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Home My WebLink AboutCDP 2020-0010; BOX RESIDENCE; UPDATED GEOTECHNICAL REPORT; 2020-11-23EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Joe & Darcy Box 5380 Los Robles Drive Carlsbad, California 92008 10925 HARTLEY ROAD, SUITE "I" SANTEE, CALIFORNIA 92071 TEL. 619-258-7901 November 23, 2020 Project No. 16-1126G2 Subject: Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition Reference: 5380 Los Robles Drive Carlsbad, California 92008 "Limited Geotechnical Investigation, Proposed Residential Addition (Box Residence), 5380 Los Robles Drive, City of Carlsbad, California 92008", Project No. 16-l 126G2, Prepared by East County Soil Consultation and Engineering, Inc., Dated February 9, 2016. Dear Mr. and Mrs. Box: In accordance with your request, we are pleased to submit this updated geotechnical report for the proposed residence remodel and second story addition. We have reviewed our previous geotechnical report (Figure 1, Reference No. 5), dated February 9, 2016, reinspected the site and performed additional subsurface exploration and soil testing. The recommendations presented in our previous geotechnical report have been partially modified and updated to reflect changes in the industry standard of practice and the California Building Code. SITE CONDITIONS The site location is shown on the attached Vicinity Map, Figure 2. We reinspected the site on November 11, 2020. The site conditions are similar to those described in the referenced geotechnical report. PROPOSED CONSTRUCTION The proposed construction consists of remodeling the existing residence and constructing a second story addition. Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 ADDITIONAL SUBSURFACE SOIL EXPLORATION Page 2 November 23, 2020 Project No. 16-1126G2 For this updated report we performed additional subsurface exploration consisting of drilling three hand auger test borings to a maximum depth of 3 feet at the locations shown on the attached Figure 3. The borings were drilled adjacent to the existing residence. Logs of the test borings are presented on Figure 4. In addition, a shallow test pit was excavated next to the existing footing adjacent to Boring B-2. SUBSURFACE SOIL CONDITIONS The subsurface materials encountered in the test borings consisted of approximately 1 foot of dry to moist, loose, silty sand topsoil over moist, medium dense to dense, silty sand terrace deposits. The existing footing was found to be 12 inches deep. GEOLOGY From geologic maps published by the State of California, the site is underlain 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 residence is subject to ground shaking and possible damage from earthquakes on nearby, or more distant, active faults. SEISMIC DESIGN VALUES Updated seismic design values are presented on the attached Figure S. CONCLUSIONS The site is suitable for the proposed residence remodel and construction of the second story addition. The following recommendations should be incorporated into the design and construction of the project. RECOMMENDATIONS SITE GRADING a. Site Clearing The area of the proposed construction should be cleared of vegetation and other unsuitable materials, which should be properly disposed of off-site. All holes, trenches, or loose soil EAST COUNTY SOIL CONSULTATION AND ENGINEERING. INC. Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 Page3 November 23, 2020 Project No. 16-1126G2 pockets left by the removal of these objects should be properly backfilled with compacted fill materials. b. Removal and Recompaction of Loose Surface Soils Beneath Floor Slabs Beneath new floor slabs, the existing, loose topsoil should be removed and recompacted to a depth of approximately 1 foot. Actual depths should be determined by our field representative. c. Compaction and Method of Filling All fill and trench backfill should be compacted to a minimum relative compaction of 90 percent as determined by ASTM DI 557. Fill should be placed at a moisture content slightly above optimum moisture content, in lifts 6 to 8 inches thick, with each lift compacted by mechanical means. 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. FOUNDATIONS a. The proposed second-story addition may be supported on deepened, existing footings and/or new, continuous and/or individual spread footings extending through the upper topsoil and at least 12 inches into the underlying, medium dense to dense, terrace deposits. Terrace deposits were encountered at a depth of about 1 foot in the test borings, hence deepened footings and new footings should have a minimum depth of 2 feet below existing grade. Deepened footings should also extend at least 12 inches below the bottoms of the existing footings. Typical deepened footing details are shown on the attached Figure 6. b. New, continuous footings should be at least 15 inches wide and reinforced with four #4 steel bars placed two at the top and two at the bottom. Individual footings should be at least 18 inches square and reinforced with a grid of #5 bars spaced 12 inches on centers ( each way) and placed on concrete blocks at the bottom of the footing. c. An allowable soil bearing value of 2,000 pounds per square foot may be used for the design of continuous and/or individual spread footings. This value may be increased by one-third for short term wind or seismic loads. d. Lateral loads may be resisted by an equivalent fluid passive soil pressure of 300 pounds per cubic foot. A coefficient of friction of 0.4 may also be used. If passive and friction values are used together, the friction value should be reduced by one-third. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Geotecbnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 Page4 November 23, 2020 Project No. 16-1126G2 e. All footing excavations should be inspected and approved by our representative. f. For design purposes, total and differential settlements of½ inch may be utilized. FLOOR SLABS New floor 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 slab. The reinforcing steel should be supported on steel chairs or concrete blocks. Floor slabs should be underlain by 2 inches of clean sand over a 10-mil visqueen moisture barrier over 2 inches of clean sand. To minimize the potential for shrinkage cracks, foundation and floor slab concrete should have a minimum 28-day compressive strength of 3,000 psi and maximum water cement ratio of 0.5. Special testing of concrete is not required. Some shrinkage cracks are still possible. LIMIT A TIO NS OF INVESTIGATION Our updated geotechnical report was prepared 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 regarding 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. This report is issued with the understanding that it is the responsibility of the owner, or 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, this report is subject to review and should be updated after a period of two years. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 ADDffiONAL SERVICES Page5 November 23, 2020 Project No. 16-1126G2 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. 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: Figure I through 6 EAST COUNTY SOIL CONSULTATION AND ENGINEERING. INC. Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition Page6 November 23, 2020 Project No. 16-1126G2 5380 Los Robles Drive Carlsbad, California 92008 FIGURE 1 VICINITY MAP ,. I.:.. ' ;:arr 5380 Los RoblH Or. Cartsbad, CA 92008 CARLSBAD RANCH :~ s:?:;, t• .-,: ...,~ ets EAST COUNTY SOJL CONSULTATION AND ENGINEERING, rNC. Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 FIGURE 2 LOCATIONS OF TEST BORINGS LEGEND 8-3 • APPROXIMATE LOCATION OF TEST BORING Page 7 November 23, 2020 Project No. l6-1126G2 EAST COUNTY SOIL CONSULTATION AND ENGINEERING, rNC. Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 DEPTH Surface 0.5' 2.0' DEPTH Surface 1.0' 1.5' 3.0' DEPTH Surface 1.0' 2.0' FIGURE 4 LOGS OF TEST BORINGS TEST BORING B-1 SOIL DESCRIPTION TOPSOIL dark brown, moist, loose, porous, silty sand with rootlets TERRACE DEPOSITS reddish brown, dry to moist, medium dense to dense, silty sand bottom oftest boring, no caving, no groundwater test boring drilled and backfilled 11/11/2020 TEST BORING B-2 SOIL DESCRIPTION TOPSOIL dark brown, moist, loose, porous, silty sand ,vith rootlets TERRACE DEPOSITS reddish brown, moist, medium dense to dense, silty sand " ft " " " It bottom of test boring, no caving, no groundwater test boring drilled and backfilled 11/11/2020 TEST BORING B-3 SOIL DESCRIPTION TOPSOIL dark bro,11,n, moist, loose, porous, silty sand '"ith rootlets TERRACE DEPOSITS reddish brown, moist, medium dense to dense, silty sand bottom of test boring, no caving, no groundwater test boring drilled and backfilled 11/11/2020 Page8 November 23, 2020 Project No. 16-1126G2 y M y M 115.9 8.9 y M -------------------------------------·------------------------------------------------------------------ Y == DRY DENSITY IN PCF M == MOISTURE CONTENT IN % EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. Updated Geotechnical Re1>ort for Proposed Residence Remodel and Second Story Addition Page 9 November 23, 2020 Project No. 16-1126G2 5380 Los Robles Drive Carlsbad, California 92008 FIGURE4 SEISMIC DESIGN VALUES 5380 Los Robles Dr, Carlsbad, CA 92008, USA Date O.slgn Code R.terence Document Risk Category Site Class Type Value Ss 1.12 Si 0.403 S..,s: 1.178 s,.,1 null -See Section 11.4.8 S:,s 0.785 S:,: null -See Section 11.4.8 Type Value soc null -See Section 11.4.8 F • 1.052 F, null -See Section 11.4.8 Description Description 11/19/2020, 2;01:23 PM ASCE7·16 n D -Stiff Soil MCE" ground motion. {for 0.2 second period) MCE'I ground motion. (for 1.0s period) Site-modified spectral acceleration value Site-modified spectral acceleration value Numeric 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 amplification factor at LO second EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC. • Updated Geotechnical Report for Proposed Residence Remodel and Second Story Addition 5380 Los Robles Drive Carlsbad, California 92008 FIGURE6 Page 10 November 23, 2020 Project No. 16-1126G2 TYPICAL DEEPENED FOOTING DETAILS GROUND S ACE NO. 4REBAR DOWELS/ ANCHORS @ 18" ON CENTERS 24"' MIN DEEPENED FOOTING I< 18" MIN. EXTERIOR WALL EXISTING FLOOR Notes: 1) Reinforcing steel should have at least 3 inches clearance/cover from outer edges of deepened footing, 2) Reinforcing steel should be tied together with No. 3 rebar stirrups spaced approximately 2 feet apart on centers, 3) Steel rebar dowels/anchors should be drilled and epoxy cemented in place in accordance with ICC ESR-2508 using Simpson SET-XP epoxy adhesive. EAST COUNTY SOIL CONSULTATION AND ENGINEERING, INC.