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HomeMy WebLinkAboutCDP 2025-0004; FORREST RESIDENCE TAMARACK AVENUE; GEOTECHNICAL SOILS REPORT; 2022-09-13EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 92071 TEL. 619-258-7901 Robert & Lillian Appleby 23 918 Ingomar Street West Hills, California 91304 Subject: Geotechnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, California 92008 Dear Mr. & Mrs. Appleby: September 13, 2022 Project No. 22-1106G6 In accordance with your request, we have performed a geotechnical investigation at the subject site to determine the geotechnical site conditions and provide recommendations for design and construction of the proposed two-story, single-family residence. SCOPE OF SERVICES The following scope of work was performed for this investigation: 0 Site reconnaissance and review of published geologic and geotechnical reports and maps pertinent to the project area. 0 Subsurface exploration consisting of excavating two test pits within the general area of the proposed construction. The test pits were logged by our project supervisor. 0 Collection of representative soil samples at selected depths. The obtained samples were stored in moisture-resistant containers and transported to our soil testing laboratory for subsequent analysis. 0 Laboratory testing of soil samples obtained during the subsurface exploration. 0 Geotechnical analysis of the field and laboratory data, which provided the basis for our conclusions and recommendations. 0 Preparation of this report, which summarizes the results of our analysis and presents our findings and recummem.lation:s fu1 L11t:: prupu:st::d cun:strucliun. Geotechnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, CA 92008 SITE DESCRIPTION AND PROPOSED CONSTRUCTION Pagel September 13, 2022 Project No. 22-1106G6 The site location is shown on the attached Vicinity Map, Figure 1. The site consists of a rectangular-shaped, residential lot located on the north side of Tamarack Avenue in Carlsbad, California (see Figure 2). The lot is presently vacant and slopes gently down to the south. The lot is bordered by Tamarack Avenue to the south and other homes to the west, east and north. Site vegetation consists of ice plants, shrubs and a few trees. The proposed construction consists of a two-story, single~family residence. The building will be wood-framed and supported on continuous and/or individual spread footings with a slab-on-grade floor. SUBSURFACE EXPLORATION AND LABORATORY TESTING The subsurface exploration was performed on August 16, 2022 and consisted of excavating two test pits to a maximum depth of 8 feet with a mini-excavator. The approximate locations of the test pits are shown on Figure 2. Logs of the test pits are presented on Figure 3. Following the subsurface exploration, laboratory testing was performed on representative soil samples to evaluate the pertinent engineering properties of the foundation materials. The laboratory tests included moisture content, dry density, maximum density and optimum moisture content, sieve analysis and an expansion index test. The tests were performed in accordance with ASTM standards. The test results are shown on the Logs of the Test Borings, Figure 3 and on Figure 4, Results of Laboratory Tests. SUBSURFACE SOIL CONDITIONS The subsurface soil descriptions were interpreted from conditions encountered during the subsurface exploration and/or inferred from the geologic literature. Detailed descriptions of the subsurface soils are presented on the logs of the test pits presented on Figure 3. The following is a generalized description of the soils. Fill: Fill was encountered in the test pits with a thickness of 4 to 5 feet and consisted of light to dark reddish brown, silty sand that was dry, loose to medium dense in the upper 2 feet; below that the fill was medium dense to dense. Slopewash: Slopewash was encountered in test pit T-2 below the fill with a thickness of 2 feet. The slopewash consisted of dark reddish brown, moist, medium dense, silty sand. Terrace Deposits: Terrace deposits were encountered beneath the fill and slopewash to the maximum depth explored of 8 feet. The terrace deposits consisted of reddish brown, dry to moist, medium dense to dense, silty sand. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. GeotechnicaJ Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, CA 92008 SOIL PROPERTIES a. Compressible Soils Page3 September 13, 2022 Project No. 22-1106G6 Our field observations and testing indicate that loose to medium dense fill soils exist to a depth of about 2 feet below existing grades. b. Expansive Soils An expansion index test (ASTM D 4829) was performed on a representative sample of the fill soils. The results of the test are shown on Figure 4. An expansion index of O was obtained which indicates the fill soils are very low expansive. c. Groundwater Static groundwater was not encountered to the depths of the test pits. The proposed building is located at an elevation over 150 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. GEOLOGY From published geologic maps, the site is underlain at depth by sedimentary terrace deposits. There are no known geologic hazards such as landslides, liquefaction-prone areas, or earthquake faults at the site. However, the proposed building is subject to ground shaking and possible damage from earthquakes on nearby, or more distant, active faults. SEISMIC DESIGN VALUES Seismic design values are presented on Figure 5. CONCLUSIONS Construction of the proposed single-family residence is feasible from a geotechnical standpoint, provided the recommendations presented in this report are properly implemented during construction. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Geotechnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, CA 92008 RECOMMEND A TIO NS SITE GRADING a. Site Clearing Page4 September 13, 2022 Pro.iect No. 22-1106G6 The area of the new building should be cleared of vegetation, concrete fragments and debris, surface and subsurface obstructions and other deleterious materials. These materials should be properly disposed of off-site. b. Temporary Slopes and Excavations Temporary vertical slopes and excavations should not exceed 5 feet in height. Temporary slopes and excavations greater than 5 feet in height should be shored or laid back at a maximum inclination of 1 : 1 (horizontal to vertical). c. Surface Soil Removals Within the new building area and to a distance of at least 5 feet outside building limits, the fill soils should be removed to a minimum depth of 2 feet, and replaced with properly compacted fill. Actual removal depths should be confirmed during grading by our field representative. d. Compaction and Method of Filling Prior to fill placement, the exposed subgrade soils should be scarified to a depth of 6 to 8 inches, moisture-conditioned slightly above the optimum moisture content and compacted to at least 90 percent relative compaction. The on-site soils may be reused as compacted fill, provided they are free of organic materials and debris, and rocks or cobbles over 6 inches in dimension. Any imported fill soils should be predominantly granular and very low expansive (EI less than 20) and approved by our field representative. All fill should be compacted to a minimum relative compaction of 90 percent as determined by ASTM D1557. Fill should be placed at a moisture content slightly above the optimum moisture content, in lifts 6 to 8 inches thick, with each lift compacted by mechanical means. Utility trench backfill and retaining wall backfill should also be compacted to at least 90 percent relative compaction. All grading, fill placement, and compaction should be performed in accordance with the grading requirements of the City of Carlsbad. Fill placement and compaction should be observed and tested as necessary by our field representative. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Geotecbnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, CA 92008 EROSION CONTROL Page5 September 13, 2022 Project No. 22-1106G6 Due to the predominantly sandy nature of the on-site soils, areas of recent grading or exposed ground may be subject to erosion. During construction, surface water should be controlled via benns, gravel/sandbags, silt fences, straw wattles, siltation or bioretention basins, positive smface grades or other method to avoid damage to the finish work or adjoining properties. All site entrances and exits must 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 pennanent drainage and erosion control measures have been installed. After completion of grading, all excavated surfaces should exhibit positive drainage and areas where water might pond should be eliminated. FOUNDATIONS AND FLOOR SLABS • Continuous and/or individual footings should be founded in properly compacted fill at a minimum depth of 18 inches below building pad grade or lowest adjacent finished grade, whichever is deeper. • Continuous footings should be at least 15 inches wide and reinforced with a minimum of four #4 steel bars, with two bars placed near the top of the footings and the other two bars placed near the bottom of the footings. Individual footings should be at least 18 inches square and reinforced with a grid of #4 bars spaced 12 inches on centers ( each way) and placed on concrete blocks at the bottom of the footing. • 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 2019 California Building Code. This value may be increased by 400 psf for each additional foot of depth or width to a maximum value of 4,000 psf. • Lateral loads may be resisted by an equivalent fluid passive soil pressure of 350 pounds per cubic foot. A coefficient of friction of 0.35 may also be used. If passive and friction values are used together, the passive value should be reduced by one-third. • All footing excavations should be observed and approved by our field representative. Footing excavations should be thoroughly cleaned prior to concrete pour. • For design purposes, total and differential settlements of½ inch and¼ inch respectively may be assumed. • Floor slabs, including garage slabs, should be at least 5 inches thick and reinforced with #4 bars placed at 18 inches on centers in two directions in the middle of the slabs. The reinforcing steel should be supported on steel chairs or concrete blocks. Floor slabs should be underlain by 2 EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Geotechnical Investigation for ProJ)osed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, CA 92008 Page6 September 13, 2022 Project No. 22-1106G6 inches of clean sand over a 10-mil visqueen moisture barrier over 2 inches of clean sand. To minimize the potential for shrinkage cracks, concrete should have a minimum compressive strength of 3,000 psi and maximum water-cement ratio of0.5. No special inspection of concrete is required. Some shrinkage cracks are still possible. SURFACE DRAINAGE Surface water should not be allowed to pond next to buildings. Finished grades should slope at least 2 percent away from buildings and along drainage swales. Roof gutters and downspouts connecting to solid, outlet pipes are recommended. Outlet pipes should be discharged to an approved outlet. LIMITATIONS OF INVESTIGATION Our investigation was performed using the skill and degree of care ordinarily exercised under similar circumstances by reputable soil 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 provides no warranty, either expressed or implied, concerning future building performance. Future damage from geotechnical or other causes is a possibility. 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, test borings 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/her 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, thls report is subject to review and should be updated after a period of two years. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Geotechnical Investigation for Pro11osed, Two-Story, Single-Family Residence 1644 Tamarack A venue Carlsbad, CA 92008 DEPTH FIGUREJ LOGS OF TEST PITS TEST PIT T-1 SOIL DESCRIPTION Surface FILL 0.5' 1.5' 2.0' 2.5' 3.5' 4.0' 5.0' reddish brown, dry, loose to medium dense, silty sand II ti II II II It " " II II II II dark reddish brown, dry, medium dense to dense, silty sand " II " " II TERRACE DEPOSITS " II II " II II II reddish brown, dry to moist, medium dense to dense, silty sand bottom of test pit, no caving, no grow,dwater test pit excavated and backfilled 8/16/2022 Page 10 September 13, 2022 Project No. 22-1106G6 y M 116.2 2.6 111.8 4.7 124.7 4.9 126.5 4.6 ---------------------------------------------------------------------------------------------------------------------------------- TEST PIT T-2 DEPTH SOIL DESCRJPTION Surface FILL 1.5' 2.0' 5.0' 6.0' 7.0' 8.0' reddish brown, dry, loose to medium dense, silty sand tt ti n ft tt If ft dark reddish brown, dry, medium dense to dense, silty sand SLOPEWASH dark reddish brown, moist, medium dense, silty sand It tt tt tt ti It " TERRACE DEPOSITS reddish brown, dry to moist, medium dense to dense, silty sand bottom of test pit, no caving, no groundwater test pit excavated and backfilled 8/16/2022 Y = DRY DENSITY IN PCF M = MOISTURE CONTENT IN % EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. y M 111.8 6.4 121.7 10.0 Geotechnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Page 11 September 13, 2022 Project No. 22-1106G6 Carlsbad, CA 92008 TEST LOCATION T-1 @ 2.0' TEST LOCATION T-1 @ 2.0' FIGURE4 RESULTS OF LABORATORY TESTS INITIAL MOISTURE CONTENT (%) 9.1 SOIL TYPE/ EXPANSION INDEX TEST (ASTM D 4829) SATURATED INITIAL MOISTURE DRY CONTENT(%) DENSITY (PCF) 18.0 112 .2 MAXIMUM DENSITY TEST (ASTM D 1557) SOIL PROCEDURE DESCRIPTION 1 U.S. Standard Sieve Size 2" I" 1/2" 3/8" #4 #8 #16 #30 #50 #IO0 #200 uses FILL: REDDISH BROWN, Sll.,TYSAND PARTICLE SIZE ANALYSIS (ASTMD422) EXPANSION INDEX 0 MAXIMUM DRY DENSITY (PCF) 129.0 Percent Passing T-1 @2.0' Fill --- 100 99 99 98 89 53 23 18 SM EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. EXPANSION POTENTIAL VERY LOW OPTIMUM MOISTURE CONTENT(%) 9.0 Geotechnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Page 12 September 13, 2022 Project No. 22-1106G6 Carlsbad, CA 92008 FIGURES SEISMIC DESIGN VALUES 1644 Tamarack Ave, Carlsbad, CA 92008, USA Lat1tud , , , ,r Date Design Code Reference Document Risk Category Sit• Class Type Value Ss 1.033 51 0.375 SMs 1.122 SM: null -See Section 11.4.8 Sos 0.748 So: null -See Section 11.4.8 Type Value SDC null -See Section 11.4.8 Fa 1.087 Fv null -See Section 11.4.8 Description Description 8/29/2022, 200:56 PM ASCE7-16 Ii D -Sti' Soil MCEi, ground motion. (for 0.2 second period) MCE;;, ground motion. (for 1.0s period) Site-modified spectral acceleration value Site-modifed spectral acceleration value umer'c seismic design value at 0.2 second SA Numeric seismic design value at 1.0 second SA Seismic design category Site amplification factor at 0.2 second Site ampli ication factor at 1.0 second EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Geotecbnical Investigation for Proposed, Two-Story, Single-Family Residence 1644 Tamarack Avenue Carlsbad, CA 92008 REFERENCES Page 13 September 13, 2022 Project No. 22-1106G6 1. "2019 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. "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. 5. "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. 6. "Bearing Capacity of Soils, Technical Engineering and Design Guides as Adapted from the US Anny Corps of Engineers, No. 7", Published by ASCE Press, 1994. 7. "Foundations and Earth Structures, Design Manual 7.2", by Department of Navy Naval Facilities Engineering Command, May 1982, Revalidated by Change 1 September 1986. 8. "Ground Motions and Soil Liquefaction during Earthquakes", by H.B. Seed and I.M. Idriss, 1982. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC.