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Home My WebLink AboutPD 2020-0027; 3481 SEACREST DRIVE SLOPE REHIBILITATION; SLOPE STABILITY INVESTIGATION AND REPAIR RECOMMENDATIONS; 2020-08-17 ENVIRONMENTAL • GEOTECHNICAL • GEOLOGY • HYDROGEOLOGY • MATERIALS • INSPECTION CARLSBAD: 7040 AVENIDA ENCINAS SUITE 104‐469, CARLSBAD, CA 92011 • Phn: (760) 937‐4608 BISHOP: 169 WILLOW STREET, BISHOP CA 93514• Phn: (760) 937‐4789 MAMMOTH LAKES: POB 5024, MAMMOTH LAKES, CA 93546 • Phn: (760) 937‐4608 www.sgsi.us August 17, 2020 Project No. 3.31684 Richard Feld 3481 Seacrest Drive Carlsbad, CA 92010 dainesphoto@earthlink.net Subject: SLOPE STABILITY INVESTIGATION AND REPAIR RECOMMENDATIONS 3481 Seacrest Drive and 3470 Charter Oak Drive Carlsbad, California This report presents the results of our slope stability investigation and repair recommendations for the surficial slope failure which occurred between the two properties in April 2020. Based on the results of our field investigation and analysis, it is our finding that the surficial failure occurred within the shallow fill and surficial topsoil sections, as a result of saturated conditions, and an inadequate and overloaded drainage system. Rehabilitation of the eroded slope is feasible from a geotechnical standpoint as long as the recommendations included herein are incorporated into the grading and drainage plan and implemented during construction. The conclusions and recommendations presented herein are considered site specific and based upon the subsurface conditions encountered at the locations of the explorations. We appreciate the opportunity to be of service to you. Should you have any questions regarding this report, please do not hesitate to contact us. Respectfully, SIERRA GEOTECHNICAL SERVICES, INC. Joseph A. Adler Thomas A. Platz President Principal Engineer CEG 2198 (exp 3/31/2021) PE 41039 (exp 3/31/2021) SIE ,INC. ( TABLE OF CONTENTS PAGE 1. INTRODUCTION AND SCOPE .............................................................................................................. 1 2. SITE DESCRIPTIONS .............................................................................................................................. 1 2.1 Site Slope ................................................................................................................................. 2 3. SLOPE FAILURE ....................................................................................................................................... 2 4. GEOLOGY AND SUBSURFACE CONDITIONS ............................................................................... 3 4.1 Subsurface Exploration ..................................................................................................... 3 4.1.1 Subsurface Conditions ............................................................................................ 3 4.2 Groundwater .......................................................................................................................... 4 5. SLOPE STABILITY ................................................................................................................................... 4 6. CONCLUSIONS AND RECOMMENDATIONS ............................................................................... 4 7. LIMITATIONS ......................................................................................................................................... .. 6 LIST OF ATTACHMENTS FIGURE 1 SITE LOCATION MAP FIGURE 2 SLOPE FAILURE AREA FIGURE 3 SITE GEOLOGIC MAP FIGURE 4 SUBSURFACE LOCATION MAP APPENDICES APPENDIX A EXPLORATORY TEST LOGS APPENDIX B LABORATORY TESTING APPENDIX C SLOPE STABILITY ANALYSIS APPENDIX D GENERAL EARTHWORK AND GRADING RECOMMENDATIONS APPENDIX E SITE PHOTOGRAPHS SfE August 17, 2020 Project No. 3.31684 Page 1 1. INTRODUCTION AND SCOPE Presented herein are the results of slope stability investigation and repair recommendations for the approximate overall 25’ x 17’ x 2’ (though depth varied from approximately 1 to 3-feet) surficial failure which occurred on and across the subject sites in April 2020. The project site area is shown on Figure 1. The slope area covered by this report is shown on Figure 2, Plate 1. Site coordinates are 33.1665, -117.3253. Our study included field exploration, laboratory testing, and engineering analysis to identify the physical and mechanical properties of the on-site materials. Results of our field exploration and laboratory testing are included in this report and form the basis for all conclusions and recommendations. Our scope of services included the following:  A site reconnaissance by a member of our engineering staff to evaluate the surface conditions at the project site.  Review of selected published geologic maps, reports and literature pertinent to the site and surrounding areas.  Performance of a subsurface exploration consisting of the excavation, logging, and sampling of two exploratory test pits in order to evaluate subsurface soils conditions at the subject sites.  Performance of laboratory tests on representative soil samples obtained from the excavations to evaluate the physical and engineering properties of the subsurface soils.  Geologic and geotechnical evaluation and analysis of the collected field and laboratory data.  Preparation of this written report presenting the results of our findings, conclusions, geotechnical recommendations, and construction considerations for the proposed development. 2. SITE DESCRIPTIONS The 3481 Seacrest Drive property is occupied by a two-story, single-family residence and is located on a west facing terrace edge which was graded to provide level pads for residential construction in the early 1970’s. The entry level of the residence is below the level of Seacrest Drive. The residence is surrounded by hardscape, and a pool and patio are present behind the residence. A slope descends from the rear yard patio approximately 25-feet to the base of the yard at 3470 Charter Oak Drive. The slope is bisected by a north/south wooden fence located along the property line. The upper portion of the slope contains solar panels for heating the swimming pool. The property has a subterranean drainage system that ties in the roof gutters and yard box drains as well as a 4-inch perforated French drain located between the west August 17, 2020 Project No. 3.31684 Page 2 property fence and the solar water heater. The drain system was routed through the Charter Oak property along the north side. The adjacent 3470 Charter Oak property to the west, consists of a one-story, single- family residence. This house too was built in the early 1970’s. The rear yard includes concrete hardscapes, planter areas, a grass area, and the ascending slope which is approximately 16-feet tall and is heavily vegetated. Most of the property is relatively flat except for the slope. 2.1 Site Slope An approximate 25-foot tall west facing slope spans the two properties. The slope is approximately 9-feet tall on the Seacrest side, and 16-feet tall on the Charter Oak side. The slope appears to be “fill” over the native Terrace/Paralic deposits on the Seacrest side, and primarily topsoil/vegetation over the Terrace/Paralic deposits on the Charter Oak side. The finished slope angle on the Seacrest side is approximately 2:1 (H:V) but transitions to approximately 1.8:1 on the Charter Oak property. The slope angle of the underlying native deposits is approximately 1.6:1 (Figure 2). On the Charter Oak side, the vegetated slope at the north end had been terraced in the past. The wood used for the terrace was deteriorated and had been overgrown with plants. Terracing was not present on the south or within the failure areas. 3. SLOPE FAILURE After a series of storms with heavy rainfall, a surficial failure/washout occurred on the slope between the two properties on April 10, 2020. The failure area starts on the south side of the Seacrest property approximately 17-feet above the toe, and directly below the solar panels. The overall failure area was approximately 25’ x 17’ x 2’ (Figure 2). The deeper depth was near the top of the failure in the fill area, and from there thinned to approximately 12-inches across the face of the slope. Soil from the failure flowed down the slope and accumulated over the south patio concrete and against the east exterior wall. After the failure water was reportedly observed flowing out of the drainpipe. Neither additional failures, slumps, or tension cracks were observed outside of the failure area. No water seepage was observed on the slope surface or at the toe of slope area. August 17, 2020 Project No. 3.31684 Page 3 4. GEOLOGY AND SUBSURFACE CONDITIONS Regional: The project site is located within the coastal portion of the Peninsular Ranges Geomorphic Province of California. This province, which extends approximately 900 miles from Southern California to the southern tip of Baja California, is characterized by northwest-trending structural blocks. The coastal portion of the province in San Diego County is typically comprised of upper Cretaceous-aged to Tertiary-aged (1.8 million to 65 million years) marine and non-marine sedimentary bedrock units that have been deposited within a northwest trending basin known as the San Diego Embayment (Norris & Webb, 1976). Recent geologic uplift along the San Diego coastal margin, combined with sea level changes, have created marine terraces and associated deposits consisting of near-shore marine, beach estuarine, and lagoonal facies. These deposits range from early to mid-Quaternary-aged (45,000 to 1.5 million years) and are designated in geologic literature as Paralic Deposits. Local: The site area is located near the western margin of the coastal terrain and is underlain by Very old paralic deposits, Unit 12 composed of poorly sorted, moderately permeable, reddish-brown, interfingered strand-line, beach, estuarine and colluvial deposits composed of siltstone, sandstone and conglomerate (Kennedy and Tan, 2007) (Figure 3). 4.1 Subsurface Exploration Our subsurface exploration was conducted on June 16, 2020 and consisted of logging and sampling of a two-hand dug exploratory test pits within the failure areas. Bulk soil samples were obtained from the excavations. The samples were transported to our in-house geotechnical laboratory for testing. The approximate location of the exploratory test pits is shown on Figure 4. Logs of the test pits are included in Appendix A. Laboratory test results are included in Appendix B. 4.1.1 Subsurface Conditions Up to approximately 3-feet of granular fill overlying early to middle Pleistocene-aged paralic deposits were encountered in TP-1. In general, the fill consisted of a dark brown, damp to moist, loose to dense, silty, very fine to coarse sand (Unified Soil Classification Symbol: SM). The expansion potential as tested was very low (EI = 0). The paralic deposits consisted of a light reddish-brown, moist, dense to very dense, moderately cemented, silty, very fine to coarse SANDSTONE. The expansion potential as tested was very low (EI = 0). Native paralic deposits similar to that observed in TP-1 were encountered in TP-2. There had previously been up to approximately 12-inches of surficial topsoil over the native deposits, but this material had subsequently been dislocated in the washout. August 17, 2020 Project No. 3.31684 Page 4 4.2 Groundwater Groundwater was not encountered during our field investigation. No water seepage was observed in the test pits, or on the slope surface or at the toe of slope area. The groundwater table is below a depth that will influence the planned improvements. 5. SLOPE STABILITY The stability of the slope has been analyzed using the Janbu Method rotational analysis. Our analyses indicate that the factors of safety for the existing native slope is more than 1.5. Based on results of the analyses, the slope satisfies the minimum requirements for global slope stability and can be effectively used for reconstruction with only minor re- grading needed. The input parameters and the resulting safety factors, as well as the cross sections of the slope and their locations are presented in Appendix C. 6. CONCLUSIONS AND RECOMMENDATIONS Based on our geotechnical investigation, the rehabilitation of the slope is feasible from a geotechnical standpoint as long as the recommendations included herein are incorporated into any grading and drainage plans and implemented during construction. The failure occurred within the fill and surficial topsoil sections, as a result of saturated conditions, and an inadequate and overloaded drainage system. Except for minor erosional rilling, the underlying Sandstone was not affected and based upon the stability analysis, is globally stable and can be effectively used for reconstruction with only minor re-grading needed. The localized slope restoration may be accomplished by grading and drainage improvements. In order to restore the slope and maintain a minimum 2:1 (H:V) slope, we recommend the following in conjunction with the recommendations included in Appendix D: Earthwork: Earthwork should be performed in accordance with the General Earthwork and Grading Specifications in Appendix D and the following recommendations. The recommendations contained in Appendix D are general grading specifications provided for typical grading projects. Some of the recommendations may not be strictly applicable to this project. The specific recommendations contained below supersede the general recommendations in Appendix D.  All loose soils and organic matter shall be removed from the slope failure area and to at least 5-feet beyond all edges.  The exposed surface shall be benched in general accordance with the following detail. The detail is meant as a general representation and shall be incorporated as needed into the slope profile design detail developed by the project Civil Engineer. August 17, 2020 Project No. 3.31684 Page 5 1) Key width “B” should be a minimum of 4-feet. The bottom of the key should be graded horizontal or inclined slightly into the natural slope. 2) The outside of the key should be below a minimum of at least 2-feet deep into dense formational material. 3) Bench heights shall not exceed 2-foot vertical.  Site soils are suitable for use as compacted fill as long as they are processed in accordance with the recommendations in Appendix D.  Approved fill soils should be placed in thin lifts (max 8-inches loose thickness) and moisture conditioned to at least optimum moisture content. All fill should be compacted to a minimum of 90-percent of the laboratory maximum dry density per ASTM D1557.  Any import soils shall be tested for suitability in advance by the project Geotechnical Engineer. Earth fill material shall not contain more than 1-percent of organic materials (by volume). Imported fill shall have a maximum plasticity index of ≤ 12, and a liquid limit less than 40 when measured in accordance with ASTM D 4318.  We recommend a minimum horizontal setback distance of 5-feet from the face of slopes for all footings and settlement-sensitive structures (i.e. fences, walls, etc.). This distance is measured from the outside edge of the bottom of the footing,  Site grading should be observed by SGSI. Such observations are considered essential to identify field conditions that differ from those anticipated by the investigation, to adjust design to actual field conditions, and to determine that the grading is accomplished in general accordance with the recommendations of this TYPICAL BENCHING DETAIL Finish Grade Remove All Unsuitable Material As Recommended By Consultant Slope To Be Such That Sloughing Or Sliding Does Not Occur Original Ground r Finish Slope Surface Varies •9• See Note 1 See Note 2 No Scale August 17, 2020 Project No. 3.31684 Page 6 report. Earthwork and grading recommendations which include guidelines for site preparation fill compaction, slope work, temporary excavations, and trench backfill are provided in Appendix D. Drainage:  The damaged French drain system in-place along the property line of the Seacrest property, should be removed and replaced with a new 4” SDR 35 (or equivalent) non-perforated “tightline”. The new pipe may be connected from the box inlet on the south side of the property to a new drop inlet located on the north.  A concrete swale should be placed along the fence line at western edge of the Seacrest Drive property. The swale should be a minimum 4-foot wide, and 6” thick, with a minimum 1-percent fall to the north. A drain in the swale at its north end should be tie-into the site draianage system which outlets on the north side of the Charter Oak property.  Drainage should be designed by the project Civil Engineer. 7. LIMITATIONS This document has been prepared for the sole use and benefit of our client. The conclusions of this document pertain only to the site(s) investigated. The consulting provided, and the contents of this document may not be perfect. Any errors or omissions noted by any party reviewing this document and/or any other geologic or geotechnical aspects of the project should be reported to this office in a timely fashion. The client is the only party intended by this office to directly receive this advice. Unauthorized use of or reliance on this document constitutes an agreement to defend and indemnify Sierra Geotechnical Services Incorporated from and against any liability, which may arise as a result of such use or reliance, regardless of any fault, negligence, or strict liability of Sierra Geotechnical Services Incorporated. Conclusions presented herein are based upon the evaluation of technical information gathered, experience, and professional judgment. Other consultants could arrive at different conclusions and recommendations. Final decisions on matters presented are the responsibility of the client and/or the governing agencies. No warranties in any respect are made as to the performance of the project. Please also note that our evaluation was limited to assessment of the geologic aspects of the project, and did not include evaluation of structural issues, environmental concerns or the presence of hazardous materials. APPENDIX A EXPLORATORY TEST PIT LOGS A subsurface field investigation was performed on June 16th, 2020 and consisted of logging and sampling of a two-hand dug exploratory test pits within the failure area. The approximate location of the exploratory test pits is shown on Figure 4. Logs of the exploratory test pits are presented herein. Representative soil samples were obtained during the field investigation for laboratory testing (Appendix B). SIERRA GEOTECHNICAL SERVICES INC. 7040 AVENIDA ENCINAS, SUITE 104‐469 CARLSBAD, CA 92011 TEST PIT LOGS JOB NO: 3.31684 PROJECT: 3481 Seacrest Drive and 3470 Charter Oak Drive DATE: 6/16/2020 LOGGED BY: JA_ EQUIP: Hand Dug Excavations TEST PIT DEPTH U.S.C.S. GROUP SYMBOL SAMPLE DEPTH PERCENT MOISTURE DRY DENSITY (pcf) DESCRIPTION . 1 0 –3 3 – 4 SM SM 0 - 18” FILL Dark brown, damp to moist, loose to dense, silty, very fine to coarse SAND, with minor gravels and rootlets. OLD PARALIC DEPOSITS Light reddish-brown, moist, dense to very dense, moderately cemented, silty, very fine to coarse SANDSTONE. Massive. --------------------------------------------------------- Total Depth – 4‐feet. No groundwater. 2 0 – 18” SM 0 - 18” OLD PARALIC DEPOSITS Light reddish-brown, moist, dense to very dense, moderately cemented, silty, very fine to coarse SANDSTONE. Massive. Massive. --------------------------------------------------------- Total Depth – 18”. No groundwater. APPENDIX B LABORATORY TESTING Laboratory tests were performed on the representative test samples to provide a basis for development of design parameters. Soil materials were visually classified in the field according to the Unified Soil Classification System (USCS). Laboratory tests were performed in general accordance with the American Society of Testing and Materials (ASTM) procedures. The results of our laboratory testing are presented herein. USCS classifications are presented on the test pit logs (Appendix A). Selected samples were tested for the following parameters: Classification Soils were visually and texturally classified in accordance with the Unified Soil Classification System (USCS) in general accordance with ASTM D 2488. Direct Shear Test Direct shear tests were performed on relatively undisturbed samples in general accordance with ASTM D 3080 to evaluate the shear strength characteristics of the selected materials. Expansion Index The expansion potential of selected samples was evaluated by the Expansion Index Test per ASTM D4829. Gradation Analysis Gradation analysis tests were performed on a selected representative soil sample in general accordance with ASTM D 422. These test results were utilized in evaluating the soil classifications in accordance with the USCS. Proctor Density Tests The maximum dry density and optimum moisture content of selected representative soil samples were evaluated using the Modified Proctor method in general accordance with ASTM D 1557. Date: 7/13/2020 Fill (Upper Part of Failure) Description: Silty Sand (SM) Friction Angle: 27 degrees Cohesion: 224 psf Dry Density: 112 pcf (remolded to 90%) PROJECT: Seacrest/Charter Oak Slope Failure 3.31684 y = 0.5182x + 224 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500SHEAR STRENGTH (psf)NORMAL STRESS (psf) DIRECT SHEAR DIAGRAM SIER , INC. ·--·-- ~ / V / ~ / V / Date: 7/13/2020 Native Paralic Sandstone Description: Silty Sand (SM) Friction Angle: 28 degrees Cohesion: 320 psf Dry Density: 116 pcf (remolded to 90%) PROJECT: Seacrest/Charter Oak Slope Failure 3.31684 y = 0.5345x + 320 0 500 1000 1500 2000 2500 3000 3500 0 500 1000 1500 2000 2500 3000 3500SHEAR STRENGTH (psf)NORMAL STRESS (psf) DIRECT SHEAR DIAGRAM ,INC. ~ / V ... / / V ./ / V ./ v SIERRA GEOTECHNICAL SERVICES, INC. ENVIRONMENTAL • GEOTECHNICAL • GEOLOGY • HYDROGEOLOGY • MINING • MATERIALS Caltrans Lab #214 Sampled By Sampled Date Delivered By Deliver Date JA Test No Test Date Test Time Test Pit No Boring No Depth Specific Gr (Gs)Tested By Reviewed By 1 7/7/2020 24 Hours n/a TP-1 0-18" 2.7 GC JA 0EI -0.2692 0-20 -0.2692 21-50 51-90 0 91-130 0 >130 Remarks: Classification of Expansive Soil Remolded Dry Density (pcf) Degree of Saturation Remolded Wet Density (pcf) Remolded Dry Density (pcf) Degree of Saturation Soil has Very Low Expansion Potential. ContactClient Source Soil Description Feld Very Low Low Medium High Very High EXPANSION READINGS 2049.1 Moisture Content (%) 161.1 151.1 0 6.2 Tare Weight (g) Wet Weight + Tare (g) Dry Weight + Tare (g) Tare Weight (g) Moisture Content (%) Dry Weight + Tare (g) Sample + Tare Weight (g) Tare Weight (g) Wet Weight + Tare (g) 2012.4 368.2 Corrected Expansion Index, EI EXPANSION INDEX OF SOILS (ASTM 4829) Project No.Seacrest / Charter Oaks 3.31684 TEST DATA INITIAL SETUP DATA FINAL TAKE-DOWN DATA Silty Sand Project Name Sample + Tare Weight (g) Tare Weight (g) Moisture Content Data Moisture Content Data - 133.7 121.9 101.4 Uncorrected Expansion Index Initial Volume (ft3) Initial Gauge Reading (in) Final Gauge Reading (in) Expansion (in) Potential Expansion - 126 118.6 50 Remolded Wet Density (pcf) Initial Volume (ft3) 368.2 2049.1 1850.3 368.2 9.7 I I I I I I MAMMOTH LAKES OFRCE: PO BOX 5()24, MAMMOTH LAKES, CA 93546 • Phn: (760) 937-4608 BISHOP LAB: 873 NORTH MAIN STREET, SUITE 150, BISHOP, CA 93514 • Phn: (760) 937-4789 PALM DESERT: 44489 TOWN CENTER WAY, SUITE D-478, PALM DESERT, CA 92260 WWW.§g§i. U§ SIERRA GEOTECHNICAL SERVICES, INC. ENVIRONMENTAL • GEOTECHNICAL • GEOLOGY • HYDROGEOLOGY • MINING • MATERIALS Caltrans Lab #214 Sampled By Sampled Date Delivered By Deliver Date JA Test No Test Date Test Time Test Pit No Boring No Depth Specific Gr (Gs)Tested By Reviewed By 1 7/9/2020 24 Hours n/a TP-2 0-18" 2.7 GC JA 0EI -0.6908 0-20 -0.6908 21-50 51-90 0 91-130 0 >130 Remarks: Classification of Expansive Soil Remolded Dry Density (pcf) Degree of Saturation Remolded Wet Density (pcf) Remolded Dry Density (pcf) Degree of Saturation Soil has Very Low Expansion Potential. ContactClient Source Soil Description Feld Very Low Low Medium High Very High EXPANSION READINGS 2107.1 Moisture Content (%) 171.8 162.4 0 5.5 Tare Weight (g) Wet Weight + Tare (g) Dry Weight + Tare (g) Tare Weight (g) Moisture Content (%) Dry Weight + Tare (g) Sample + Tare Weight (g) Tare Weight (g) Wet Weight + Tare (g) 2008.9 368.2 Corrected Expansion Index, EI EXPANSION INDEX OF SOILS (ASTM 4829) Project No.Seacrest / Charter Oaks 3.31684 TEST DATA INITIAL SETUP DATA FINAL TAKE-DOWN DATA Silty Sand Project Name Sample + Tare Weight (g) Tare Weight (g) Moisture Content Data Moisture Content Data - 138.4 128 101.5 Uncorrected Expansion Index Initial Volume (ft3) Initial Gauge Reading (in) Final Gauge Reading (in) Expansion (in) Potential Expansion - 130 123.2 50.5 Remolded Wet Density (pcf) Initial Volume (ft3) 368.2 2107.1 1936.4 368.2 8.1 I I I I I I MAMMOTH LAKES OFRCE: PO BOX 5()24, MAMMOTH LAKES, CA 93546 • Phn: (760) 937-4608 BISHOP LAB: 873 NORTH MAIN STREET, SUITE 150, BISHOP, CA 93514 • Phn: (760) 937-4789 PALM DESERT: 44489 TOWN CENTER WAY, SUITE D-478, PALM DESERT, CA 92260 WWW.§g§i. U§ PARTICLE SIZE DISTRIBUTION REPORT PER ASTM TEST METHODS 02487 .t 0691.J SIEVE SIZE . ~~~~~ . . .. ... ~ ~ ~ ~ ~ ~ ~~ 8 ~ ~ (() -... ...... 100 -- 90 80 70 ~ ~ 60 ~ ..... ~ 50 G !l5 Q; 40 .JO 20 10 0 100 10 1 0.1 0.01 0.001 PARTTCLE SIZE IN MILUMETERS X >.J• X GRAVEL XSANO XRNES Coarse Fine Coarse Medium Fine Slit Clay 0 5.6 2.6 0.4 17.7 59.0 12.9 n/a SIEVE PERCENT PERCENT SPECIREO PASS? SIZE RETAINED PASSING PERCENT (Yes or No) .J-1/2· SOIL DESCRIPTION 3• 2-1/2· SIity sand 2· 1-1/2· 0 100 ATTERBERG LIMITS 1· 1.8 98.2 PL= 0 LL= 0 Pl= NP .J/4. 5.6 94.4 1/2· 7.1 92.9 COEFFICIENTS .J/8. --085= n/a 060= 0.32 050= 0.26 No. 4 8.2 91.8 030= 0.20 0 15= n/a o,o= n/a No. 8 --Cu= n/a Cc= n/a No. 10 8.6 91.4 Na. 16 --CLASS/FICA TION No. 20 10.0 90.0 uses= SM AASHTO = n/a No . .JO 14.6 85.4 No. 40 26 . .J 7.J.7 REMARKS No. 50 --Specific Gravity (per ASTM 0854) = n/a Na. 60 58.2 41.8 Na. 100 76.2 2.J.8 Na. 140 81.9 18.1 No. 200 85..J 12.9 PROJECT• Seacrest Dr./ CLIENT• Richard Feld ----Charter Oak Dr., Carlsbad, CA , ~fir -, ~ SAMPLE DEPTHo MATERIAL• TEST PIT 1 0 o-1a· ALL SAMPLED• DELIVERO TESTED• TESTED BY• IE 11 ~hHNlC R Vl")"'?i• INC. 6/16/2020 6/17/2020 6/29/2020 GC ""4\ I JllB 111., DRAnED BY• REVIE\IED BY• 3.31684 DD JA PARTICLE SIZE DISTRIBUTION REPORT P£R ASTl,I TEST METHODS 02487 ,k 0691.J SIEVE SIZE . ~~~~;t-. • .. .... ~~ ~ ~ ~ ~ :is~ 8 ~ ~ <o ... ... ...... 100 ... ... 90 80 70 ~ ~ 60 ~ .... ~ 50 ll:i ci:: 40 30 20 10 0 100 10 1 0. 1 0.01 0.001 PARTTCL£ SIZE IN MILLIMETERS X >3• X GRAVEL XSANO X FINES Coarse Fine Coarse Medium Fine Silt Cloy 0 0 0.6 0.2 19.2 62.6 17.4 n/o SIEVE PERCENT PERCENT SPECIFIED PASS? SIZE RETAINEO PASSING PERCENT {Yes or No} 3-1/2# SOIL DESCRIPTION 3• 2-1/2# S17ty sand 2· 1-1/2· A TTERBERG LIMITS 1· PL= 0 LL= 0 Pl= NP 3/4# 1/2# 0 100 COEFACIENTS 3/8# --Oss= n/a 060= 0.23 050= 0.23 No. 4 0.6 99.4 0.10= 0.17 o,s= n/a o,o= n/a No. 8 --Cu= n/a Cc= n/a No. 10 0.8 99.2 No. 16 --CLASS/RCA TION No. 20 2.0 98.0 uses= SAi AASHTO = n/a No. 30 6.8 93.2 No. 40 20.0 80.0 REMARKS No. 50 --Specific Gravity {per ASTM 0854} = n/a No. 60 55.1 44.9 No. 100 72.9 27.1 No. 140 78.8 21.2 No. 200 82.6 17.4 PROJECT• Seacrest Or./ CLIENT• ---Charter Oak Or., Carlsbad, CA Richard Feld ~ (.~ ,, ~ SAMPLE DEPTHo MATERIAL• TEST PIT 2 0 o-1s· TERRACE/PARALIC DEPOSITS ~ti'1~J't ~~ HNIC SAMPLEI), DELIVEREl)o TESTO TESTED BY• IE Rv .. ,w,INC. 6/16/2020 6/17/2020 6/29/2020 GC '-'' , ..oBND.o DRAFTED BY• REV!E',/ED BY• 3.31684 00 JA Caltrans Lab #214 per ASTM D1557 Sampled By Delivered By JA JA Proctor No Test Date Native Belt Cut Screen Chute Stockpile Truck Tested By Reviewed By 1 6/23/20 X GC DD/JA Laboratory Data: Soil &Wet Percent Dry Mold Max. Dry Optimum Test # Mold (lb) Mold (lb) Soil (lb) Density (pcf) Moisture Density (pcf) Volume (cf) Density (pcf) Moisture (%) 1 13.676 9.690 3.986 120.8 4.4 115.6 0.03300 124.5 9.5 2 14.018 9.690 4.328 131.2 7.5 122.0 3 14.110 9.690 4.420 133.9 12.3 119.3 With Rock Correction n/a Note: ZAV=Zero Air Voids per Specific Gravity of Soil Solids Test Pit 1 SIERRA GEOTECHNICAL SERVICES GEOTECHNICAL • GEOLOGY • HYDROGEOLOGY • ENVIRONMENTAL • MINING • MATERIALS MAXIMUM DENSITY-MOISTURE CURVE (PROCTOR) Project Name Project No. Seacrest Dr./Charter Oak Dr., Carlsbad, CA 3.31684 Deliver Date 6/16/2020Richard Feld Client Contact Material Location Top Upper 0 -18" 100 105 110 115 120 125 130 135 140 145 0 5 10 15 20Dry Density (lbs/cu ft)Moisture (%) ZAV=2.4 ZAV=2.5 ZAV=2.6 ZAV=2.7 ZAV=2.8 Dry Density 105 110 115 120 125 0 5 10 15 20Dry Density (lbs/cu ft)Moisture (%) ZAV=2.4 ZAV=2.5 ZAV=2.6 ZAV=2.7 ZAV=2.8 Dry Density 110.0 115.0 120.0 125.0 130.0 0 5 10 15 20Dry Density (lbs/cu ft)Moisture (%) ZAV=2.3 ZAV=2.4 ZAV=2.5 ZAV=2.6 ZAV=2.7 Dry Density \ \ I\ \ \ \ \ \ \ \ \ \ \ I \ \ \ \ \ \ \ \ \ \ i----," \ I\ /\ \ K \ V I\ ~ \ \ ----+--I \ \ \ \ \ ------) \ \ ' \ \ ------6-- I \ \ \ \ \ ) \ \ \ \ \ \ ----- I \ \ I\ \ \ - J \ \ \ \ \ ~ \ \ \ \ I\ \ \ \ \ \ \ I\ \ \ \ ~ \ \ \ \ I\ \ \ \ \ I\ \ \ \ \ \ I I I I I I I I Caltrans Lab #214 per ASTM D1557 Sampled By Delivered By JA JA Proctor No Test Date Native Belt Cut Screen Chute Stockpile Truck Tested By Reviewed By 2 6/23/20 X GC DD/JA Laboratory Data: Soil &Wet Percent Dry Mold Max. Dry Optimum Test # Mold (lb) Mold (lb) Soil (lb) Density (pcf) Moisture Density (pcf) Volume (cf) Density (pcf) Moisture (%) 1 14.030 9.690 4.340 131.5 5.8 124.3 0.03300 129.0 9.5 2 14.326 9.690 4.636 140.5 9.0 128.9 3 14.268 9.690 4.578 138.7 12.2 123.6 With Rock Correction n/a Note: ZAV=Zero Air Voids per Specific Gravity of Soil Solids Material Test Pit 2 Location Bottom Lower 0 -18" Seacrest Dr./Charter Oak Dr., Carlsbad, CA 3.31684 Client Contact Deliver Date Richard Feld 6/16/2020 SIERRA GEOTECHNICAL SERVICES GEOTECHNICAL • GEOLOGY • HYDROGEOLOGY • ENVIRONMENTAL • MINING • MATERIALS MAXIMUM DENSITY-MOISTURE CURVE (PROCTOR) Project Name Project No. 100 105 110 115 120 125 130 135 140 145 0 5 10 15 20Dry Density (lbs/cu ft)Moisture (%) ZAV=2.4 ZAV=2.5 ZAV=2.6 ZAV=2.7 ZAV=2.8 Dry Density 105 110 115 120 125 0 5 10 15 20Dry Density (lbs/cu ft)Moisture (%) ZAV=2.4 ZAV=2.5 ZAV=2.6 ZAV=2.7 ZAV=2.8 Dry Density 115.0 120.0 125.0 130.0 135.0 0 5 10 15 20Dry Density (lbs/cu ft)Moisture (%) ZAV=2.3 ZAV=2.4 ZAV=2.5 ZAV=2.6 ZAV=2.7 Dry Density I I I I \ \ \ \ I\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ _\ I\ \ X \ \ \ \j ., \ \ \ ' ----+-- \ I\ \ " \ ~ ------V \ \ ' \ ------6-- • If'\ \ I\ 1 I\ - \ \ \ f \ ----- \ I\ \ \ \ - \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ I\ \ \ I\ \ \ \ \ I\ \ \ I\ \, \ I\ \ \ \ \ \ \ ' I I I I I I I I APPENDIX C ROTATIONAL ANALYSIS (JANBU DIMENSIONLESS PARAMETERS) Shear Stress Parameters Unit Weight 𝜸 – pcf 127 pcf Cohesion c 224 Angle of Friction 𝛷 27 Tan 𝛷 1 Calculations Slope Height H 21.5 𝜸H/c = 12.2 𝝺 𝛷 c = 𝜸H/c (Tan 𝛷) 12.2 Factor of Safety (FS) = Ncf x c/ 𝜸H Ncf (from Janbu Curves) Slope ½:1 = 15 ¾:1 = 18 1:1 = 21 2:1 = 33 FS ½:1 = 1.39 ¾:1 = 1.67 1:1 = 1.93 2:1 = 3.04 Seacrest Drive/Charter Oak Project Number 3.31684 8/17/2020 z l\l <,.) ~ ..... ~ w ~ cg ~ ~ .... 0 ~ 0 0 q ~ :=ti -z ~ ~ ~ >-: ~ ~ ~ ,. ~- ~ 111 ~ en -I z 8 G) r IJJ ::0 0 ~ m (') (fJ --i 7' 0 1J 111 0, ~ z w 0 5 111 Ci) ~ m m -· EXPLANATION (Jsf Quaternary surficial gailure Qop 12 Very old paralic deposits, Unit 12 Qaf Quaternary artifical fill \._____., Geologic contact '? . \.... --Fill contact (queried where uncertain} .A, e 0 f2 ~ .----0 20 C m 0 " 6° 27'0QtLE---t2 ·c --- SCALE: 1" = 20' I i 40 60 t;~ c.)e o< ....,n ~~ ~ (,)• o,- =-~ ~- ..... ~ 0 ~ ~ 0 ~ q ~ "'-!l ~ ~ R□JECT, GEOLOGIC CROSS SECTION LOCA.110N MAP Lots 83 &-90, Seocn,st £states No. 2, Carlsbad, Son Diego, CA □URCE, CALE1 DRAIIING, JOB N□,1 PASCO LARET SUITER & ASSOC/A TES TOPOGRAPHIC SURVEY MAP SHEET 1 of 1 DATE• 1"=20' 8/5/2020 DRAIIN BY, PLATE 1.DWG DD TITLE, 3.31684 PLATE 1 S 63 W f>-,, A A' 320 1 3201 310 1 3101 EXISTING TOPOGRAPHY 300 1 Qaf 3001 290 1 Qop 12 --.......:: 2901 --.......::: " -----...:::: 280 -------------------280' ELEVATION IN FEET ABO !If" MEAN SEA LEl!f"L lif"RTICAL SCALE· 1"=5' HORIZONTAL SCALE· 1"=5' EXPLANATION {Jsf Quaternary surficia/ gailure {Jop 12 Very old paralic deposits, Unit 12 {Jaf Quaternary artifical fill \.____., Geologic contact ? . \..... --Fill contact (queried where uncertain} S 63 W B B' 3201 3201 3101 3101 3001 3001 Qaf 2901 Qop 12 2901 Tsd 280 ------------------280' ELEVATION IN FEET ABO !If" MEAN SEA LEl!f"L lif"RTICAL SCALE· 1 "=5' HORIZONTAL SCALE· 111=5' PR□JECT, GEOLOGIC CROSS SECTION .A-A I ~ B-B' Lots BJ ct 90, St1acrt1st Estates No. 2, Carlsbad, San O/Bgo, CA S□URCE, SCALE, DRAIIING, J□B N□,1 PASCO LARET SUITER & ASSOC/A TES TOPOGRAPHIC SURl!f"Y MAP SHEET 1 of 1 DATE• 1"=5' 8/5/2020 DRAIIN BY, PLATE 2.DWG DD TITLE• 3.31684 PLATE 2 APPENDIX D GENERAL EARTHWORK AND GRADING These general earthwork and grading specifications are for the grading and earthwork shown on the approved grading or construction plan(s) and/or indicated in the geotechnical report(s). Earthwork and grading should be conducted in accordance with applicable grading ordinances, the current California Building Code, and the recommendations of this report. The following recommendations are provided regarding specific aspects of the proposed earthwork construction. These recommendations should be considered subject to revision based on field conditions observed by the geotechnical consultant during grading. Geotechnical Consultant of Record Prior to commencement of work, the owner shall employ the Geotechnical Consultant of Record. The Geotechnical Consultant shall be responsible for reviewing the approved geotechnical report(s) and accepting the adequacy of the preliminary geotechnical findings, conclusions, and recommendations prior to the commencement of grading or construction. During grading and earthwork operations, the Geotechnical Consultant shall observe, map, and document the subsurface exposures to verify the geotechnical design assumptions. If the observed conditions are found to be significantly different than the interpreted assumptions during the design phase, the Geotechnical Consultant shall inform the owner, recommend appropriate changes in design to accommodate the observed conditions, and notify the review agency where required. Subsurface areas to be geotechnically observed, mapped, elevations recorded, and/or tested include natural ground, after it has been cleared for receiving fill but before it has been placed, bottoms of all “remedial removal areas, all key bottoms, and benches made on sloping ground to receive fill. The Geotechnical Consultant shall observe the moisture-conditioning and processing of the subgrade and fill materials and perform relative compaction testing of fill to determine the attained level of compaction. The Geotechnical Consultant shall provide the test results to the owner and the contractor on a routine and frequent basis. The Earthwork Contractor The Earthwork Contractor shall be solely responsible for performing the grading in accordance with the plans and specifications. The Earthwork Contractor shall review and accept the plans, geotechnical report(s) and these Specifications prior to the commencement of grading. The Earthwork Contractor shall have the sole responsibility to provide adequate equipment and methods to accomplish the earthwork in accordance with applicable grading codes and agency ordinances, these Specifications, and the recommendations in the approved geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant unsatisfactory conditions, such as unstable soil, improper moisture condition, inadequate compaction, adverse weather, etc… are resulting in a quality of work less than required in these Specifications, the Geotechnical Consultant shall reject the work and may recommend to the owner that construction be stopped until the conditions are rectified. Site Preparation General: Site preparation includes removal of deleterious materials, unsuitable materials, and existing improvements from areas where new improvements or new fills are planned. Deleterious materials, which include vegetation, trash, and debris, should be removed from the site and legally disposed of off-site. Unsuitable materials include loose or disturbed soils, undocumented fills, contaminated soils, or other unsuitable materials. The Geotechnical Consultant shall evaluate the extent of these removals depending on specific site conditions. Earth fill material shall not contain more than 1-percent of organic materials (by volume). Nesting of the organic materials shall not be allowed. If potentially hazardous materials are encountered, the contractor shall stop work in the affected area, and a hazardous material specialist shall be informed immediately for proper evaluation and handling of these materials prior to continuing to work in that area. As presently defined by the State of California, most refined petroleum products (gasoline, diesel fuel, motor oil, grease, coolant etc. have chemical constituents that are hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the ground may constitute a misdemeanor, punishable by fine and/or imprisonment and shall not be allowed. Any existing subsurface utilities that are to be abandoned should be removed and the trenches backfilled and compacted. If necessary, abandoned pipelines may be filled with grout or slurry cement as recommended by, and under the observation of, the Geotechnical Consultant. Excavation Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only. The actual extent of removal shall be determined by the Geotechnical Consultant based on the field evaluation of exposed conditions during grading. Where fill-over- cut slopes are to be graded, the cut portion of the slope shall be made, evaluated, and accepted by the Geotechnical Consultant prior to placement of materials for construction of the fill portion of the slope, unless otherwise recommended by the Geotechnical Consultant. In addition to removals and over-excavations recommended in the approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich, highly fractured, or otherwise unsuitable ground shall be over-excavated to competent ground as evaluated by the Geotechnical Consultant during grading. All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide the survey control for determining elevations of processed areas, keys, and benches. Compaction The onsite soils are suitable for placement as compacted fill provided the organics, oversized rock (greater than 6-inches in diameter) and deleterious materials are removed. Rocks greater than 6-inches and less than 2-feet in diameter can be placed in the bottom of deeper fills or approved areas provided they are selectively placed in such a manner that no large voids are created. All rocks shall be placed a minimum of 4-feet below finish grade elevation unless used for landscaping purposes. Any import soils shall be tested for suitability in advance by the project Geotechnical Engineer. After making the recommended removals prior to fill placement, the exposed ground surface should be scarified to a depth of approximately 8-inches, moisture conditioned as necessary, and compacted to at least 90-percent of the maximum dry density obtained using ASTM D1557 as a guideline. Surfaces on which fill is to be placed which are steeper than 5:1 (Horizontal to vertical) should be benched so that the fill placement occurs on relatively level ground. For the parking areas and other improvements a one-foot removal is recommended depending on site conditions (i.e. depth of root zone, and depth of disturbance which may have locally deeper removal depths). The removal bottom should be observed (tested as needed) by the geotechnical consultant prior to placing fill soils. The upper 12-inches of subgrade material along with the Class II Aggregate Base and the Asphaltic concrete shall be compacted to a minimum of 95-percent of the materials maximum dry density as determined by ASTM D1557. The subgrade and aggregate base shall be moisture-conditioned and compacted to 95-percent of the material’s maximum dry density as determined by ASTM D1557 to a depth of 12-inches. All fill and backfill to be placed in association with the proposed construction should be accomplished slightly over optimum moisture content using equipment that is capable of producing a uniformly compacted product throughout the entire fill lift. Fill materials at less than optimum moisture should have water added and the fill mixed to result in material that is uniformly above optimum moisture content. Fill materials that are too wet can be aerated by blading or other satisfactory methods until the moisture content is as required. The wet soils may be mixed with drier materials in order to achieve acceptable moisture content. The fill and backfill should be placed in horizontal lifts at a thickness appropriate for equipment spreading, mixing, and compacting the material, but generally should not exceed 8-inches in loose thickness. Retaining wall backfill shall be composed of a granular material (maximum ≤ 3-inch rock) with an expansion index (EI) of no greater than 50 and a sand equivalent (SE) greater than 30. No fill soils shall be placed during unfavorable weather conditions. When work is interrupted by rains or snow, fill operations shall not be resumed until the field tests by the geotechnical engineer indicate that the moisture content and density of the fill are as previously specified. Slopes All slopes shall be compacted in a single continuous operation upon completion of grading by means of sheepsfoot or other suitable equipment, or all loose soils remaining on the slopes shall be trimmed back until a firm compacted surface is exposed. Slope compaction tests shall be made within one foot of slope surface. Cut and fill slopes shall be a maximum of 2:1 (horizontal to vertical) unless approved by the Geotechnical Consultant. Planting and irrigation of cut and fill slopes and/or installation of erosion control and drainage devices should be completed due to the erosion potential of the soil. APPENDIX E ‐ SITE PHOTOGRAPHS 3481 Seacrest Drive – View to the southwest. 3470 Charter Oak – View to the northeast. Note Seacrest property in background (red arrow). Slope Failure – Charter Oak property, rear yard. View to the southeast. Charter Oak property, rear yard, unaffected north area of slope. Note terracing. View to the northeast. Slope Failure – Charter Oak property, rear yard. View to the northeast. Head of Failure Area– Note failed French drain system. Head of Failure Area– Note failed French drain system. Slope Failure – Charter Oak property, rear yard. Oblique view. Note fill contact (red arrow). Seacrest Property – Slope and solar water heaters. Note head of failure (red arrows). Seacrest Property – Slope and solar water heaters. Note head of failure (red arrows).