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HomeMy WebLinkAboutHMP 15-01; MARTIN RESIDENCE; GEOTECHNICAL PLAN REVIEW; 2013-11-07""' -.. .. -- --.. ------ - - - -- --- .. - - Geotechnical Plan Review Update Proposed Single-Family Residential Development . Adams Street; Carlsbad (A.P;N. 206-200-03) November 7, 2013 Prepared For: Mr. Neil A. Martin 1878 Shadetree Drive San Marcos, California 92078 Prepared By: VINJE & MIDDLETON ENGINEERING, INC. 2450 Auto Park Way Escondido, California 92029 Job #13-234-P ... .... •. ..... - - ---- - - ----- -- - - GEOTECHNICAL PLAN REVIEW UPDATE PROPOSED SINGLE-FAMILY RESIDENTIAL DEVELOPMENT ADAMS STREET, CARLSBAD (A.P .N. 206-200-03) I. INTRODUCTION Project most current Preliminary Grading Plan for the proposed single-family residential construction at the above-referenced property, prepared by So:wards & Brown Engineering (dated October 15, 2013), was provided to us for review and comments. A copy of the Preliminary Grading Plan is reproduced herein and included with this transmittal as a Geotechnical Map, Plate 1. The project property is a vacant lot located on a modest south facing hillside on the north margin of the Agua Hedionda Lagoon, within the limits of City of Carlsbad. Approximate site location is shown on a Vicinity Map included on Plate 1. The approximate site coordinates are 33.1450 ° N latitude and -117.3268 °W longitude. Surface and subsurface geotechnical conditions at the project property, and adjacent properties, were previously studied by this office for the purpose of a planned residential development, as proposed at that time. Our findings, conclusions, and recommendations were presented in the following written technical report: "Preliminary Soil and Geotechnical Investigation Parcels A, 8, C APN # 260-200-03, 04, & 05 Adams Street Carlsbad, California" Job #98-257-P, report dated August 10, 1998. The referenced report was reviewed in connection with this effort and a copy is attached to this transmittal as and an Attachment. The project property is designated as Parcel A in the referenced report. The purpose of this work was to review the project Preliminary Grading Plan to assure its compatibility with the site indicated geotechnical conditions as presented in the referenced report, and to provide update and/or amended recommendations consistent with the current codes and engineering standards. The updated and/or amended recommendations provided in the following sections wiUsupplement or supersede those given in the attached report where specifically applicable. Our effort in connection with the preparation of this update report also included a site visit by our engineering geologist on August 22, 2013 to observe current surface conditions. A shallow test pit was also excavated during our recent site visit for collection of a representative soil sample used to perform additional pertinent laboratory testing. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way • Escondido, California 92029-1229 • Phone (760) 743-1214 - -... --... .. -.. --- ... --• .. --- --- Geotechnical Plan Review Update, Proposed Single-Family Residential Page 2 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 II. SITE DESCRIPTION . Based on our recent site visit, the project property remains substantially unchanged from conditions described in the attached report. The project property chiefly consists a modest south facing natural hillside that descends from Adams Street to the Agua Hedionda Lagoon at gradients generally approaching 4: 1 maximum. Surface areas are locally mantled by grass and weeds. Site drainage is sheetflows over the terrain to the lagoon. Excessive scoudng or erosion is not in evidence at the property Ill. PROPOSED DEVELOPMENT The project Preliminary Grading Plan (Plate 1) depicts the construction of a multi-level single-family residential strL,Jcture in the central portion of the property. Access to the residence will be provided from Adam Street via a S-shaped driveway that descends at gradients approaching 20% maximum to a level motor court and detached garage. Retaining walls and backfills against the garage northern basement type wall approaching 12 feet high are incorporated into the design for achieving the upper driveway profiles and lower motor court/garage pad grades near 51 feet elevation above mean sea level (MSL). The residence will consist of split level construction with a lower basement type floor proposed at near 33 feet and 36 feet elevation (MSL). Vertical cut excavations on the order of 12 and transition retaining wall on the order of 15 feet high are proposed for establishing residence's lower basement grades and upper floor levels at 51 feet elevation • (MSL) near the motor court/garage grades. Associated improvements will consist of a swimming pool and spa with surrounding concrete decking along the lower southern margins near 37 feet elevation (MSL), concrete stairs and transition retaining walls. Also included are bio retention basins with gravels and perforated pipes along the eastern and western property margins which will connect to storm drain facilities, underground BMP vaults, and BMP cistern . Exposed graded cut or fill embankments are not planned . All ground transitions will be achieved by retaining and building basement type walls. Project earthwork associated with development of level building surfaces will chiefly consist of cut excavations and wall backfilling operations. Actual earthwork quantities are currently unknown, however, it is anticipated that the project will chiefly be a balanced grading operation. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 - - ... ◄ -- ... ----- 11111 - ---- - --- - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 4 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 Explanation: Ss: Mapped MCE, 5% damped, spectral response acceleration parameter at short periods. S1: Mapped MCE, 5% damped, spectral response acceleration parameter at a period of 1-second. Fa: Fv: Site coefficient for mapped spectral response acceleration at short periods. Site coefficient for mapped spectral response acceleration at 1-second period. SMs: The MCE, 5% damped, spectral response acceleration at short periods adjusted for site class effects (SMs=FaSs). Sos: So1: The MCE, 5% damped, spectral response acceleration at a period of 1-second adjusted for site class effects (SM1=FvS1) . Design, 5% damped, spectral response acceleration parameter at short periods (Sos=%SMs). Design, 5% damped, spectral response acceleration parameter at a period of 1-second (So1=%SM1 ). Site peak ground accelerations(PGA) based on 2 percent probability of exceedance in 50 years defined as Maximum Considered Earthquake (MCE) with a statistical return period of 2,475 years is also evaluated herein in accordance with the requirements of CBC Section 1613 arid ASCE Standard 7-05. Based on our analysis, the site PGAMcE was estimated to be 0.54g using the web-based United States Geological Survey (USGS) ground motion calculator. The design PGA determined as two-thirds of the Maximum Considered Earthquake (MCE) was estimated to be 0.36g. VI. ADDITIONAL SAMPLING·, LABORATORY TESTING AND TEST RESULTS A shallow test pit was excavated at a selected location as part of this effort to collect a representative sample of onsite near surface soils for subsequent added laboratory testing for a corrosion assessment in the support of this update study. The following added tests were completed on the recently collected sample and will supplement those previously performed and presented in the enclosed Attachment: 1. pH and Resistivity Test: pH and resistivity of representative near surface soils was determined 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 4. TABLE 2 L :·s;~m~Ie;~q_a~H~1\:· ~'.A i,:;,. >> ~<l:.s.:~u·;ty'e~<;;;:; .;:::: :;' n.;~.:t~ini~Jm:f1.t~~,~t1.vli~:1BMl,1f~M1\.:,1.; + ::;eH. ::· ._ ~--1 I Surface Soil I Red brown silty sand I 1848 I 6.9 I YINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 7;43-1214 ... - -.. ... - ----- - ,,,. - ... -- ... ------- -- - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 7 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 IX. CONCLUSIONS & RECOMMENDATIONS The project most current development plan, reproduced herein as Plate 1, proposes a feasible construction method considering site indicated geotechnical conditions . Geotechnical conditions reported in the referenced report dated August 10, 1998 (Attachment) remain unchanged, and all conclusions and recommendations provided therein are valid . Conclusions and recommendations provided in the referenced report should be incorporated into the final designs and implemented during the construction phase except where specifically superseded or amended below. Landslides, faults or significant shear zones are not present at the project property and are not considered a geotechnical factor in planned 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 factor in the development of the project property provided our earthworks and foundation recommendations are followed . The following are appropriate: 1. The project redevelopment will consist of the construction of a multi-level residential development as depicted into the enclosed Plate 1. Modest ground alterations are proposed to establish final pad grades and achieve design elevations. 2. Construction of large graded cut and fill slopes are not proposed in connection with the planned ground modifications and building pad development. Elevation differences between building surfaces will be achieved by the construction of site and building basement type retaining walls as shown on the enclosed Plate 1 . 3. Project anticipated earthwork operations will chiefly consist of basement type excavations, remedial grading, and backfilling behind the transition retaining walls. Actual earthwork quantities are unknovvn at this time, however, the project development may be expected to balance . 4. Removals of all existing vegetation, trees, roots, stumps, underground tanks, pipes, conduits and all other unsuitable materials and deleterious matter from the project development areas should be completed as specified in the referenced report. All trash, debris, organic matter and unsuitable materials generated from site clearing efforts should be properly removed and disposed of from the site. 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. The prepared ground should be inspected and approved by the project geotechnical consultant or his designated field representative prior to grading and earthworks. VINJE & MIDDLETON ENGINEERING, I NC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 .. -- .. -... --.. -.... .. ------.. .. - -.. - - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 8 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 5. The property is generally mantled by shallow deposits of existing loose surficial soil over dense and competent Terrace Deposits and formational rocks. Regrading of the upper compressible.soil mantle should be completed in order to construct safe and stable building and improvement surfaces. All excavations, grading, earthworks, foundation constructions and bearing soil preparations should be completed iri accordance with Chapter 18 (Soils and Foundations) and Appendix "J" (Grading) of the 2010 Californi_a Building Code . (CBC), the Standard Specifications for Public Works Construction, City of Carlsbad Grading Ordinances, and requirements of the referenced report (Attachment) and this update transmittal, wherever appropriate and as applicable. 6. All site existing surficial soils and upper weathered exposures of the underlying Terrace Deposits and formational rocks in the areas of planned· new fills, buildings, improvements, drainage facilities, structures, and improvements plus 10 horizontal feet outside the perimeter, where possible and as directed in the field, should be removed (stripped) to the underlying dense , and competent Terrace Deposits/formational rocks, as approved in the field , and recompacted. Actual removal (stripping)· depths should be established by the project geotechnical consultant at the time of remedial grading operations based on exposed field conditions. Typical removal depths based on available subsurface exploratory excavations are expected to range to nearly 7 feet below the existing ground ·surfaces. Locally deeper removals may be necessary as directed in the field and should be anticipated. Bottom of all removals should be additionally prepared and recompacted in-place to a minimum depth of6 inches as directed in the field . All ground steeperthan 5:1 receiving fills or backfills should also be properly benched and keyed as directed in the field. Exploratory test pits excavated in connection with the original study at the indicated locations (see Plate 1) 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 . 7. Daylight filling is proposed against the Adams Street road embankment to achieve final design grades. For this purpose, the existing roadway embankment should be properly cleared and grubbed, adequately benched out and new fills/wall backfills tightly keyed into the prepared slope as directed in the field. 8. Wall backcut excavations on the order of 12 feet will be needed for portions of the lower level basement wall type constructions. Added care will be required to avoid any undermining or damages to the adjacent structures and improvements to remain, neighboring properties, public right-of-ways , and nearby street improvements due to site excavations, earthwork grading and construction works. Y INJE & MIDDLETON E NGINEER.ING, INC. 0 2450 Auto Park Way • Escondido, California 92029-1 229 • Phone (760) 743-1214 - -.. .. .... - ... -... ------ - - , ... ---- --- - - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 9 Development, Adams Street, Carlsbad (A.P .N. 206-200-03) November 7, 2013 All site excavations, removals and trenching should be performed under observations of the project geotechnical engineer. Top of temporary construction slopes should be adequately set-back from the adjacent property lines, existing foundations and nearby 'improvements as directed and approved in the field. Temporary wall backcut and basement excavations developed into the project dense Terrace Deposits and formational rock units may be constructed at near vertical gradients up to a maximum height of less than 10 feet, unless otherwise noted or directed in the field. However, limited alternate vertical cut slot-excavations or shoring support may also become required based on actual field exposures and condition of existing adjacent structures and improvements to remain, as determined in the field. For limited alternate vertical cut slot excavations, the entire excavation slope should be first laid back at 1 :1 gradients maximum. Subsequently, alternate sections may be cut at vertical gradients. For this purpose, limited initial sections are cut and construction of transition or building basement type retaining walls is completed. Upon approval of the project engineer, vertical sections are then excavated and wall construction in the remaining alternate areas are followed. Stockpiling the excavated materials or establishing equipment staging areas near the top of excavations should not be allowed. Face of temporary slopes and backcut excavations should be protected from excessive runoff or rainfall. Continuous shoring support may also be required for local exposures where stability of excavations or its potential impacts on the adjacent foundations, neighboring properties, underground facilities or public right-of-way becomes a concern, as determined in the field. In this case, any effective shoring system suitable to the site subsurface conditions such as drilled reinforced cast-in-place piles with concrete or wood lagging, closely spaced cast-in-place mini-piles, or tie-backs with reinforced shot-crete facing may be considered. Specific shoring designs should be provided by the project geotechnical consultant, if becomes necessary. Surficial soils including existing fills, topsoil, and colluvial deposits exposed within upper portions of larger (greater than 5 feet) temporary slopes or wall backcut excavations should be laid back at 1 :1 gradients. Elsewhere, project excavations and trenching developed within the site surficial soils may be constructed at near vertical gradients to a maximum total height of 5 feet, unless otherwise directed in the field. Larger excavations and trenching should be laid back at 1 :1 gradients or provided with trench shield or shoring support, unless otherwise directed in the field. The exposed wedge of laid back backcut slopes should be properly benched out and new backfills tightly keyed-in as the fill placemerit progresses. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 - --... ... .. ... -- - - ""' ----- -· ---- - Geotechn_ical Plan Review Update, Proposed Single-Family Residential Page 10 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 Site excavations, temporary slope, trenching and wall backcuts will requ ire continuous geotechnical observation during the constructions. Continuous monitoring will be required for the protection of workmen and nearby foundations, properties and public improvements in the case of the exposed vertical backcuts and temporary slopes. Potential surficial failures, if any identified, should be removed to reestablish safe conditions and hard hats shall be worn at all time . Construction slopes exposing potentially adverse bedding or fractured conditions or loose fill deposits will be subject to revised recommendations including more gentle gradients, laid back backcuts, smaller alternate slot-excavations or possible shoring. The project contractor shall also obtain appropriate perm_its, as needed, and conform to the CAL-OSHA and local governing agencies requirements for trenching/open excavations and safety of the workmen during construction. Excavation permits shall also be obtained from the adjacent property owner(s) or public agencies, if appropriate and applicable. 9. Ground transition from excavated cut to compacted fills should not be permitted underneath the proposed buildings, structures, and improvements (including paving, utilities and drainage structures), unless otherwise specifically designed. Site structural foundations, slabs, and improvements should be supported uniformly on · compacted fills or founded entirely on competent cut ground exposing dense undisturbed Terrace Deposits or formational rocks. Transition pads and bearing/subgrade daylight exposures will require special earthwork mitigation or design methods. The cut portion of the cut-fill transitions plus 5 feet outside the perimeter, where possible and as directed in the field, should be undercut to a sufficient depth to provide for 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(s), whichever is more. Alternatively, foundations straddling over cut-fill daylight lines may be designed as grade beams with heavier re inforcements. Specific recommendations should be provided by the project geotechnical consultant at the foundation plan review phase. In the improvement areas, there should be a minimum of 12 inches of compacted fill below rough finish subgrade, as directed in the field. 10. Soil generated from the site removals, stripping, excavations and over-excavations are generally considered suitable for reuse as site new fills and backfills. However, excavations of clayey surficial deposits are also expected to generate some expansive soils which should be mixed with an abundance of site sandy soils to manufacture a very low expansive mixture or adequately buried in deeper fills 3 feet below rough pad grades (or 12 inches below the deepest footing, whichever is more). Expansive clayey soils are also not suitable for wall and trench backfills and good sandy granular soil should be used for this purpose. VINJE & MIDDLETON ENGINEERING, I NC. • 2450 Auto Park Way • Escondido, California 92029-1229 • Phone (760) 743-1214 ... - .. .. -- - -.. -- -· ------ --- ·---- - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 11 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 Import soils, if used, should be non-corrosive, very low expansive sandy granular soils (100% passing 1-inch sieve, more than 50% passing #4 sieve and less than 18% passing #200 sieve with expansion index less than 20), inspected, tested as necessary, and approved by the project geotechnical consultant prior to delivery to the site. Import soils should also meet or exceed the design parameters given in the following sections. 11 . Fill and backfill materials, processing, placement, compaction procedures and requirements, as well as engineering observations and testing protocol will remain the same as specified in the referenced report. Uniform bearing and subgrade soil conditions should be constructed at the site by the grading operations. Site fills should be adequately processed, thoroughly mixed, moisture conditioned to slightly above (2%-3%) the optimum moisture levels as directed in the field, placed in thin (8 inches maximum) uniform horizontal lifts and mechanically compacted with heavy construction equipments to a minimum 90% of the corresponding laboratory maximum dry density per ASTM 0-1557, unless otherwise_specified. The upper 12 inches of subgrade soils below the base layer under roadway asphalt paving surfaces should also be compacted to minimum 95% compaction levels. 12. Shallow stiff stem wall/stepped and spread pad foundations may be considered for the support of the proposed buildings and structures. Shallow foundations should be uniformly founded on undisturbed competent formational rocks or well compacted fills as approved in the field by the project geotechnical consultant. Continuous strip concrete foundations should be sized at least 15 inches wide and 18 inches deep. Spread pad footings, if any, should be at least 30 inches square and 18 inches deep and structurally interconnected with the continuous strip footings with grade beams. 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 footings should enclose the entire building perimeter. Continuous interior and exterior foundations should be reinforced with a minimum of 4-#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. Grade beams should also be reinforced with minimum 2-#4 bars top and bottom. Reinforcement details for spread pad footings should be provided by the project architect/structural engineer. Foundations can only be constructed on level surfaces and should be stepped in sloping ground conditions (more than 1 unit vertical in 10 units horizontal or 10%), as necessary. Top and bottom of stepped foundations shall be level. Individual steps in continuous footings shall not exceed 18 inches in height and the slope of a series of such steps shall not exceed 1 unit vertical to 2 units horizontal (50%) VJNJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 - ---... 1111 . ... .. .. ----- ---- ----- Geotechnical Plan Review Update, Proposed Single-Family Residential Page 12 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 unless otherwise specified. The steps, and foundation reinforcement requirements shall be designed by the project structural consultant and detailed on the project structural drawings. The local effects due to the discontinuity of the steps shall also be considered in the design of foundations as appropriate and applicable; 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. There should be minimum 7 feet horizontal setback from the bottom outside edge of the footing to daylight for foundations, and at least 10 feet to daylight for swimming pools and more sensitive structures which cannot tolerate minor movements . 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 near the slab mid- height. Slabs should be underlain by at least 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 are used . Provide re-entrant corner reinforcement for all interior slabs per Plate 8 of the referenced report. Interior slabs should also be provided with "softcutll contraction/control joints consisting of sawcuts 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 2 hours after final finish at each control joint location or 150 psi to 800 psi. The softcuts should be a minimum of 1-inch in depth but should not exceed 1 ¼-inches 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. * 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. 13. Post construction settlement after completion of grading works as specified herein, is not expected to exceed approximately 1-inch and should occur below the heaviest loaded footing(s). The magnitude of post construction differential settlements of site fill deposits as expressed in terms of angular distortion is not anticipated to exceed ½-inch between similar elements in a 20-foot span. V INJE & MIDDLETON ENGINEERING, I NC. • 2450 Auto Park Way • Escondido, California 92029-1 229 • Phone (760) 743-1214 ... .. .. ... .. -.... - --.. -- ---.. - -- - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 13 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 14. Soil design parameters including bearing and·lateral earth pressures, will remain the same as specified in the referenced reports (see Attachment). However, an additional seismic force due to seismic increment of earth pressure may also be appropriate in the project designs in case of building walls with greater than 6-feet soil differential on each side or retaining walls 12 feet or taller, as determined by the project design consultant. A seismic lateral inverted triangular earth pressure of 21 pcf (EFP) acting at 0.6H (His the retained height) above the base of the wall should also be considered, if appropriate and applicable. The seismic lateral earth pressure should be considered in addition to the specified static earth and surcharge (due to nearby foundations and vehicular traffic loading) pressures. 15. All exterior slabs (walkways, patios, pool decks, etc.) supported on very low expansive subgrade soils should be a minimum of 4 inches in thickness, reinforced with 6X6-10X10 welded wire mesh carefully placed near the slab mid-height. The subgrade soils should be compacted to minimum 90% compaction levels atthetime of fine grading and before placing the slab reinforcement. Reinforcements lying on sub grade 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 (dowel baskets) at 18 inches on centers maximum placed mid-height in the slab (9 inches on either side of the joint). 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% 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 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 exceed 1 ¼- inch deep maximum. In case of softcutjoints, 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. • Joints shall intersect free-edges at a 90° angle and shall extend straight for a minimum of 1½ feet from the edge. The minimum angle between any two intersecting joints shall be 80°. 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.) . V 1NJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way • Escondido, California 92029-1229 • Phone (760) 743-1214 ,.. -- .. .. - .. .. ---- """ .. - ' ----- ---- - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 14 Development, Adams Street, Carlsbad (AP.N. 206-200-03) November 7, 2013 All exterior slab designs should be confirmed in the final as-graded compaction report. 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 . 16. Specific pavement designs can 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 initial planning phase cost estimating purposes only (not for construction): * A minimum section of 4 inches asphalt on 6 inches Caltrans Class 2 aggregate base or the minimum structural section required by City of Carlsbad, whichever is more, may be co_nsidered for t~e on-site asphalt paving surfaces outside the private and public right-of-way. -The Class 2 aggregate base shall meet or exceed the requirements set forth in the , current California Standard Specification (Caltrans Section 26-1 .02). In the areas where the longitudinal grades exceed 10%, ½-inch asphalt should be added to the design asphalt thickness for each 2% increase in grade or portions thereof. PCC paving should be considered for longitudinal grades greater than 15% maximum. Actual design will also depend on the design Tl and approval of the City of Carlsbad. * Base materials should be compacted to a minimum 95% of the corresponding maximum dry density (ASTM D-1557). Subgrade soils beneath the asphalt paving surfaces should also be compacted to a minimum 95% of the corresponding maximum dry densitywithin the upper 12 inches. 17. Residential PCC driveways and parking supported on very low expansive (expansion index less than 20) granular subgrade soils should be a minimum 5½ inches in thickness, reinforced with #3 reinforcing bars at 18 inches on centers each way placed at mid-height in the slab. Subgrade soils beneath the PCC driveways and parking should also be compacted to a minimum 90% of the corresponding maximum dry density. In the areas where longitudinal grades exceed 15%, provide minimum 8 inches wide by 8 inches deep pavement anchors dug perpendicularto the pavement longitudinal profile into the approved subgrade at each 25-feet interval maximum. The pavement anchors should be poured monolithically with the concrete paving surfaces. Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center (not to exceed 15 feet maximum) each way. The larger dimension of any panel shall not exceed 125% of the smaller dimension. Tool or cut as soon as the slab will support the weight and can be operated ~ithout disturbing the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to V INJE & M lDDLETON ENGINEERING, I NC. • 2450 Auto Park Way• Escondido, California 92029-J229 • Phone (760) 743-1214 ---.. - .. ... --- - - - - - - - .. -- - - Geotechnical Plan Review Update, Proposed Single-Family Residential . Page 15 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 800 psi. Tool or softcuts should be a minimum of 1-inch in depth but should not exceed 1 ¼-inches 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. Joints shall intersect free edges at a 90° angle and shall extend straight for a minimum of 1½ feet from the edge. The minimum angle between any two intersecting joints shall be 80°. Align joints of adjacent panels. Also, align joints in attached curbs with joints in slab panels. Provid·e adequate curing using approved method (curing compound maximum coverage rate= 200 sq. ft./gal.) . 18. The pool and spa excavations are expected to chiefly expose dense undisturbed Terrace Deposits with very low expansive potential. Project natural undisturbed Terrace Deposits will adequately support the planned new pool and spa, however, pool/spa designs and construction should be completed based on very low expansive soils (expansion index 20) and lateral earth pressures provided in this · report. The pool and spa shells should also be provided with a minimum 15 inches wide by 18 inches deep perimeter grade beam reinforced with minimum 2-#4 bars top and bottom around the top of the concrete shell. Pool/spa shell thickness and reinforcements per structural details. Deepened pool wall foundations shall be required for the southern outside pool wall(s) planned on the adjacent descending slope to provide a minimum of 10 feet horizontal distance or set back to daylight. Reinforcement for deepened footings should be provided by the project architect/structural engineer. • 19. A well-constructed back drainage .system should be installed behind all site and building basement type retaining walls at the project site.. The wall back drainage system should consist of a minimum 4-inch diameter, Schedule 40 (SDR 35) perforated pipe surrounded with'a minimum of 1½ 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 where they daylight or graded or natural surfaces. All subdrain pipes and outlet locations should be shown on the final grading or site plan. A typical wall back drain system is depicted on the Plate 9 of the referenced report (see Attachment). Provide appropriate waterproofing where applicable as indicated on the pertinent project construction plans. VINJE & MIDDLETON ENGINEERING, !Ne. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 - --... -.. -- -· ---.. ----- - - -- .. -- - Geotechnical Plan Review Update, Proposed Single-Family Residential Page 16 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 20. Control of site surface drainage and potential for development of post construction subsurface water caused by surface water infiltrations is one of the most significant geotechnical factors with regards to the future performance of the new building site with lower basement type level and associated improvement and structures. Surface flow, run-off drainage and subsurface water should not impact graded surfaces, saturate site fills, wall backfills, bearing and subgrade soils, or cause erosion. Drainage structures and erosion control measurements should be provided at as discussed in the referenced report and shown on the project grading and drainage improvement plans. 21. 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%) from a line 9 inches above the bottom edge of the footing, and not closer than 18 inches from the face of such footing. 22. 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. X. GEOTECHNICAL ENGINEER OF RECORD (GER) Vinje & Middleton Engineering, 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, Vinje & Middleton Engineering, 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 Job.s Between Consultants. 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 Vinje & Middleton Engineering, 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). VINJE & MIDDLETON E NGJNEERING, !Ne. • 2450 Auto Park Way • Escondido, California 92029-1229 • Phone (760) 743-1214 --- ---.. .. -- - -- - ... .... --- Geotechnical Plan Review Update, Proposed Single-Family Residential Page 17 Development, Adams Street, Carlsbad (A.P.N. 206-200-03) November 7, 2013 XI. LIMITATIONS The conclusions and recommendations provided herein have been based on all available data obtained from the review of pertinent geotechnical documents, current site observations, shallow sampling and added laboratory testing, 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/or natural exposures. 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 ifrequired. 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 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 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 corners, and floor surface cracks up to 1/a-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. 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 geotechnical engineer is not provided the opportunity of making these reviews, he can assume no responsibility for misinterpretation of his recommendations. VINJE & MIDDLETON ENGfNEERING, INC. • 2450 Auto Park Way • Escondido, California 92029-1 229 • Phone (760) 743-1214 ------ -- -- --- - •· - • -- ""' --- REFERENCES -Annual Book of ASTM Standards, Section 4 -Construction, Volume 04.08: Soil and Rock (I); D 420 -D 5876, 2012. -Annual Book of ASTM Standards, Section 4 -Construction, Volume 04.09: Soil and Rock (II); D 5876 -Latest, 2012. -Highway Design Manual, Caltrans. Fifth Edition. -Corrosion Guidelines, Caltrans, Version 1.0, September 2003. -California Building Code, Volumes 1 & 2, International Code Council, 2010. -"Green Book" Standard Specifications for Public Works Construction, Public Works Standards, Inc., BNi Building News, 2003 Edition. -California Department of Conservation, Division of Mines and Geology (California Geological Survey), 1997, Guidelines for Evaluating and Mitigating Seismic Hazards in California, DOG Special Publication 117, 71 p. -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. -EQFAUL T, 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 byT. Leslie Youd and lzzat 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, OM 7.01. -"Foundations & Earth Structures," Naval Facilities Engineering Command, OM 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, RecencyandCharacterofFaultingAlongtheElsinoreFaultZone 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, AL 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 of Geotechnical & Geoenvironmental Engineering, Volume 124, #4, 1998. -"Minimum Design Loads For Buildings and Other Structures," ASCE 7-05, American Society of Civil Engineers. - ... -.. - ----ATTACHMENT - ---- ... .,, ·- ... ------ - - - - - - - ... .. ------ - -.. ----- - - -- Preliminary Soil and Geotechnical Investigation Parcels A, B, C APN #260-20-03, 04 and 05 Adams Street Carlsbad, California August 10, 1998 Prepared For: Mr. Gene Huber The Prudential California Realty 523 Encinitas Boulevard, Suite 100 Encinitas, California 92024 Job #98=257-P ----------- -,.., -- --- ------.. ... - -- TABLE OF CONTENTS PAGE NO. I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 II. SITE DESCRIPTION . . . . .. .. . . .. . . . . . . . .. . . . .. . . . . . . . . . .. . .. . . . . . . . 1 Ill. PROPOSED DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 IV. SITE INVESTIGATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 V. FINDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 A. Earth Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 8. Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 C. Faults/Seismicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 D. Geologic Structure/Slope Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 E. Geologic Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 F. Laboratory Testing/Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 VI. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 VII. RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 A. Grading and Earthworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. Foundations and Slab-On-Grade Floors . . . . . . . . . . . . . . . . . . . . . . . . . . 11 C. Exterior Concrete Slabs/Flatworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 D. Soil Design Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 E. Asphalt Pavement Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 F. General Recommendations ..................................... 15 VIII. LIMITATIONS ................................................... 17 TABLES Fault Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Soil Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Maximum Dry Density and Optimum Moisture Content . . . . . . . . . . . . . . . . . . . . . 3 Moisture-Density Tests (Undisturbed Chunk Samples) ..................... 4 Direct Shear Test ..................................... -. . . . . . . . . . . . . . . 5 Expansion Index Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Removals and Over-Excavations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 PLATES Geotechnical Map ... II •• I •• II •••• I • a •••••••••••••••• 0 •••• I ••••• I •• I • II • • 1 Test Trench Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........... 2-5 Fault-Epicenter Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Geologic Cross-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Isolation Joints and Re~Entrant Corner Reinforcement . . . . . . . . . . . . . . . . . . . . . 8 Retainnng Wall Drain Detail ................. , . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - .... ·-- -- -- .. - ----- - -- .. - -- - Preliminary Soil and Geotechnical Investigation Parcels A, B, C I. INTRODUCTION APN #260-20-03, 04 and 05 Adams Street, Escondido, California The property investigated in this work is divided into three similar parcels. Parcel "A" - 4475 Adams Street, Parcel "B"-4485 Adams Street, and Parcel "C"-4495 Adams Street. They are contiguous hillside lots on the south side of Adams Street and adjacent to the Aqua Hedionda Lagoon in the City of Carlsbad. Consequently, the property location is shown on the Geotechnical Map, Plate 1. We understand the three parcels are planned for individual residential development and that Parcel B, will be developed first. Cut/fill grading is proposed to create level building surfaces for the residence and associated structures. Consequently, the purpose of this study was to determine the general site geologic and soil conditions and their influence on planned improvements. • • Test Trenches were excavated, and soil sampling and testing were performed in connection with this· investigation, which resulted in the ·development recommendations provided herein. II. SITE DESCRIPUON The subject parcels are rectangular shaped and encompass hillside terrain characterized by gentle slopes that descend southward to the shoreline of the Aqua Hedionda Lagoon. The property is in a natural condition overall and is mantled with wild grasses, weeds and scattered bush. Fill deposits .located along the upper reaches of the properties are likely derived from the grading activities for the cons_truction of Adams Street, and are shown on Plate 1. Site drainage sheet flows southward over project terrain with minor scouring in evidence. Groundwater was not encountered in project test excavations. Ill~ PROPOSED DEVELOPMENT The three parcels studied during this investigation are planned for individual residential development. Parcel B is planned to be developed first and Parcels A and C at a later date. We understand that cut-fill grading is planned to create level building surfaces for the residence and associated structures on Parcel B. Retaining walls will be utilized along the upper (north) margin. However, details of the proposed grading and foundation configuration are unknown. VINJE & MIDDLETON ENGINEERING, INC. 0 2450 Anto Park Way • Escondido, California 92029-1229 • Phone (760) 743-1214 -- - - --- - ---- --- -- ---- - PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 2 AUGUST 10, 1998 Detailed building plans were also not available for review at this time. IV. SITE INVESTIGATION The geotechnical conditions at the project lots were determined from geologic mapping of available surface exposures and the excavation of 8 test trenches dug with a tractor- mounted backhoe. The trenches were logged by our project geologist who also retained representative soil/rock samples for laboratory testing. Test results are presented in a following section. The test trench locations are shown on Plate 1 and the logs of the trenches are attached to this report as Plates 2-5. V. FINDINGS Study properties are chiefly natural hillside terrain underlain by sandstone bedrock units that a~e mantled by younger surface soils. A. Earth Materials The project site is underlain by tertiary to quaternary aged marine sedimentary sandstone . deposits, The older tertiary aged formational bedrock unit which is exposed in the lower reaches of the site is an off-white colored, fine to coarse grained, cemented, massive sandstone. Overlying this formational bedrock unit is the younger quaternary aged terrace deposit that is tan to light brown colored, fine to medium grained sandstone. Loose sand deposits also occur within the upper terrace deposit, as exposed in test trench T-7 (see plate 5). Colluvial and topsoil materials mantle the terrace deposit and consist of brown colored, silty sands to sandy clays that are in a loose to stiff condition. Fill soils comprised of brown colored, silty sands, are found along Adams Street and are in a dry and loose condition. Details of the earth materials at the project are given on the enclosed Plates 2-9. Laboratory tests are summarized in a following section. B. Groundwater Groundwater was hot encountered in our test trench excavations to the depths explored. However, like all hillside properties, the proper control of surface and near surface drainage is a critical element in the continued stability of the property. V JNJE & MIDDLETON E NGINEERING, I NC. • 2450 Auto Park Way • Escondido, California 92029-1229 • Phone (760) 743-1214 PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 4 AUGUST 10, 1998 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 County coastal areas with moderate to locally heavy ground shaking resulting 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 which 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 which includes a series of parallel breaks trending southward from La Jolla Cove through San Diego Bay toward the Mexican border. Recent trenching along the fault in Rose Canyon indicated that at that location the fault was last active 6,000 to 9,000 years ago. Thus, the fault is classified as "active" by the State of California which defines faults that evidence displacement in the previous 11,000 years as active. More active faults (listed on the preceding page) are considered most likely to impact the region during the lifetime of the project. The faults are periodically active and capable of generating moderate to locally high levels of ground shaking site. Ground separation as a result of seismic activity is not expected at the property. D. Geologic Structure/Slope Stability Large-scale landslide terrain are known to impact hillside terrain in the vicinity of the project site. The slides are related to weak earth materials or unsupported geologic structure in an inclined condition. V!NJE & MIDDLETON ENGINEERfrKi, INC. 0 2450 Auto Park Way• Escondido, Caiifornia 92029-1229 ° Phone (760; 743-1214 PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 8 AUGUST 10, 1998 * * * * Groundwater conditions were not encountered during our investigation and are not expected to be a problem in development of the site as planned. Potentially expansive clayey soils were indicated at the site and are expected to be in minor quantities (upper colluvium/topsoils). Attempts should be made to bury expansive soils in deeper fills below the upper three from the rough finish grade using the select grading techniques. Maximum post construction settlement is not expected to exceed approximately 1-inch, and should occur below the heaviest loaded footings provided our recommendations for remedial grading and site development are followed. The magnitude of post construction differential settlements (as expressed in terms of angular distortion) is not anticipated to exceed ½-inch between similar elements, in a 30-foot span. Liquefaction and seismically induced settlements and will not impact the proposed development and structures provided our recommendations for remedial grading and site development are followed. • Soil collapse will not be a factor in development of the study site provided our recommendations for site development are followed. VII. RECOMMENDATIONS The following recommendations are consistent with the project geotechnical conditions. Recommendations given below should be incorporated in to final plans and implemented during the construction phase. A. Grading and Earthworks Conventional grading techniques may be used in order to achieve final design grades and improve soil conditions beneath the structures and improvements. All grading and earthworks should be completed in accordance with Appendix Chapter 33 of the Uniform Building Code, City of Carlsbad grading ordinances and the requirements of the following section wherever applicable. 1. Clearing and Grubbing: Surface vegetation and other deleterious materials should be removed from areas to receive fills, structures and improvements. Removals should be inspected and approved by the project geotechnical engineer or his designated field representative prior to grading. VINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760.J 743-1214 -.. --- -.. --- -- -- - - - -- ------ PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 10 AUGUST 10, 1998 difficulties during removal and construction operations. Grading scheme and project architectural plans were not available to us at the time of preparation of this report. Mitigation will depend on design grades/architect plan and may include temporary shoring, soil treatment using grading options and in- situ soil improvement techniques. Appropriate recommendations should be given by the project soil engineer at the time of grading and foundation plan review when details of construction are known . Elsewhere temporary construction slopes required during removal operations should not exceed 1: 1 gradients maximum. Minor sloughing the temporary slopes may occur and should be anticipated. 5. Fill Materials/Compaction: Removed soils are suitable for reuse as compacted site fill. Fill soils should be moisture conditioned to near optimum levels and mechanically compacted in thin, horizontal lifts to at least 90% of the corresponding laboratory maximum density value per ASTM D-1557-91 unless otherwise specified. 6. Graded Slopes: Graded cut and fill slopes at the project site should be programmed for 2: 1 gradients maximum. Cut and fill slopes constructed at 2: 1 gradients will be grossly stable with respect to deep seated and surficial failures for the maximum anticipated design heights. Grade fill slopes should be compacted to minimum 90% out to the slope face. Overbuilding and cutting back to the compacted core or backrolling at minimum 4 feet vertical increments and "track-walking" the slope face is recommended. • Graded cut slopes exposing loose sandy and erodible deposits should be reconstructed as a stabilization fill slopes. For this purpose an equipment wide keyway should be established at the toe of the slope. The keyway should be at least 2 feet deep below rough pad grade and heeled back a minimum of 2% into the natural hillside. Actual keyway dimensions should be determined in the field based upon actual exposures. Additional recommendations should be given at the time of grading plan review when the project grading scheme is known . Reconstructed slope should maintain finish gradients no steeper than 2: 1 (horizontal to vertical) and compacted to minimum 90% out to the slope face. VINJE & MIDDLETON E NGINEERING, INc. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 ... 11111 - ,,. - .... --- - - - - ·-- - --- ·- -.. --- PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 11 AUGUST 10, 1998 7. Inspections: Site grading operations should be tested and inspected by the project geotechnical engineer or his designated field representative on a continuous basis. Particular attention should be given to over-excavations and removals, and fill compaction. Geotechnical engineering observations and testing should be presented in a formal as-graded compaction report at the completion of rough grading. 8. Surface Drainage/Erosion Control: A critical element to the continued stability of the graded building pads and slopes is adequate surface drainage system, and protection of the slope face. This can most effectively be achieved by appropriate vegetation cover and the installation of the . following systems: * Drainage swales should be provided at the top and toe of the slopes per project civil engineer design. * Building pad and slope· surface run-off should be collected and directed to a selected location in a controlled manner. * • The finish slope should be planted soon after completion 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 life should be provided. B. Foundations and Slab-On-Grade Floors The following recommendations are consistent with very low expansive foundation . bearing soils (EI(21) anticipated at the study site. Fin~I foundation and slab design will depend on expansion characteristics of finish grade soils and differential fill thickness. All foundations and slab recommendations should be confirmed and/or revised as necessary in the site final as-graded compaction report. Revised recommendations may be necessary and should be anticipated. 1. The proposed building may be supported on stiff shallow foundations. The shallow foundations should be founded on certified bearing soils. Acceptable foundations should include a system of concrete spread pad and strip footings and slab-on-grade floors. 2. Continuous strip foundations should be sized at least 12 inches wide by 12 inches deep for single-story structures and 15 inches wide by 18 inches deep for two-story structures. Spread pad footings should be at least 24 YINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 - -------- - - - - --- -- PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 12 AUGUST 10, 1998 inches square and 12 inches deep. All depths are measured from the lowest finish rough grades not including the recommended sand underlay beneath the slabs. Exterior continuous strip footings should enclose the entire building perimeter. 3. Continuous strip foundations should be reinforced with a minimum of 4-#4 reinforcing bars. Place 2-#4 bars 3 inches above the bottom of the footing and 2-#4 bars 3 inches below the top of the footing. Reinforcement for the spread pad footings should be designed by the project structural engineer. 4. . All interior slabs should be a minimum of 4 inches in thickness and reinforced with #3 bars spaced 18 inches on center each way placed mid- height in the slab. Slabs should be underlain with 4 inches of clean sand (SE 30 or greater). Place a six-mil plastic moisture barrier mid-height in the . clean sand. 5. Subgrade soils should be tested for proper moisture and specified comp.action levels and approved by the project geotechnical ·consultant within 72 hours prior to the placement of concrete. 6. Provide contraction joints consisting of sawcuts spaced 10 feet on center each way within 24 hours of concrete pour for all interior slabs. The sawcuts should be a minimum of ¾-inch in depth but should not exceed 1 ½-inches in depth or the reinforcing may be damaged. 7. Provide re-entrant corner reinforcement for all interior slabs. Re-entrant corners will depend on slab geometry and/or interior column locations. The enclosed Plate 8 may be used as a general guideline. C. Exterior Concrete Slabs/Flatworks 1. All exterior slabs (walkways, and patios) should be a minimum of 4 inches in thickness reinforced with 6x6/10x10 welded wire mesh placed at mid- height of the slab. 2. PCC driveways and parking should be a minimum of 5 inches in thickness and reinforced with #3 reinforcing bars spaced 18 inches on center each way, placed at mid-height of the slab. Subgrade soils beneath the PCC driveways and parking should be compacted to a minimum of 95% of the corresponding maximum dry density within the upper 6 inches. In the case VINJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park Way • Escondido, California 92029-1229 ° Phone (760) 743-1214 - -,.. -.. .. -- --.. ---- ---- ------ PRELIMINARY-SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD PAGE 13 AUGUST 10, 1998 of potentially expansive soils (EI)20), provide a minimum of 6 inches of 95% compacted Caltrans Class II . base under PCC driveways and parking. 3. Provide weakened joints consisting of sawcuts spaced 10 feet on center (not to exceed 12 feet maximum) each way within 24 hours of concrete pour. The sawcuts should be a minimum depth of ¾-inch but should not exceed 1 ½- inches deep. 4. All exterior slab designs should be confirmed in the final as-graded compaction report . 5. . Sub and base grade soils should be tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant within 72 hours prior to the placement of concrete. D. Soil Design Parameters The following soil design parameters are based on the tested representative samples of on-site earth deposits. All parameters should be re-evaluated · when the characteristics of the final as-graded soils have been specifically determined. Revised recommendations may be necessary and should be anticipated . 1. Design wet density of soil = 125. 7 pcf. 2. Design angle of internal friction of soil = 34 degrees. 3. Design active soil pressure for retaining structures= 36 pcf (EFP), level backfill, cantilever, unrestrained walls . 4. Design active soil pressure for retaining structures·= 54 pcf (EFP), 2:1 backfill surface, cantilever, unrestrained walls. 5. Design at-rest soil pressure for retaining structures = 55 pcf (EFP), non-yielding, restrained walls. 6. Design passive soil pressure for retaining structures = 444 pcf (EFP), level . surface at the toe . 7. Design coefficient of friction for concrete on soils= 0.40. 8. Allowable foundation pressure for certified compacted on-site soil= 1900 psf. 9. Allowable lateral bearing pressure (all structures except retaining walls) for . certified on-site soils = 150 psf/ft . Notes: * Because large movements must take place before maximum passive resistance can be developed, a minimum safety factor of two should be considered for VINJE & MIDDLETON E NGJNEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 --- -.. -.. ..... -.. --,.. - -.. --- PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD F. General Recommendations < PAGE 15 AUGUST 10, 1988 1. The minimum foundation design and steel reinforcement provided herein is based on soil characteristics only and is not intended to be in lieu of reinforcement necessary for structural considerations. All recommendations should be evaluated and confirmed by the project architecUstructural engineer . 2. Footings located on or adjacent to the top of slopes should be extended to a sufficient depth to provide a minimum horizontal distance of 7 feet or one-third of the slope height, whichever is greater (need not exceed 40 feet maximum) between the bottom edge of the footing and face of slope. This requirements applies to all improvements and structures including fences, posts, pools, spas, etc. Concrete and AC improvements should be provided with a thicken edge to satisfy this requirement. 3. 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. Retaining walls should be provided with a back drainage in general accordance with the attached Plate 9. 4. All underground utility trenches should be compacted to a minimum of 90% of the maximum dry density of the soil unless otherwise specified by the respective agencies. Care should be taken not to crush the utilities or pipes during the compaction of the soil. Non-expansive, granular backfill soils should be used. 5. Site drainage over the finished pad surface should flow away from structures onto the street in a positive manner. Care should be taken during the construction, improvement, 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 building and structures to a suitable location. Considerations should be g·iven by the project architect to adequately damp proofing/water proofing the basement walls/foundations and provide the planter areas adjacent to the foundations with an impermeable liner and a subdrainage system. 6. Finish surfaces for all improvements and hard scape including placement of asphalt and concrete, should be completed within 72 hours after.the approval of base/subgrade by the project soils engineer. Additional inspection, testing and certification of the base/subgrade receiving finish surfaces will be necessary in the event the specified time period is not met. Y INJE & MlDDLETON ENGINEERING, INC. • 2450 Auto Park Way• Escondido, California 92029-1229 • Phone (760) 743-1214 --- --- .. ... ----- - --- - - ---- PRELIMINARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,8,C, ADAMS STREET, CARLSBAD PAGE 16 AUGUST 10, 1998 7 .. Final grading and foundation plans should reflect preliminary recommendations given in this report and should be reviewed by this office prior to grading. More specific recommendations should be provided when final drawings are available. 8. All foundation trenches should be inspected to assure adequate footing embedment and confirm competent bearing soils. Foundation and slab reinforcements should also be inspected and approved by the project geotechnical consultant. 9. The amount of shrinkage and related cracks that occurs in the concrete slab-on- grades, flatworks and driveways depends on many factors, the most important of which is the amount of water in a 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 three-eights inch maximum size aggregate usually requires about 40 lb~ more (nearly 5 gal.) water per cubic yard than concrete with one 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. 10. 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. V INJE & MIDDLETON ENGINEERING, INC. 0 2450 Auto Park Waye Escondido, California 92029-1229 • Phone (760) 743-1214 -- -.. -- --- --- - - - - - - PREUM!NARY SOIL AND GEOTECHNICAL INVESTIGATION PARCELS A,B,C, ADAMS STREET, CARLSBAD VIII. LIMITATIONS PAGE 17 AUGUST 10, 1998 The conclusions and recommendations provided herein have been based on available data obtained from pertine·nt 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 our laboratory testing are believed representative of the total area; however, earth materials may vary in characteristics between excavations. Of necessity we must assume a certain degree of continuity between 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 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 insure 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 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 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/a-inch wide in 20 feet may develop as a result of normal concrete shrinkage (according to the American Concrete Institute). 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 repo1i must be presented to us for review and possible revision. V INJE & MIDDLETON ENGINEERING, INC. • 2450 Auto Park w_ay • Escondido, California 92029-1229 • Phone (760) 743-1214