_J --J --] --J ---i -.J --- •~---••,.,...v PRELIM:IN;rl.RY SOIL AND GEOTECHNICAL :INVESTIGATION GIBRALTA:R STREE'l', LA COSTA AREA OF CARLSBAD PAGB 11 FEBRUARY 20 1 1991 Footi:ng excavations and foundation/slab reinforcement should also be inspected and approved by the project geotechnical consultant. L. Preoonstruction conference -A preconstruction meeting between representatives of this office and the property owner or planner, as well as the grading contractor/builder, is recommended in order to discuss grading/construction details associated with site development. VII • l!,D!:ITA'l'IONS The conclusions and recommendations provided herein have been based on all available data obtained from our field investigation and laboratc•ry analyses, as well as our experience with the soils and formatic,nal materials located in the general area. The materials encountE1red on the project site and utilized in our laboratory testing are believed representative of the total area; however, earth mcLterials may vary in characteristics between excavations. Of neces:sity we must assume a certain degree of continuity between explorat~ory excavations and/or natural exposures. It is necessary, therefore, that all observations, conclusions, and recommendations be ver:lfied during the grading operation. In the event discrepnncies are noted, we should be contacted immediately so that an inspElction can be made and additional recommendations issued if required. The recommendations made in this report are applicable to the site at the time this report was prepared. It is the responsibility of the owrter/developer to insure that these recommendations are carried out in the field. It is ,almost impossible to predict with certainty the future perform,:lnce of a property. The future behavior of the site is also depende1:1t on numerous unpredictable variables, such as earthquakes, rainfall, and on-site drainage patterns. The fix,n of MV ENGINEERING, INC. shall not be held responsible for changes to the physical conditions of the property such as addition of fill soils or changing drainage patterns which occur subsequent to issu,ance of this report. · This report should be considered valid for a period of one year and is subject to review by our firm following that time. If significant modifications are made to your tentative development plan, especially with respect to the height and location of cut and fill slopes, this report must be presented to us for review and possible revision. - --] --l -~, ... -J ----I --J --j --.1 --J --l --j --J - --,·~·~ PRELIMIN;~RY SOIL AND GEOTECHNICAL INVESTIGATION GIBRALTA:R S'l'REE'l', LA COSTA AREA QF CARLSBAD PAGE 12 FEBRUARY 20, 1991 MV Engineering, Inc. warrants that this report has been prepared within the limits prescribed by our client with the usual thoroughness and competence of the engineering profession. No other warranty or representation, either expressed or implied, is included or intended. Onoe agcdn, should any questions arise concerning this report, please d.o not hesitate to contact this office. Reference to our Job #1017-91 will expedite response to your inquiries. RMV /OM/J~mh a: 1017-!Jl.pre --.. ()-:: ."·Yl'f ., "*-{; EXIST CONC DITCH PRELIMINM<Y GMO/NG r'I.IW • • ----------------------·------------------=---=~=~== ~=-=----~= VICINITY MAP I NO SCALE SCALE: l"-20' LEGEND al Exl1tlng 1111 QI Terrace deposit 10ll1 Td e.-drock/Formatlonal rook· \. Location of teat pit ti, Approximate 1url■ce contact L_j Cro11-Sectlon llnea e Recommandad ramoval alevatlon PREPARED BY ZOMORROOI ES6INEERING MARCH 31. 1590 ICamblr~: - ARCHITECl\JRE & PLANNING ""' -., .. Cll80, CA. ... ,. ...... UARY 1981 JOB NO 1017·91 RFS:FRFNC-:F MV FNAINEERING REPORT DATED FEBR ·1 i .. 1 ··7 i I I I i ··1 I l ) l J . l i ! ,.I I J .1 ..J I .! C fl J ·-----'--··-~- ___ ___r-------, ---. -. 70 STREET £ PROPOSED GRADE~ f--.. ---,--· · -~-- . . . . ·. feriace'. be;_osi~\:fo · -• S 0 ~ ·. · :--::~ '--_:, ·F~~~ational-Rock (Td) 60 B 90 ~-r :-:------------. -r ·· , .. -·-··-'-· ----r---_j_ --··-·· ---· _L__ , --~ -·---,--L---r-. . -. --.!. A 100 STREET It. -~ -, ---·····-·---····l. ·--·----_)_ c· 100 GEOLOGIC CROSS-SECTIONS 80 -··-··--I A' 120 100 80 B' 120 100 80 PLATE 2 •: -I -I -·, --, --l .. ~1 •; -·1 ! -; -·1 -~ -) -I ---.. J -.. l -:.J -.1 - : _j -j ------_, PRIMARY DIVISIONS GRAVELS MORE THAN HALF OF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE SANDS MORE THAN HALF OF COARSE FRACTION IS SMALLER THAN NO. 4 SIEVE CLEAN GRAVELS (LESS THAN 5% FINES) GRAVEL WITH FINES CLEAN SANDS (LESS THAN 5% FINES) SANDS WITH FINES SIL TS AND CLAYS LIQUID LIMIT IS LESS THAN 50% SILTS AND CLAYS LIQUID LIMIT IS GREATER THAN 50% GROUP SYMBOL SECONDARY DIVISIONS GW Well graded gravels, gravel·sand mixtures, Hille or no fines. GP Poorly graded gravels or gravel-sand mixtures, llllle or no fines. GM SIity gravels, gravel•sand•slll mixtures, non-plastlc lines. GC Clayey gravels, gravel•sand•clay mixtures, plastic lines. SW Well graded sands, gravelly sands, lllHe or no lines. SP Poorly graded sands or gravelly sandS, Ullle or no fines. SM Silty sands, sand•sllt mhdures, non-plasllc lines. SC Clayey sands, sand•clay mixtures, plastic fines. ML CL OL MH CH OH lnorgan~ sllls and very fine sands, rock Hour, sUty or clayey fine sands or clayey •Ills with slight plasticlty. Inorganic clays of low lo medium plasllclty, gravelly clays, sandy clays, silly clays, lean clays. Organic silts and organic sllty clays of low plastk:ily. Inorganic slits, mlcaceous or dlatomaceoua line sandy or sllly soils, elasllc sills. . Inorganic clays of high plaallclty, fat clays. Organic clays of medium lo high plasllclly, organic silts. HIGHL.Y ORGANIC SOILS PT Peat and other highly organic solls. GRAIN'SIZES U.S. STANDARD SERIES SIEVE CLEAR SQUARE SIEVE OPENINGS 200 40 10 4 3/4" 3" 12" SANO GRAVEL SILTS ANO CLAYS FINE I MEDIUM I COARSE I COARSE COBBLES BOULDERS ANE RELATIVE DENSITY CONSISTENCY SANDS, GFIAVELS ANO NON-PLASTIC SILTS BLOWS/FOOT CLAYS AND PLASTIC SILTS STRENGTH BLOWS/FOOT VERY LOOSE LOOSE MEDIUM DENSE DENSE VERY DENSE 0·4 4 • 10 10 • 30 30 · 60 OVER 50 VERY SOFT SOFT FIRM STIFF VERY STIFF HARD O•¼ ¼·½ Y, · 1 1 • 2 2·4 OVER 4 0·2 2·4 4·8 8 · 16 16 • 32 OVER 32 1. Blow count, 140 pound hammer falling 30 Inches on 2 Inch 0.0. split spoon sampler (ASTM 0·1586) 2. Unconfined compressive strength per SOILTEST pocket penetrometer CL-700 6 = undisturbed chunk sample D = disturbed sample Q = sand cone test MV ENGINEERING, INC. I 246 = Standard Penetration Test (SPT) (ASTM D-1586) with blow counts per 6 inches 11 246 = Californla Sampler with blow counts per 6 inches KEY TO EXPLORATORY BORING LOGS Unified Soil Classification System (ASTM D-2487) ZOMORRODI ENGINEERING GILBRALTAR STREET NEAR JEREZ COURT, LA COSTA PROJECT NO. PLATE 1017-91 3 KEY .... i L --. l ---l --. 1 ---, --, ·1 ---I --:· I --"J --: I --J --.I --J --_J --J --I - -_j --..l --j - UNIFIED SOIL CLASSIFICATION Identifying criteria I • .Q.<>ARSE GRAINED (more than 50% larger than #;mo sieve). GJ~ayels (more than 50% lc1rger than #4 sieve btlt smaller than 3 '') , nc>n-plastic. sands (more than 50% smaller than #4 sieve}, non-plastic. II. lllgE GRAINED (more than 501 smaller than #200 si~we). Liquid Limit less than 50. Symbol GW soil Description Gravel, well-graded gravel- sand mixture, little or no fines. GP Gravel, poorly graded, gravel-sand mixture, little or no fines. GM Gravel, silty, poorly graded, gravel-sand-silt mixtures. GC Gravel, clayey, poorly graded, gravel-sand-clay mixtures. SW Sand, well-graded, gravelly sands, little or no fines. SP Sand, poorly graded gravelly sand, little or no fines. SM Sand, silty, poorly graded, sand-silt mixtures • SC ML sand, clayey, poorly graded, sand-clay mixtures. Silt, inorganic silt and fine sand, sandy silt or clayey-silt-sand mixtures with slight plasticity. CL Clay, inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays. -------------------------------------- I l . J -I . , . j l J 1 I J 1 .1 ' ! -· _J unified soil Classification Page 2 II. FIHE GRAINED -continued Liquid Limit greater than so. III. HIGHLY ORGANIC SOILS OL silt, organic, silts and organic silts-clays of low plasticity. MH Silt, inorganic silts, micaceous or dictomaceous, fine sand or silty soils, elastic silts • CH clay, inorganic, clays of medium to high plasticity, fat clays. OH Clay, organic clays of medium to high plasticity. PT Peat, other highly organic swamp soils. .. ----I ---l --J -_-, :, :J :·1 -J ------J --J --J --J --l -• -,I ----- TEST PIT 1 · FILL (af): llght brown clayey sand mottled, aoft to loose. BEDROCK (Td): sandstone, ltght colored, l~ouly cemented upper 2', Dense and well cemented at 5' rOTAL DEPTH 14' TEST PIT 2 FILL (af): pale brown clayey Hnd, mottled, Include• sandstone fragments. moist and looae -....------ BEDROCK (Td): siltstone, ohooolate brown, fractured, firm, with white carbonate seams. FILL/TOPSOIL: dark brown clay,-----------------~ moist, stiff . TOTAL DEPTH 5' 3' PLATE #4 --~, --J --'I --l -_., --_l :] :·"I :1 --:1 : ..I -} --, - -1 - i -i j ----- TEST PIT 3 TOTAL DEPTH l' TEST PIT -4 light lo dark brown, lr1cludea eoattered bedrook fragments. moist, loose, '----------------r--------------:r!"':" 4.5' 6' -----=--:.-::.=.::.r-TOPSOIL: dark biown ctav:-- mols t, soft' to stiff, TERRACE DEPOSIT (Qt): brown sift, weathered, soft, gradatfonal contact above; 8.5' -- TOTAL DEPTH 8,5' PLATE #5 --! I --l --I --l --l ---- -__J - -_J ---} -j ------- TEST PIT 5 BEDROCK (Td): siltstone/sandstone, pale brown. tight. cut by white oarbonate seams. TOTAL Df:PTH 5' TEST PIT 6 FILL (af): light colored clayey sllt, dry, loose, mottted, FILL (af): brown sandy cl ■ moist. loose. 2' ): sepdslone, Ian br~wn, TERRACE QEPOSIT (Qt):. brown olay, dry, dense. · soft to stiff, with scattered ....._ ______ ,,_ ___ ""I gypsum se-ama. --- TOTAL DEPTH 8' PLATE #6 ------I -l -I :-1 -l 4• -_!_ - -J :1 ---j --J --J --I --J ----J --- ----,~ TEST PIT 7 FILL (af): light colored clayey sllt lo sand, dry, loose. TERRACE DEPOSIT (Qt): brown clay, soft to stiff. TOTAL DEPTH 10' 8' L BEDROCK (Td): sandstone, tan l>rown damp to moist, cemented PLATE 117 ~ --1 - - - - - --··1 -- -·1 -. : .J : .J : J -_J --J --j --_J --- -----· ISOLATION JOINTS AND RE-ENTRANT CORNER REINFORCEMENT Typical -no scale. (a) isolation joints contraction joints re-entrant corner reinforcement .-----~~ No. 4 bars placed _"'_._~ H" below top of slab contraction joints (c) (b) potential re-entrant corner crack Notes: (1) Isolation joints around the columns should be either circular as shown in (a) or diamond shaped as shown in (b). If no isolation joints are used around columns, or if the corners of the isolation joints do not meet the contraction joints, radial cracking as shown in (c) may occur (reference ACI), (2) In order to control cracking at the re-entrant corners (±270° corners), provide (3) reinforcement as shown in (c}. Re-entrant corner reinforcement shown herein is provided as a general guideline only and is subject to verification and changes by the project architect and/or structural engineer based upon slab geometry, location, and other engineering and construction factors. Plate 118 - - --j :-1 :J :1 : l ---1 --J --I .. -l -----I -! ... • --- ---· BACK DRAIN DETAIL 5• MIN. OVERLAP 314•-1-112• CLEAN GRAVEL* (311?/ft. MIN. SEE T-CONNECTION DETAIL ,4•~ -~-~-~ NON-PERFORAT PERFORATED PIP~-PIPE1cft ---FILTER FABRIC ENVELOPE (MIRAFI 140N OR APPROVED EQUIVALENT)* . 4• MIN. BEDDING SUBDRAIN TRENCH DETAIL · ,-...._ 10' MIN. PERFORATED 1-..LJ EACH SIDE PIPE~t· ,-1 · CAP 1 • NON-PERFORATED . OUTLET PIPE T-CONNECTION DETAIL SPECIFICATIONS FOR CALTRANS CLASS II PERMEABLE MATERIAL *If Caltrans Class II permeable material is used in place of 3/4"-H" gravel, fabric filter may be deleted, **SUBDRAIN TYPE -Subdrain type should be Acrylonitrile Butadiene Stryene {A.B.S,), Polyvinyl Chloride (PVC) or approved equiva- lent. Class 125, SDR 32,5 should be used for maximum fill depths of 35 feet, Class 200, SDR 21 should be used for maximum fill depths of 100 feet, U.S. Standard Sieve Size l" 3/4" 3/811 No. 4 No. 8 No. 30 No. 50 No. 200 Sand Equivalent :t Passing 100 90-100 40-100 25-40 18-33 5-15 0-7 0-3 75 PLATE# 9 - - - - --~I --J :,-] : J :·1 :1 -.J - : J --J -J --_I --·1 --_J --- APPENDIX "B" - --·1 - --:1 ----, - -'j ::1 : ·1 : . l ---I - :J -. I --J --_J ---.. 1 --- SPECIFICATIONS FOR CONSTRUCTION OF CONTROLLED FILLS GENERAL DESCRIPTION 8/88 1. The following grading specifications have been prepared for the subject site and are consistent with the Preliminary Investigation Report performed by this firm. 2. The grading contractor shall be responsible to perform ground preparation and compaction of fills in strict compliance with the specifications outlined herein. All earthwork including ground preparations, placing, watering, spreading, and compacting of fills should be done under the supervision of a state registered geotechnical engineer. The project geotechnical engineer should be consulted if any deviations from the grading requirements provided herein are desired by the owner/developer. 3. The construction of controlled fills shall consist of clearing and removal of existing structures and foundations, preparation of land to be filled, excavation of earth and· rock from cut area, compaction and control of the fill, and all other work necessary to complete the grading of the filled areas to conform with the lines, grades, and slopes as shown on the accepted plans. CLEARING AND PREPARATroN OF AREAS TO BE FILLED 1. All fill control projects shall have a preliminary soil investigation or a visual examination (depending upon requirements of the governing agency and the nature of the job) by a qualified geotechnical engineer prior to grading. 2. All timber, trees, brush, vegetation, and other rubbish shall be removed, piled, and burned, or otherwise disposed of to leave the prepared areas with a finished appearance, free from unsightly debris • 3. Any soft, swampy, or otherwise unsuitable areas shall be corrected by drainage or removal of compressible material, or both, to the depths indicated on the plans and as directed by the geotechnical engineer. 4. The natural ground which is determined to be satisfactory for the support of the proposed fill shall then be plowed or scarified to a depth of at least six inches (611 ) or deeper as specified by the geotechnical engineer. The surface should be free from ruts, hummocks, or other uneven features which would tend to prevent uniform compaction by the equipment to be used. 1 - - -· 1 - - - -_., :·.1 : -i --l --l --J --.I ---j -j ---------- s. No fill shall be placed until the prepared native ground has been approved by the geotechnical engineer or his representative on site. 6. Where fills are made on hillsides with slopes greater than 5:1 (horizontal to vertical), horizontal benches shall be cut into firm, undisturbed, natural ground. A minimum two-foot deep keyway, one blade width, should be cut. The geotechnical engineer shall determine the width and frequency of all succeeding benches which will vary with the soil conditions and the steepness of slope. 7. After the natural ground has been prepared it shall be brought to the proper moisture content and compacted to not less than 90% of maximum density per ASTM D-1557-78. s. Expansive soils may require special compaction specifications as directed in the preliminary soil investigation by the geotechnical engineer. 9. In order to reduce the potential for differential settlement for structures placed on a transition area of the lot, the out portion should be undercut a minimum depth of three feet below the proposed pad grade or to a minimum depth of twelve inches below the bottom of the footing, whichever is greater, and replaced as structural fill. The undercut should extend a minimum horizontal distance of ten feet outside the building perimeter. 10. caution should be used during the grading and trench excavations so that existing adjacent or underground structures/improvements are not distressed by the removals. Appropriate setbacks will be required and should be anticipated. All existing utilities on or in the vicinity of the property should be located prior to any grading or trenching operations. These precautions are the responsibility of the owner/contractor. MV ENGINEERING, INC. will not be held responsible for any damage or distress. MATERIALS The fill soils shall consist of select materials, graded so that at least 40 percent of the material passes the :#4 sieve. The material may be obtained from the excavation, a borrow pit, or by mixing soils from one or more sources. The materials used shall be free from vegetable matter and other deleterious substances. Oversized rocks greater than two feet in maximum diameter should not be included in fills. Rocks greater than 12 inches (12 11 ) in diameter should be properly buried ten feet or more below grade, measured vertically. Rocks should be placed per project geotechnical engineer or his representative to assure filling of all voids with compacted soils. Rocks greater than six inches (611 ) 2 - - --1 :1 :J : J - -_I - -l - -J ------- in diameter should not be allowed within the upper three feet of all graded pads. Rock fills require a special inspection and testing program under direct supervision of the project geotechnical engineer or his. representative. If excessive vegetation, rocks, or soils with unacceptable physical characteristics are encountered these materials shall be disposed of in waste areas designated on the plans or as directed by the geotechnical engineer. No material of a perishable, spongy, or otherwise unstable nature shall be used in the fills. If soils are encountered during the grading operation which were not reported in the preliminary soil investigation further testing will be required to ascertain their engineering properties. Any special treatment recommended in the preliminary or subsequent soil reports not covered herein shall become an addendum to these specifications. Laboratory tests should be performed on representative soil samples to be used as compacted fills in accordance with appropriate testing procedures specified by ASTM in order to determine maximum dry density and optimum moisture content of the fill soils. PLACING. SPREADING. AND COMPACTION Of FILL MATERIAL 1. The selected fill material shall be placed in layers which shall not exceed six inches (6 11 ) when compacted. Each layer shall be spread evenly and shall be thoroughly blade-mixed during the spreading to insure uniformity of material and moisture in each layer. 2. When the moisture content of the fill material is below that specified by the geotechnical engineer water shall be added until the moisture content is near optimum as determined by the geotechnical engineer to assure thorough bonding during the compaction process. This is to take place even if the proper density has been achieved without proper moisture. 3. When the moisture content of the fill material is above that specified by the geotechnical engineer the fill material shall be aerated by blading and scarifying or other satisfactory methods until the moisture content is near optimum as determined by the geotechnical engineer. 4. After each layer has been placed, mixed, and spread evenly it shall be thoroughly compacted to not less than the recommended minimum compaction requirements per specified maximum density in accordance with ASTM D-1557-78. Compaction shall be by means of tamping or sheepsfoot rollers, multiple-wheel pneumatic-tired rollers, or other types of rollers. Rollers shall be of such design that they will be able to compact the fill to the specified density~ Rolling each layer shall be continuous over its entire 3 -.. -----I ---.. ] --I --l --. I --: I --. I ----I --J ------j ------- ,__,..,,,.,._, __ ,. .. area and the rollers shall make sufficient passes to obtain the desired density. The entire area to be filled shall be compacted to the specified density. 5. Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compacting of the slopes shall be accomplished by backrolling the slopes in increments of three to five feet (3 1 -5 1 ) in elevation gain or by overfilling and cutting back to the design configuration or other methods producing satisfactory results. If the method of achieving the required slope compaction selected by the contractor fails to produce the necessary results, the contractor shall rework or rebuild such slopes until the required degree of compaction is obtained. 6. Field density tests shall be made in accordance with ASTM Method D-1556-82 by the geotechnical engineer for approximately each foot in elevation gain after compaction, but not to exceed two feet (2 1 ) in vertical height between tests • The geotechnical engineer shall be notified to test the fill at regular intervals. If the tests have not been made after three feet of compacted fill has been placed, the contractor shall stop work on the fill until tests are made. The location of the tests shall be spaced to give the best possible coverage and shall be taken no farther than 100 feet apart. Tests shall be taken on corner and terrace lots for each two feet {2 1 ) in elevation gain. The geotechnical engineer may take additional tests as col')sidered necessary to check on the uniformity of compaction. Where sheepsfoot rollers are used, the test shall be taken in the compacted material below the disturbed surface. No additional layers of fill shall be spread until the field density tests indicate that the specified density has been obtained. 7. The fill operation shall be continued in six-inch (611 ) compacted layers, as specified above, until the fill has been brought to the finished slopes and grades as shown on the accepted plans. SUPERVISION Supervision by the geotechnical engineer or his representative shall be made during the filling and compacting operation in order to verify that the fill was constructed in accordance with the preliminary soil report or agency requirements. The specifications and soil testing of subgrade and basegrade material for roads or other public property shall be done in accordance with specifications of the governing agency unless otherwise directed. 4 ... ... ----. I --. l -. I --.l --.I --: I --I --I ----I --_j ----I ,I --J -I -_I -! -. j --- ~--,-, It should be understood that the contractor shall supervise and direct the work and shall be responsible for all construction means, methods, techniques, sequences, and procedures. The contractor will be solely and completely responsible for conditions at the job site, including safety of all persons and property during the performance of the work. Intermittent or continuous inspection by the geotechnical engineer is not intended to include review of the adequacy of the contractor's safety measures in, on, or near the construction site. SEASONAL LIMITS No fill material shall be placed, spread, or rolled during unfavorable weather conditions. When the work is interrupted by heavy rain, grading shall not be resumed until field tests by the geotechnical engineer indicate that the moisture content and density of the fill are as previously specified. In the event that, in the opinion of the engineer, soils unsatisfactory as foundation material are encountered, they shall not be incorporated in the grading; disposition will be made at the engineer I s discretion. 5 "" -; .. -.. .. ill C C APPENDIXF C C C C C C [ [ C [ C C C C Design Maps Summary Report IIUSGS Design Maps Summary Report User-Specified Input Report Title 400 Gibraltar Street, Carlsbad Mon December 10, 2018 18 35:55 UlC Building Code Reference Document ASCE 7-10 Standard (which utilizes USGS hazard data available in 2008) Site Coordinates 33.0859°N, 117.2475°W Site Soll Classlflcatlon Site Class D -"Stiff Soil" Risk Category I/II/III c.lsb..r USGS-Provlded Output s. = 1.042 g S, = 0.403 g s .. = 1.129 g SN1 = 0.643 g Sos= 0.752 g So1 = 0.429 g For information on how the SS and S1 values above have been calculated from probabilistic (risk-targeted) and deterministic ground motions in the direction of maximum horizontal response, please return to the application and select the "2009 NEHRP" building code reference document. ""' i 11,:: ;i "'" u,IH MCE• Respollff Sp«tn,m For PGAM, TL, c .. , and c., values, please view the detailed report. l>ffllm Rnponsl' Spectrum 1 ') /1 {\/'){\ 1 0 Design Maps Detailed Report ■IJSGS Design Maps Detailed Report ASCE 7-10 Standard (33.0859°N, 117.2475°W) Site Class D -"Stiff Soil", Risk Category I/II/III Section 11.4.1 -Mapped Acceleration Parameters Note: Ground motion values provided below are for the direction of maximum horizontal spectral response acceleration. They have been converted from corresponding geometric mean ground motions computed by the USGS by applying factors of 1.1 (to obtain Ss) and 1.3 (to obtain 51), Maps in the 2010 ASCE-7 Standard are provided for Site Class B. Adjustments for other Site Classes are made, as needed, in Section 11.4.3. From Figure 22-1 111 Ss = 1.042 g From Figure 22-2 121 S1 = 0.403 g Section 11.4.2 -Site Class The authority having jurisdiction (not the USGS), site-specific geotechnical data, and/or the default has classified the site as Site Class D, based on the site soil properties in accordance with Chapter 20. Table 20.3-1 Site Classification Site Class Vs Nor N.., A. Hard Rock >5,000 ft/s N/A --B. Rock 2,500 to 5,000 ft/s N/A -Su N/A N/A C. Very dense soil and soft rock 1,200 to 2,500 ft/s >50 >2,000 psf Page I of 6 D. Stiff Soil 600 to 1,200 ft/s 15 to SO 1,000 to 2,000 E. Soft clay soil F. Soils requiring site response analysis in accordance with Section 21.1 psf <600 ft/s <15 <1,000 psf Any profile with more than 10 ft of soil having the characteristics: • Plasticity index PI > 20, • Moisture content w ~ 40%, and • Undrained shear strength Su < 500 psf ------ See Section 20.3.1 For SI: lft/s = 0.3048 m/s 11b/ft2 = 0.0479 kN/m2 https://prod02-earthquake.cr.usgs.gov/designmaps/us/report. php?template=minimal&lati... 12/10/2018 .. -----------------------.. ------------- Design Maps Detailed Report Page 2 of 6 Section 11.4.3 -Site Coefficients and Risk-Targeted Maximum Considered Earthquake (MCER) Spectral Response Acceleration Parameters Site Class A B C D E F Site Class A B C D E F Table 11.4-1: Site Coefficient F. Mapped MCE R Spectral Response Acceleration Parameter at Short Period Ss ::5 0.25 Ss = 0.50 Ss = 0.75 Ss = 1.00 0.8 0.8 0.8 0.8 1.0 1.0 1.0 1.0 1.2 1.2 1.1 1.0 1.6 1.4 1.2 1.1 2.5 1.7 1.2 0.9 See Section 11.4. 7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of Ss For Site Class= D ands.= 1.042 g, F. = 1.083 Table 11.4-2: Site Coefficient F. Ss ~ 1.25 0.8 1.0 1.0 1.0 0.9 Mapped MCE R Spectral Response Acceleration Parameter at 1-s Period S1 ::5 0.10 S1 = 0.20 S1 = 0.30 S1 = 0.40 S1 ~ 0.50 0.8 0.8 0.8 0.8 0.8 1.0 1.0 1.0 1.0 1.0 1.7 1.6 1.5 1.4 1.3 2.4 2.0 1.8 1.6 1.5 3.5 3.2 2.8 2.4 2.4 See Section 11.4. 7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of S1 For Site Class = D and s. = 0.403 g, F. = 1.597 https:/ /prod02-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&lati... 12/10/2018 Design Maps Detailed Report Equation (11.4-1): SMs = F.Ss = 1.083 X 1.042 = 1.129 g Equation (11.4-2): SMl = FvS1 = 1.597 X 0.403 = 0.643 g Section 11.4.4 -Design Spectral Acceleration Parameters Equation (11.4-3): Sos =½ SMs = ½ X 1.129 = 0.752 g Equation (11.4-4): S01 = ½ SM1 = ½ X 0.643 = 0.429 g Section 11.4.5 -Design Response Spectrum From Figure 22-12 13l TL = 8 seconds Figure 11.4-1: Design Response Spectrum I j I tll Sr.,.= 0 752 I T < T0 : S0 = S.. ( 0.4 + 0.6 TIT 1 ) T,sTsT,:S.=S01 r, <rs TL : s. = s01 , T T>TL: s. = SOITL/1'1 Si,1 = OA 29 --,-----------" ---------I T•=0.11-1 T, = 0 570 1.000 l'ntlld. T t,tt) Page 3 of 6 https://prod02-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&lati... 12/10/2018 Design Maps Detailed Report Page 4 of 6 Section 11.4.6 -Risk-Targeted Maximum Considered Earthquake {MCER) Response Spectrum The MCE. Response Spectrum is determined by multiplying the design response spectrum above by 1.5. i • Ill I 1 i Ill s~t< = 1.129 I S~11 = 0.643 _,_ ----------I To=0.114 Ts = 0.570 1.000 Ptrlod, T(e:) https://prod02-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&lati... 12/10/2018 Design Maps Detailed Report Page 5 of 6 Section 11.8.3 -Additional Geotechnical Investigation Report Requirements for Seismic Design Categories D through F From Figure 22-7141 PGA = 0.405 Equation (11.8-1): PGA,.. = FPGAPGA = 1.095 x 0.405 = 0.443 g Table 11.8-1: Site Coefficient F,... Site Mapped MCE Geometric Mean Peak Ground Acceleration, PGA Class PGA ~ PGA = PGA = PGA = PGA :2': 0.10 0.20 0.30 0.40 0.50 A 0.8 0.8 0.8 0.8 0.8 B 1.0 1.0 1.0 1.0 1.0 C 1.2 1.2 1.1 1.0 1.0 D 1.6 1.4 1.2 1.1 1.0 E 2.5 1.7 1.2 0.9 0.9 F See Section 11.4. 7 of ASCE 7 Note: Use straight-line interpolation for intermediate values of PGA For Site Class = D and PGA = 0.405 g, F.,.. = 1.095 Section 21.2.1.1 -Method 1 (from Chapter 21 -Site-Specific Ground Motion Procedures for Seismic Design) From Figure 22-17 c5i CRs = 0.970 From Figure 22-18 1•1 CR1 = 1.028 https://prod02-earthquake.cr.usgs.gov/designmaps/us/report.php?template=minimal&lati... 12/10/2018 -.. ------------------- -------------.. -- Design Maps Detailed Report Section 11.6 -Seismic Design Category Table 11.6-1 Seismic Design Category Based on Short Period Response Acceleration Parameter RISK CATEGORY VALUE OF Sos I or II III IV Sos< 0.167g A A A 0.167g :5i Sos < 0.33g B B C 0.33g :5i Sos < O.SOg C C D 0.50g :5i Sos D D D For Risk Category= I and Sos= 0.752 g, Seismic Design Category= D Table 11.6-2 Seismic Design Category Based on 1-5 Period Response Acceleration Parameter RISK CATEGORY VALUE OF So1 I or II III IV So1 < 0.067g A A A 0.067g :5i So1 < 0.133g B B C 0.133g :5i So1 < 0.20g C C D 0.20g :5i So1 D D D For Risk Category = I and So1 = 0.429 g, Seismic Design Category = D Note: When 51 is greater than or equal to 0.75g, the Seismic Design Category is E for buildings in Risk Categories I, II, and III, and F for those in Risk Category IV, irrespective of the above. Seismic Design Category = "the more severe design category in accordance with Table 11.6-1 or 11.6-2" = D Note: See Section 11.6 for alternative approaches to calculating Seismic Design Category. References 1. Figure 22-1: Page 6 of 6 https ://earthquake. usgs.gov/hazards/desig nmaps/downloads/pdfs/201 O_ASCE-7 _Figure_22-1.pdf 2. Figure 22-2: https://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7 _Figure_22-2.pdf 3. Figure 22-12: https ://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7 _Figure_22-12. pdf 4. Figure 22-7: https ://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/201 O_ASCE-7 _Figure_22-7. pdf 5. Figure 22-17: https ://earthquake. usgs.gov/hazards/designmaps/downloads/pdfs/201 O_ASCE-7 _Figure_22-17. pdf 6. Figure 22-18: https://earthquake.usgs.gov/hazards/designmaps/downloads/pdfs/2010_ASCE-7 _Figure_22-18.pdf https:/ /prod02-earthquake.cr. usgs.gov /designmaps/us/report. php?template=minimal&lati ... 12/10/2018 \