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Home My WebLink AboutCT 2017-0007; TAMARACK BEACH HOMES; LIMITED GEOTECHNICAL INVESTIGATION; 2017-10-12F.E. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 92071 (619) 258-7901 Fax 258-7902 October 12, 2017 Project No. 17-1106F6 Mr. Ben Ryan Tourmaline Properties 944 Archer Street San Diego, California 92109 Subject: Limited Geotechnical Investigation Five Proposed Single-Family Residences 438 Tamarack Avenue City of Carlsbad, California 92008 Dear Mr. Ryan: RIECF YVED JUL 312018 LAND DEVELOPMENT ENGINEERING In accordance with your request, we have performed a limited geotechnical investigation at the subject site to discuss the geotechnical aspects of the project and provide recommendations for the proposed residential development. Our investigation has found that the subject site is underlain by an approximately 2-foot layer of topsoil and dense terrace deposits to the explored depth of 8 feet below existing grade. It is our opinion that the construction of the proposed single-family residences is geotechnically feasible provided the recommendations herein are implemented in the design and construction. Should you have any questions with regard to the contents of this report, please do not hesitate to contact our office. RCE 54071, GE 2704 MSD/md TOURMALINE PROPERTIES/ 438 TAMA RACK A VENUE PROJECT NO. 17-1106F6 TABLE OF CONTENTS INTRODUCTION..............................................................................................................................................3 SCOPEOF SERVICES......................................................................................................................................3 SITE DESCRIPTION AND PROPOSED CONSTRUCTION ........................................................................3 FIELD INVESTIGATION AND LABORATORY TESTING........................................................................4 GEOLOGY.........................................................................................................................................................4 GeologicSetting....................................................................................................................................4 SiteStratigraphy....................................................................................................................................4 SEISMICITY......................................................................................................................................................5 RegionalSeismicity...............................................................................................................................5 SeismicAnalysis ...................................................................................................................................5 2016 CBC Seismic Design Criteria......................................................................................................5 GeologicHazard Assessment................................................................................................................6 GEOTEC1-IN1CAL EVALUATION ................................................................................................................... 7 I Compressible Soils ................................................................................................................................7 ExpansiveSoils......................................................................................................................................7 Groundwater..........................................................................................................................................7 CONCLUSIONS AND RECOMMENDATIONS............................................................................................7 GRADINGAND EARTHWORK ...................................................................................................................... 8 Clearingand Grubbing ..........................................................................................................................8 Structural Improvement of Soils ............................................................................................................ 8 Transitions Between Cut and Fill .... ..................................................................................................... 9 Method and Criteria of Compaction......................................................................................................9 ErosionControl......................................................................................................................................9 StandardGrading Guidelines.................................................................................................................9 FOUNDATIONSAND SLABS ........................................................................................................................9 SETTLEMENT............................................................................................................................................. . ... 10 PRESATURATION OF SLAB SUBGRADE.................................................................................................10 TEMPORARYSLOPES ................................................................................................................... . .............. 11 TRENCHBACKFILL ...................................................................................................................... . ................ 11 PAVEMENTS.................................................................................................. . ................................................ 11 Asphalt Concrete (AC) or Concrete (PCC) ......................................................................................... 11 PermeablePayers (PICP).....................................................................................................................12 DRAINAGE......................................................................................................................................................12 FOUNDATIONPLAN REVIEW....................................................................................................................12 LIMITATIONS OF INVESTIGATION .........................................................................................................12 ADDITIONAL SERVICES ............................................................................................................................13 PLATES Plate 1- Location of Exploratory Boreholes Plate 2 - Summary Sheet (Exploratory Test Pit Logs) ......................................................................14 Plate 3 - USCS Soil Classification Chart PAGE L- 1, LABORATORY TEST RESULTS..............................................................................................16 REFERENCES.................................................................................................................................................17 2 TOURMALINE PROPERTIES! 438 TAMARACK AVENUE PROJECT NO. 17-1106F6 INTRODUCTION I This is to present the findings and conclusions of a limited geotechnical investigation for five proposed single-family residences to be located at 438 Tamarack Avenue, in the City of Carlsbad, California. The objectives of the investigation were to evaluate the existing soils conditions and provide I recommendations for the proposed development. SCOPE OF SERVICES The following services were provided during this investigation: I 0 Site reconnaissance and review of published geologic, seismological and geotechnical reports and maps pertinent to the project area I 0 Subsurface exploration consisting of six (6) boreholes within the limits of the proposed area of development. The boreholes were logged by our Staff Geologist. I 0 Collection of representative soil samples at selected depths. The obtained samples were sealed in moisture-resistant containers and transported to the laboratory for subsequent analysis. I 0 Laboratory testing of samples representative of the types of soils encountered during the field investigation 0 Geologic and engineering analysis of the field and laboratory data, which provided the basis for our conclusions and recommendations 1 0 Production of this report, which summarizes the results of the above analysis and presents our findings and recommendations for the proposed development SITE DESCRIPTION AND PROPOSED CONSTRUCTION The subject site is a nearly rectangular-shaped residential lot located on the northwest corner of I Tamarack Avenue and Hibiscus Circle, in the City of Carlsbad, California. The property which encompasses an area of approximately 17,600 square feet is presently occupied by a one and two- story, single-family residence with a second dwelling unit. The site is gently sloping to the west. Vegetation consisted of grass, shrub and a few trees. The parcel is bordered by Tamarack Avenue to the south, Hibiscus Circle to the east, and Nautical Drive to the north and west. The preliminary architectural and grading plans prepared by Golba Architecture, Inc. of San Diego and Pasco Laret Suiter & Associates of Solana Beach, California indicate that the proposed I construction will include five single-family residences following demolition of the existing structures. The new structures will be two and three-story, wood-framed and founded on continuous footings with slab-on-grade floors. Associated Improvements will include a private I driveway with pervious payers, a masonry retaining wall, landscaping and other appurtenances. 1 3 TOURMALINE PROPERTIES! 438 TA MARIICK AVENUE PROJECT NO. I7-1106F6 FIELD INVESTIGATION AND LABORATORY TESTING On September 20, 2017, six (6) boreholes were excavated to a maximum depth of approximately 8 feet below existing grade with a hand auger. The approximate locations of the boreholes are shown on the attached Plate No. 1, entitled "Location of Exploratory Boreholes". A continuous log of the soils encountered was recorded at the time of excavation and is shown on Plate No. 2 entitled "Summary Sheet". The soils were visually and texturally classified according to the filed identification procedures set forth on Plate No. 3 entitled "USCS Soil Classification". Following the field exploration, laboratory testing was performed to evaluate the pertinent engineering properties of the foundation materials. The laboratory-testing program included moisture and density, particle size analysis and expansion index tests. These tests were performed in general accordance with ASTM standards and other accepted methods. Page L-1 and Plate No. 2 provide a summary of the laboratory test results. GEOLOGY Geologic Setting I The subject site is located within the southern portion of what is known as the Peninsular Ranges Geomorphic Province of California. The geologic map pertaining to the area (Reference No. 6) indicates that the site is underlain by Pleistocene terrace deposits (Qti). I Site Stratigraphy The subsurface descriptions provided are interpreted from conditions exposed during the field investigation and/or inferred from the geologic literature. Detailed descriptions of the subsurface materials encountered during the field investigation are presented on the exploration logs provided on Plate No. 2. The following paragraphs provide general descriptions of the encountered soil types. Topsoil Topsoil is the surficial soil material that mantles the ground, usually containing roots and other organic materials, which supports vegetation. Topsoil observed in the boreholes was generally 18 to 24 inches thick and consisted of dark brown, silty sand that was thy, loose and porous in consistency with some organics (rootlets). Terrace Deposits (00 Terrace deposits were underlying the topsoil layer. They generally consisted of reddish brown, silty sand that was thy to moist and medium dense to dense in consistency. Li I I I I I I 1 I I I TOURMALJNE PROPERTIES! 438 TAMARACK A VENUE PROJECTNO. 17-1106F6 SEISMICITY Regional Seismicity Generally, Seismicity within California can be attributed to the regional tectonic movement taking place along the San Andreas Fault Zone, which includes the San Andreas Fault and most parallel and subparallel faults within the state. The portion of southern California where the subject site is located is considered seismically active. Seismic hazards are attributed to groundshaking from earthquake events along nearby or more distant Quaternary faults. The primary factors in evaluating the effect an earthquake has on a site are the magnitude of the event, the distance from the epicenter to the site and the near surface soil profile. According to the Fault-Rupture Hazard Zones Act of 1994 (revised Alquist-Priolo Special Studies Zones Act), quaternary faults have been classified as "active" faults, which show apparent surface rupture during the last 11,000 years (i.e., Holocene time). "Potentially-active" faults are those faults with evidence of displacing Quaternary sediments between 11,000 and 1.6 million years old. Seismic Analysis I Based on our evaluation, the closest known "active" fault is the Rose Canyon Fault located approximately 4.9 miles (7.8 kilometers) to the west. The Rose Canyon Fault is the design fault of the I project due to the predicted credible fault magnitude and ground acceleration. The Seismicity of the site was evaluated utilizing the 2008 National Hazard Maps from the USGS website and Seed and Idriss methods for active Quaternary faults within a 50-mile radius of the subject site. The site may be subjected to a Maximum Probable Earthquake of 6.9 Magnitude along the Rose Canyon Fault, with a corresponding Peak Ground Acceleration of 0.44g. The maximum Probable Earthquake is defined as the maximum earthquake that is considered likely to occur within a 100-year time period. The effective ground acceleration at the site is associated with the part of significant ground I motion, which contains repetitive strong-energy shaking, and which may produce structural deformation. As such, the effective or "free field" ground acceleration is referred to as the I Repeatable High Ground Acceleration (RHGA). It has been determined by Ploessel and Slosson (1974) that the RHGA is approximately equal to 65 percent of the Peak Ground Acceleration for earthquakes occurring within 20 miles of a site. Based on the above, the calculated Credible I RHGA at the site is 0.29g. 2016 CBC Seismic Design Criteria A review of the active fault maps pertaining to the site indicates the location of the Rose Canyon Fault Zone approximately 7.8 km to the west. Ground shaking from this fault or one of the major active faults in the region is the most likely happening to affect the site. With respect to this hazard, the site is comparable to others in the general area. The proposed single-family residences should be designed in accordance with seismic design requirements of the 2016 California Building F 1 5 TOURMALINE PROPER TIES/ 438 TAMARACK A VENUE PROJECTNO. 17-1106F6 Code or the Structural Engineers Association of California using the following seismic design parameters: PARAMETER VALUE 2016 CBC & ASCE 7 REFERENCES Site Class D Table 20.3-1/ ASCE 7, Chapter 20 Mapped Spectral Acceleration For Short Periods, 5' 1.151g Figure 1613.3.1(1) Mapped Spectral Acceleration For a 1-Second Period, S1 0.441g Figure 1613.3.1(2) Site Coefficient, Fa 1.040 Table 1613.3.3(l) Site Coefficient, F 1.559 Table 1613.3.3(2) Adjusted Max. Considered Earthquake Spectral Response Acceleration for Short Periods, SMS 1.1 97g Equation 16-37 Adjusted Max. Considered Earthquake Spectral Response Acceleration for 1-Second Period, SMI 0.688g Equation 16-38 5 Percent Damped Design Spectral Response Acceleration for Short Periods, SOS 0.798g Equation 16-39 5 Percent Damped Design Spectral Response Acceleration for i-Second Period, S01 0.459g Equation 16-40 Geologic Hazard Assessment Ground Rupture Ground rupture due to active faulting is not considered likely due to the absence of known fault traces within the vicinity of the project; however, this possibility cannot be completely ruled out. The unlikely hazard of ground rupture should not preclude consideration of "flexible" design for on-site utility lines and connections. I Liquefaction Liquefaction involves the substantial loss of shear strength in saturated soils, usually sandy soils with a loose consistency when subjected to earthquake shaking. Based on the absence of shallow groundwater and consistency of the underlying bedrock materials, it is our opinion that the potential for liquefaction is very low. Landsliding There is no indication that landslides or unstable slope conditions exist on or adjacent to the project site. There are no obvious geologic hazards related to landsliding to the proposed development or adjacent properties. Tsunamis and Seiches The site is not subject to inundation by tsunamis due to its elevation. The site is also not subject to seiches (waves in confined bodies of water). I 1 6 I I n 1 I Li I I I I I I I TOURMALINE PROPERTIES! 438 TAMARACK A VENUE PROJECTNO. I7-1106F6 GEOTECHNICAL EVALUATION Based on our investigation and evaluation of the collected information, we conclude that the proposed residential development is feasible from a geotechnical standpoint provided the recommendations provided herein will be properly implemented during construction. In order to provide a uniform support for the proposed structures, overexcavation and recompaction of the structural portions of the building pads will be required. The new foundations may consist of reinforced continuous and/ or spread footings with reinforced slabs. Recommendations and criteria for foundation design are provided in the Foundation and Slab recommendations section of this report. Compressible Soils Our field observations and testing indicate low compressibility within the terrace deposits, which underlie the site at shallow depths. However, loose topsoil was typically encountered to a depth of approximately 2 feet below surface grades. These soils are compressible. Due to the potential for soil compression upon loading, remedial grading of the near-surface soils, including overexcavation and recompaction will be required. I Following implementation of the earthwork recommendations presented herein, the potential for soil compression resulting from the new development has been estimated to be low. The low-settlement assessment assumes a well-planned and maintained site drainage system. Recommendations I regarding mitigation by earthwork construction are presented in the Grading and Earthwork Recommendations section of this report. I Expansive Soils An expansion index test was performed on a representative sample of the terrace deposits to determine volumetric change characteristics with change in moisture content. An expansion index of 0 was obtained which indicates a very low expansion potential for the foundation soils. I Groundwater I Static groundwater was not encountered to the depths of the boreholes. The building pads are located at an elevation over 45 feet above Mean Sea Level. We do not expect groundwater to affect the proposed construction. Recommendations to prevent or mitigate the effects of poor i surface drainage are presented in the Drainage section of this report. CONCLUSIONS AND RECOMMENDATIONS The following conclusions and recommendations are based upon the analysis of the data and information obtained from our soil investigation. This includes site reconnaissance; field I investigation; laboratory testing and our general knowledge of the soils native to the site. The site is suitable for the proposed residential development provided the recommendations set forth are implemented during construction. 1 7 I I 1 I I 7 Ll TOURMALINE PROPERTIES! 438 TAMARACK AVENUE PROJECTNO. 17-1106F6 I GRADING AND EARTHWORK Based upon the proposed construction and the information obtained during the field investigation, we anticipate that the proposed structure will be founded on continuous and/ or spread footings, which are supported by properly compacted fill. The following grading and earthwork recommendations are based upon the limited geotechnical investigation performed, and should be verified during construction by our field representative. Clearing and Grubbing All areas to be graded or to receive fill and/or structures should be cleared of vegetation and concrete waste from the demolition of the existing structures. Vegetation and the debris from the clearing operation should be properly disposed of off-site. The areas should be thoroughly inspected for any possible buried objects, which need to be rerouted or removed prior to the inception of, or during grading. All holes, trenches, or pockets left by the removal of these objects should be properly backflhled with compacted fill materials as recommended in the Method and Criteria of Compaction section of this report. Structural Improvement of Soils Information obtained from our field and laboratory analysis indicates that loose topsoil covers the subject site to a depth of approximately 2 feet below existing grade. These loose surficial soils are susceptible to settlement upon loading. Based upon the soil characteristics and the preliminary grading plan, we recommend the following: * All topsoil and other loose natural soils should be removed from areas, which are planned to receive compacted fills and/or structural improvements. The bottom of the removal area should expose competent materials as approved by ECSC&E geotechnical representative. Prior to the placement of new fill, the bottom of the removal area should be scarified a minimum depth of 6 inches, moisture-conditioned within 2 percent above the optimum moisture content, and then recompacted to at least 90 percent relative compaction (ASTM Dl557 test method). * Overexcavation should be completed for the structural building pads to a minimum depth of 2 feet below the bottom of the proposed footings. The limit of the required areas of overexcavation should be extended a minimum of 5 feet laterally beyond the perimeter footings (building footprints). * Soils utilized as fill should be moisture-conditioned and recompacted in conformance with the following Method and Criteria of Compaction section of this report. The actual depth and extent of any overexcavation and recompaction should be evaluated in the field by a representative of ECSC&E. 8 TOURMALINE PROPERTIES! 438 TAMARACK A VENUE PROJECTNO. I7-II06F6 Transitions Between Cut and Fill The proposed structures are anticipated to be founded in properly compacted fill. Cut to fill transitions below the proposed structures should be completely eliminated during the earthwork construction as required in the previous section. Method and Criteria of Compaction Compacted fills should consist of approved soil material, free of trash debris, roots, vegetation or other deleterious materials. Fill soils should be compacted by suitable compaction equipment in uniform loose lifts of 6 to 8 inches. Unless otherwise specified, all soils subjected to recompaction should be moisture-conditioned within 2 percent over the optimum moisture content and compacted to at least 90 percent relative compaction per ASTM test method D1557. On-site soils, after being processed to delete the aforementioned deleterious materials, may be used for recompaction purposes. Should any importation of fill be planned, the intended import source(s) should be evaluated and approved by ECSCE prior to delivery to the site. Care should be taken to ensure that these soils are not detrimentally expansive. Erosion Control Due to the granular characteristics of on-site soils, areas of recent grading or exposed ground may be I subject to erosion. During construction, surface water should be controlled via berms, gravel/ sandbags, silt fences, straw wattles, siltation or bioretention basins, positive surface grades or other method to avoid damage to the finish work or adjoining properties. All site entrances and exits must I have coarse gravel or steel shaker plates to minimize offsite sediment tracking. Best Management Practices (BMPs) must be used to protect storm drains and minimize pollution. The contractor should take measures to prevent erosion of graded areas until such time as permanent drainage and I erosion control measures have been installed. After completion of grading, all excavated surfaces should exhibit positive drainage and eliminate areas where water might pond. I Standard Grading Guidelines Grading and earthwork should be conducted in accordance with the standard-of-practice methods for this local, the guidelines of the current edition of the California Building Code, and the requirements of the jurisdictional agency. Where the information provided in the geotechnical report differs from the Standard Grading Guidelines, the requirements outlined in the report shall govern. FOUNDATIONS AND SLABS a. Continuous and spread footings are suitable for use and should extend to minimum depths of 18 and 24 inches for the proposed two and three-story structures respectively into the properly compacted fill soils. Continuous footings should be at least 15 and 18 inches in width respectively and reinforced with a minimum of four #4 steel bars; two bars placed near the top of the footings and the other two bars placed near the bottom of the footings. Isolated or spread footings should have a minimum width of 24 inches. Their reinforcement should consist of a minimum of #4 bars 1 9 TOURMALINE PROPERTIES! 438 TAMARACK A VENUE PROJECTNO. 17-1106F6 spaced 12 inches on center (each way) and placed horizontally near the bottom. These recommendations are based on geotechnical considerations and are not intended to supersede the structural engineer requirements. Interior concrete floor slabs should be a minimum 4 inches thick. Reinforcement should consist of #3 bars placed at 16 inches on center each way within the middle third of the slabs by supporting the steel on chairs or concrete blocks "dobies". The slabs should be underlain by 2 inches of clean sand over a 10-mil visqueen moisture barrier. The effect of concrete shrinkage will result in cracks in virtually all-concrete slabs. To reduce the extent of shrinkage, the concrete should be placed at a maximum of 4-inch slump. The minimum steel recommended is not intended to prevent shrinkage cracks. Where moisture-sensitive floor coverings are anticipated over the slabs, the 10-mil plastic moisture barrier should be underlain by a capillary break at least 2 inches thick, consisting of coarse sand, gravel or crushed rock not exceeding 3/4 inch in size with no more than 5 percent passing the #200 sieve. An allowable soil bearing value of 2,000 pounds per square foot may be used for the design of continuous and spread footings at least 12 inches wide and founded a minimum of 12 inches into properly compacted fill soils as set forth in the 2013 California Building Code, Table 1806.2. This value may be increased by 400 psf for each additional foot of depth or width to a maximum value of 4,000 lb/fl2. Lateral resistance to horizontal movement may be provided by the soil passive pressure and the friction of concrete to soil. An allowable passive pressure of 250 pounds per square foot per foot of depth may be used. A coefficient of friction of 0.35 is recommended. The soils passive pressure as well as the bearing value may be increased by 1/3 for wind and seismic loading. I SETTLEMENT Settlement of compacted fill soils is normal and should be anticipated. Because of the type and minor thickness of the fill soils anticipated under the proposed footings, total and differential settlement should be within acceptable limits. I PRESATURATION OF SLAB SUBGRADE Due to the granular characteristics of the subgrade soils, presoaking of subgrade prior to concrete pour is not required. However, subgrade soils in areas receiving concrete should be watered prior to concrete placement to mitigate any drying shrinkage, which may occur following site preparation and foundation excavation. 1 I 1 10 I I LI I 1 I I I I I I Li I 11 TOURMALINE PROPERTIES/ 438 TAMARACK A VENUE PROJECT NO. 17-1106F6 TEMPORARY SLOPES For the excavation of foundations and utility trenches, temporary vertical cuts to a maximum height of 4 feet may be constructed in fill or natural soil. Any temporary cuts beyond the above height constraints should be shored or further laid back following a 1:1 (horizontal to vertical) slope ratio. OSHA guidelines for trench excavation safety should be implemented during construction. TRENCH BACKFILL Excavations for utility lines, which extend under structural areas should be properly backfilled and compacted. Utilities should be bedded and backfilled with clean sand or approved granular soil to a depth of at least one foot over the pipe. This backfill should be uniformly watered and compacted to a firm condition for pipe support. The remainder of the backfill should be on-site soils or non-expansive imported soils, which should be placed in thin lifts, moisture-conditioned and compacted to at least 90% relative compaction. PAVEMENTS Asphalt Concrete (AC) or Concrete (PCC) Based on an estimated R-value of 40, and in conformance with Caltrans Standard Flexible Pavement Design Procedures, the following pavement sections for the assumed traffic index were obtained. The actual design and adoption relative to allowable road gradients should be developed by the civil designer based on the City of Carlsbad requirements. Location Traffic Index Pavement Section Driveways/Parking 5.0 3.0" AC over 5.0" AB or 6" PCC on Compacted Subgrade The upper 12 inches of subgrade should be moisture-conditioned and compacted to at least 95 percent relative compaction (ASTM D1557). Aggregate base should also be compacted to a minimum of 95 percent relative compaction. PCC pavement should be a minimum of 3,500 psi concrete. It is recommended that steel reinforcement be provided for PCC pavements which will be subject to heavy impact loading, such as trash and fire trucks. Minimum reinforcement should consist of #3 deformed rebar placed at 18-inch centers each way. Placement of concrete, control/ expansion joints, and any reinforcement should be conformance with ACI specifications and the Structural Engineer's design. I I I 1 I I I I I I I I I Li I I TOURMALINE PROPERTIES/ 438 TAMARACK AVENUE PROJECT NO. 17-1106F6 Permeable Payers (PICP) Based on the anticipated soil conditions following site grading, the following permeable interlocking concrete pavement section is recommended in accordance with the Interlocking Concrete Pavement Institute (ICPI) specifications. Minimum 3 1/8 -inch pervious concrete payers 1.5" to 2"-inch bedding course (Typ. No. 8 Aggregate) 4-inch No. 57 stone open-graded base 6-inch No. 2 stone subbase wrapped in Mirafi 180N geotextile or equivalent Compaction of subgrade soils should be conducted as specified for asphalt pavements above. DRAINAGE Adequate measures should be undertaken to finish-grade the site after the structures and other improvements are in place, such that the drainage water within the site and adjacent properties is directed away from the foundations, footings, floor slabs and the tops of slopes via rain gutters, downspouts, surface swales and subsurface drains towards the natural drainage for this area. In accordance with the 2016 California Building Code, a minimum gradient of 2 percent is recommended in hardscape areas adjacent to the structures. In earth areas, a minimum gradient of 5 percent away from the structures for a distance of at least 10 feet should be provided. If this requirement cannot be met due to site limitations, drainage can be done through a swale in accordance with Section 1804.4 of the 2016 California Building Code. Earth swales should have a minimum gradient of 2 percent. Drainage should be directed to approved drainage facilities. Proper surface and subsurface drainage will be required to minimize the potential of water seeking the level of the bearing soils under the foundations, footings and floor slabs, which may otherwise result in undermining and differential settlement of the structures and other improvements. FOUNDATION PLAN REVIEW Our firm should review the foundation plans and details during the design phase to assure conformance with the intent of this report. During construction, foundation excavations should be observed by our representative prior to the placement of forms, reinforcement or concrete for conformance with the plans and specifications. LIMITATIONS OF INVESTIGATION Our investigation was performed using the skill and degree of care ordinarily exercised, under similar circumstances, by reputable soils engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. This report is prepared for the sole use of our client and may not be assigned to others without the written consent of the client and ECSC&E, Inc. The samples collected and used for testing, and the observations made, are believed representative of site conditions; however, soil and geologic conditions can vary significantly between exploration 1 12 F~ F_J I 1 I I I LI I I I I [1 I I I I TOURMALINE PROPER TIES/ 438 TAMARACK A VENUE PROJECTNO. 17-1106F6 I trenches, boreholes and surface exposures. As in most major projects, conditions revealed by construction excavations may vary with preliminary findings, if this occurs, the changed conditions I must be evaluated by a representative of ECSC&E and designs adjusted as required or alternate designs recommended. This report is issued with the understanding that it is the responsibility of the owner, or of his representative to ensure that the information and recommendations contained herein are brought to the attention of the project architect and engineer. Appropriate recommendations should be incorporated into the structural plans. The necessary steps should be taken to see that the contractor and subcontractors carry out such recommendations in the field. The findings of this report are valid as of this present date. However, changes in the conditions of a property can occur with the passage of time, whether they are due to natural processes or the works of I man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside of our control. Therefore, this report is subject to i review and should be updated after a period of two years. ADDITIONAL SERVICES I The review of plans and specifications, field observations and testing under our direction are integral parts of the recommendations made in this report. If East County Soil Consultation and Engineering, I Inc. is not retained for these services, the client agrees to assume our responsibility for any potential claims that may arise during construction. Observation and testing are additional services, which are I provided by our firm, and should be budgeted within the cost of development. Plates No. 1 through 3, Page L-1 and References are parts of this report. 1 I I r L I I 1 13 4 I- EAST EAST COUNTY SOIL CONSULTATION & ENGINEERING, INC. 10925 HARTLEY RD.. SUITE 1. SANTEE CA 92071 (619)258-790, Fax(619)258-7902 ' - I I I I 1 I I I I I I I I I I I I I I I TOURMALINE PROPERTIES/ 438 TAMARACK AVENUE PROJECT NO. 17-1106F6 PLATE NO.2 SUMMARY SHEET BOREHOLE NO. 1 DEPTH SOIL DESCRIPTION Surface TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets 1.5' TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand 3.0' 5.5'''cc cc '' 44 44 6.0' bottom of borehole, no caving, no groundwater borehole backfilled 9/20/17 ----------------------------------------------------------------------------------------------------- BOREHOLE NO.2 DEPTH SOIL DESCRIPTION Surface TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets 2.0' TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand 5.0' bottom of borehole, no caving, no groundwater borehole backfilled 9/20/17 ----------------------------------------------------------------------------------------------------- BOREHOLE NO.3 DEPTH SOIL DESCRIPTION Surface TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets 1 '' 64 4C 94 2.5' TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand 8.0' bottom of borehole, no caving, no groundwater borehole backfilled 9/20/17 ----------------------------------------------------------------------------------------------------- BOREHOLE NO. 4 DEPTH SOIL DESCRIPTION Surface TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets 2.0' TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand 5.0' bottom of borehole, no caving, no groundwater borehole backfilled 9/20/17 14 Y M 4.1 5.7 6.0 h'l M Y M 110.1 4.5 Y M 114.7 5.2 I I I 1 I I I I I I I I I I I I I I I TOURMALINE PROPER TIES/ 438 TAMARACK A VENUE PROJECT NO. 17-1106F6 PLATE NO. 2 (Continued) SUMMARY SKEET BOREHOLE NO. S DEPTH SOIL DESCRIPTION Y Surface TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets 2.0' TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand 5.0' bottom of borehole, no caving, no groundwater borehole backfi lied 9/20/17 --------------------------------------------------------------------------------------------------------------------- BOREHOLE NO. 6 DEPTH SOIL DESCRIPTION Y Surface TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets 2.0' TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand 4.0' bottom of borehole, no caving, no groundwater borehole backfilled 9/20/17 Y = DRY DENSITY IN PCF M = MOISTURE CONTENT IN % 15 M MU SOIL CLASSIFICATION CHART SYMBOLS TYPICAL MAJOR DIVISIONS GRAPH LETTER DESCRIPTIONS GRAVEL CLEAN GRAVE- — . & I • I' WELL-GRADED GRAVELS, GRAVEL - SAND MUCTURES, LITTLE ORNOFINES AND GRAVELLY SOILS (LITTLE OR NO FINES) GP - DM E ' OR N5 RAVEL OFINES COARSE GRAINED GRAVELS WITH , SILTY GRAVELS, GRAVEL-SAND-SILT SOILS MORE THAN SO% FINES '' MIXTURES OF COARSE FRACTION RETAINED ON NO.4 SIEVE (APPRECIABLE AMOUNT ,.,. CLAYEY GRAVELS, GRAVEL- SAND - OF FINES) " CLAY MIXTURES CLEAN SANDS SW WELL-GRADED SANDS, GRAVELLY SAND :-:•:•:-:-:-:-:- SANDS. LITTLE OR NO FINES MORE ThAN 50% AND OF MATERIAL IS SANDY LARGER THAN NO. 200 SIEVE SIZE SOILS (LITTLE OR NO FINES) SP POORLY-OWED SANDS GRAVELLY SAND, L17TLE OR NO FINES SANDS WITH SM SILTY SANDS. SAND SILT MIXTURES UORETHAN 5O% FINES OF COARSE FRACTION PASSING ON NO.4 SIEVE (APPRECIABLE AMOUNT sc CLAYEY SANDS, SAND - CLAY OF FINES) MXTURES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY " INORGANIC CLAYS OF LOW TO MEDIUM FINE SILTS LIQUID LIMIT GRAINED AND CLAYS ESS THAN 50 CL PLASTiCITY. GRAVELLY CLAYS. SANDY CLAYS. SILTY CLAYS. LEAN CLAYS SOILS DL ORGANIC SILTS AND ORGANIC SILTY CLAYS CF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS, MICACEOUS OR OF MATERIAL IS MM DIATOMACEOUS FINE SAND OR SILTY SMALLER THAN NO. SOILS 200 SIEVE SIZE SILTS LIQUID LIMIT AND GREATER THAN 50 CM INORGANIC CLAYS OF HIGH PLASTICITY CLAYS ru '.., ri ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS ' PT { PEAT, HUMJS. SWAMP SOILS WITH HIGH ORGANIC CONTENTS NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFiCA'IONS I Li I LI E I I I CLASSIFICATION RANGE OF GRAIN SIZES U.S. STANDARD GRAIN SIZE IN SIEVE SIZE MILLIMETERS BOULDERS I Above 12 Inches Above 305 COBBLES 12 Inches To 3 Inches 305 To 76.2 GRAVEL 3 Inches to No, 4 76.2 to 4.76 Coarse 3 Inches to Y Inch Fine % Inch to No.4 76.2 to 1 9. 1 19.1 to 4.76 SAND No. 4 to No. 200 4.76 to 0.074 Coarse No.4 to No. 10 476 to 2.00 Medium No. 10 to No. 40 2.00 to 0.420 Fine No. 40 to No. 200 0.420 to 0.074 SILT AND CLAY Below No. 200 Below 0,074 KALN SILL CHART EAST COUNTY SOIL CONSULTATION & ENGINEERING, INC. 10925 HARTLEY RD.. SUITE I, SANTEE, CA .92071 (619) 258-7901 Fax (619) 258.7902 70 00 30 I/CL so - -..- - - - - - - mmkok 10 t 111k. 0 10 20 10 110 00 05 70 80 00 too 110010 UIlT (LI). S PLASTICITY CHART c5 fr5iW / '/7 5//YC,4Y7cW z://4e,7_ TOURMALINE PROPERTIES/ 438 TAMARACK A VENUE PROJECT NO. 17-1106F6 I PAGE L-1 LABORATORY TEST RESULTS I EXPANSION INDEX TEST (ASTM D4829) I INITIAL SATURATED INITIAL DRY MOISTURE MOISTURE DENSITY EXPANSION CONTENT(%) (PCfl INDEX LOCATION I CONTENT(%) 9.2 17.3 110.6 0 BH-1 @3.0' PARTICLE SIZE ANALYSIS (ASTM D422) U.S. Standard Sieve Size Percent Passing BH-1 @ 1.5' Ten-ace DepositsO Percent Passing 131-1-1 @3.0' Tece Deposits Percent Passing BH-1 @ 5.5' Terrace Deposits 1/2" - - - 3/8" - - - #4 100 - - #8 99 100 - #16 99 99 100 #30 92 91 90 #50 46 49 44 #100 23 26 21 #200 17 20 16 USCS SM SM SM I I I I I LI 1 16 1 I I I I I TOURMALINE PROPERTIES! 438 TAMARACK A VENUE PROJECT NO. 17-1106F6 REFERENCES "2016 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2", Published by International Code Council. "Geologic Map of the San Diego 30' x 60' Quadrangle, California", by Michael P. Kennedy and Siang S. Tan, 2008. "Geotechnical and Foundation Engineering: Design and Construction", by Robert W. Day, 1999. "1997 Uniform Building Code, Volume 2, Structural Engineering Design Provisions", Published by International Conference of Building Officials. "Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada to be used with 1997 Uniform Building Code", Published by International Conference of Building Officials. "Geologic Maps of the Northwestern Part of San Diego County, California", Department of Conservation, Division of Mines and Geology, by Siang S. Tan and Michael P. Kennedy, 1996. "Bearing Capacity of Soils, Technical Engineering and Design Guides as Adapted from the US Army Corps of Engineers, No. 7", Published by ASCE Press, 1994. "Foundations and Earth Structures, Design Manual 7.2", by Department of Navy Naval Facilities Engineering Command, May 1982, Revalidated by Change 1 September 1986. "Ground Motions and Soil Liquefaction during Earthquakes", by H.B. Seed and I.M. Idriss, 1982. 17