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HomeMy WebLinkAboutCP 91-04; 300 Block of Tamarack Avenue; Preliminary Geotechnical; 1991-09-25PRELIMINARY GEOTECHNICAL LA VERCIA CONDOS 300 BLOCK OF TAMARACK AVENUE CARLSBAD, CALIFORNIA FOR ARC GROUP 5751 PAIMER WAY, SUITE H CARLSBAD, CALIFORNIA 92008 W.O. 1347-SD SEPTEMBER 25, 1991 GeoSofls, Inc. TABLE OF CONTENTS SITE DESCRIPTION 1 PROPOSED DEVELOPMENT 2 FIELD EXPLORATION 3 EARTH MATERIALS 3 Topsoil 4 Terrace Deposits 4 GROUNDWATER 5 FAULTING AND REGIONAL SEISMICITY 5 LABORATORY TESTING 7 Field Moisture and Density 7 Laboratory Maximum Dry Density and Optimum Moisture Content 8 Expansion Tests 8 Direct Shear Test 8 CONCLUSIONS AND RECOMMENDATIONS 9 Recommendations-Earthwork Construction 10 RECOMMENDATIONS-POST EARTHWORK 12 Foundations 12 Retaining Walls 15 Additional Site Improvements 17 Additional Earthwork 18 Footing Trench Excavation 18 Drainage 18 Landscape Maintenance 20 Utility Trench Backfill 20 PLAN REVIEW 21 LIMITATIONS 22 GeoSoils, Inc. Geotechnical Engineering • Engineering Geology 5741 Palmer Way • Carlsbad, California 92008 • (619) 438-3155 • FAX (619J 931-0915 September 25, 1991 W.O. 1347-SD ARC GROUP 5751 Palmer Way, Suite H Carlsbad, California 92008 Attention: Mr. Michael Dooley Subject: Preliminary Geotechnical Study La Vercia Condos 300 block of Tamarack Avenue Carlsbad, California Gentlemen: In accordance with your request, GeoSoils Inc. has performed a preliminary geotechnical study concerning the proposed development at the subject site. The purpose of our study was to evaluate earth materials underlying the area and to provide recommendations for project design and construction based on our findings. SITE DESCRIPTION The subject site is a relatively level, rectangular shaped lot located on the south side of Tamarack Avenue between 351 and 295 Tamarack Avenue in the City of Carlsbad, California (Figure 1). A retaining wall is constructed along the eastern property line with an adjacent multi-family residential lot. This wall ascends Los Angeles Co. (818) 785-2158 • Orange Co. (714)647-0277 • Riverside Co. (714J 677-9651 adapted from "The Thomas Guide, 1990 San Diego County Edition"scale 1" = 2900' &&&. "W f*-»rrCcoSoils, Inc t* s f*,.^ < , V"., « LOCATION NAP DATE W.O.i.w.sn BY Soil Mechanics • Geology • Foundation Engineering figure 1 ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 2 approximately three (3) to five (5) feet from the adjacent lot to existing grade of the subj ect property. A wooden fence, approximately three (3) feet in height, is constructed at the top of the wall. A former house site currently occupied by a concrete slab is located at the northern section of the lot. During the field exploration phase of our evaluation, 3/4 inch rock and tile lines for a septic system leach field were encountered south of the existing slab in the central portion of the lot. Vegetation onsite consists predominantly of grasses and small bushes. Pine and other large trees are present in the vicinity of the concrete slab. Drainage onsite appears to be relatively poor with some sheet flow runoff directed to Tamarack Avenue. PROPOSED DEVELOPMENT As indicated on the plans provided, proposed development of the site is to consist of ground preparation for and construction of five two story condominiums along the western and southern portions of the property with driveway access to Tamarack Avenue provided along the eastern portion. A 1/8" = I1 scale first floor plan prepared by the ARC Group is used as a base for the enclosed geotechnical map (Plate 1). GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 3 FIELD EXPLORATION Subsurface conditions were explored by excavating five exploratory test pits with a rubber tire backhoe. Test pits ranged from 3.5 to 7 feet in depth across the site. Logs of these test pits are included with this report in Appendix I. Field exploration was performed on August 28, 1991 by a staff geologist who logged the test pits and obtained samples of representative materials for laboratory testing. The approximate location of the test pits are indicated on the enclosed Geotechnical Map (Plate 1). EARTH MATERIALS Earth material encountered onsite are artificial fill soils, topsoil and terrace deposits. A review of published geologic maps indicate that terrace deposits underlying the site have been mapped by Weber (1982) as unnamed coastal terrace deposits. Artificial Fill Artificial fill occurs onsite as backfill behind the existing retaining wall along the eastern property line. Fill materials consist of brown to red brown, dry to moist, loose to medium dense silty sand. Fill thickness observed in test pits varies between approximately three and six feet adjacent to the wall and GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 4 rapidly thins to zero within three feet from the wall along a steep contact with topsoil and terrace deposits. The uppermost two to three feet of backfill is in a dry and relatively loose condition and should not be used for structural support. This unsuitable material may be used as fill provided it is removed, moisture conditioned and placed as compacted fill. Topsoil Topsoil consists of a surficial layer, approximately 1 to 1 1/2 feet in thickness across a majority of the site. Topsoil is gray brown, dry, loose and porous silty sand with many roots in the upper 3 inches. Topsoil is dry, loose and porous and is therefore considered unsuitable for structural support. Topsoil may be used as fill material provided it is removed, moisture conditioned and placed as compacted fill. Terrace Deposits Terrace deposits underlying the site consists of yellow brown to light red brown, dry to moist, medium dense silty sand. The upper 1 foot of terrace deposits may contain krotovina (animals burrows) filled with brown, loose sand across the site. The uppermost zone of terrace deposits containing krotovina are not considered suitable for structural support in its present condition. Material in this zone may be used as fill material provided it is removed to competent terrace deposits, moisture conditioned and placed as compacted fill. GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 5 Structure was not observed within the excavations, however, it is assumed that the regional structure of formational materials in this vicinity are relatively flat lying or gently (<5 degrees) dipping westward. GROUNDWATER Groundwater was not encountered in any of our test pits and is not anticipated to affect site development. These observations reflect site conditions at the time of this investigation and do not preclude changes in local groundwater conditions in the future from heavy irrigation or precipitation. FAULTING AND REGIONAL SEISMICITY No known active or potentially active faults are shown on published maps in the vicinity of the site (Jennings, 1975). No evidence for faulting was encountered in any of our exploratory excavations. There are a number of faults in the Southern California area which are considered active and would have an effect on the site in the form of ground shaking, should they be the source of an earthquake. These include the San Andreas Fault, the San Jacinto GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 6 Fault, the Elsinore Fault, the Coronado Bank Fault Zone and the Rose Canyon Fault Zone. The possibility of ground acceleration (Greensfelder, 1974) , or shaking, at the site may be considered as approximately similar to the Southern California region as a whole. The relationship of the site location to the major mapped faults within Southern California is indicated on the Fault Map of Southern California (Figure 2). Peak horizontal ground site accelerations on the order of 0. 3g would be anticipated based on an attenuation curve developed by Joyner and Boore (1982) assuming a magnitude 6.5 earthquake on the Rose Canyon Fault, approximately 4 miles west of the site or 0.18g assuming a magnitude 7.0 earthquake on the Elsinore Fault located 25 miles to the east. To date there is no published or unpublished consensus on the seismic activity of the Rose Canyon Fault Zone. Some authors have suggested Holocene activity at one location on the fault (Lindvall et. al. 1989) while others disagree with this interpretation. Given the relatively greater degree of historic seismicity along the Elsinore Fault, the Elsinore Fault is considered most significant to site design. Other Hazards Considered: The following listing includes other seismic related hazards that have been considered for our GeoSoils, Inc. 35' lie Modified after Friedman and Others, 1976 FAULT MAP OF SOUTHERN CALIFORNIA W.O. NO.1347-SO BY re Soil Mechanics • Geology • Foundation Engineering figure 2 ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 7 evaluation of the site. These hazards are considered negligible and/or completely mitigated as a result of typical site development procedures: * Surface Fault Rupture * Ground Lurching or Shallow Ground Rupture * Liquefaction * Seismic settlement or consolidation * Potential for tsunamis * Seiche LABORATORY TESTING General Laboratory tests were performed on representative samples of the onsite earth materials in order to evaluate their physical characteristics. Field Moisture and Density The field moisture content and dry unit weight were determined for "undisturbed" samples of onsite earth materials. The dry unit weight was determined in pounds per cubic foot and the field moisture content was determined as a percentage of the dry unit weight. The results of these tests are presented in the following table. Field Field Location Description Density fpcf) Moisture % TP-1 @ 5.5' silty SAND 112.1 7.8 TP-2 @ 3' silty SAND 115.3 6.4 TP-4 @ 21 silty SAND 99.3 3.2 GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 8 Laboratory Ma vim™ Dry Density and Optimum Moisture Content To determine the compaction character of a representative sample of onsite soil, laboratory testing was performed in accordance with ASTM Test Method D-1557-78. The maximum dry density and optimum moisture content from this test is summarized below: Maximum Density Optimum Location Description Density fpcf} Moisture % TP-2 Brown silty SAND 126.0 11.0 Composite Expansion Tests A swell test was performed on a remolded sample of near surface soil. The sample was prepared at 80 percent of the optimum moisture and at 90 percent of the maximum dry density, placed under a 60 pound per square foot surcharge, and submerged in water for 24 hours. The percent swell was then recorded as the amount of vertical rise compared to the original one inch sample height. Test results are summarized below: Location Swell % Expansion Index Expansion Potential TP-2 0 — low composite Direct Shear Test Direct shear tests were performed on remolded and undisturbed soil samples in a strain control-type direct shear machine. The CeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 9 rate of deformation was approximately 0.025 inches per minute. The samples were sheared and resheared under varying confining loads in order to determine the Coulomb shear strength parameters, cohesion, and angle of internal friction. The samples were tested in an artificially saturated condition. The results are plotted on the enclosed Shear Test Diagrams, Plates SH-1 and SH-2. CONCLUSIONS AND RECOMMENDATIONS General Based on our field exploration, laboratory testing, engineering and geological analysis, it is our opinion that the site is suited for the proposed development from a geotechnical engineering and geologic viewpoint, provided that the recommendations presented below are incorporated into the final design, and construction phase of development. The engineering analyses concerning site preparation and the recommendations prepared below, have been completed using the information provided. In the event that any significant changes are made to current design, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the recommendations of this report verified or modified in writing by this office. GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 10 -Earthwork Construction Demolition: 1. Following demolition all debris should be removed from the site. 2. All subsurface structures, such as the foundation system and utilities should be removed. 3. If a septic tank is located within the site it is recommended that it be pumped out and the tank removed. Any leach lines or other pipes associated with the septic system should be removed. Tile lines were encountered during our field exploration at an approximate depth of 18 inches below the surface. Efforts should be made to locate the entire system. 4. After demolition and removal of structures the ground surface should be cleared of debris, loose soil and organic materials. Treatment of Existing Ground: 1 . Debris , vegetation and other deleterious materials should be removed from the building area prior to the start of construction. 2. For foundation support, the upper 3 feet of earth material should be removed within the building area and GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 11 extending a minimum of 5 feet laterally beyond the building envelope. If lateral removals are limited by property line restrictions, additional foundation recommendations will need to be made. Beneath driveway areas a minimum of 2 feet of material should be removed and recompacted. Locally, deeper removals may be necessary due to buried structures i.e. septic leach lines, foundations etc. 3. All removal areas should be observed by a representative of this office to evaluate if adequate removal depths have been obtained. 4. When removals are completed, the exposed surface should be scarified to a depth of 1 foot, brought to at least optimum moisture content and recompacted. 5. Subsequent to ground preparation, the excavated onsite soils may be placed in thin (6+/~ inch) lifts, cleaned of vegetation and debris, brought to at least optimum moisture content, and compacted to a minimum relative compaction of 90 percent of the laboratory standard. General: If soil is to be imported to the site for use as compacted fill, it should be evaluated by this office prior to importing. This GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 12 should be accomplished to determine if the proposed import material is compatible with the existing onsite soils. Care should be taken during grading and construction to avoid damage to the existing retaining wall along the eastern property line. Soil removal and recompaction next to this structure may necessitate the use of small equipment or hand work. Vibrations from equipment should be kept at a minimum. Any earthwork should be performed in accordance with the recommendation presented in this report, requirements of the City of Carlsbad and to the minimum standards of Chapter 70 of the Uniform Building Code. RECOMMENDATIONS-POST EARTHWORK Foundations Design: 1. Conventional spread and continuous strip footings may be used to support the proposed structure provided they are founded entirely in competent terrace deposits or properly compacted fill. 2. Preliminary analysis indicates that an allowable bearing value of 2000 pounds per square foot may be used for design of continuous footings which maintain a minimum width of 12 GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 13 inches and a minimum depth of at least 18 inches into the properly compacted fill. The bearing value may be increased by one-third for seismic or other temporary loads. The above bearing value is valid for onsite materials only. Import fill material will require additional testing and evaluation. 3. A coefficient of friction of 0.4 may be used for the rough concrete surface and compacted material or bedrock. 4. Passive earth pressure may be computed as an equivalent fluid having a density of 250 pounds per cubic foot with a maximum earth pressure of 2500 pounds per square foot. 5. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one- third. 6. All footings should maintain a minimum 7 foot horizontal set back from the base of the footing and any descending slope. Construction: Along the western side of Units 1 through 4 a trench for a sump drainage system is located three feet from the buildings with the drain pipe located at an approximate depth of 4.5 feet to 5.0 feet. Footings within three (3) feet of the trench should penetrate a minimum of six (6) inch below a 1:1 projection from GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 14 the top of the drain pipe. The depth of footing excavations should be determined in the field during installation of the drainage system. It may be assumed that the footing depth would increase approximately 1/2 foot along the west side of units 1 through 3 and a portion of unit 4. Based upon our observations and laboratory test data, low expansive soils exist onsite. The following preliminary recommendations provide for these soils existing at pad grade. Import material will need to be evaluated for its expansion potential, and bearing value. Import material should be low expansive. Expansion tests should be performed at the completion of grading, specific recommendations will be presented at that time. 1. Footings may be constructed according to standard building code requirements regarding width and depth. No reinforcement is necessary due to expansion. However, consideration should be given to placing one No. 4 reinforcing bar near the top and bottom of footings. 2. Concrete slabs, where moisture condensation is undesirable, should be underlain with a vapor barrier consisting of a minimum of six mil polyvinyl chloride or equivalent membrane with all laps sealed. This membrane should be covered with GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 15 a minimum of two inches of sand, to aid in uniform curing of the concrete. 3. Concrete slabs, should be a minimum of 4 inches thick and reinforced with No. 3 reinforcing bars on 18 inch centers or six inch by six inch. No. 6 by No. 6 welded wire mesh. All slab reinforcement should be supported to ensure proper positioning during placement of concrete. 4. No specific presaturation is required, however, footing trenches and soil at pad grade should be moisture conditioned prior to pouring concrete. Retaining Walls General: It is our understanding that the existing retaining wall is proposed to accommodate additional pavement, a safety fence, and traffic surcharge. In the event that the existing wall is retrofitted, all existing wall backfill should be removed. Field exploration indicated those portions of the wall observed did not have a backdrain. Cross-sections of the wall at two locations are included in Appendix I. Due to limited access and safety considerations, a complete detail of wall construction was not made. GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 16 The design parameters provided below assume that low to moderately expansive soils are used to backfill any retaining walls. If high to very highly expansive soils are used to backfill the proposed walls, increased active and at-rest earth pressures will need to be utilized for retaining wall design. Foundations for retaining walls should be designed in accordance with the recommendations presented in the preceding Foundation Design section except where otherwise noted. Restrained Walls: Any retaining walls that will be restrained prior to placing and compacting backfill material, should be designed for at-rest equivalent fluid pressures of 55 pcf, plus any applicable surcharge loading. Cantilevered Walls: The recommendations presented below are for cantilevered retaining walls up to 10 feet high. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are given below for specific slope gradients of the retained material. These to not include other GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 17 superimposed loading conditions such as traffic, structures, seismic events. Surface Slope of Equivalent Retained Material Fluid Weight Horizontal to Vertical P.C.F. Level 35 2 to 1 55 Wall Backfill and Drainage: All retaining walls should be provided with an adequate backdrain system, to prevent buildup of hydrostatic pressures and be designed in accordance with minimum standards of the City of Carlsbad. In addition, gravel used in backdrain systems should be a minimum of 12 inches of Class II filter material or 3/4 inch clean crushed rock wrapped in filter fabric. Where the void to be filled is confined, the use of crushed rock base or panel drains is recommended. The surface of the backfill should be sealed by pavement or the top 24 inches compacted with native soil. Proper surface drainage should also be provided. Additional Site Improvements Recommendations for exterior concrete flatwork design and construction can be provided upon request. If in the future, any additional improvements are planned for the site, recommendations concerning the geotechnical aspects of GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 18 design and construction of said improvements could be provided upon request. Additional Earthwork This office should be notified in advance of any fill placement, or trench backfilling. Footing Trench Excavation All footing trench excavations should be observed by a representative of this office prior to placing reinforcement. Footing trench spoil and any excess soils generated from trench excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Drainage General: Positive site drainage should be maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from the foundation system and not allowed to pond and/or seep into the ground. Pad drainage should be directed toward the street or other approved area. Roof gutters and down spouts should be considered to control and convey roof drainage to an appropriate outlet. Sump Drainage: The site development pian shows a sump drainage system proposed along the southern and western sides of the property which drains GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 19 to a future 12" storm drain lateral in Tamarack Avenue. Along the western side of Units 1 through 4 the drain trench is located three feet from the buildings with the drain pipe located at an approximate depth of 4.5 feet with 5.0 feet. The minimum distance for positive drainage away from any structure along the western side of the property may be revised from 5 feet to 3 feet provided the following recommendations are incorporated into the final design and construction of the project: 1) Design slope gradients are maintained and water is not allowed to pond against any foundations. 2) Clean sand should be placed to 6 inches above the drain pipe. 3) All backfill placed within the trench and around drain risers should be compacted to greater than 90 percent of the laboratory maximum dry density as determined by ASTM D-1557- 78. 4) Footings within three (3) feet of the trench should penetrate 1:1 projection from the top of the drain pipe a minimum of 6 inches. The depth of footing excavations should be determined in the field during installation of the drainage system. It may be assumed that the footing depth would increase approximately 1/2 foot along the west side of units 1 through 3 and a portion of unit 4. The proposed drainage system should be sufficient to adequately remove runoff from the western side of the property provided that a regular maintenance program is established to prevent clogging GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 20 of the drain and drain inlets. Realizing that in all probability clogging of the drain may occur, a second outlet to the storm drain is recommended recommend that roof drains be installed to reduce the amount of runoff directed to this area. Downspouts for roof drains should not be tied into the drainage system along the western property line. Landscape Maintenance Water is known to weaken the inherent strength of all earth materials and cause soil expansion. Only the amount of water necessary to sustain plant life should be provided. Over watering the landscape areas could adversely affect proposed site improvements. We would recommend that all planters adjacent to proposed improvements be eliminated for a minimum distance of 10 feet. As an alternative, closed bottom type planters could be utilized placing a drain in the bottom to properly outlet away from the structure or any exterior improvements. Consideration should be given to the type of vegetation chosen for the site and their potential affect upon exterior improvements. Utility Trench Backfill Utility trench backfill should be placed to the following standards: GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 21 1. Ninety percent of the laboratory standard. 2. For the interior of the slab, it is recommended that 90 percent relative compaction be obtained. Observation, probing, and if deemed necessary, testing may be required to verify adequate results. 3. Exterior trenches, paralleling a footing and extending below a 1:1 plane projected from the outside bottom edge of the footing should be compacted to 90 percent of the laboratory standard. Sand backfill should not be allowed in these trench backfill areas. Density testing along with probing should be accomplished to verify the desired results. 4. All trench excavations should conform to all applicable local safety codes. PLAN REVIEW Final foundation plans should be submitted to this office for review and comment as they become available, to minimize any misunderstandings between the plans and recommendations presented herein. In addition, foundation excavations and earthwork construction performed on the site should be observed and tested by this office. If conditions are found to differ substantially GeoSoils, Inc. ARC GROUP SEPTEMBER 25, 1991 W.O. 1347-SD PAGE 22 from those stated, appropriate recommendations would be offered at that time. LIMITATIONS The materials encountered on the project site and utilized in our laboratory study are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Since our study is based upon the site materials observed, selective laboratory testing and engineering analysis, the conclusion and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice and no warranty is expressed or implied. GeoSoils, Inc. ARC GROUP W.O. 1347-SD SEPTEMBER 25, 1991 PAGE 23 If you have any questions concerning this report, please call Very truly yours, GeoSoils, Inc. Robert G. Crisman Staff Geologist ^Vitha^A Singh^iet, GE 782 eotechnical Engineer 'imoth Principal RGC/VS/TEM/rC Enclosures: Reference List Appendix I, Test Pit Logs Plates SH-1 and SH-2, Shear Tes Plate 1, Geotechnical Map GeoSoils, Inc. REFERENCES Greensfelder, Roger, 1974, Maximum credible rock acceleration from earthquakes in California, Calif. Div. Mines and Geology, Map sheet 23. Joyner, W.B. and Boore, D.M. (1981), "Peak Horizontal Acceleration and Velocity from Strong-Motion Records Including Records from the 1979 Imperial Valley, California, Earthquake," Bulletin of the Seismological Society of America, vol. 71, no. 6, pp. 2011-2038. Joyner, W.B. and Boore, D.M. (1982), Prediction of Earthquake Response Spectra, U.S. Geological Survey Open-File Report 82-977, 16 pp. Jennings, Charles W., 1975, Fault Map of California; Calif. Div. of Mines and Geology, Geologic Data Map series No. 1, to 750,000 scale. Schanbel, P.B., Seed, H.B., 1973, Accelerations in Rock For Earthquakes in the Western United States: Bulletin of the Seismological Society of America, v. 63. no. 2, pp. 501-516. Weber, F.H., 1982, Geologic Map of the Central-North Coastal Area of San Diego County, Cali fornia, Showing Recent Slope Failures and Pre-Development Landslides: California Div. Of Mines and Geology Open-File Report 82-12 LA, Plate 1. GeoSoils, Inc. APPENDIX I TEST PIT LOGS GeoSoils, Inc. TP-1 EAST existing retaining wall WEST Artificial Fill water line (abandoned) *^ tile line Artificial Fill- Brown to red brown, dry, loose silty SAND, Becomes moist and medium dense with depth. Topsoil- Gray brown, dry, loose, porous silty SAND. Many roots in upper 3". Terrace Deposits- Yellow brown, dry, loose to medium dense silty SAND. •3* becomes moist and medium dense 94* becomes red brown scale 1" - 2' no groundwater hole backfilled DATE TEST PIT LOG, TP-1 9/91 W.O. NO. 1347-SD BY re Soil Mechanics • Geology • Foundation Engineering TEST PIT LOG Location Depth (ft.l TP-2 0-1 1-4 Material Description TOPSOIL: Gray brown, dry, loose, porous silty SAND. Many roots in upper 3". TERRACE DEPOSITS: Yellow brown, dry, medium dense, silty SAND. Few roots and krotovina. Krotovina filled with brown loose silty SAND. @2! Pale red brown, slightly moist, medium dense, silty SAND. Total depth= 4 feet No groundwater Hole backfilled TP-3 0-1 1-3.5 TOPSOIL: Gray brown, dry, loose, porous silty SAND. Many roots in upper 3". TERRACE DEPOSITS: Yellow brown, dry, medium dense, silty SAND. Few roots and krotovina. Krotovina filled with brown loose silty SAND. @2' Pale red brown, slightly moist, medium dense, silty SAND. Total depth= 3.5 feet No groundwater Hole backfilled GeoSofls, Inc. EAST TP-4 scale 1" - 2' WEST 0' existing retaining wall \ 2' parking /lot 4' footing r— Artificial Fill- Brown to red brown, dry, loose silty SAND. Becomes moist and medium dense with depth. Topsoll- Gray brown, dry, loose and blocky, porous silty SAND. Many roots in upper part. Terrace Deposits- Light red brown, slightly moist, medium dense silty SAND and SAND with silt. no groundwater hole backfilled TEST PIT LOG, TP-4 DATE 9/91 W.O.1347-SD BY re Soil Mechanics * Geology • Foundation Engineering THE ARC GROUP W.O. 1347-SD SEPTEMBER 27, 1991 TEST PIT LOG Location Depth fft.)Material Description TP-5 0-1.5 1.5-4 TOPSOIL: Gray brown, dry, loose, porous, silty SAND with many roots. TERRACE DEPPSITS: Yellow brown and red brown, dry, medium dense, silty SAND. Few layer roots present at south end of test pit. Total depth= 4 feet No groundwater Hole backfilled GeoSoils, Inc. 3.0 2.5 2.0 u. CO oz UJocI-OT oz UJz W 1.5 1.0 0.5 phi angle = 30° cohesion = 0.5 ksf 0 0.5 1.0 1.5 2.0 NORMAL PRESSURE-KSF EXPLANATION O RESHEAR - AT SATURATED MOISTURE CONTENT • PEAK - AT SATURATED MOISTURE CONTENT 2.5 3.0 DIRECT SHEAR REMOLDED TO 90%RELATIVE DENSITY; THEN SATURATED PCF % MOISTURE % SATURATED MOISTURE CONTENT UNDISTURBED NATURAL SHEAR SATURATED 13.2 % SATURATED MOISTURE CONTENT GeoSoils, Inc. SHEAR TEST DIAGRAM UNDISTURBED SHEAR. TP-1 9 5.5' DATE !5L W.O.1347-SD Soil Mechanics * Geology * Foundation Engineering FORM 87/8-2A PLATE SH-1 3.0 2.5 2.0 wX.IXI-oz UJ w oz UJ ICO 1.5 1.0 0.5 phi angle - 34° cohesion = 0.240 ksf 0 0.5 1.0 1.5 2.0 NORMAL PRESSURE-KSF EXPLANATION O RESHEAR - AT SATURATED MOISTURE CONTENT • PEAK - AT SATURATED MOISTURE CONTENT ... 2.5 3.0 DIRECT SHEAR REMOLDED TO 90%RELATIVE DENSITY; THEN SATURATED PCF % MOISTURE % SATURATED MOISTURE CONTENT UNDISTURBED NATURAL SHEAR SATURATED % SATURATED MOISTURE CONTENT GeoSof Is, Inc. SHEAR TEST DIAGRAM REMOLDED SHEAR TP-2 COMPOSITE DATE 9/91 W.O. MH 1347-SD Soil Mechanics • Geology • Foundation Engineering FORM 87/8-2A PLATE SH-2