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HomeMy WebLinkAboutCDP 2020-0001; PATEL RESIDENCE; RESPONSE TO THIRD PARTY GEOTECHNICAL REVIEW FOR PROPOSED TWO-STORY RESIDENCE WITH BASEMENT GARAGE; 2021-01-13Mr. Rajesh Patel 3170 Vista Way EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 92071 TEL. 619-258-7901 Oceanside, California 92056 January 13 , 2021 Project No. 19-l 126G3 Subject: Response to Third-Party Geotechnical Review for Proposed Two-Story Residence with Basement Garage 5462 Carlsbad Boulevard Carlsbad, California 92008 Dear Mr. Patel: In accordance with your request, we have prepared this report in response to the Third-Party Geotechnical Review prepared by Hetherington Engineering, Inc. (for the City of Carlsbad), dated November 9, 2020 and December 8, 2020, for the proposed residence at the subject site. Comment No. 1 A location map has been provided in the updated geotechnical investigation report which is provided separately with this response letter. Comment No. 2 A geotechnical update report has been prepared and is provided separately with this response letter (see attached Reference 4). Updated seismic design values are included in the report. Comment No. 3 We have reviewed the project grading plans prepared by BRA, Inc., Land Planning, Civil Engineering and Surveying of Carlsbad, California, as well as the foundation drawings, plans and details prepared by John W. Starlin, S.E. of San Marcos, California, for the proposed two-story residence with basement garage. The grading plans, foundation plans and foundation details are in accordance with the recommendations presented in our updated report (Reference No. 4). Please note, no shoring plans have been provided at this time. There is sufficient space to excavate for the basement without shoring. Temporary basement slopes over 5 feet in height will be excavated at a 3/4:1 H:V maximum inclination in accordance with CAL-OSHA guidelines and should be stable at this inclination. Response to Third-Party Geotechnical Review for Pro11osed Two-Story Residence with Basement Garage 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 2 January 13, 2021 Project No. 19-1126G3 Trus opportunity to be of service is appreciated. If you have any questions, or we can be of further service, please do not hesitate to call or contact us. Respectfully Submitted, Martin R. Owen, PE, GE Geotechnical Engineer Attachment: References EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Response to Third-Party Geotechnical Review for Proposed Two-Story Residence with Basement Garage 5462 Carlsbad Boulevard Carlsbad, California 92008 REFERENCES Page 3 January 13, 2021 Project No. 19-1126G3 1. "Review of Grading Plans and Supplemental Geotechnical Recommendations, Proposed Single-Family Residence, 5462 Carlsbad Boulevard, California 92008, Project No. 19- 1126G3, Prepared by East County Soil Consultation and Engineering, Inc., Dated November 11 , 2020. 2. "Review of Foundation Drawings, Plans and Details for Proposed Single-Family Residence, Carlsbad Boulevard, APN 210-115-08, Project No. 19-1126G3, Prepared by East County Soil Consultation and Engineering, Inc., Dated October 24, 2020. 3. "Response to EsGil Review, Proposed Single-Family Residence, 5462 Carlsbad Boulevard, Carlsbad, California 92008", EsGil plan Check No. PC2020-0040, Project No. 19-l 126G3, Prepared by East County Soil Consultation and Engineering, Inc., dated October 17, 2020. 4. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence), 5462 Carlsbad Boulevard, APN 210-115-08, Carlsbad, California 92008, Project No. 19-1126G3, Prepared by East County Soil Consultation and Engineering, Inc., Dated January 12, 2021. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Mr. Rajesh Patel 3170 Vista Way EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 92071 TEL. 619-258-7901 Oceanside, California 92056 January 13 , 2021 Project No. 19-1126G3 Subject: Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard, APN 210-115-08 Carlsbad, California 92008 Dear Mr. Patel: In accordance with the request of the Third-Party Geotechnical Reviewer for the City of Carlsbad we have prepared this updated geotechnical investigation report. We previously (in 2019) performed a limited geotechnical investigation at the subject site to determine the geotechnical aspects of the project and provide recommendations for the proposed development. Following are our findings, conclusion and updated recommendations. SCOPE OF SERVICES The following scope of work was performed for this investigation: 0 Site reconnaissance and review of published geologic, seismological and geotechnical reports and maps pertinent to the project area 0 Subsurface exploration consisting of three (2) test pits within the limits of the proposed area of development. The test pits were logged by our Staff Geologist. 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. 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 0 Production of this report, which summarizes the results of the above analysis and presents our findings and recommendations for the proposed development Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 SITE DESCRIPTION AND PROPOSED CONSTRUCTION Page 2 January 13, 2021 Project No. 19-1126G3 The subject site is a rectangular-shaped residential lot located on the east side of Carlsbad Boulevard, in the City of Carlsbad, California (See attached Location Map, Figure 1 ). The property, which encompasses an area of approximately 7,245 square feet is vacant and gently sloping to the west. Vegetation consisted of grass and ice plant. Site boundaries include Carlsbad Boulevard to the west, a vacant parcel to the south and similar residential developments to the remaining directions. The preliminary plans prepared by Design Decisions of Poway; California indicate the proposed construction will include a single-family residence. The structure will be two-story, wood-framed over a basement garage and founded on continuous footings with slab-on-grade floors. Associated improvements will include a swimming pool, pavements and landscaping. FIELD INVESTIGATION AND LABO RA TORY TESTING On June 18, 2019, three (3) test pits were excavated to a maximum depth of approximately 10 feet below existing grade with a Caterpillar mini-excavator equipped with a 24-inch bucket. The approximate locations of the test pits are shown on the attached Figure 2 entitled "Locations of Test Pits". A continuous log of the soils encountered was recorded at the time of excavation and is shown on Figure 3, Logs of Test Pits. The soils were visually and texturally classified according to the filed identification procedures set forth on Plate No. 3 entitled "USCS Soil Classification". Bulk soil samples were collected, sealed in moisture-resistant containers and transported to the lab for testing. 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. Figure 4 provides a summary of the laboratory test results. GEOLOGY Geologic Setting 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 (Qt). 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 EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 3 January 13, 2021 Project No. 19-1126G3 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 was observed in the test pits with a thickness of approximately 12 inches. It consisted of dark brown, silty sand that was moist, loose and porous in consistency with some organics (roots and rootlets). Terrace Deposits (Qt) Terrace deposits were underlying the topsoil layer. They generally consisted of reddish brown, sand with silt and silty sand that were dry to moist and medium dense to dense in consistency. 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 to 1,600,000 years old. Seismic Analysis Based on our evaluation, the closest known "active" fault is the Newport-Inglewood Fault located approximately 6.2 kilometers (3 .9 miles) to the west. The Newport-Inglewood Fault is the design fault of the 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 SO-mile radius of the subject site. The site may be subjected to a Maximum Probable Earthquake of 7.5 Magnitude along the Newport-Inglewood Fault, with a corresponding Peak Ground Acceleration of 0.45g. The maximum Probable Earthquake is defined as the maximum earthquake that is considered likely to occur within a 100-year time period. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 4 January 13, 2021 Project No. 19-1126G3 The effective ground acceleration at the site is associated with the part of significant ground 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 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 RHGA at the site is 0.29g. Seismic Design Values Updated seismic design values conforming to ASCE 7-16 are presented on the attached Figure 5. 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. 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 terrace deposits, 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). GEOTECHNICAL EVALUATION Based on our investigation and evaluation of the collected information, we conclude that the proposed construction is feasible from a geotechnical standpoint provided the recommendations provided herein will be properly implemented during structural development. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Pages January 13, 2021 Project No. 19-1126G3 It is our understanding that the basement garage of the proposed structure will be excavated into the dense terrace deposits. Therefore, no remedial grading 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 dense terrace deposits, which underlie the site at shallow depths. However, loose topsoil was encountered to a depth of approximately 12 inches below surface grades. These soils which are compressible will not impact the proposed construction because the basement will be excavated into the dense terrace deposits. Fallowing implementation of the 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. Expansive Soils An expansion index test was performed on a select sample of the terrace deposits to determine volumetric change characteristics with change in moisture content. An expansion index of O was obtained which indicates a very low expansion potential for the foundation soils. Groundwater Static groundwater was not encountered to the depths of the test pits. The subject site is located at an elevation over 50 feet above Mean Sea Level. We do not expect groundwater to affect the proposed construction. Recommendations to prevent or mitigate the effects of poor 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 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. CLEARING AND GRUBBING The area of the proposed construction should be cleared of vegetation and deleterious materials. Vegetation and debris from the clearing operation should be properly disposed of off-site. The area should be thoroughly inspected for any possible buried objects, which need to be rerouted or removed EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 6 January 13, 2021 Project No. 19-1126G3 prior to construction. All holes, trenches, or pockets left by the removal of these objects should be properly backfilled with compacted fill materials. Our field investigation indicates that dense terrace deposits underlie the site at shallow depths. These soils will be adequate for the support of the proposed structure without detrimental settlement. Foundation excavations should be observed by our representative to verify competent bearing soils. FOUNDATIONS AND SLABS a. Continuous and spread footings are suitable for use and should extend to a minimum depth of 24 inches below the lowest adjacent grade into the dense terrace deposits. Continuous footings should be at least 18 inches wide 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 spaced 12 inches on center (each way) and placed horizontally near the bottom. The minimum reinforcement recommended is based on soil characteristics and is not intended to supersede the structural engineer requirements. b. Interior concrete floor slabs should be a minimum 5 inches thick. Reinforcement should consist of #4 bars placed at 18 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. Actual slab thickness and reinforcement may be designed by the project structural engineer using a coefficient of sub grade reaction of 225 pci. c. 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. d. 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 the dense terrace deposits. This value may be increased by 400 psf for each additional foot of depth or width to a maximum value of 6,000 lb/:ft2. e. 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 300 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. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 SETTLEMENT Page 7 January 13, 2021 Project No. 19-1126G3 Since footings for the proposed structure are anticipated to be supported by the dense terrace deposits, total and differential settlement should be within acceptable limits. For design purposes, a differential settlement up to one-half (1/2) inch and a total settlement up to three-quarter (3/4) inch across the structural span may be used. PRESATURATION OF SLAB SUBGRADE Because of the granular characteristics of the surficial 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 foundation excavation. RETAINING WALLS Cantilevered retaining walls should be designed for an "active" lateral earth pressure of 35 psf/ft (35 pcf EFP) for approved granular and level backfill conditions. Cantilever walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one-third (1/3) the anticipated surcharge pressure. Restrained walls such as basement walls should be designed utilizing an "at-rest" earth pressure of 60 psf/ft ( 60 pcf EFP) for approved granular and level backfill conditions. Restrained walls subject to uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one- half (1/2) the anticipated surcharge. For earthquake motions, additional lateral pressures of 26 and 39 pcf (EFP) may be applied for non restrained and restrained conditions respectively using an inverted triangular distribution if required. Soil design criteria, such as bearing capacity, passive earth pressure and sliding resistance as recommended under the Foundation and Slab recommendations section, may be incorporated into the retaining wall design. Footings should be reinforced as recommended by the structural engineer and appropriate back drainage provided to avoid excessive hydrostatic wall pressures. As a minimum we recommend a fabric-wrapped crushed rock and perforated pipe system. At least 2 cubic feet per linear foot of free- drainage crushed rock should be provided. The proposed basement wall foundations will be founded in medium dense to dense terrace deposits, therefore no remedial grading will be required. Furthermore, due to the limited space between the property boundaries and the proposed building, the recommended drainage behind the basement walls, consisting of a fabric wrapped drain rock and a perforated pipe system, may be replaced with a J-Drain 400 wall drainage system or equivalent. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 8 January 13, 2021 Project No. 19-1126G3 The remaining wall backfill should consist of approved granular material. This fill material should be compacted to a minimum relative compaction of 90 percent as determined by ASTM D-1557 test method. Flooding or jetting of backfill should not be permitted. Granular backfill should be capped with 18 inches (minimum) of relatively impervious fill to seal the backfill and prevent saturation. The contractor should take appropriate precautions during the backfill placement to avod damaging the wall. PAVEMENTS Asphalt Concrete (AC) or Concrete (PCC) Based on an estimated R-value of 50, 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 jurisdictional requirements. Location Traffic Index Pavement Section Driveway 5.0 3. 0" AC over 4. 0" AB, or 6" PCC on Compacted Subgrade The upper 12 inches of subgrade should be moisture-conditioned within 2 percent over optimum and compacted to at least 95 percent relative compaction (ASTM Dl557). Aggregate base should also be compacted to a minimum of 95 percent relative compaction. PCC pavements 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. Permeable Pavers (PICP) Based on the type and consistency of the subgrade soils, 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 pavers • 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 or concrete pavements above. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 TEMPORARY SLOPES Page9 January 13, 2021 Project No. 19-1126G3 For the excavation of the basement and utility trenches, temporary vertical cuts to a maximum height of 5 feet may be constructed in natural soils. Any temporary cuts beyond the above height constraints should be shored or further laid back at a 3/4: 1 (horizontal to vertical) slope ratio. CAL-OSHA guidelines for excavation safety should be implemented during construction. The plot plan indicates that the proposed basement wall on the north side is located at the property line. Therefore, shoring will be required and may be designed with the following soil parameters: • Active Pressure • Passive Pressure • Coefficient of Friction TRENCH BACKFILL 30 ps£'ft (30 pcf EFP) 300 ps£'ft (300 pcf EFP) 0.35 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. DRAINAGE Adequate measures should be undertaken after the structure 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 structure. In earth areas, a minimum gradient of 5 percent away from the structure 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 structure and other improvements. FOUNDATION PLAN REVIEW Our firm should review the foundation plans during the design phase to assure conformance with the intent of this report. During construction, foundation excavations should be observed by our EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 10 January 13, 2021 Project No. 19-1126G3 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 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 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 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 review and should be updated after a period of two years. ADDITIONAL SERVICES 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, 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 provided by our firm, and should be budgeted within the cost of development. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotecbnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 Page 11 January 13, 2021 Project No. 19-1126G3 This opportunity to be of service is appreciated. If you have any questions, or we can be of further service, please do not hesitate to call or contact us. Respectfully Submitted, Martin R. Owen, PE, GE Geotechnical Engineer Attachments: Figures 1 through 6 EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) Page 12 January 13, 2021 Project No. 19-1126G3 5462 Carlsbad Boulevard Carlsbad, California 92008 rn Mar Point~ " FIGURE 1 LOCATION MAP SITE Carlsbad Beach 9 Highlights of San Diego, Inc. Ken Grody\~qrd -tr 1 A San Otego rdro'D,ealer T ft BJ s Re~~{~Want ~ r Jke T & Brewtiouse T ln-N-Out Burger McDonalds EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 LEGEND FIGURE2 PLOT PLAN ~ APPROXIMATE LOCATION OF TEST PIT Page 13 January 13, 2021 Project No. 19-1126G3 EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 DEPTH Surface 1.0' 2.0' 3.0' 4.0' 5.0 ' 7.0' 8.0 ' 10.0' DEPTH Surface 1.0' 2.0' 3.0' 5.0' 6.0' DEPTH Surface 1.0' 2.0' 3.0' 5.0' 6.0' FIGURE3 LOGS OF TEST PITS TEST PIT T-1 SOIL DESCRIPTION TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand " " " " " " reddish brown, dry to moist, medium dense to dense, sand with silt becomes light reddish brown and moist bottom of test pit, no caving, no groundwater test pit backfilled 6/18/19 TEST PIT T-2 SOIL DESCRIPTION TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets TERRACE DEPOSITS (Qt) reddish brown, dry to moist, medium dense to dense, silty sand " " " " " " reddish brown, dry to moist, medium dense to dense, sand with silt " " bottom of test pit, no caving, no groundwater test pit backfilled 6/18/19 TEST PIT T-3 SOIL DESCRIPTION TOPSOIL dark brown, dry, loose, porous, silty sand with rootlets TERRACE DEPOSITS (Qt) reddish brown, dry, medium dense, silty sand " " " " " reddish brown, dry to moist, medium dense to dense, sand with silt becomes light reddish brown and moist bottom of test pit, no caving, no groundwater test pit backfilled 6/18/19 Y = DRY DENSITY IN PCF M = MOISTURE CONTENT IN % y 117.1 115.7 112.6 115.4 y 115.3 120.4 y 108.9 Page 14 January 13, 2021 Project No. 19-1126G3 M 3.0 5.0 5.3 6.2 M 2.5 4.7 M 3.3 EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 FIGURE4 LABORATORY TEST RESULTS EXPANSION INDEX TEST (ASTM D4829) INITIAL DRY Page 15 January 13, 2021 Project No. 19-1126G3 INITIAL MOISTURE CONTENT(%) SATURATED MOISTURE CONTENT(%) DENSITY EXP ANSI ON (PCF) INDEX LOCATION 9.7 18.2 112.0 0 T-1 @ 4.0' PARTICLE SIZE ANALYSIS (ASTM D422) U.S. Standard Percent Passing Percent Passing Percent Passing Sieve Size TP-2 @ 2.0' TP-1 @ 4.0' TP-2 @ 10.0' Terrace Deposits Terrace Deposits Terrace Deposits l " --- 1/2" --- 3/8" --- #4 --- #8 --- #16 100 100 100 #30 91 91 89 #50 44 41 42 #100 17 17 17 #200 12 .2 11 11 uses SM SP-SM SP-SM EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) Page 16 January 13, 2021 Project No. 19-1126G3 5462 Carlsbad Boulevard Carlsbad, California 92008 FIGURE 5 SEISMIC DESIGN VALUES 5462 Carlsbad Blvd, Carlsbad, CA 92008, USA Date Design Code Reference Document Risk Category Site Class Type Value Ss 1.125 S: 0.404 S,., L81 s,.,: null -See Sectio 11.4.8 S:is 0.787 S:::: null -See Section 11.4.8 Type Value soc null -See Section 11.4.8 F, 1.05 F. null -See Section 11.4.8 Description Description 1/11/2021, 3:25:59 PM ASCE7-16 D -Stiff Soil MCE, ground motion. (for 0.2 second period) MCE, ground motion. (for 1.0s period) Site-modified spectral acceleration value Site-modified spectral acceleration vak,e Numeric seismic design value at 0.2 second SA Numeric seismic design value at 1.0 second SA Seismic design category S te amplificat,on factor at 0.2 second Site amplification factor at 1.0 second EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Report of Geotechnical Investigation for Proposed Single-Family Residence (Patel Residence) 5462 Carlsbad Boulevard Carlsbad, California 92008 FIGURE6 REFERENCES Page 17 January 13, 2021 Project No. 19-1126G3 1. "2016 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2", Published by International Code Council. 2. "Geologic Map of the San Diego 30' x 60' Quadrangle, California", by Michael P. Kennedy and Siang S. Tan, 2008. 3. "Geotechnical and Foundation Engineering: Design and Construction", by Robert W. Day, 1999. 4. "1997 Uniform Building Code, Volume 2, Structural Engineering Design Provisions", Published by International Conference of Building Officials. 5. "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. 6. "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. 7. "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. 8. "Foundations and Earth Structures, Design Manual 7.2", by Department of Navy Naval Facilities Engineering Command, May 1982, Revalidated by Change 1 September 1986. 9. "Ground Motions and Soil Liquefaction during Earthquakes", by H.B. Seed and I.M. Idriss, 1982. 10 . "Geology of the San Diego Metropolitan Area, California", Bulletin 200, by Michael P. Kennedy and G.L. Peterson, 1975 . EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC.