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HomeMy WebLinkAbout7.1 Attachment 1 BGC BERLOGAR GEOTECH N ICAl CONSULTANTS SOIL ENGINEERS ENGINEERING GEOLOGISTS ~.." \ ." 1'\ , "?," m'~ 1 ( 'ji~ / ' '-o..' "',~ '/ .,,, .,~, ;~ ~.~. ,,;t, .s Lcil)t!5' ~ F:JDA. /.If' -. . . . GEOTECHNICAL INVESTIGATION SLOPE STABILITY CONCERNS DOUGHERTY HILLS PARK DUBLIN, CALIFORNIA FOR CITY OF DUBLIN . . April 25, 1996 Job No. 2090.000 . BERLOGAR GEOTECHNICAL CONSULTANTS City of Dublin 100 Civic Plaza P.O. Box 2340 Dublin, California 94568 I r April 25, 1996 Job No. 2090.000 r Attention: Mr. Lee Thompson Subject: Geotechnical Investigation Slope Stability Concerns Dougherty Hills Park Dublin, California r Gentlemen: I INTRODUCTION This report presents the results of our geotechnical investigation to evaluate areas of slope stability concern at Dougherty Hills Park in Dublin, California. The study is shown in relation to Amador Valley Boulevard and Dougherty Road on the attached Vicinity Map, Plate 1. The study area included the following areas: 1) a recently active landslide located upslope of Lot 66 on Jade Circle, 2) a recently active landslide located upslope of Lot 74 on Jade Circle, 3) a recently active landslide upslope of Lot 141 on Crossridge Drive, 4) a recently active landslide upslope of Lot 143 on Crossridge Drive, and 5) a cut slope on the east side of Lots 110 through 145 on Crossridge Drive. The purposes of this project have been to evaluate the areas of slope stability concern noted above, to provide conclusions regarding the stability of those areas and to provide recommendations for remedial alternatives. Preparation of remedial grading plans and specifications were not within the scope of our investigation. Our scope of services include the following: 1. Review of available geotechnical reports and plans, pertinent to the study area. 2. Examination of stereo paired aerial photographs of the study area. 3. Review of pertinent geologic maps and literature. 4. Excavation and logging of 61 test pits ranging from about 4 to 15 feet deep. 5. Drilling of 2 borings ranging from about 40 to 42 feet deep using auger drilling and drive sampling methods. SOIL ENCINELRS . ENCINEERING GEOLOGISTS. 5587 SUNOL BOULEVARD · PLtASANTON, CA 94566 · (510) 484-0220 · FAX: (510) 846-9645 .. . April 25, 1996 Job No. 2090.000 Page 2 . 6. In our laboratory, the field classifications were confirmed and samples selected for testing. The laboratory testing program included moisture content, dry density and strength (direct shear) testing as deemed appropriate. 7. Geotechnical engineering analysis was performed to evaluate areas of slope stability concern. Existing slope configurations and recommended remedial approaches were analyzed using two dimensional, limit equilibrium computer modeling methods. . 8. This report was prepared presenting the findings of the investigation including field and laboratory data. . A geologic map of the study area is presented on Plate 2. Cross sections of each of the recommended remedial grading areas are included on Plate 3. Boring logs and logs of test pits area presented on Plates 4 through 22 and laboratory test results are included on Plates 23 through 28. The results of our slope stability analysis are contained in an appendix to this report. Study Area Historv Jade Circle - A geotechnical investigation report for the Jade Circle subdivision was prepared by Terrasearch, Inc., dated June 13, 1980. Grading plans for the project were prepared by Bissell & Karn, Inc, dated July, 1983. Records indicate that the development was mass graded during the summer of 1983. During the winter of 1995/1996, landslides occurred upslope of Lots 66 and 74. Crossridge Drive - A geotechnical investigation report for the Crossridge Drive subdivision was prepared by Kleinfelder & Associates, Inc., dated April 15, 1986. No landslides were identified in the Kleinfelder report. Grading plans for the project were prepared by Tetrad, dated April 16, 1986. Records indicate that the development was mass graded during the summer of 1986. During the winter of 1995/1996, landslides occurred upslope of Lots 141 and 143. FINDINGS Study Area Description . The areas of slope stability concern under investigation are located on existing cut slopes that were graded in conjunction with mass grading for subdivisions on the east and west sides of Dougherty Hills Park. Dougherty Hills Park is dominated topographically by a north/south trending ridge. Cut slopes for the Jade Circle subdivision appear to have gradients of about 2 horizontal to 1 vertical (2H: 1 V) and range up to about 80 feet high. Cut slopes for the Crossridge Drive subdivision range up to about 70 feet high. The northern portion of the cut slope appears to have a gradient of about 21/2H:1V. The southern portion of the cut slope (at the rear of Lots 139 through 145) appears to have a gradient of about 2H: 1 V. . BERLOGAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 3 . Geologic Setting . Regional geologic maps indicate that the study area is underlain by bedrock of the Tassajara Formation (Dibblee, 1980). The Tassajara Formation is a poorly indurated, nonmarine, sedimentary rock of Plio-Pleistocene age. Recent Landslides Recently active landslides are distinguished by sharp, conspicuous and essentially uneroded head and/or lateral scarps as well as prominent bulges at the downslope extremities. The recently active landslides in the study area have all impacted downslope V -ditches and have resulted in temporary blockage of storm water runoff. The recently active landslides appear to involve dark brown, silty clay soils ranging from about 1 to 3 feet thick. Landslide/Colluvial Deposits . Landslide/Colluvial deposits have been mapped in the study area based on examination of aerial photographs, site reconnaissance and test pit exploration. Swales containing thicker soil deposits, where evidence of previous downslope movement is uncertain, have been identified as Landslide/Colluvial deposits. The landslide/colluvial deposits may be older landslides where features indicative of previous downslope movement have been modified by erosion and vegetative overgrowth over time. Discontinuous slickensides and sheared soils were observed at the base of some of the older landslide deposits (TP-3,TP-33). Our interpretation of the landslide/colluvium thicknesses, based on the findings of the test pits and borings, are depicted on the attached cross sections. The landslide/colluvium thicknesses appear to vary from about 5 feet to as thick as about 15 feet. The landslide/colluvium appears to consist primarily of dark brown silty clay and based on visual examination appears to be highly expansive. The identified landslide/colluvial deposits are shown in relation to residential lots on the Geologic Map. Grading for the subdivisions has included cuts in each of the identified landslide/ colluvium areas. Colluvium Soil deposits encountered in two swales adjacent to the northern portion of Crossridge Drive were mapped as colluvium. Colluvium is relatively young soil that has been deposited by sheet wash and downslope creep of soil materials. The colluvial deposits appear to range up to about 10 feet thick and consist primarily of dark brown, silty clay and sandy clay. -. . BERLOGAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 4 . Tassaiara Formation . Bedrock in the study area was found to consist predominately of interbedded siltstone and sandstone. Minor interbedded claystone and conglomerate were encountered. The bedrock encountered was generally poorly indurated, friable, highly fractured and thickly bedded. Bedding contacts appear to be poorly developed and distinct bedrock structure was observed in only two test pits, TP-26 and TP-52. Lineations on the cut slope on the north side of Jade Circle indicate a northwest strike and easteriy dip. Ground Water . No free water was encountered in the test pit and boring exploration. Soil materials involved in the recent landslides were observed to be nearly saturated. Stability Analyses . Laboratorv Results - To provide a basis for selection of appropriate soil parameters to be used for our stability analyses, "simple" direct shear tests were performed on both relatively undisturbed and remolded samples to determine peak maximum strength and residual strength (sheared repeatedly until minimum shear resistance obtained) parameters of various materials obtained in our investigation. The results of laboratory tests performed on the undisturbed materials are summarized as follows: SUMMARY OF "SIMPLE" DIRECT SHEAR TESTS ON RELATIVELY UNDISTURBED SAMPLES Shear Strength Peak Strength Values Residual Strength Va1ues Cohesion "C" (psf) 225 - 290 70 - 130 Internal Friction "0" (degrees) 25 - 25% 241/2 Shear strength tests were performed on various on-site materials remolded to approximately 90 percent relative compaction (based on ASTM D1557-91) at moisture contents of about 2 percent above optimum moisture content. The results of laboratory tests performed on remolded materials are summarized as follows: . . BERLOGAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 5 . SUMMARY OF "SIMPLE" DIRECT SHEAR TESTS ON MATERIALS REMOLDED TO 90 PERCENT RELATIVE COMPACTION Shear Strength Values Clay Soils Cohesion "C" (pst) 440 - 640 370 Internal Friction "0" (degrees) 15 - 20 27 . Bedrock Materials (Sandstone and Siltstone) . . Stability Analyzes - Stability analyses were performed on three critical cross-sections, to model: 1) existing slope conditions; 2) 3 horizontal to 1 vertical (3H: 1 V) cut slope configurations; and 3) conceptual remedial grading 2H: 1 V buttress slopes with subdrainage. Based on the results of our laboratory tests, we conservatively selected the following strength parameters to model various critical cross-sections for our analyzes. In addition, the clayey fill materials may lose strength over time due to desiccation cracks and repetitive wet/dry cycles. Therefore, it is our opinion that the long term residual strength for the clayey materials should not include cohesion (i.e., C = 0). SUMMARY OF SHEAR STRENGTH PARAMETERS USED FOR SLOPE STABILITY ANALYSES Shear Strength Parameters Modelled Unit Condition Weight (pct) Cohesion "C" Internal Friction (pst) "0" (degrees) Existing Cut Slope Soil 120 70 241,/i (2H: 1 V) Cut Slope Soil 120 70 241/2 (3H: 1 V) 2H: 1 V Buttress Slope Soil 120 70 24'h consisting predominantly Clayey Fill 120 440 - 640 15 - 20 of Clayey Fill Clayey Fill 0 15 - 20 (residual) 2H: I V Buttress Slope Soil 120 0 24'h consisting predominantly of Sandstone and Sandstone and 120 370 27 Siltstone derived Fill Siltstone Fill . . BERLOGAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 6 . Phreatic surfaces modelled in our stability analyzes assume high ground water conditions with the phreatic surface at the ground surface of the landslide, except for buttress fills where sub drainage would be installed. For buttress fills phreatic surfaces modelled were assumed to be at subdrainage levels and extended along the bottom of the buttress fill. . Results of Stability Analyzes - We performed a series of slope stability analyzes for the static condition and assuming soil and bedrock parameters, and phreatic surfaces discussed above, using the computer program GSLOPE. The results of stability analyzes (static condition) for cross-sections are summarized in the following table. The stability analysis computer output data for various configurations analyzed are include in the Appendix. In general, safety factors greater than 1.5 for static conditions are considered stable. SUMMARY OF SLOPE STABILITY ANALYZES COMPUTED FACTORS OF SAFETY (STATIC CONDmON) . Minimum Factor of Safety (F.S.) Condition Fully Saturated Condition "Dry" Condition Ground Water Collected at Keyway Subdrain 2H: 1 V Cut Slope 3H: I V Cut Slope 2H: 1 V Buttress consisting predominantly of Clayey Fill - Peak Strength 0.77 1.15 1.45 2.10 1.68 - 1.78 2H: I V Buttress consisting predominantly of Clayey Fill - Long Term (Residual Strength) 0.94 - 1.06 2H: 1 V Buttress consisting predominantly of Sandstone and Siltstone derived Fill 2.15 - 2.38 CONCLUSIONS AND RECOMMENDATIONS General Based on the results of our stability analyzes, long term "static" stability of the existing slopes, 3H: 1 V cut slopes, and 2H: 1 V buttress slope (long term residual strength condition) consisting predominantly of silty clay soils show F.S. results below 1.5; as such, these would be considered potentially unstable for long-term conditions. The 2H: 1 V buttress slope conSisting predominantly of siltstone and sandstone bedrock materials show F. S. above 1.5; therefore, these would be considered stable for long-term conditions. On this basis, it is recommended that remedial grading for landslide repairs of the subject slopes include the construction for landslide repairs of the subject slopes include the construction of buttress fill slopes consisting of siltstone . BERLOGAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 7 . . and sandstone bedrock materials, with appropriate subdrainage. Construction of the slopes using bedrock materials will require a borrow site as a source of these bedrock materials. The borrow site should be backfilled with the materials excavated from the remedial grading areas. Our recommendations for site preparation, grading and subdrainage are presented in the following sections of this report. Buttress Fill Slopes . The stability of the buttress fill slopes depends on proper keyways, subdrainage, fill material, fill compaction and slope gradients. The following should be incorporated in the buttress fill slope design: · Keyways will be constructed at the toe of the buttress fill slopes; · Subdrainage will be installed at the rear of the keyways; and . · Benching will extend through surficial soils into bedrock. Generally, the maximum keyway width should be 20 feet (see Cross Section, Plate 3 for details). Horizontal benches should be excavated into bedrock to key fills into bedrock during construction of the slopes. The buttress fill slopes should be constructed of predominantly sandstone and siltstone materials. In general, buttress fill slope gradients should not be steeper than 2H: 1 V. Fill slopes higher than 30 feet should have intermediate benches generally spaced no further apart than 25 feet vertically. Benches should be a minimum of 8 feet wide and have a concrete-lined V -ditch to intercept runoff. Subdrainalfe We recommend that subdrainage be provided in the following areas: 1. At all springs and seepage areas; 2. At rear of the keyway bottoms; and 3. Lateral subdrains and/or finger drains to be extended upslope within the buttress fill area. . Subdrains should consist of ABS perforated pipe conforming to ASTM Designation D2751, Type SDR 23.5. Perforations should be placed down. Subsidiary subdrains should be at least 4 inches in diameter and central drains should be at least 6 inches in diameter. All subdrains should have a shading cover of at least 18 inches and be underlain by at least 6 inches of Class 2 "Permeable Material", as defined in Section 68-1.025 of the Caltrans Standard Specifications (July, 1992). Subdrain trenches should be at least 18 inches wide and at least 4 feet deep. Final trench configurations should be approved by the soils engineer. Subdrain trenches should be . BERLOCAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 8 . capped with engineered fill or topsoil, depending upon the subdrain location. Subdrains should be positioned along the upslope side of all keyway excavations. Subdrainage systems should be discharged into storm drain structures, if possible. . Subdrains should be field located by surveyors and an as-built subdrain plan should be drawn upon completion of the mass grading. Site Preparation and Gradine . All grading operations should be done in accordance with the following recommendations: 1. Areas to be graded should be cleared and stripped of all vegetation. Strippings can be stockpiled and reused as topsoil or stripping can be placed as fill, disposed in a designated disposal area and in a manner recommended by the project geotechnical engineer. . 2. Landslide debris should be removed in areas to receive fill. The landslide remedial treatments are shown on the attached Cross Sections. 3. Where zones of soft or saturated soils are encountered during excavation and compaction, deeper excavation may be required to exposed competent materials. This should be determined in the field by the geotechnical engineer. 4. Areas where fill will be placed should be scarified to a minimum depth of 12 inches. Scarified materials should be moisture conditioned to at least two percent above optimum moisture content and be compacted to at least 90 percent relative compaction Relative compaction refers to the in-place dry density of soil expressed as a percentage of the maximum dry density of the same soil, as determined by the ASTM D1557-91 compaction test method. Optimum moisture is the water content (percentage by dry weight) corresponding to the maximum dry density. 5. Predominately sandstone and siltstone materials are recommended to be used as engineered fill. In addition, the engineered fill should be free of vegetation and all deleterious materials. 6. All fill and backfill materials should be subject to evaluation by the soil engineer prior to use. 7. Rock fragments greater than 6 inches in largest dimension should not be used in the buttress fill. . . BERLOGAR GEOTECHNICAL CONSULTANTS . April 25, 1996 Job No. 2090.000 Page 9 . 8. Fill should be placed in thin lifts (normally 6 to 8 inches thick, depending on compaction equipment), moisture conditioned to at least two percent over optimum moisture content, and be compacted to at least 93 percent relative compaction. . 9. Fills should be benched through soil and slide deposits into competent bedrock. 10. Preferably, fill slopes should be overfilled and cut back to expose a firm and compacted surface. Alternatively, the slope surface can be trackrolled to at least 85 percent relative compaction within 1 foot of the surface and 90 percent relative compaction below 1 foot from the surface. . 11. Observations and soil density tests should be carried on during grading to assist the contractor in obtaining the required degree of compaction and the proper moisture content. Where compaction is less than required, additional compaction effort should be made with adjustment of the moisture content as necessary until the specified compaction is obtained. . 12. The soil engineer should be notified at least 48 hours prior to any grading operation. The procedures and methods of grading may then be discussed between the developer, contractor and the soil engineer. This can facilitate the performance of grading operations and minimize possible construction delays. Topaz Circle Slumps Two slumps developed on the "knuckles" of Topaz Circle this winter. Our scope of work did not include investigation of these two areas. From surface inspection, it appears that these two slumps could be repaired in a manner similar to those presented previously in this report. If you elect to proceed in this fashion, this office must closely observe all work. Additional Soil Engineering: Services Prior to construction, we should review the final plans and specifications for conformance with the intent of our recommendations. In the event that changes in the nature, design or location of the proposed improvements are planned, the conclusions and recommendations presented in this report shall be not considered valid unless the changes are reviewed by us and the conclusions either verified or modified as required in writing. . To a degree, the performance of these structures are dependent on the procedures and quality of the construction. Therefore, we should provide full-time on-site observations of the contractor's procedures and the exposed soil conditions, together with field and laboratory testing during placement and compaction of fill and backfill. These observations will allow us to check the contractors' work for conformance with the intent of our recommendations and to observe any unanticipated soil conditions that could require modification of our recommendations. In . BERLOGAR GEOTECHNICAL CONSULTANTS . . . . . . . April 25, 1996 Job No. 2090.000 Page 10 addition, we would appreciate the opportunity to meet with the contractor prior to the start of construction to discuss the procedures and methods used. This can facilitate the performance of the construction operation and minimize possible misunderstandings and construction delays. LIMIT A TIONS The conclusions and recommendations in this report are based upon the information provided to us regarding the site improvements, subsurface conditions encountered in test pits and borings, our geologic reconnaissance, and professional judgment. This study has been conducted in accordance with current professional geotechnical engineering and engineering geologic standards; no other warranty is expressed or implied. The location of tests pits and boring were determined by pacing from established features and other points of reference indicated on grading plans provided to us. Site conditions described in the text are those existing at the time of our field reconnaissance in April 1996, and are not necessarily representative of such conditions at other locations and times. Respectfully submitted, BERLOGAR GEOTECHNICAL CONSULTANTS ~L ';' Cl \\ / {:1-,~v 9L- p' ilip T e - Principal Engineer ~ Raymond P. Skinner Principal Geologist CEG 1239 Attachments: Plate 1 - Vicinity Map Plate 2 - Geologic Map Plate 3 - Geologic Cross Sections Plates 4 through 7 - Boring Logs Plate 8 - Key to Boring Log Symbols Plates 9 through 22- Test Pits Logs Plates 23 through 28 - Laboratory Test Results Appendix - Slope Stability Analysis wp511 report/351 0 BERLOGAR GEOTECHNICAL CONSULTANTS . . . LL LL ;.: CD . <0 Ol ..t C\l ..t W .... . <( a ". . " o o o ci Ol o C\l a: w CD ~ ~ z CD o -, SCALE: 1'= 2000' VICINITY MAP DOUGHERTY HILLS PARK DUBLIN, CALIFORNIA FOR CITY OF DUBLIN BASE: PORTION OF U.S"G-S. 7.5 MINUTE TOPOGRAPHIC QUADRANGLE, DUBLIN, CALIFORNIA, PHOTOREVISED 1980, AT A SCALE OF 1:24,000. PLATE 1 BERLOGAR GEOTECHNICAL CONSULTANTS . BaR I NG LOG B-1 JOB NUMBER: 2090.000 DATE DRILLED: 3-15-96 JOB NAME: Dougherty Hills Park SURFACE ELEVATION: 456 +/- feet DRI LL RIG: Solid Flight Auger DA T U M: Mean Sea Level . SAMPLER TYPE: . 2.5 inch 1.0. Split Barrel DRIVE WEIGHT - LB 140 HEIGHT Of FALL - IN 30 . .....l:R 1-1- Z ..!..z (/') I- ~I- - J: . (/')(/')O 3=LL.. ::;lZ zc.:l'+-: J: u(/')- 1-..... :::;l_~ 1-1- (f)"",tl- DESCRI PTlON oCt:: (1)1- :>- LLJ c.. a...LLJ :::;l-l..;r -I LLJ -z Ct::3= UU IDa... 00 LLJLLJ LU 0 o LL.. LL.. CL SILTY CLAY, dark gray-brown, wet, stiff, trace to some fine to 16 20 109 medium~grained sand, trace fine gravel . below 4 feet, becomes moist, very stiff 5 27 14 108 CL SILTY CLAY, light gray-brown, moist, very stiff, some fine to medium-grained sand . SILTY SANDSTONE, light gray-brown, highly weathered, friable, 120 21 99 low hardness, some fine gravel, caliche stains and veins 10 . 15 CLAYEY SILTSTONE, light gray-brown, highly weathered, friable, low hardness, trace fine gravel and caliche stains . 68 19 98 . SILTY CLAYSTONE, light olive-brown, highly weathered, friable, low hardness, slightly sheared, caliche stains 81 23 102 . 20 . PLATE 4 BERLOGAR GEOTECHNICAL CONSULTANTS . . . . . . . . . . . JOB NUMBER: BaR I NG LOG 2090.000 OF: 2 B-1 2 SHE ET : JOB NAME: NOT ES: Dougherty Hills Park DE PT H: 20 TO 39 feet 8 inches .....l:R l--l-- :z ..!..Z (J') l-- 0:::1- z::c,...: - (I) (I) 0 3=1.1- ~z :::l~oe..:i ::c U(I) - 1-..... l--l-- (I)-<;tl-- DESCRI PTION 00::: (1)1- >- w 0.. o...w :::l--l <l: ....Jw -z 0:::3= u:2 co 0... 00 Ww Eu 0 01.1- 1.1- SIL TV CLAYSTONE, light olive-brown, highly weathered, friable, low hardness, slightly sheared, caliche stains 50 30 87 25- r--. - SANDY SILTSTONE, light gray-brown, highly weathered, friable, low hardness, fine-gralned sand, limonite stains 95 15 101 r-- GRAVELLY SANDSTONE, light gray-brown, highly weathered, 30 I'--...... friable, low hardness, poorly cemented, fine to medium-grained sand, fine gravel, limonite stains SANDSTONE, light gray-brown, highly weathered, friable, low hardness, poorly cemented, fine to medium-grainecl sand, trace fine gravel, limonite stains below 33 feet, fine to coarse-grained sand 63 16 98 35 l- I- below 37 feet, becomes gravelly I- 100' - - ~ 2" 40 I- Boring tenninated at 39 feet 8 inches. No free water encountered. PLATE 5 BERLOGAR GEOTECHNICAL CONSULTANTS . BaR I NG LOG B-2 DATE DRI LLED: 3-15-96 JOB NUMBER: 2090.000 JOB NAME: Douohertv Hills Park SURFACE ELEVATION: 448 +/- feet DRI Ll RIG: Solid Flight Auger DA T U M: Mean Sea Level . SAMPLER TYPE: . 2.5 inch I.D. Split Barrel DRIVE WEIGHT - LB 140 HEIGHT Of FALL - IN 30 . LLl~ ~~ Z ..!..z (f) ~ 01:1- -:I: . - (f)(f)O 3:1..L.. :JZ zC,:l""': :I: U(f)i= I-LLl :::)-c.:: ~~ DESeRI PTION o~ (/)1- >- LLJ CL (f)-<I:-<[ ...J LLJ -z ~3: Q.LLJ :::)...Ju CD Q. 00 LLJLLJ u_ I:u 0 OI..L.. I..L.. ~ CL SIL TV CLAY, dark gray-brown, saturated to wet, stiff 19 26 96 - 15 28 91 5- below 5 feet, becomes wet to moist - below 7 feet, trace to some flne-grained sand 13 - - CLAYSTONE, light gray-brown, highly weathered, friable, low 10 hardness, some heavy caliche stains 48 37 83 >- .... .... 15 SILTSTONE, light gray-brown, highly weathered, friable, low 60 22 99 hardness, moderate to heavy caliche stains - ---- - - CLAYSTONE, light olive-brown, highly weathered, friable, low hardness, minor limonite stains 46 25 92 20 I . .. -. . . . . . PLATE 6 BERLOGAR GEOTECHNICAL CONSULTANTS BOR I NG LOG B-2 . 2 JOB NUMBER: 2090.000 SHE ET : OF: 2 JOB NAME: Dougherty Hills Park DE PT H: 20 TO 41-1/2 feet NOTES: . . LLJl:R 1-1- :z: 2..:z: (f) I- O!::I- - J: . - (f)(f)O 3:...... :JZ zt:)'+-: J: u(f)1- I-LLJ :;:)-~ 1-1- DESCRI PTION aCt: (,1')1- >- l.LJ c. (f)4:<[ ....J l.LJ -z lX3: a..l.LJ :=.....Ju m a.. 00 l.LJl.LJ u_ Eu 0 0...... ...... 46 25 92 CLAYSTONE. light olive-brown, highly weathered, friable, low hardness minor limonite stains SILTSTONE, light gray.brown, highly weathered, friable, low hardness SILTY SANDSTONE, light gray-brown, highly weathered, friable, 25 low hardness, poor1y cemented, flne-grained sand 73 12 96 - - SILTY CLAYSTONE, light gray-brown, highly weathered, friable, low hardness, caliche stains 46 25 97 30 - ~ f- 35 47 33 89 CLAYSTONE, light green-gray, moderately weathered, friable, - low hardness, slightly sheared, minor caliche stains - - 63 28 92 40 I / Boring terminated at 41-1/2 feet. No free water encountered. . . . . . . . PLATE 7 BERLOGAR GEOTECHNICAL CONSULTANTS . . ::t:: :<:: fi >-< >J:I . \0 7\ I ..j" N I ..j" ::.t.l Ie< -<X: ;::l . ,::::> ,::::> <::::> o 0\ ~ r-::: w ,:q ;:E:: ::::J Z ~ o '"J . . . MAJOR DIVISIONS CLASSI FI- TYPICAL NAMES CATION CLEAN GRAVELS GW WELL GRADED GRAVELS, GRAVEL - SAND MIXTURES WITH LITTLE OR (f) NO FINES ...J GRAVELS _tr: GP POORLY GRADED GRAVELS, GRAVEL - SAND MIXTURES O~ '.10RE THAN HALF (f)a: COARSE FRACTION Cl j w IS LARGER THAN GRAVEL WITH GM SILTY GRAVELS. POORLY GRADeD GRAVEL - SAND - SILT MIXTURES W !!!~ NO. 4 SIEVE SIZE OVER 12% FINES Z... _ - ..J" GC CLAYEY GRAVELS. POORLY GRADED GRAVEL - SAND - CLAY MIXTURES <(..:~ a::I: <.:l :z ... SW ..: :z CLEAN SANDS WELL GRADED SANDS. GRAVELLY SANDS W:I:" en : ~ WITH LITTLE a: a:: SANDS OR NO FINES SP <(9 POORL Y GRADED SANDS. GRAVELLY SANDS 0"" MORE THAN HALF U COARSE FRACTION IS SMALLER THAN SM SILTY SANDS. PODRLY GRADED SANO - SILT MIXTURES "10_ 4 SIEVE SIZE SANDS WITH OVER '2~ FINES SC CLAYEY SANOS. POORL Y GRAOED SAND - CLA Y MIXTURES :z 'ML INORGANIC SILTS ANO VERY FINE SANDS. ROCK FLOUR. SILTY OR ..: CLAYEY FINE SANDS. OR CL.AYEY SILTS WITH SLIGHT PLASTICITY, (f):I: ...Jf- -a: SIL TS AND CLAYS INORGANIC CLAYS OF LOW TO MEQIUM PLASTICITY. GRAVELLY CLAYS. OW CL (f)~ LIQUID LIMIT LESS THAN 50 SANDY CLAYS, SILTY CLAYS. LEAN CLAYS. O"w ::;: ::- W"'W OL ORGANIC CLAYS ANO ORGANIC SILTY CLAYS OF LOW PLASTICITY Z"'- -'" 4: ~ g INORGANIC SILTS. MICACEOUS OR DIATOMACIOUS FINE SANOY OR a:~~ MH SILTY SOILS. ELASTIC SILTS <.:l- :z W" SIL TS AND CLAYS CH INORGANIC CLAYS OF HIGH PLASTICITY. FAT CLAYS 2; u:~ LIQUIO LII/.IT GREATER THAN 50 0 ORGANIC CLAYS OF MEQIUM TQ HIGH PLASTICITY, ORGANIC SIL TS ::;: OH HIGHLY ORGANIC SOILS Pt PEAT AND OTHER HIGHLY QRGANIC SILTS UNIFIED SOIL CLASSIFICATION SYSTEM al... (f)..::e '" - ::; e r ""- ~ "" ~- ;:: e.: >-..cL.L. c.eal U'- D DESCRIPTION "" -....,e ....cE'u "'.- D .... Q)'_ al (f)"'_ .- c: ~ o:Jalo.. o .... :J"'''' -Q) DC cae. :2U S- uCJ X Bulk sample 2.5" 1.0. Split Barrel Sample NOTE: Soils described as 2.8" 1.0. Shelby Tube Sample dry, moist, and VlIet are estimated to be dry of No sample recovered optimum. near optimum, and wet of optimum moisture content, respect- / Standard Penetration Test interval ively. Saturated soils are estimated to be within - Well defined stratum change areas of free ground- ~ Gradual stratum change water. ---- I nterpreted stratum change '5l. Apparent ground water level at date noted. Seasonal - weather conditions, site topography, etc., may cause changes in water level indicated on logs KEY TO BORING LOG SYMBOLS PLATE 8 BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills landslides Dublin, California TEST PIT LOGS . Test Pit Number Depth (Feet) Description TP-1 0-5 Silty Clay, dark gray brown, wet, medium stiff, high plasticity. . 3-11 Silty Clay, brown, moist, stiff, low plasticity, little sand and gravel (Ols?). 11-13 Interbedded Siltstone and conglomerate, light gray-brown, friable, crushed, thickly bedded (QTt). . Total Depth 13 feet No free water encountered TP-2 0-2 Silty Clay (CH). dark brown, moist, medium stiff. 2-7 Siltstone, light brown, moist to dry, weak, thickly bedded, no observable bedding, highly fractured (QTt). Total Depth 7 feet No free water encountered . TP-3 0-6 Silty Clay (CH). dark brown, moist, medium stiff. 6-10 Silty Clay (Cl). light brown, dry to moist, medium dense, locally sandy (subrounded to subangular clasts), (Qls? IQc). . 1 0-11 Siltstone Bedrock (QTt). light brown, dry, medium stiff, crushed, friable, moderately sheared, caliche veins and zones. Shear surfaces observed at soil-bedrock contact, gently dipping (- 1 00) downhill. Total Depth 1 1 feet No free water encountered . TP-4 0-6 % Silty Clay (CH), dark brown, wet grading to moist, soft grading to medium stiff. 6 %-8 % Silty Clay (CLl, light brown, moist, medium dense, local sand and gravel (Qls/Qc). . 8%-10% Silty Clay, medium brown, moist, medium dense (Qls/Qc). 10%-11Y, Siltstone, light brown, friable to weak, locally crushed (QTt). . Total Depth 11 Y, feet No free water encountered wp51/r"'~l;IrtJ3513tP PLATE 9 . BERLOGAR GEOTECHNICAL CONSULTANTS . / Job No. 2090.000 Dougherty Hills landslides Dublin, California TEST PIT LOGS . Test Pit Number Depth (Feet) Description TP-5 O-Yo Silty Clay (CHl, dark brown, wet, soft. . Yo-4 Siltstone, light brown, generally weak, locally friable, crushed, thickly bedded, local wet clay seams to 2 inches. No bedding observed (OTt). Total Depth 4 feet No free water encountered . TP-6 0-2 Y. Silty Clay (CHl, dark brown, moist, medium stitt. 2 Yo-4 Siltstone, light to medium brown, generally weak, locally friable, crushed, thickly bedded, some caliche veins and zones. No bedding observed (OTt). '. Total Depth 4 feet No free water encountered TP-7 0-3 Silty Clay (CHl, dark brown, moist, medium stitt. . 3-5 Siltstone, light to medium brown, generally weak, locally friable, crushed, thickly bedded, some caliche veins and zones. No bedding observed (OTt). . Total Depth 5 feet No free water encountered TP-8 0-3 Silty Clay (CH), dark brown, moist medium stitt grading to stitt. 4-5 Silty Clay with Sand (Cl), dark brown, moist, stiff (Ols/Oc). . 5-7 Silty Sandstone, light brown, dry, poorly indurated, no evident fractures or bedding, sand is fine-grained (OTt). Total Depth 7 feet No free water encountered . TP-9 0-8 Silty Clay (CHl, dark brown, wet grading to moist, soft grading to medium stiff, - 5 % pebbles and sand, no shear surfaces evident (Oc). 8-10 Siltstone, light brown, dry, weak to friable, crushed, local caliche veins, (OTt). . Total Depth 10 feet No free water encountered wp51/reportl3513tp PLATE 10 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS . Test Pit Number Depth (Feet) DescriPtion TP-l 0 0-7 Y, Silty Clay (CH), dark brown, wet grading to moist, soft grading to medium stiff, -5% pebbles, local gravel to 2 inches, (Qc). . 7 Y,-9 Sandstone, light brown to orange-brown, dry, weak, local caliche, (QTt). Total Depth 9 feet No free water encountered . TP-l 1 0-3 Silty Clay (CH), dark brown, moist, medium stiff (Qc). 3-6 Siltstone, light brown, dry, weak, local minor caliche, (QTt). Total Depth 6 feet No free water encountered TP-12 0-3 Silty Clay (CHl, dark brown, moist, medium stiff (Qc). . 3-7 Sandstone, light brown, dry, fine to medium grained, < 10% fines, weathered to a loose SP (easily scraped from test pit walls with very little pressure) (OTt). Total Depth 7 feet No free water encountered . TP-l 3 0-8 Silty Clay (CHl, dark brown, moist, medium stiff {Qcl. 8-10 Siltstone, light brown, dry, weak, minor caliche veins, (QTt). . Total Depth 10 feet No free water encountered TP-14 0-6 Silty Clay, dark brown, wet grading to moist, medium stiff, no shear surfaces (Qcl. . 6-8 Interbedded Sandstone and Pebbly Sandstone, light brown to dark gray, dry to moist, poorly indurated, possible bedding at 130/305 (S50E/30S) (OTt). . Total Depth 8 feet No free water encountered wp51/repont3513tp PLATE 11 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS T est Pit Number Depth (Feet) Description . TP-15 0-6 Silty Clay, dark brown, wet grading to moist, medium stiff. . 6-8 Interbedded Sandstone and Siltstone, medium brown to light gray, dry, bedding distinct in lower west wall (dips 2:650 south, strike unknown), bedding in distinct east wall. . Total Depth 8 feet No free water encountered TP-16 0-2 Silty Clay (CH), dark brown, wet grading to moist, medium stiff. 2-15 Gravelly Sandstone, -40% Sand, -20% Gravel, -40% Fines, light brown, moist, friable, gravel to 2 inches locally, caliche veins and zones. . Total Depth 15 feet No free water encountered . TP-17 0-2 Silty Clay (CH). dark brown, wet, medium stiff, no shear surfaces. 2-13 Gravelly Sandstone Bedrock, light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, - 20% gravel, -40% fines (generally CH and MH). caliche veins and zones, (OTt). -. 13-14 Claystone Bedrock, light brown, moist, friable to weak, many sheared surfaces (OTol. Total Depth 14 feet No free water encountered . TP-18 0-1 Silty Clay (CHI, dark brown, wet, soft, locally intermixed with light brown subsoil. 1-9 Gravelly Sandstone (OTt) , light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, - 20% gravel, -40% fines, caliche veins and zones, (OTt). . 9-10 Sandstone, light brown, moist, fine-grained, friable, (OTt). Total Depth 10 feet No free water encountered . wp51/reportJJ513tp PLATE 12 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS Test Pit Number Depth (Feet) DescriPtion . TP-19 0-1 Y, Silty Clay (CH), dark brown, wet, medium stiff. . 1 Y,-6 Gravelly Sandstone (QTt), light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, -20% gravel, -40% fines (generally CH and MH), caliche veins and zones, (QTt). 6-7 Sandstone, light brown, moist, fine-grained, friable, (QTt). . Total Depth 7 feet No free water encountered TP-20 0-1 Silty Clay (CH), dark brown, wet, medium stiff. . 1-6 Gravelly Sandstone (QTt), light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, -20% gravel, -40% fines (generally CH and MH), caliche veins and zones, (QTt). . Total Depth 6 feet No free water encountered TP-21 0-3 Fill (?), Silty Clay, intermixed light brown and dark brown clays with local pebbles, wet, medium stiff. '. 3-4 Silty Clay (CH), dark brown, wet, medium stiff, contact with fill parallel to ground surface. 4-10 Silty Clay (CH), dark brown, moist, stiff to very stiff, local sand and pebbles (Qls/Qc). i. Total Depth 10 feet No free water encountered TP-22 0-7 Silty Clay (CH), dark brown, wet grading to moist, medium stiff, local sand and gravel, no shear surfaces noted. . 7-8 Gravelly Sandstone (QTt) , light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, -20% gravel, -40% fines (generally CH and MH), caliche veins and zones, (QTt). . Total Depth 8 feet No free water encountered wp51/relJort/3513lP PLATE 13 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS . Test Pit Number Depth (Feet) Description TP-23 0-7 Silty Clay (CH), dark brown, wet grading to moist, soft grading to medium stiff, local sand and gravel, no shear surfaces. . 7-8 Gravelly Sandstone (OTt), light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, -20% gravel, -40% fines (generally CH and MH), caliche veins and zones, (OTt). . Total Depth 8 feet No free water encountered TP-24 0-3 Silty Clay (CH), dark brown, wet grading to moist, soft grading to medium stiff, local sand and gravel, no shear surfaces. -. 3-6 Gravelly Sandstone (OTt) , light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, -20% gravel, -40% fines (generally CH and MH), caliche veins and zones, no shear surfaces (OTt). Total Depth 6 feet No free water encountered . TP-25 0-4 Silty Clay (CH), dark brown, wet grading to moist, soh grading to medium stiff, local sand and gravel, no shear surfaces. 4-6 Gravelly Sandstone (OTt), light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, - 20% gravel, -40% fines (generally CH and MH), caliche veins and zones, (OTt). :. Total Depth 6 feet No free water encountered . TP-26 0-2 Yi Silty Clay, dark brown, moist, medium dense. 2 Yi-3 Gravelly Sandstone, medium brown, moist, friable. 3-3 Yi Siltstone, medium brown, moist, friable, (OTt), no shearing noted. Bedding contact generally sharp, local stringers, dips moderately into hill, 16S/55W. . 3 Yi-5 Gravelly Sandstone (OTt), light brown, moist, friable, local gravel to 2 inches maximum, -40% sand, -20% gravel, -40% fines (generally CH and MH), caliche veins and zones, (OTt). . Total Depth 5 feet No free water encountered Vyp51 'I'l!lp(lft13513tp PLATE 14 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills landslides Dublin, California TEST PIT lOGS Test Pit Number Depth (Feet) Description . TP-27 0-2 Silty Clay, dark brown, moist, medium dense (CHI. . 2-3 Siltstone, gray-brown, moist, friable, local caliche. 3-5 Claystone, medium brown, moist, weak (more cemented or indurated than overlying siltstone), caliche rich. . Total Depth 5 feet No free water encountered TP-28 0-2Y. Silty Clay (CH), dark brown, moist, medium dense. . 2%-8% Interbedded Siltstone and Claystone (OTt), medium brown, generally weak, locally friable, local caliche. Total Depth 8 % feet No free water encountered . TP-29 0-6 Silty Clay (CH), dark brown, moist, medium stiff, local healed fissures. 6-8 % Sandstone (OTt) , medium brown, moist, friable, local fine gravel, local caliche. ". I Total Depth 8 % feet No free water encountered TP-30 0-3 Silty Clay (CH), dark brown, moist, medium stiff. . 3-8 Y. Siltstone (OTt), medium brown, moist, weak to friable, local caliche filled fractures, steeply dipping. Compositional differences in trench walls suggest westerly dipping bedding. Total Depth 8 Yo feet No free water encountered . TP-31 0-% Silty Clay (CH), dark brown, moist, medium stiff. %-6 Interbedded Sandstone and Siltstone (OTt), brown, moist, friable, no bedding evident, no shearing evident. . Total Depth 6 feet No free water encountered wp51/repoflt3513tp PLATE 15 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS Test Pit Number Depth (Feet) Description . TP-32 0-4 Silty Clay (CH), dark brown, moist, medium stiff. . 4-8 Sandy Siltstone with gravel, medium brown, moist, friable. Total Depth 8 feet No free water encountered . TP-33 0-4 Silty Clay (CH), dark brown, moist, medium stiff, no shear structure observed. 4-7 Silty Clay (CH) (Oc or Ols), dark brown, moist, medium stiff to stiff, numerous steeply eastward dipping (downhill) shear surfaces, fissure surfaces, or both, local gravel to 2 inches. . 7-8 Sandy Siltstone (OTt), medium brown, moist, weak. Total Depth 8 feet No free water encountered . TP-34 0-3 Silty Clay (CH), dark brown, moist, medium stiff, local fissure surfaces. 3-6 Silty Clay (CH) (Ols/Oc), dark brown, moist, stiff, clay plucks out in blocky fragments, numerous rootlets exposed along block surfaces. . 6-8 Sandy Siltstone (OTt), medium brown, moist to dry, weak, local minor fine gravel. Total Depth 8 feet No free water encountered . TP-35 0-3 Silty Clay (CH), dark brown, moist, medium stiff, local fissure surfaces. 3-8 Interbedded Sandstone and Siltstone, light to medium brown, dry to moist, weak, bedding not distinct. . Total Depth 8 feet No free water encountered . wp51ltepofIJ'3513tp PLATE 16 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS . Test Pit Number Depth (Feet) Description TP~36 0~2% Silty Clay (CH) mixed with QTt (Fill). intermixed zones apparent, former "grassline" not present. . 2%~12% Silty Clay with Sand and Fine Gravel (Qc/Qlso), moist, medium stiff grading to stiff. Total Depth 12 % feet No free water encountered . TP-37 0-5 Silty Clay. 5-8 Silty Clay with Sand and Fine Gravel (Qls/Qc), moist, medium stiff grading to stiff. . 8-9 Sandy Siltstone (QTt), medium brown, moist, friable to weak. Total Depth 9 feet No free water encountered . TP-38 0-2 Silty Clay (CH), dark brown, moist, medium stiff, no shear structures. 2-7 Silty Sandstone with Gravel (QTt) , medium brown, moist, friable, local siltstone stringers, possible bedding (not continuous across test pit walls). dips moderately west. . Total Depth 7 feet No free water encountered . TP-39 0-4 Silty Clay (CH). dark brown, moist, medium stiff, N5S. 4-8 Interbedded Silty Sandstone and Claystone (QTt). light medium brown, moist, friable to weak N5S. . Total Depth 8 feet No free water encountered TP-40 0-5 Silty Clay (CH). dark brown, moist, medium stiff. 5-14 Silty Clay (Qls/Qc). medium brown, moist, medium stiff to stiff, N5S, local gravel. . Total Depth 14 feet No free water encountered wp51/fl!llJ)on/3513tp PLATE 17 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS Test Pit Number Depth (Feet) Description . TP-41 0-5 Silty Clay (CH), dark brown, moist, medium stiff. . 5-13 Silty Clay (Ols/Oc), medium brown, moist, medium stiff to stiff, local gravel. 13-14 Silty Sandstone (OTt) , light brown, moist, friable. . Total Depth 14 feet No free water encountered TP-42 0-5 Silty Clay (CH), dark brown, moist, medium stiff. . 5-8 Silty Clay (Ols/Oc), medium brown, moist, medium stiff to stiff, numerous thin caliche veins along fissure surfaces, clods break up blocky along fissure surfaces. 8-13 Silty Clay (Ols/Oc). medium brown, moist, stiff, no caliche, does not break up blocky. . 1 3-14 Yt Silty Sandstone (OTt). light brown, moist, friable to weak, local caliche. Total Depth 14 Yt feet No free water encountered . TP-43 0-3 Silty Clay (CH). dark brown, moist to wet, stiff. 3-7 Silty Clay (Oc), medium-dark brown, moist, very stiff, local gravel. . 7-8 Sandy Siltstone (OTt), light brown, moist, friable to weak, no bedding evident. Total Depth 8 feet No free water encountered . TP-44 0-3 Y. Silty Clay (CH), dark brown, moist, medium stiff. 3Y.",,8Yt Silty Clay (Oc). medium brown, moist, very stiff, breaks into irregular blocks (along healed fissures?). local thin caliche veins (along healed fissure surfaces?). . 8Yt-10 Sandy Siltstone (OTt) , light brown, moist, friable, no bedding evident. Total Depth 10 feet No free water encountered wp51!reponr3513tp PLATE 18 . BERLOCAR GEOTECHNICAL CONSULTANTS (' Job No. 2090.000 Dougherty Hills Landslides Dublin, California I TEST PIT LOGS r- T est Pit Number Depth (Feet) Description TP-45 0-3 Silty Clay (CHI, dark brown, moist, medium stiff. 3-6 Sandy Siltstone, light brown, moist, friable, no bedding evident. Total Depth 6 feet No free water encountered TP-46 0-3 % Silty Clay (CH). dark brown, moist, medium stiff. 3%-7 Silty Sandstone (QTt) , light brown, moist, friable, no bedding evident. Total Depth 7 feet No free water encountered TP-47 0-4 Silty Clay (CHI, dark brown, moist, medium stiff. 4-12 Silty Claystone (QTt). medium brown, moist, friable, no sedimentary structure. 12-14 Sandy Siltstone, light brown, moist, friable, no bedding observed. Total Depth 14 feet No free water encountered I TP-48 0-3 % Silty Clay (CH). dark brown, moist, medium stiff. 3%-14Y, Gravelly Silty Sandstone (QTt). medium brown, moist, friable, becomes lighter in color at 12 feet, gravel to 2 inches about 25 %. I Total Depth 14 % feet No free water encountered '"' TP-49 0-2 Silty Clay (CH), dark brown, moist, medium stiff. ~ 2-8 Gravelly Sandstone (QTt). medium brown, moist, friable, very little fines ( <8%). Total Depth 8 feet No free water encountered , PLATE 19 wps. 1 /(l!Ipott/3513tp BERLOGAR GEOTECHNICAL CONSULTANTS . - . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS . Test Pit Number Depth (Feet) Description TP-50 0-4 Silty Clay (CH). dark brown, moist, medium stiff. . 4-7 Silty Clay (Qc), dark brown, moist, stiff, local pebbles. 7-9 Silty Sandstone (QTt). light brown, moist, friable. Total Depth 9 feet No free water encountered . TP-51 0-5 Silty Clay, dark brown, moist, medium stiff. 5-6 Silty Clay, medium brown, moist, stiff. . 6-7% Interbedded Sandstone and Siltstone (OTt), light to medium brown, moist, friable to weak, no sedimentary bedding. Total Depth 7 Yo feet No free water encountered . TP~52 0-2 Silty Clay (CH), dark brown, moist, medium dense. 2-7 Interbedded Sandstone and Siltstone, light brown to dark brown, moist, friable to weak, sedimentary structures suggests bedding at 145/15E. . Total Depth 7 feet No free water encountered TP-53 0-3 Silty Clay, dark. .. 3-11 Interbedded Sandstone and Conglomerate, light to medium brown, moist, friable to weak. Total Depth 11 feet No free water encountered . Tp.54 0-2% Silty Clay (CH), dark brown, moist, medium stiff. 2%-7 Siltstone (QTt). light brown, moist, friable to weak. . Total Depth 7 feet No free water encountered wp51 H"'pcrV3513tP PLATE 20 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS T est Pit Number Depth (Feet) Description . TP-55 0-6 Silty Clay (CH). dark brown, moist, medium stiff. . 6-11 Silty Clay (Qc), medium brown, moist, stiff, local gravel. 11-12 Siltstone (QTt), light brown, moist, friable. Total Depth 12 feet No free water encountered . TP-56 0-4 Silty Clay (CH), dark brown, moist, medium stiff. 4-10 Silty, Sandy Clay, CH (Qc), medium brown, moist, stiff, local gravel. . 1 0-1 2 Interbedded Sandstone and Siltstone (QTt). light brown, moist, friable. Total Depth 12 teet No free water encountered . TP-57 0-5 Silty Clay (CH), dark brown, moist, medium stiff. 5-6 Silty Clay with Gravel, CH, (Qc). medium brown, moist, stiff. 6-9 Interbedded Sandstone, Siltstone and Local Conglomerate (QTt). light brown, friable to weak. . Total Depth 9 feet No free water encountered . TP-58 0-5 Intermixed Clay, Silt, Sand and Gravel, difference soil types are in discontinuous lenses and zones with random orientations. Shearing evident in clay and silt zones. Material is dark brown to gray-green, moist, medium stiff, Compacted Fill (Qat?). . 5-9 Intermixed Material as above but very stiff to hard (Qaf). Compacted Fill. Total Depth 9 feet No free water encountered . wp51/repon13513tp PLATE 21 . BERLOGAR GEOTECHNICAL CONSULTANTS . Job No. 2090.000 Dougherty Hills Landslides Dublin, California TEST PIT LOGS Test Pit Number Depth (Feet) Description . TP-59 0-13 Intermixed Clays, Silts, Sands, Gravel, and Weathered Bedrock Fragments (Qat). . Material is intermixed with local horizontal continuous layers of different colored materials (lifts). Zones ot dark brown CH extend throughout to 13 feet. No voids or man-made materials encountered, Compacted Fill. . Total Depth 13 feet No free water encountered TP-60 0-5 Interbedded Sandstone and Siltstone (QTt), light-medium brown, MSS, moist, friable. . Total Depth 5 feet No free water encountered TP-61 OA Silty Clay, dark brown, moist, medium stiff. . 4-8 Silty Sandstone (QTt), light brown, moist, triable, NSS, no bedding. Total Depth 9 feet No tree water encountered . . . . wp51/repoftJ3513tp PLATE 22 . BERLOGAR GEOTECHNICAL CONSULTANTS . . . . . . o 8 o 0) o C\l c: W 1Il :2 => Z 1Il o ""J SYMBOLS LOCATION LIQUID PLASTICITY USCS LIMIT INDEX CLASSIFICATION . B+ 1 at 1 foot 48 26 CL . B-2 at 1/2 foot 52 30 CH ATTERBERG LIMITS TEST DATA PLATE 23 BERLOGAR GEOTECHNICAL CONSULTANTS . . 1500 . :J: 1250 ~ 0 >= co . Peak, upper bound c=290 pst, <p=25O 1000 I I ...... III Residual, upper bound e=225 pst, <P = 2 5 - 1 /20 c.. <.D vi (,/') en LU I . ("1 c::: N I- ....- I (,/') 750 "t" Uj c::: <{ ./ ~ LiJ I 0 (,/') /' /' . 500 0 Peak, lower bound c=130 pst, <p=24-1/2O 0 /' 0 /' ci en /' . 0 250 N ...-::: 6:: /' ---- Residual, lower bound c=70 pst, <p=24-1/2O LiJ co /' :E ~ => Z "..- co 0 . -, 0 0 250 500 750 1000 1250 1500 NORMAL STRESS, psf 0 B-1, 1 ft. 0 B-2, 1 ft 0 B-2. 4 ft . 181 B-1, 1 ft.-Residual 181 B-2, 1 ft.-Residual 181 B-2, 4 ft.-Residual . SUMMARY OF DIRECT SHEAR TEST RESULTS PLATE 24 . BERLOGAR GEOTECHNICAL CONSULTANTS . . . . ::I: :::E Cl ;;..: ClJ . CJ:) O'l I M . N , '<t Uj ~ Cl . 0 0 0 ci O'l . 0 N 6:: uJ ClJ :::E :J Z ClJ 0 ..., . . 4500 . "" .. . "" Sandstone/Siltstone, c=370 psf, cP=2r~.. . "" () . "" . -..... "" . ""( 1 ..... ..... "" ...... ---- . ...... "" ......... ~ "" . .. ..... ------ "" .( ~ "" ~ ... ~ . .. . .- Best Fit, c=640 psf, cP= 150 I ~ C...... d r'" "".......- ~ ..... ~ -- ...... ( f/ Lower Bound, c=440 psf, cP=20" ....... --". , , , , , , , , I 4000 3500 3000 - 11'I a. uf 2500 IJ) UJ c::: Ii; ~ 2000 UJ :r: IJ) 1500 1000 500 o o 500 1000 1500 2000 2500 3000 3500 4000 4500 NORMAL STRESS, psf o TP-3, 11 ft. Silty Clay, tan o TP-21, 2 ft. Clay, dark gray o TP-58, 4 ft. Sandstone and Siltstone Materials SUMMARY OF DIRECT SHEAR TEST RESULTS Remolded to 90% Relative Compaction at +2% Over Optimum PLATE 25 BERLOGAR GEOTECHNICAL CONSULTANTS I . . 130 :r: ~ . 0 >- CD ::: ::i 120 -S.l en g . >- I- co Ci5 m Z ~ W (\J 0 ~ >- 110 w a: I- 0 <{ . 0 100 0 '. 8 ci m 0 (\J c: 90 '" L_ .t :!. ~ => . Z CD 0 -:> 80 . . . o 150 5 10 MOISTURE (%) 15 20 25 30 140 OPTIMUM MAX. DRY SYMBOL LOCATION DESCRIPTION MOISTURE DENSITY CONTENT(% (oct) 0 TP.3 at 11 feet SILTY CLAY,light brown 14.5 110.0 COMPACTION TEST DATA PLATE 26 BERLOGAR GEOTECHNICAL CONSULTANTS . . . 130 I :f 0 . ;>: III ,.... ::: ::i 120 ~ !Il ..c = . >- I- co (j) m z ..t w N 0 ..t >-110 a: w 0 l- e:( 0 . 100 0 . 8 ci m 0 N a: 90 .., L_ -t !!. ::2 :J Z . III 0 . 80 . . . o 5 10 MOISTURE (%) 15 20 150 140 25 30 OPTIMUM MAX. DRY SYMBOL LOCATION DESCRIPTION MOISTURE DENSITY CONTENT (%) (pef) 0 TP-58 at 4 feet SANDSTONE and 9.0 118.0 SILTSTONE MATERIALS brown & gray COMPACTION TEST DATA BERLOGAR GEOTECHNICAL CONSULTANTS PLATE 27 . o 150 5 10 . 140 . 130 I :2 0 --- . >- ~ III :i 120 .Q Ul .c 0::::- >- t: en z . w 0 ~ >- 110 a: ..t 0 ('\/ ..t w I- 0:( . 0 100 0 . 8 90 0 ()) 0 ('\/ a: '., L :!. ~ => z 80 . III 0 ...., MOISTURE (%) 15 20 25 30 OPTIMUM MAX. DRY SYMBOL LOCATION DESCRIPTION MOISTURE DENSITY CONTENT (%) (pet) 0 TP-58 at 4 teet SANDSTONE and 9.0 118.0 SILTSTONE MATERIALS brown & gray . . . COMPACTION TEST DATA PLATE 28 BERLOGAR GEOTECHNICAL CONSULTANTS . . . . APPENDIX . Slope Stability Analysis Computer Output Data . . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . . t '{- tw Jt, 'tr>~i Material Unit Wt C Phi Piezo Ru . pef psf deg Surf. Silty Clay 120 70 24.5 1 0 BEDROCK 130 1000 24.5 1 0 Berlogar Geoteeh - Pleasanton 2090.000 Dublin Slides slope Analysis April 12, 1996 Analysis of 74-74' . 2090A.GSL 70 + - 70 . 60 - 60 F .. .767 50 - 50 40 - 40 30 - 30 20 - 20 . 10 -10 0 -0 I I I I 0 100 200 300 . . '. . . BERLOGAR GEOTECHNICAL CONSULTANTS . . Material Unit Wt C Phi Piezo Ru . pef psf deg Surf. Silty Clay 120 70 24.5 1 0 BIlDROCK 130 1000 24.5 1 0 Berlogar Geotech - Pleasanton 20~0.000 Dublin Slides Slope Analysis April 12, 1~~6 Analysis of 74-74' . 20~OB.gsl 70 + - 70 . 60 F ~ 1.451 - 60 50 - 50 "- 40 "- - 40 30 "- - 30 20 "- - 20 . "- 10 "- -10 0 '---- SL -0 '- I I I I 0 100 200 300 ;. I . .. . . BERLOGAR GEOTECHNICAL CONSULTANTS . . Material Unit Wt C Phi Piezo Ru . pc:f psf deg Surf. Silty Clay 120 70 24.5 1 0 BBDROCK 130 1000 24.5 1 0 . 70 ., 60 50 40 30 20 . 10 0 I 0 100 . . . . . + F - 1.472 Berlogar Geotech ~ Pleasanton 2090.000 Dublin Slides Slope Analysis April 12, 1996 Analysis of 74-74' 2090A. GSL - 70 - 60 - 50 - 40 - 30 - 20 - 10 -0 I I 200 300 BERLOGAR GEOTECHNICAL CONSULTANTS . . Material Unit Wt C Phi Piezo Ru Berlogar Geoteeh - Pleasanton . pef psf deg surf. 2090.000 silty Clay 120 70 24.5 1 0 Dublin Slides Slope Analysis .BBDROCK 130 1000 24.5 1 0 April 12, 1996 Analysis of 74-74' . + 2090B.gsl F ~ 2.075 70 - 70 . 60 - 60 "'- 50 - 50 "'- 40 "'- - 40 30 "'- - 30 20 "'- - 20 "'- . 10 "'- -10 0 '-- - Sl. -0 I I I I 0 100 200 300 . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . 3~/ {fAr sitU-- . Material Unit Wt C Phi Piezo Ru . pef psf deg Surf. Silty Clay 120 70 24.5 1 0 BBDROCK 130 1000 24.5 1 0 Berlogar Geotech - Pleasanton 20~0.000 Dublin Slides Slope Analysis April 15, 1~96 Analysis of 74-74' 3:1 Cut Slope . 20~OC.gsl 70 + - 70 . 60 - 60 F ~ 1.147 - 50 50 40 - 40 30 - 30 20 - 20 . 10 -10 0 -0 I I I 0 100 200 300 . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . . Material Unit Wt C Phi piezo RU . pef psf deg Surf. silty Clay 120 70 24.5 1 0 BllDROCK 130 1000 24.5 1 0 Berlogar Geoteeh - Pleasanton 2090.000 Dublin slides Slope Analysi~ llpril 15, 1996 Analysis of 74-74' 3:1 cut Slope . 2090C.9Sl 70 - 70 . 60 + - 60 50 ......... - 50 ......... 40 .......... - 40 30 - 30 20 - 20 . 10 ......... - 10 0 ----- -0 I I I I 0 100 200 300 . '. . . . BERLOGAR GEOTECHNICAL CONSULTANTS . 2 ;. / J..u:t1,(,d',> vJ / )-v.~"'.;..'V\ . Material Unit Wt C Phi Piezo Ru Berlogar Geotech - Pleasanton . pef psf deg Surf. 2090.000 Engineered Fill 120 640 15 1 0 Dublin Slides Slope Analysis Silty Clay 120 70 24.5 1 0 Bedrock 130 1000 25 1 0 April 15, 19% Analysis of 74-74' 2:1 Buttress Slope . 2090D.GSL 70 + - 70 . 60 - 60 F " 1. 783 50 - 50 40 - 40 30 - 30 20 - 20 . 10 -10 0 -0 I I I I 0 100 200 300 . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . z :.j ~#p/h {.;J / )1,;. ~ An..: V' . Material Unit Wt C Phi Piezo Ru Berlogar Geotech - pleasanton . pet psf deg Surf. 20~0.000 Engineered Fill 120 640 15 1 0 Dublin Slides Slope Analysis Silty Clay 120 70 24.5 1 0 Bedrock 130 1000 25 1 0 April IS, 1996 Analysis of 74-74' 2:1 Buttress Slope . 20~OD.GSL 70 + - 70 . 60 - 60 F _ 1. 783 50 - 50 40 - 40 30 - 30 20 - 20 . 10 - 10 0 -0 I I I I 0 100 200 300 . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . . Material Unit Wt C Phi Piezo RU Berlogar Geotech - Pleasanton . pct psf deg Surf. 20~0.000 Engineered Fill 120 440 20 1 0 Dublin Slides Slope Analysis Silty Clay 120 70 24.5 1 0 Bedrock 130 1000 25 1 0 April 15, 1996 Analysis of 74-74' 2:1 Buttress Slope . 20901>' gsl 70 + - 70 . 60 - 60 F - 1.679 50 - SO 40 - 40 30 - 30 20 - 20 . 10 - 10 0 -0 I I I I 0 100 200 300 I . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . "J - 0 i'" V-r.,,~ ,-J /"5 ,,~,l...~ . ....0 '- Material Unit Wt C Phi Piezo Ru Berlogar Geoteeh - pleaeanton . pet pet deg Surf. 2090.000 llngineered Fill 120 0 20 1 0 Dublin Slidee Slope Analyeis Silty Clay 120 70 24.5 1 0 Bedrock 130 1000 25 1 0 April 19, 1996 Analyeie of 74-74' 2:1 Buttrees Slope . 209011.GSL 70 - 70 60 + - 60 . 50 - 50 F ~ .938 40 - 40 30 - 30 20 - 20 . 10 - 10 0 -0 I I I 0 100 200 300 . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS . . Material Unit Wt C phi Piezo Ru Berlogar Geotech - Pleasanton . pcf paf deg Surf. 2090.000 Engineered Fill 120 0 15 1 0 Dublin Slides slope Analysis Silty clay 120 70 24.5 1 0 Bedrock 130 1000 25 1 0 April 19, 1996 + Analysis of 74-74' 1. 056 2:1 Buttress Slop.. . F m 20900.GSL 70 - 70 . 60 - 60 50 - 50 40 - 40 30 - 30 20 - 20 -. 10 -10 0 -0 I I I I 0 100 200 300 . . . . . BERLOGAR GEOTECHNICAL CONSULTANTS r 'i4 . ;,1 :.- . /, ! ;.../ ~/,;';/, /1"a./i,;...f I:J-/i -ilL ~.A,' / ' , . I ,r)' / :::J\.~"'~-l""O'.~ Material Unit Wt c Phi Piezo Ru . pcf p..f deg Surf. Engineered Fill 120 370 27 1 0 Silty Clay 120 0 24.5 1 0 Bedrock DO 1000 25 1 0 Berlogar Geotech - Pleasanton 2090.000 Dublin Land..lide.. April 19, 1996 Cro....-Section 74-74' . with good material buttress 209074.g..l F 2.148 . 500 - 500 480 - 480 460 - 460 440 - 440 . 420 - 420 ~ :"I 400 -...;;: ,-, - 400 I I I I I I 0 100 200 300 400 500 . . .. . ~ . BERLOGAR GEOTECHNICAL CONSULTANTS r . Material Unit Wt C Phi Piezo Ru Berlogar Geotech ~ Pleasanton . pcf psf deg Surf. 2090.000 Engineered Fill 120 370 27 1 0 Silty Clay 120 0 :l4.5 1 0 Dublin Landslides Bedrock 130 1000 25 1 0 April 18, 1996 Cross-Section 65-65' l- t with good material buttress 209065.gs1 F 2.354 ~ 500 . - 500 480 - 480 460 - 460 440 - 440 420 . - 420 400 -...;:: - 400 380 J I I I - 380 I I I 0 100 200 300 400 500 . . , . I"'" . BERLOGAR GEOTECHNICAL CONSULTANTS (" . Material Unit Wt C Phi Piezo Ru . pet pef deg Surf. Engineered Fill 120 370 27 1 0 Silty Clay 120 0 24.5 1 0 Bedrock 130 1000 25 1 0 F - 2.379 .1' 490 'leo 470 'l60 'lSO 'l'l0 430 'l20 'l10 400 I 0 I I 200 . " , . I I 100 . . ~. 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