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HomeMy WebLinkAbout3416; AVENIDA ENCINAS EXTENSION; PRELIMINARY & ADDENDUM GEOTECHNICAL INVESTIGATION; 1993-12-13CARDIFF GEOTECHNICAL CONSULTING ENGINEERS AND GEOLOGISTS December 13, 1993 Fraser Engineering, Inc. 2191 El Camino Real Oceanside, CA 92054 Subject: PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Extension and Widening of Avenida Encinas Carlsbad, California Dear Mr. Wall and Mr. Pasko: In response to your request, we have performed a preliminary geotechnical investigation at the subject site for the proposed street extension and widening of Avenida Encinas. The findings of the investigation, laboratory test results and recommendations for grading and pavement sections are presented in this report. From a geotechnical point of view, it is our opinion that the site is suitable for the proposed development, although special consideration will be required for the underlying alluvial/soil deposits during the grading and construction phases. If you have any questions, please do not hesitate to contact us at 753-3697. This opportunity to be of service is appreciated. Respectfully submitted, CARDIFF GEOTECHNICAL J s's' Mark Burwell Geologist OESSIO4, SIN 782 rn EXP. 123193 1 4d Vithay Singhanet, P.E. Geotechnical Engineer I OF C P, 135 LIVERPOOL DRIVE • SUITE A • CARDIFF • CA 92007 (619) 753-3697 • FAX (619) 753-4158 PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Extension and Widening of Avenida Encinas Carlsbad, California Prepared For: Fraser Engineering, Inc. 2191 El Camino Real Oceanside, California December 13, 1993 W.O. #P-121103 Prepared By: CARDIFF GEOTECHNICAL 135 Liverpool Drive Suite A Cardiff, California 92007 TABLE OF CONTENTS INTRODUCTION. . . . . . . . . . . . . . . . ............ . . . . . . . . . ........ . . . 1 SITE CONDITIONS . . . . . . . . . . . . . . . . . . . . . .......... . . . . . . . .......1 PROPOSED DEVELOPMENT ............................ ... . . . . . . . . . . 2 SITE INVESTIGATION............................ ...... LABORATORY TESTING.......................... . . . . . . . ...... .. 3 GEOTECHNICAL CONDITIONS . . . . . . . . . . . . . . . . ............ . . . . . . . . . 4 DISCUSSION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 PRELIMINARY PAVEMENT DESIGN....... . . . . . . . . . . . . . . . . ....... . . . 8 CONCLUSIONS AND RECOMMENDATIONS.......... . . . .. . . . . . . . . . . . . .10 GENERAL GRADING CONSIDERATIONS ................ 10 EARTHWORK. . . . . . ........... . . . . . . . . . . . . . . . . . . . . 12 OBSERVATION AND DENSITY TESTING.......... . . . . .14 D • DRAINAGE. . . • . . . . . . . . . . . . . . . 6 . . . . . . . . . . . . . . . . . .14 E • LIMITATIONS ................... ......... ....... 15 APPENDICES APPENDIX A ....................... LABORATORY TEST RESULTS TABLE S-i PLATE S-i TRENCH LOGS TOPOGRAPHIC OVERLAY PORTION OF GRADING PLAN TYP. STABILIZATION FILL DESIGN TYPICAL SECTIONS APPENDIXB ....................... GRADING GUIDELINES GEOTECHNICAL MAP December 13, 1993 W.O. #P-121103 Page 1 INTRODUCTION This report presents the results of our preliminary geotechnical investigation on the subject property. The purpose of this study is to evaluate the nature and characteristics of the earth materials underlying the site and their influence on the construction of the proposed street improvements. SITE CONDITIONS The subject property includes a coastal segment of land extending from the terminus of Avenida Encinas, near Poinsettia Lane north to Palomar Airport Road, in the city of Carlsbad. The southern portion of the site consists of relatively flat cultivated terrain. However, the northern portion of the site includes 10 to 12 foot high slopes which descend along the western side of Avenida Encinas at gradients approaching 1½:1. Except for the most southern segment, the majority of Avenida Encinas and its proposed extension generally parallels the Atchison Topeka and Santa Fe Railroad line. The northern portion of Avenida Encinas is bounded.along the east by commercial structures. A review of topographic maps, prior to the development of structures and the graded portion of Avenida Encinas, indicates a large canyon (Canyon De Las Encinas) and several westerly and southeasterly ravines transecting the northern and central portions of the site (See enclosed topographic overlay). December 13, 1993 W.O. #P-121103 Page 2 Apparently, one or more culverts were required to transfer water 0i G aot.OGsST VISIT StlE.' I F So under the elevated railway line. rw T.%ATCuvE.T(S) WJ REøiulD UJ40W flAt4Y rI4aR.e PROPOSED DEVELOPMENT Plans for the extension and widening of Avenida Encinas were prepared by Fraser Engineering. The project includes the connection of the existing half street improvements from the terminus of Avenida Encinas near Poinsettia Lane north, to the southern texinus of the street near Palomar Airport Road. The T 50 r .W T,çi..mi,js is Caspgp i' 506m OF PA S project also includes widening of the existing northern street segment. The overall length of the project, including the widening of the northern street segment and the construction of the new road segment, is approximately 5400 C era feet. . iRi~ Lim WAL. Additional improvements will consist of curb, gutter, sidewalk, asphaltic concrete paving and storm drain facilities. Several utility lines are present along the proposed road alignment. Of significant concern is the 12 inch diameter high pressure gas line. Grading of the southern portion of the road segment will be limited to minor cuts and fills, up to 4.0 feet. However, cuts and fill slopes, up to 9.0 feet and 11.5 feet, respectively, are planned along the northern and central road segments. SITE INVESTIGATION Eight exploratory trenches were excavated on the site with a December 13, 1993 W.O. #P-121103 Page 3 tractor-mounted backhoe to a maximum depth of 14 feet. Earth materials encountered were visually classified and logged by our field geologist. Undisturbed, representative samples of the earth materials were obtained at selected intervals. Samples were obtained by driving a thin walled steel sampler into the desired strata. The samples are retained in brass rings of 2.5 inches outside diameter and 1.0 inches in height. The central portion of the sample is retained in close fitting, waterproof containers and transported to our laboratory for testing and analysis. LABORATORY TESTING Classification The field classification was verified through laboratory examination, in accordance with the Unified Soil Classification System. The final classification is shown on the enclosed exploratory Logs. Moisture/Density The field moisture content and dry unit weight were determined for each of the undisturbed soil samples. This information is useful in providing a gross picture of the soil consistency or variation among exploratory excavations. The dry unit weight was determined in pounds per cubic foot. The field moisture content December 13, 1993 W.O. #P-121103 Page 4 was determined as a percentage of the dry unit weight. Both are shown on the enclosed Appendix A. Maximum Dry Density/Optimum Moisture Content The maximum dry density and optimum moisture content were determined for selected samples of earth materials taken from the site. The laboratory standard tests were in accordance with ASTM D-1557€? The results of the tests are presented in Appendix "A".• w' 'cii ccvrioo ? GEOTECHNICAL CONDITIONS The southern portion of the site is underlain by nearly flat- lying, friable Pleistocene sands mantled by relatively thin soil deposits. However, in •the north-central portion of the site significant alluvial/soil deposits are present. These deposits are generally soft and compressible and will require special consideration during the grading phase. A brief description of the earth materials is discussed below. Alluvium/Soil (Undifferentiated) In the vicinity of Trench Nos. 1, 2 and 3, up to 10.5 feet of dark brown slightly sandy clay was encountered. These deposits are compressible and ghIy—expansive-.)It. is likely that significant amounts of these alluvial/soil deposits are present in the central portion of Canyon De Las Encinas (vicinity of STA. December 13, 1993 W.O. #P-121103 Page 5 68). Additional alluvial/soil deposits are present in the transecting ravines in the northern portion of the site (vicinity of STA. 81). In the southern portion of the site, the alluvial/soil deposits thin to approximately 6.0 feet, in the vicinity of Trench No. 4. The southern extent of these deposits is in the vicinity of STA. 50. Soil Based on exploratory Trench Nos. 5 through 7, the southern portion of the site is generally mantled by 1.5 to 2.5 feet of clayey sand. The upper 1.0 foot of these deposits have been cultivated. In the vicinity of Trench No. 8, approximately 2.0 feet of clay was encountered below the soil deposits. The clay may represent a former drainage course. Terrace Deposits Late Pleistocene terrace deposits underlie the surf icial materials on the site. The sedimentary deposits consist of poorly consolidated fine and medium-grained sands. The reddish brown sand is generally clayey and weathered in the upper 2.0 feet, but becomes increasingly dense and competent with depth. Expansive Soils The majority of the terrace deposits are composed of granular deposits which have a potential expansion in the low, range. December 13, 1993 W.O. #P-121103 Page 6 However, the clayey alluvial/soil deposits encountered have a potential expansion in the high range. U)ikP1 TtE FoCPAMSIOP Groundwater No evidence of perched groundwater was observed in the terrace deposits, along the southern portion of the site. However, surface water was observed in areas along the base of the descending slopes (vicinity of STA. 81). It is likely that shallow groundwater tables are present in the transecting canyon and ravine areas (See enclosed topographic overlay). Seismicity Based on a review of pertinent geological maps, no active faults have been recognized on the subject property. The nearest active fault is the Rose Canyon Fault located about four miles west of the site. Other active faults which could affect the site are listed on the enclosed Table S-i. Although the likelihood of ground rupture on the site is remote, it is almost a certainty the property will be exposed to ground motion resulting from the release of energy along the numerous known and unknown faults in Southern California. Table S-i indicates seismic parameters for active faults which could affect the site. The enclosed Seismic Map (Plate S-i) shows the general proximity of active faults. December 13, 1993 W.O. #P-121103 Page 7 DISCUSSION The most southern portion of the site is mantled by relatively thin soil deposits. However, significant alluvial/soil deposits and high groundwater conditions should be anticipated in the central and northern portions of the project. 2. The clayey alluvial/soil deposits are compressible. In order to reduce the adverse affects on pavement, 4eto Tb 5 T1 - ___ ______ ëbnsolidation, bremodãid C—rQadway,Te.. T%SIS UP VJS UNV.FOP. Fi\Rvhv PtoJE.c.1 E%PEREtz Sou O?Tr Tns TL $o' To ?j $iPCV vmwwrs _ In the vicinity of STA. 76+00 and STA 80 +60., the proposed fill slopes may adversely affect the 12 inch diameter high pressure gas line. Exploratory. trenches are recommended in this area to evaluate the geotechrica]. conditions underlying the gas line. ta~~I~ropobed—f U17 (See enclosed Typical YouoL OT P, rUiY, Ir Is P DE1GI$. C. Testing of representative- samples of the 'clayey alluvial/soil deposits indicate an(i le_of5Thlss? It Peug R-VAw 1ST SaE.TS may be feasible to utilize on-site granular in the upper 2.0 feet of the: street ubgrade; h an approach RTED As 5 December 13, 1993 W.O. #P-121103 Page 8 would significantly improve the resistance value of the subgrade soils. The structural sections recommended in. this report generally represent the "worst" and "best" types of soils encountered on the site. Final structural sections should be based on R-value testiyfof the specific - soils used in the street w 1 E S T Now subgrade. WE )Et The ST CflON As P 9r OF ThE. PE.'GP3. It is our understanding that the proposed improvements to Avenida Encinas will be constructed in four separate segments Th11tia1 OhstIuctip will consist of Segment followed byZ, C and D. Our conclusions and recommendations are presented in this sequential manner. PRELIMINARY PAVEMENT DESIGN R-value tests were performed on representative samples of clayey alluvial materials and Pleistocene terrace deposits. The results of testing indicate an R-value of 5 or less for the clayey materials and an R-value of 34 for sandy terrace deposits. As per our conversations with the city of Carlsbad, Avenida Encinas is classified as a secondary arterial street with an anticipated taffic Index of Preliminary structural sections presented below are based on R-value data and the subsurface conditions encountered during exploration. December 13, 1993 W.O. #P-121103 Page 9 Preliminary Structural Section . .AvenidaEncinas (Sta. 5-'00t88+38) R-value5 (clayey soils), Traffic Index of 8 .4.0 inches of asphaltic paving on 18 inches of Class 2 Aggregate Base on 12 inches of compacted native soil AvenidaEncinas (Sta. 40+20 to 50+00) - R-value 34 (sandy terrace deposits), Traffic Index of 8 4.0 inches of asphaltic paving on 10.5 inches of Class 2 Aggregate Base on I • 12 inches of compacted-terrace deposits Subgrade soils should be arified, moistened to optimum moisture content and .compactedto the thickness indicated in the above structural •section, and left in a condition to receive base materials. C1i2ase_matilTshould have.aiiiiiiiJ 1t1JfL7ë' and a Subgrade- (7si Qpercent- -*of —tlfe-ir7 laboratory muiff-7dFy—_d&-nifities* —f or. the -- • .- - All section changes should beG transitioñed. If adverse conditions are encountered during the prepaation of subgrade materials, special construction methods-may need to be employed. based on ttin.g Ala -.• No u 15 Th'E 7iiw E. performed-after.- grading_is-complete.. December 13, 1993 W.O. #P-121103 Page 10 CONCLUSIONS AND RECOMMENDATIONS General Grading Considerations Segment A (STA. 40+20 to 58+55) -TRE T,,r 441°rP In general, the southern portion of the site includes relatively thin soil deposits overlying Pleistocene terrace sands. Grading along STA. 40+20 to 50+100 will requi of the surf icial materials and weathered terrace deposits. Minor cuts and fill, in this area may be graded at an inclination of 1½:1 (horizontal to vertical). From STA. 50+00 to the end of Segment A (STA. 58+55), the site is underlain by which thicken to more than çpfet, in a northerly direction. Due to the compressible 4' A'. nature of these clayey deposits, they shouldThe_removed' to a minimum depth of properly— 341 ----------------------- compacted fill prior to the placement of additional fill or after minor cuts up to 3.0 feet, are completed. ijtis WE U-r \ FL1)LE JMEp.3T Ot,% IKS °"WE Arke W%LUM Th ic..c.PT 3o J.TICAL 4C.EmE.PJT - 1 W t"4 t W /R.g& Ot .'The proposed filpP4-srA1_L1[VG slope in the vicinity of STA. 58+55 should be constructed as a stabilization fill. A 20 foot wide key, embedded a minimum of 2.0 feet into competent material, should be constructed along the base of the proposed fill slope. - Fill should be benched into competent material. Fill slopes should be constructed a maximum gradient of 2:1 (horizontal to vertical). I Wot.c.v FiLL. Is 3't. December 13, 1993 W.O. #P-121103 Page 11 Segment B and C (STA. 58+55 to STA. 88+38) Most of the rough grading has been completed along the western portion of Segment B. However, variable height fill slopes are planned along the western extent of the project. Fill slopes should be provided with a key and benched into competent materials, as previously indicated. The subgrade deposits should be evaluated upon completion of the fill slopes. Additional recomdationsiijy_be necessary. ? E.-A pt.AIN The most extensive grading of the project is planned for Segment C. Cuts, up to 9.0 vertical feet, are planned along the western extent of Avenida Encinas. Fill slopes, up to 11.5 feet, are also planned in this area. Upon completion of the road cuts, the subgrade deposits should be evaluated. It is likely that considerable alluvial/soil deposits will be encountered in this area • A minimuni. of 3.0 foot removal and recompaction should be anticipated. The area of the proposed fill slopes in the vicinity of STA. 76+00 and STA. 80+60 is probably underlain by significant alluvial/soil deposits. isxçpimnended that additional exploratory trenches be excavated in these areas prior to grading. The purpose of the additional exploration is to evaluate the geotechnical conditions underlying the 12 inch diameter high pressure gas line. If compressible alluvial/soil deposits are present, the construction of the proposed 7.0 to 61 December 13, 1993 W.O. #P-121103 Page 12 11.5 foot fills could adversely affect the pipe. High groundwater conditions are anticipated in this area and should also be evaluated. It should be noted that removal and relocation of the high pressure gas line may be necessary in this area. $c' \ %t\ Segment D (STA. 88+38 to STA. 93+85 Only minor improvements consisting of a new sidewalk are planned along Segment D. However, the subgrade deposits in the area of the sidewalk should be evaluated during the course of grading. Additional recommendations for densification of the subsoils may be necessary. It should be noted that an alternative D.2 on the grading plans indicate a 7.0 foot widening of the street. If this alternative is chosen, the fill should be keyed and benched into competent deposits. Earthwork Grading and earthwork should be performed in accordance with the following recommendations and the Grading Specifications included in this report. Site Preparation Prior to grading, all areas to receive structural fill should be cleared of surface and subsurface obstructions, including any existing debris, and stripped of vegetation. Removed vegetation December 13, 1993 W.O.- #P-121103 Page 13 and debris should be properly disposed of off site. Holes resulting from removal or buried obstructions which extend below finished road grades should be replaced with suitable compacted fill material. All areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 6 inches, brought to near-optimum moisture conditions, and recompacted to at least 90 percent of the laboratory maximum dry density. Removal of Compressible Soils As noted previously, significant clayey alluvial/soil deposits are present. In order to reduce the adverse affects of consolidation, - 'E.dC%) 6 MQ1C4Ct%1 naterials should be r9yed_ancLrecompacteth Localized deeper removals may be necessary along the base of fill slopes and should be evaluated by additional exploration. Excavations The on-site materials are expected 'to be ri22able with modern, earthmoving equipment in good operating condition. It is estimated that the alluvial soils to be removed will undergo approximately 5 to 10 percent shrinkage when compacted as fill material to 90 percent relative compaction. Fills the -on- site - soi-1 s-are -general-ly -suitabl7e--f or-use -as -compacted' Z December 13, 1993 W.O. #P-121103 Page 14 fill provided they are free of organic material and debris. Fill should be placed in 6.0 to 8.0 inch lifts, moistened as required and compacted to a minimum of 90 percent of the laboratory maximum dry density. aosits minimum —depth —of 7__3_._0__'1f eet—be ow-. -the —proposed —road—s 69—r- Additional recommendations will be presented should any septic tanks, cistern, seepage pits or other unforeseen geotechnical conditions be encountered during grading. Slope Stability It is our opinion that proposed fill slopes constructed at inclinations of 2 to 1 (horizontal to vertical) or flatter will be stable with respect to deep-seated failure, provided the fills are keyed and benched into competent materials. Our evaluation is based on a maximum height of 15 feet using a factor of safety of 1.5 under static conditions. Observation and Density Testing Fill should be placed of this firm is sent to observe and _es j Additional recommendations may be necessary during the grading RIM?VITtIiYR IS TiE O,uc.V Drainage &.M PEA SON Paved areas should be protected from moisture migrating under the December 13, 1993 W.O. #P-121103 Page 15 pavement from adjacent water sources, such as planted or grass areas. Pad water should not be allowed to pond. LIMITATIONS This report is presented with the provision that it is the responsibility of the owner or the owner's representative to bring the information and recommendations given herein to the attention of the project's architects and/or engineers so that they may be incorporated into plans. If conditions encountered during grading appear to differ from those described in this report, our office should be notified so that we may consider whether modifications are needed. No responsibility for construction compliance with design concepts, specifications or recommendations given in this report is assumed unless on-site review is' performed during the course of construction. The subsurface conditions, excavation characteristics and geologic structure described herein are based on individual exploratory excavations made on the subject property. The subsurface conditions, excavation characteristics and geologic structure discussed should in no way be construed to reflect any variations which may occur among the exploratory excavations. Please note that fluctuations in the level of groundwater may occur due to variations in rainfall, temperature and other December 13, 1993 W.O. #P-121103 Page 16 factors not evident- at the time measurements were made and reported herein. Cardiff Geotechnical assumes no responsibility for variations which may occur across the site. The conclusions and recommendations of this report apply as of the current date. In time, however, changes can occur on a property whether caused by acts of man or nature on this or adjoining properties. Additionally, changes in professional standards may be brought about by legislation or the expansion of knowledge. Consequently, the conclusions and recommendations of this report may be rendered wholly or partially invalid by events beyond our control. This report is therefore subject to review and should not be relied upon after the passage of three years. The professional judgments presented herein are founded partly on our assessment of the technical data gathered, partly on our understanding of the proposed construction and partly on our general experience in the geotechnical field. Our engineering work and the judgments given meet present professional standards. However, in no respect do we guarantee the outcome of the project. If you have any questions, please do not hesitate to contact our office at 753-3697. The opportunity to be of service is greatly appreciated. APPENDIX "A" LABORATORY TEST RESULTS TABLE I Maximum D,y Density and Optimum Moisture Content (Laboratory Standard ASTM D-1557-78) Sample Max. Dry Optimum Location Density Moisture Content (pcf) T-1 @ 2'-4' 119.0 14.0 (Mixture of clay and sand) TABLE!! Field Dry Density and Moisture Content Sample Field Dry Field Moisture Location Density Content (pct) % 2 G T-1@3.0' 104.0 f2.'& 16.2 19.7 T-1 @ 5.0' 98.7 rgp f T-1 @ 7.0' 97.7 13.5 T-1 @ 10.0' 102.1 3.6 T-2@3.0' 105.5 17.9 (P-121103-1) TABLE!! (Cont'd) Field Dry Density and Moisture Content Sample Field Dry Field Moisture Location Density Content (pc f) T-2 @ 7.0' 112.7 17.3 T-2@9.0' 111.0 17.9 T-3 @ 3.0' 105.0 18.9 T-3 @ 5.5' 104.1 20.6 T-3@8.0' 99.8 21.2 T-4 @ 3.0' 96.8 24.2 T-4@5.0' 114.9 16.9 T-4 @ 7.0' 115.7 7.5 T-5 @ 1.5' 115.6 9.7 T-5@3.5' 112.0 9.1 T-5@7.0' 111.1 8.9 T-5 @ 10.0' 115.6 4.9 T-6 @ 1.0' 112.0 16.4 T-6@3.0' 118.6 15.2 T-6@5.0' 107.8 10.7 T-6@8.0' 108.7 5.7 T-7@3.0' 104.3 22.1 T-7@4.5' 116.7 13.3 T-7 @ 6.5' 113.2 12.9 T-8 @ 3.0' 106.3 21.2 (P-121103-2) TABLE S-i SEISMIC PARAMETERS FOR ACTIVE AND POTENTIALLY ACTIVE FAULTS Max. Max. Credible Probable Bedrock Design Earth-, Earth- Accel- Accel- Fault Distance guake Quake eration eration --Magnitude-- Rose Canyon 4 mi. S.W. 7.1 6.2 0.31g 0.20g Coronado Banks 19 mi. S.W. 6.5 6.0 0.15g 0.10g Elisnore 25 mi. N.E. 7.5 7.3 0.19g 0.12g San Jacinto 50 mi. N.E. 7.5 7.3 0.19g 0.06g San Andreas 71 mi. N.E. 8.2 8.0 0.08g 0.05g The Rose Canyon fault has recently been designated as active (C.D.M.G.) Design acceleration is commonly considered to be about 65 percent of the maximum (peak) acceleration for the site within approximately 20 miles of the epicenter. ' ••8R5TOw' SEISMIC MAP !I 'k •••• \ S A Total length of fu1t ZOne that breaks lo1occr. '\ -"• deposits or that has had seismic activity - Poo Fault segment with surface rupture during an \ historic earthquake, or with aseisic fault cr 4 0 \ .1" . \ '\ Approximate epicentrol area of earthquakes that occurred 1769 - 1933 <1899 1 CLEGflO \R/ftcS Earthquake epicenters since 1933 rCA F.. • 1907 Ref: AEG Special Publication, Oct.1973 (by Richard J. Proctor. 1948 RVERSIoE ' B .. BANNING UJE cur F6&IIT (. ,. A. 1918 i M6.8 ? PALJ,.4 1923 SPRIF1GS M63, ietz) 1599OIO IeGa % D .1937 'S' . 1910 - 1954 ' ' • I %,-rk r, ' 1968 19C 4A i. / %' M 6.5 • \ \ ..• ,'(Z S \ M P E -.R I A / L A N 0 I E 1915 0 G 0 i1356 1915 1942 M63 1 M6.3 1940 b%.. SAN I ----.-.-' __--- - \DIEGO \.• &9RiPriTh\ CERRO \. PRI&70 M, 1923 19 4 1935 L PLATE S-I EXPLORATORY TRENCHES LOGS DEPTH DESCRIPTION Trench No. 1 0-2' FILL: Sand, clayey, tan to brown, pebbles, poorly mixed, moderately dense, moist, plastic and wire debris 2'-8' ALLUVIUM: Clay, slightly sandy, dark brown, damp, stiff, veins of tan sand 8'-10' ALLUVIUM(?): Sand, fine and medium- grained, slightly moist, loose, no cementation Trench No. 2 0-1' FILL: Sand, silty and fine-grained, tan to brown, di',', moderately dense 1'-5.5' ALLUVIUM: Sand, clayey, mottled tan to brown, moist, dense 5.5'40' ALLUWUM: Clay, slightly sandy, dark brown, damp to very damp, stiff W-14' TERRACE DEPOSITS(?): Sand, slightly clayey, tan to brown, moist, moderately dense Trench No. 3 0-2.5' FILL: Sand, clayey, tan to brown, moist, loose, plastic debris 2.5'40.5' ALLUVIUM: Clay, slightly sandy, brown, caliche stringers, damp, soft in upper 4 feet (P-121103-1) 10.5'-11.5' TERRACE DEPOSITS: Sand, fine and medium-grained, tan to reddish brown, moist, dense Trench No. 4 Trench No. 5 Trench No. 6 0-2' FILL: Sand, clayey, tan to brown, slightly moist, loose 2'-6' ALLUVIUM: Clay, slightly sandy, brown, caliche stringer, damp, soft in upper 3 feet 6'-8' TERRACE DEPOSITS: Sand, fine and medium-grained, slightly clayey, slightly moist, dense TERRACE DEPOSITS: Sand, fine and medium-grained, reddish brown to gray, slightly moist, dense 0-1.5' SOIL: Sand, slightly clayey, tan to brown, slightly moist, loose, cultivated area 1.5'-2' SOIL: Sand, clayey, brown, caliche packets, moist, moderately dense 0-9' TERRACE DEPOSITS: Sand, fine and medium-grained, reddish brown to gray, moist, moderately dense @ 8'-9 very moist, weakly cemented 0-1.5' SOIL: Sand, clayey, tan to brown, blocky, slightly moist, loose, cultivated area 1.5'-8' TERRACE DEPOSITS: Sand, fine and medium-grained, slightly clayey in upper 1.5'-2.5 moist, dense below 2.5 grades to weakly cemented reddish brown to gray sand (P-1211103-2) Trench No. 7 Trench No. 8 0-1' SOIL: Sand, clayey, tan to brown, blocky, slightly moist, loose, cultivated area 1 '-2.5' SOIL: Clay, slightly sandy, grey, very damp, soft 2.5'-5' TERRACE DEPOSITS: Weathered sand, slightly clayey, blocky, brown to slightly reddish brown, dense, slightly moist 5'-7' TERRACE DEPOSITS: Sand, slightly clayey, reddish brown, moist, dense 7'-8.5' TERRACE DEPOSITS: Sand, fine and medium-grained, very slightly clayey, moist, dense 0-2' SOIL: Sand, clayey, tan to brown, slightly moist, loose, cultivated area 2'4' SOIL: Clay, slightly sandy, grey, very damp, soft 4'-6.5' TERRACE DEPOSITS: Sand, fine and medium-grained, moist dense (P-121103-3) ME 69.0 p IE 19.0 1960 TOPOGRAPIC OVERLAY (showing drainage courses prior to development) \ .- A 20' WIDE STABILIZATION FILL 14. VARIABLE 25' 2:1 40 NONPERFORATED PIPE LATERAL TO SLOPE FACE AT 100' INTERVALS 12' MINIMUM KEY DEPTH (into competent material) EQUIPMENT WIDTH KEY 20' MINIMUM TYPICAL STABILIZATION FILL DESIGN I I 04 IE: Cl qp DE Cl Ilk 131 IP IEZ**l 3D M ~C 13 GRADING GUIDELINES Grading should be performed to at least the minimum requirements of the governing agencies, Chapter 70 of the Uniform Building Code and the guidelines presented below: Site Clearing Trees, dense vegetation, and other deleterious materials should be removed from the site. Non-organic debris or concrete may be placed in deeper fill areas under direction of the Soils engineer. Light, dry grasses may be thinly scattered and incorporated into the fill under direction of the Soils Engineer, provided concentrations of organics are not developed. Subdrainage Subdrainage systems should be provided in all canyon bottoms and within buttress and stabilization fills prior to placing fill. Subdrains should conform to schematic diagrams CG-1, CG-3, and CG-4, approved by the Soils Engineer. For canyon subdrains, runs less than 500 feet may use six inch pipe. Runs in excess of 500 feet should have the lower end as eight inch minimum. Filter material should be Class 2 permeable filter material per California Department of Transportation Standards tested by the Soils engineer to verify its suitability. A sample of the material should be provided to the Soils engineer by the contractor at least two working days before it is delivered to the site. The filter should be clean with a wide range of sizes. As an alternative to the Class 2 filter, the material may be a 50/50 mix of pea gravel and clean concrete sand which is well mixed, or clean gravel wrapped in a suitable filter fabric. An exact delineation of anticipated subdrain locations may be determined at 40 scale plan review stage. During grading, the Engineering Geologist should evaluate the necessity of placing additional drains. All subdrainage systems should be observed by the Engineering Geologist and Soils Engineer during construction and prior to covering with compacted fill. Consideration should be given to having .subdrains located by the project surveyors. Outlets should be located and protected. Treatment of Existing Ground All heavy vegetation, rubbish and other deleterious materials should be disposed of off site. All surficial deposits of alluvium and colluvium should be removed (see Plate CG-1) unless otherwise indicated in the text of this report. Groundwater existing in the alluvial areas may make excavation difficult. Deeper removals than indicated in the text of the report may be necessary due to saturation during winter months. Subsequent to removals, the natural ground should be processed to a depth of six inches, moistened to near optimum moisture conditions and compacted to fill standards. Fill Placement 1. All site soil and bedrock may be reused for compacted fill; however, some special processing or handling may be required (see report). 2. Material used in the compacting process should be evenly spread, moisture conditioned, processed, and compacted in thin lifts not to exceed six inches in thickness to obtain a uniformly dense layer. The fill should be placed and compacted on a horizontal plane, unless otherwise found acceptable by the Soils Engineer. 3. If the moisture content or relative density varies from that acceptable to the Soils engineer, the Contractor should rework the fill until it is in accordance with the following: Moisture content of the fill should be at or above optimum moisture. Moisture should be evenly distributed without wet and dry pockets. Pre-watering of cut or removal areas should be considered in addition to watering during fill placement, particularly in clay or dry surficial soils. Each six inch layer should be compacted to at least 90 percent of the maximum density in compliance with the testing method specified by the controlling governmental agency. In this case, the testing method is ASTM Test Designation D-1557-78. 4. Side-hill fills should have an equipment-width key at their toe excavated through all surficial soil and into competent material and tilted back into the hill (CG-2, CG-6). As the fill is elevated, it should be benched through surficial soil and slopewash, and into competent bedrock or other material deemed suitable by the Soils Engineer. 5. Rock fragments less than eight inches in diameter may be utilized in the fill, provided: They are not placed in concentrated pockets; There is a sufficient percentage of fine-grained material to surround the rocks; The distribution of the rocks is supervised by the Soils Engineer. 6. Rocks greater than eight inches in diameter should be taken off site, or placed in accordance with the recommendations of the Soils Engineer in areas designated as suitable for rock disposal (See CG-5). 7. In clay soil large chunks or blocks are common; if in excess of eight (8) inches minimum dimension then they are considered as oversized. Sheepsfoot compactors or other suitable methods should be used to break the up blocks. 8. The Contractor should be required to obtain a minimum relative compaction of 90 percent out to the finished slope face of fill slopes. This may be achieved by either overbuilding the slope and cutting back to the compacted core, or by direct compaction of the slope face with suitable equipment. If fill slopes are built "at grade" using direct compaction methods then the slope construction should be performed so that a constant gradient is maintained throughout construction. Soil should not be "spilled" over the slope face nor should slopes be "pushed out" to obtain grades. Compaction equipment should compact each lift along the immediate top of slope. Slopes should be back rolled approximately every 4 feet vertically as the slope is built. Density tests should be taken periodically during grading on the flat surface of the fill three to five feet horizontally from the face of the slope. In addition, if a method other than over building and cutting back to the compacted core is to be employed, slope compaction testing during construction should include testing the outer six inches to three feet in the slope face to determine if the required compaction is being achieved. Finish grade testing of the slope should be performed after construction is complete. Each day the Contractor should receive, a copy of the Soils Engineer's "Daily Field Engineering Report" which would indicate the results of field density tests that day. 9. Fill over cut slopes should be constructed in the following manner: All surf icial soils and weathered rock materials should be removed at the cut-fill interface. A key at least 1 equipment width wide and tipped at least 1 foot into slope should be excavated into competent materials and observed by the Soils Engineer or his representative. The cut portion of the slope should be constructed prior to fill placement to evaluate if stabilization is necessary, the contractor should be responsible for any additional earthwork created by placing fill prior to cut excavation. 10. Transition lots (cut and fill) and lots above stabilization fills should be capped with a three foot thick compacted fill blanket. 11. Cut pads should be observed by the Engineering Geologist to evaluate the need for overexcavation and replacement with fill. This may be necessary to reduce water infiltration into highly fractured bedrock or other permeable zones,and/or due to differing expansive potential of materials beneath a structure. The overexcavation should be at least three feet. Deeper overexcavation may be recommended in some cases. 12. Exploratory backhoe or dozer trenches still remaining after site removal should be excavated and filled with compacted fill if they can be located. Grading Observation and Testing Observation of the fill placement should be provided by the Soils Engineer during the progress of grading. In general, density tests would be made at intervals not exceeding two feet of fill height or every 1,000 cubic yards of fill placed. This criteria will vary depending on soil conditions and the size of the fill. In any event, an adequate number of field density tests should be made to evaluate if the required compaction and moisture content is generally being obtained. Density tests may be made on the surface material to receive fill, as required by the Soils Engineer. Cleanouts, processed ground to receive fill, key excavations,subdrains and rock disposal should be observed by the Soils Engineer prior to placing any fill. It will be the Contractor's responsibility to notify the Soils Engineer when such areas are ready for observation. An Engineering Geologist should observe subdrain construction. An Engineering Geologist should observe benching prior to and during placement of fill. Utility Trench Backfill Utility trench backfill should be placed to the following standards: Ninety percent of the laboratory standard if native material is used as backfill. As an alternative, clean sand may be utilized and flooded into place. No specific relative compaction would be required; however, observation, probing, and if deemed necessary, testing may be required. 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, until it is similar to the inplace fill, should not be allowed in these trench backfill areas. Density testing along with probing should be accomplished to verify the desired results. JOB SAFETY General: At Cardiff Geotechnical, getting the job done safely is of primary concern. The following is the company's safety considerations for use by all employees on multi-employer construction sites. On ground per are at highest risk of injury and possible fatality on grading construction projects. The company recognizes that construction activities will vary on each site and that job site safety is the contractor's responsibility. However, it is, imperative that all personnel be safety conscious to avoid accidents and potential injury. In an effort to minimize risks associated with geotechnical testing and, observation, the following precautions are to be implemented for the safety of our field personnel on grading and construction projects. 1. Safety Meetings: Our field personnel are directed to attend the contractor's regularly scheduled safety meetings. Safety Vests: Safety vests are provided for and are to be worn by our personnel where warranted. Safety Flags: Two safety flags are provided to our field technician; one is to be affixed to the vehicle when on site, the other is to be placed atop the spoil pile on all test pits. In the event that the contractor's representative observes any of our personnel not following the above, we request that it be brought to the attention of our office. Test Pits Location, Orientation and Clearance: The technician is responsible for selecting test pit locations. The primary concern is the technician's safety. However, it is necessary to take sufficient tests at various location to obtain a representative sampling of the fill. As such, efforts will be made to coordinate locations with the grading contractors authorized representatives (e.g. dump man, operator, supervisor, grade checker, etc.), and to select locations following or behind the established traffic pattern, preferable outside of current traffic. The contractors authorized representative should direct excavation of the pit and safety during the test period. Again, safety is the paramount concern. Test pits should be excavated so that the spoil pile is placed away from oncoming traffic. The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates that the fill be maintained in a driveable condition. Alternatively, the contractor may opt to park a piece of equipment in front of the test pits, particularly in small fill areas or those with limited access. A zone of non-encroachment should be established for all test pits (see Plate CG-7). No grading equipment should enter this zone during the test procedure. The zone should extend approximately 50 feet outward from the center of the test pit. This zone is established both for safety and to avoid excessive ground vibration which typically decreases test results. When taking slope tests, the technician should park their vehicle directly above or below the test location on the slope. The contractor's representative should effectively keep all equipment at a safe operation distance (e.g. 50 feet) away from the slope during testing. The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location. In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is directed to inform both the developer's and contractor's representatives. If the condition is not rectified, the technician is required, by company policy, to immediately withdraw and notify their supervisor. The grading contractors representative will then be contacted in an effort to effect a solution. No further testing will be performed until the situation is rectified. Any fill placed in the interim can be considered unacceptable and subject to reprocessing, recompaction or removal. In the event that the soil technician does not comply with the above or other established safety guidelines, we request that the contractor brings this to technicians attention and notify our the project manager or office. Effective communication and coordination between the contractors' representative and the field technician(s) is strongly encouraged in order to implement the above safety program and safety in general. The safety procedures outlined above should be discussed at the contractor's safety meetings. This will serve to inform and remind the equipment operators of these safety procedures particularly the zone of non-encroachment. Trench Safety: It is the contractor's responsibility to provide safe access into trenches where compaction testing is needed. Our personnel are directed not to enter any excavation which 1) is 5 feet or deeper unless shored or laid back, 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench, or 3) displays any other evidence of any unsafe conditions regardless of depth. All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid back. Trench access should be provided in accordance with OSHA standards. Our personnel are directed not to enter any trench by being lowered or "riding down" on the equipment. If the contractor fails to provide safe access to trenches for compaction testing, our company policy requires that the soil technician withdraw and notify their supervisor. The contractors representative will then be contacted in an effort to effect a solution. All backf ill not tested due to safety concerns or other reasons could be subject to reprocessing and/or removal. cL. CARDIFF GEOTECHNICAL CONSULTING ENGINEERS AND GEOLOGISTS January 7, 1994 Fraser Engineering, Inc. 2191 El Camino Real Oceanside, CA 92054 Subject: ADDENDUM REPORT Proposed Extension and Widening of Avenida Encinas Carlsbad, California References: 1. RECORD OF MEETING MINUTES Avenida Encinas Extension and Widening Prepared by Fraser Engineering Dated December 22, 1993 2. PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Extension and Widening of Avenida Encinas Carlsbad, California Prepared by Cardiff Geotechnical Dated December 13, 1993 Dear Mr. Wall and Mr. Pasko: This report presents additional /revised recommendations based on our December 22, 1993 meeting with Carlsbad city representatives, the Carlsbad Municipal Water district and Fraser Engineering. In general, the revised recommendations are presented in response to budgetary constraints expressed by the city and the proximity of existing utility lines. Reference 1 (Items 1,2,3 and 8) Subgrade Preparation/Pavement Design The purpose of our initial recommendations for the removal and recompaction of compressible clayey deposits was for the purpose 135 LIVERPOOL DRIVE • SUITE A • CARDIFF • CA 92007 (619)753-3697 • FAX (619) 753-4158 January 6, 1994 W.O. P-121103-2 Page 2 of reducing potential settlement of the pavement. However, as per our meeting with city representatives, grading will be limited to scarification and compaction of the upper 12 inches of the subgrade soils. As indicated in our pavement section of the preliminary geotechnical investigation, the subgrade soils should be moistened to optimum moisture content, compacted and left in a condition to receive base materials. These preliminary pavement design recommendations remain applicable and should, be implemented. A temporary pavement section of 4.0 inches asphaltic concrete over 6.0 inches of base was suggested during the meeting. As an alternative, the subgrade and base material may be constructed as a designed section and covered by 2.0 inches of asphaltic concrete. In this case, the ultimate pavement design could be achieved by placing additional asphaltic concrete, in lieu of removal of a temporary pavement section. Reference 1 (Item 5) Gas Line Crossing As an alternative to a structural arch, it may be feasible to bridge over the gas line utilizing geogrid and special grading techniques. A typical section is illustrated on the enclosed Plate A. January 6, 1994 W.O. P-121103-2 Page 3 Reference 1 (Items 6 and 7) The proposed fill slope (Station 58+55) will require special compaction techniques in and around the gas line. If the grading contractor feels that adequate compaction cannot be obtained in these areas, lateral movement of fill could adversely affect the gas line. In this regard, an alternative approach that of utilizing a geogrid system is presented on the enclosed Plate B. As indicated in the enclosed Typical Section, Plate B, •using geogrid at 2.0 foot intervals will significantly reduce potential lateral movement. This approach will also reduce the amount of compaction effort in and around the gas line. All fill should be placed under the observation and testing of a qualified geotechnical engineer. It should be noted that additional recommendations may be necessary during the construction phase. If you have any questions, please do not hesitate to contact us at 753-3697. This opportunity to be of service is appreciated. Respectfully submitted, CARDIFF GEOTECHNICAL Burwell CO Geologist aUi 782 3:t Exp. 12-31-97 V'dW Qx &j Vithaya Singhanet, P.E. Geotechnical Engineer SUBGRADE GEOGRID D 8' BEYOND 4-XIST 12" HP EXTEND GEOGRI 1:1 PROJECTED PLANE EACH SIDE OF PIPE 1:1 PROJI 1' MIN. COVER A f MIN- GAS \ z MIN TM WHERE LATERAL EXTENTION IS CTED PLANE NOT FEASIBLE, EXTEND GEOGRID - 3' MIN BEYOND 1:1 PROJECTED PLANE AND INTO 1' DEEP TRENCH DETAIL 7 GEOGRID PROTECTION FOR GAS LINE N.T.S. TENSAR-BXI200 OR EQUILVALENT PROPOSED 2:1 FILL SLOPE \ VARIABLE HEIGHT \ MAX 16' \\ 3' EXIST GRADE __ 39 __ PROPOSED .75:1 SLOPE _\ -\- T-----7- EXIST 12 HP GAS TM - - 1r- --- I L MIRAGRID 5T OR EQUILVALMT ------------ - 2' MIN r -.4 2' MIN CLEARANCE OR MIN CLEARANCE REQUIRED BY GAS COMPANY KEY DEPTH=2' MIN. INTO COMPETENT TERRACE DETAIL 8 CEOGRID REINFORCED SLOPE N.T.S. IrE 13 PRELIMINARY GEOTECHNICAL INVESTIGATION CARDIFF GEOTECHNICAL CONSULTING ENGINEERS AND GEOLOGISTS December 13, 1993 Fraser Engineering, Inc. 2191 El Camino Real Oceanside, CA 92054 Subject: PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Extension and Widening of Avenida Encinas Carlsbad, California Dear Mr. Wall and Mr. Pasko: In response to your request, we have performed a preliminary geotechnical investigation at the subject site for the proposed street extension and widening of Avenida Encinas. The findings of the investigation, laboratory test results and recommendations for grading and pavement sections are presented in this report. From a geotechnical point of view, it is our opinion that the site is suitable for the proposed development, although special consideration will be required for the underlying alluvial/soil deposits during the grading and construction phases. If you have any questions, please do not hesitate to contact us at 753-3697. This opportunity to be of service is appreciated. Respectfully submitted, CARDIFF GEOTECHNICAL ,I4 ESS,O Mark Burwell Geologist CO 82 LU cc Exp.12.3197) ~44144- "imv-f- Vithay9a Singhanet, P.E. Geotechnical Engineer 135 LIVERPOOL DRIVE • SUITE A • CARDIFF • CA 92007 (619) 753-3697 • FAX (619) 753-4158 PRELIMINARY GEOTECHNICAL INVESTIGATION Proposed Extension and Widening of Avenida Encinas Carlsbad, California Prepared For: Fraser Engineering, Inc. 2191 El Camino Real Oceanside, California December 13, 1993 W.O. #P-121103 Prepared By: CARDIFF GEOTECHNICAL 135 Liverpool Drive Suite A Cardiff, California 92007 TABLE OF CONTENTS INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SITE CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . 1 PROPOSED DEVELOPMENT...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 SITE INVESTIGATION............ ............. . . ..............2 LABORATORY TESTING. ......... . . . . . . . . . ...... . . . . . . . . . . . . . . . . .3 GEOTECHNICAI. CONDITIONS . . . . . . . . . . . . . . . . . . . . . . ...............4 DISCUSSION...... . . .......... . . .............. . . . . . . . . . . . . . . . .7 PRELIMINARY PAVEMENT DESIGN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 CONCLUSIONS AND RECOMMENDATIONS ................. . . . . .. . . . . .10 GENERAL GRADING CONSIDERATIONS ................ 10 EARTHWORK ..................... ............. ... 12 OBSERVATION AND DENSITY TESTING ................ 14 DRAINAGE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 LIMITATIONS...... . . . ............ . . . . . . . . . . . . . .15 APPENDICES APPENDIX A ....................... LABORATORY TEST RESULTS TABLE S-i PLATE 5-1 TRENCH LOGS TOPOGRAPHIC OVERLAY PORTION OF GRADING PLAN TYP. STABILIZATION FILL DESIGN TYPICAL SECTIONS APPENDIXB ....................... GRADING GUIDELINES GEOTECHNICAL MAP December 13, 1993 W.O. #P-121103 Page 1 INTRODUCTION This report presents the results of our preliminary geotechnical investigation on the subject property. The purpose of this study is to evaluate the nature and characteristics of the earth materials underlying the site and their influence on the construction of the proposed street improvements. SITE CONDITIONS The subject property includes a coastal segment of land extending from the terminus of Avenida Encinas, near Poinsettia Lane north to Palomar Airport Road, in the city of Carlsbad. The southern portion of the site consists of relatively flat cultivated terrain. However, the northern portion of the site includes 10 to 12 foot high slopes which descend along the western side of Avenida Encinas at gradients approaching 1½:1. Except f or the most southern segment, the majority of Avenida Encinas and its proposed extension generally parallels the Atchison Topeka and Santa Fe Railroad line. The northern portion of Avenida Encinas is bounded along the east by commercial structures. A review of topographic maps, prior to the development of structures and the graded portion of Avenida Encinas, indicates a large canyon (Canyon De Las Encinas) and several westerly and southeasterly ravines transecting the northern and central portions of the site (See enclosed topographic overlay). Apparently, one or more culverts were required to transfer water under the elevated railway line. December 13, 1993 W.O. #P-121103 Page 2 PROPOSED DEVELOPMENT Plans for the extension and widening of Avenida Encinas were prepared by Fraser Engineering. The project includes the connection of the existing half street improvements from the terminus of Avenida Encinas near Poinsettia Lane north, to the southern terminus of the street near Palomar Airport Road. The project also includes widening of the existing northern street segment. The overall length of the project, including the widening of the northern street segment and the construction of the new road segment, is approximately 5400 lateral feet. Additional improvements will consist of curb, gutter, sidewalk, asphaltic concrete paving and storm drain facilities. Several utility lines are present along the proposed road alignment. Of significant concern is the 12 inch diameter high pressure gas line. Grading of the southern portion of the road segment will be limited to minor cuts and fills, up to 4.0 feet. However, cuts and fill slopes, up to 9.0 feet and 11.5 feet, respectively, are planned along the northern and central road segments. SITE INVESTIGATION Eight exploratory trenches were excavated on the site with a tractor-mounted backhoe to a maximum depth of 14 feet. Earth materials encountered were visually classified and logged by our field geologist. Undisturbed, representative samples of the earth materials were obtained at selected intervals. Samples December 13, 1993 W.O. #P-121103 Page 3 were obtained by driving a thin walled steel sampler into the desired strata. The samples are retained in brass rings of 2.5 inches outside diameter and 1.0 inches in height. The central portion of the sample is retained in close fitting, waterproof containers and transported to our laboratory for testing and analysis. LABORATORY TESTING Classification The field classification was verified through laboratory examination, in accordance with the Unified Soil Classification System. The final classification is shown on the enclosed exploratory Logs. Moisture/Density The field moisture content and dry unit weight were determined for each of the undisturbed soil samples. This information is useful in providing a gross picture of the soil consistency or variation among exploratory excavations. The dry unit weight was determined in pounds per cubic foot. The field moisture content was determined as a percentage of the dry unit weight. Both are shown on the enclosed Appendix A. Maximum Dry Density/Optimum Moisture Content The maximum dry density and optimum moisture content were determined for selected samples of earth materials taken from the site. The laboratory standard tests were in accordance with ASTM December 13, 1993 W.O. #P-121103 Page 4 D-1557-78. The results of the tests are presented in Appendix III • GEOTECHNICAL CONDITIONS The southern portion of the site is underlain by nearly flat- lying, friable Pleistocene sands mantled by relatively thin soil deposits. However, in the north-central portion of the site significant alluvial/soil deposits are present. These deposits are generally soft and compressible and will require special consideration during the grading phase. A brief description of the earth materials is discussed below. Alluvium/Soil (Undifferentiated) In the vicinity of Trench Nos. 1, 2 and 3, up to 10.5 feet of dark brown slightly sandy clay was encountered. These deposits are compressible and highly expansive. It is likely that significant amounts of these alluvial/soil deposits are present in the central portion of Canyon De Las Encinas (vicinity of STA. 68). Additional alluvial/soil deposits are present in the transecting ravines in the northern portion of the site (vicinity of STA. 81). In the southern portion of the site, the alluvial/soil deposits thin to approximately 6.0 feet, in the vicinity of Trench No. 4. The southern extent of these deposits is in the vicinity of STA. 50. Soil Based on exploratory Trench Nos. 5 through 7, the southern December 13, 1993 W.O. #P-121103 - Page 5 portion of the site is generally mantled by 1.5 to 2.5 feet of clayey sand. The upper 1.0 foot of these deposits have been cultivated. In the vicinity of Trench No. 8, approximately 2.0 feet of clay was encountered below the soil deposits. The clay may represent a former drainage course. Terrace Deposits Late Pleistocene terrace deposits underlie the surf iciál materials on the site. The sedimentary deposits consist of poorly consolidated fine and medium-grained sands. The reddish brown sand is generally clayey and weathered in the upper 2.0 feet, but becomes increasingly dense and competent with depth. Expansive Soils The majority of the terrace deposits are composed of granular deposits which have a potential expansion in the low range. However, the clayey alluvial/soil deposits encountered have a potential expansion in the high range. Groundwater No evidence of perched groundwater was observed in the terrace deposits, along the southern portion of the site. However, surface water was observed in areas along the base of the descending slopes (vicinity of STA. 81). It is likely that shallow groundwater tables are present in the transecting canyon and ravine areas (See enclosed topographic overlay). December 13, 1993 W.O. #P-121103 Page 6 Seismicity Based on a review of pertinent geological maps, no active faults have been recognized on the subject property. The nearest active fault is the Rose Canyon Fault located about four miles west of the site. Other active faults which could affect the site are listed on the enclosed Table S-i. Although the likelihood of ground rupture on the site is remote, it is almost a certainty the property will be exposed to ground motion resulting from the release of energy along the numerous known and unknown faults in Southern California. Table S-i indicates seismic parameters for active faults which could affect the site. The enclosed Seismic Map (Plate S-i) shows the general proximity of active faults. DISCUSSION i. The most southern portion of the site is mantled by relatively thin soil deposits. However, significant alluvial/soil deposits and high groundwater conditions should be anticipated in the central and northern portions of the project. 2. The clayey alluvial/soil deposits are compressible. In order to reduce the adverse affects on pavement, due to consolidation, the upper 3.0 feet of the clayey soils should be removed and replaced as compacted fill in the proposed roadway areas. December 13, 1993 W.O. #P-121103 Page 7 In the vicinity of STA. 76+00 and STA 80 +60, the proposed fill slopes may adversely affect the 12 inch diameter high pressure gas line. Exploratory trenches are recommended in this area to evaluate the geotechnical conditions underlying the gas line. It may be necessary to relocate the gas line in the proposed fill slope areas (See enclosed Typical Sections). Testing of representative samples of the clayey alluvial/soil deposits indicate an R-value of 5 or less. It may be feasible to utilize on-site granular deposits in the upper 2.0 feet of the street subgrade. Such an approach would significantly improve the resistance value of the subgrade soils. The structural sections recommended in this report generally represent the "worst" and "best" types of soils encountered on the site. Final structural sections should be based on R-value testing of the specific soils used in the street subgrade. It is our understanding that the proposed improvements to Avenida Encinas will be constructed in four separate segments. Initial construction will consist of Segment A followed by B, C and D. Our conclusions and recommendations are presented in this sequential manner. December 13, 1993 W.O. #P-121103 Page 8 PRELIMINARY PAVEMENT DESIGN R-value tests were performed on representative samples of clayey alluvial materials and Pleistocene terrace deposits. The results of testing indicate an R-value of 5 or less for the clayey materials and an R-value of 34 for sandy terrace deposits. As per our conversations with the city of Carlsbad, Avenida Encinas is classified as a secondary arterial street with an anticipated traffic index of 8. Preliminary structural sections presented below are based on R-value data and the subsurface conditions encountered during exploration. Preliminary Structural Section Avenida Encinas (Sta. 50+00 to 88+38) R-value 5 (clayey soils), Traffic Index of 8 4.0 inches of asphaltic paving on 18 inches of Class 2 Aggregate Base on 12 inches of compacted native soil Avenida Encinas (Sta. 40+20 to 50+00) R-value 34 (sandy terrace deposits), Traffic Index of 8 4.0 inches of asphaltic paving on 10.5 inches of Class 2 Aggregate Base on 12 inches of compacted terrace deposits Subgrade soils should be scarified, moistened to optimum moisture content and compacted to the thickness indicated in the above structural section, and left in a condition to receive base materials. Class 2 base material should have a minimum R-value of 78 and a minimum sand equivalent of 30. Subgrade December 13, 1993 W.O. #P-121103 Page 9 soils and base materials should be compacted to a minimum of 95 percent of their laboratory maximum dry densities for the sections indicated. All section changes should be properly transitioned. If adverse conditions are encountered during the preparation of subgrade materials, special construction methods may need to be employed. Final pavement section design should be based on testing performed after grading is complete. CONCLUSIONS AND RECOMMENDATIONS General Grading Considerations Segment A (STA. 40+20 to 58+55) In general, the southern portion of the site includes relatively thin soil deposits overlying Pleistocene terrace sands. Grading along STA. 40+20 to 50+100 will require removal and recompaction of the surficial materials and weathered terrace deposits. Minor cuts and fill, up to 3.0 feet, in this area may be graded at an inclination of 1½:1 (horizontal to vertical). From STA. 50+00 to the end of Segment A (STA. 58+55), the site is underlain by alluvial/soil deposits which thicken to more than 10 feet, in a northerly direction. Due to the compressible nature of these clayey deposits, they should be removed to a minimum depth of 3.0 vertical feet and replaced as properly compacted fill prior to the placement of additional fill or after minor cuts, up to 3.0 feet, are completed. December 13, 1993 W.O. #P-121103 Page 10 The proposed fill slope in the vicinity of STA. 58+55 should be constructed as a stabilization fill. A 20 foot wide key, embedded a minimum of 2.0 feet into competent material, should be constructed along the base of the proposed fill slope. Fill should be benched into competent material. Fill slopes should be constructed a maximum gradient of 2:1 (horizontal to vertical). Segment B and C (STA. 58+55 to STA. 88+38) Most of the rough grading has been completed along the western portion of Segment B. However, variable height fill slopes are planned along the western extent of the project. Fill slopes should be provided with a key and benched into competent materials, as previously indicated. The subgrade deposits should be evaluated upon completion of the fill slopes. Additional recommendations may be necessary. The most extensive grading of the project is planned for Segment C. Cuts, up to 9.0 vertical feet, are planned along the western extent of Avenida Encinas. Fill slopes, up to 11.5 feet, are also planned in this area. Upon completion of the road cuts, the subgrade deposits should be evaluated. It is likely that considerable alluvial/soil deposits will be encountered in this area. A minimum of 3.0 foot removal and recompaction should be anticipated. The area of the proposed fill slopes in the vicinity of STA. 76+00 and STA. 80+60 is probably underlain by significant December 13, 1993 W.O. #P-121103 Page 11 alluvial/soil deposits. It is recommended that additional exploratory trenches be excavated in these areas prior to grading. The purpose of the additional exploration is to evaluate the geotechnical conditions underlying the 12 inch diameter high pressure gas line. If compressible alluvial/soil deposits are present, the construction of the proposed 7.0 to 11.5 foot fills could adversely affect the pipe. High groundwater conditions are anticipated in this area and should also be evaluated. It should be noted that removal and relocation of the high pressure gas line may be necessary in this area. Segment D (STA. 88+38 to STA. 93+851 Only minor improvements consisting of a new sidewalk are planned along Segment D. However, the subgrade deposits in the area of the sidewalk should be evaluated during the course of grading. Additional recommendations for densification of the subsoils may be necessary. It should be noted that an alternative D.2 on the grading plans indicate a 7.0 foot widening of the street. If this alternative is chosen, the fill should be keyed and benched into competent deposits. Earthwork Grading and earthwork should be performed in accordance with the following recommendations and the Grading Specifications included in this report. December 13, 1993 W.O. #P-121103 Page 12 Site Preparation Prior to grading, all areas to receive structural fill should be cleared of surface and subsurface obstructions, including any existing debris, and stripped of vegetation. Removed vegetation and debris should be properly disposed of off site. Holes resulting from removal or buried obstructions which extend below finished road grades should be replaced with suitable compacted fill material. All areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 6 inches, brought to near-optimum moisture conditions, and recompacted to at least 90 percent of the laboratory maximum dry density. Removal of Compressible Soils As noted previously, significant clayey alluvial/soil deposits are present. In order to reduce the adverse affects of consolidation, the upper approximately 36 inches of these materials should be removed and recompacted. Localized deeper removals may be necessary along the base of fill slopes and should be evaluated by additional exploration. Excavations The on-site materials are expected to be rippable with modern, earthmoving equipment in good operating condition. It is estimated that the alluvial soils to be removed will undergo approximately 5 to 10 percent shrinkage when compacted as fill material to 00 percent relative compaction. December 13, 1993 W.O. #P-121103 Page 13 Fills The on-site soils are generally suitable for use as compacted fill provided they are free of organic material and debris. Fill should be placed in 6.0 to 8.0 inch lifts, moistened as required and compacted to a minimum of 90 percent of the laboratory maximum dry density. As previously indicated, clayey alluvial deposits should be removed and replaced as compacted fill to a minimum depth of 3.0 feet below the proposed road subgrade. Additional recommendations will be presented should any septic tanks, cistern, seepage pits or other unforeseen geotechnical conditions be encountered during grading. Slope Stability It is our opinion that proposed fill slopes constructed at inclinations of 2 to 1 (horizontal to vertical) or flatter will be stable with respect to deep-seated failure, provided the fills are keyed and benched into competent. materials. Our evaluation is based on a maximum height of 15 feet using a factor of safety of 1.5 under static conditions. Observation and Density Testing Fill should be placed while a representative of this firm is present to observe and test. Additional recommendations may be necessary during the grading phase. Drainage Paved areas should be protected from moisture migrating under the December 13, 1993 W.O. #P-121103 Page 14 pavement from adjacent water sources, such as planted or grass areas. Pad water should not be allowed to pond. LIMITATIONS This report is presented with the provision that it is the responsibility of the owner or the owner's representative to bring the information and recommendations given herein to the attention of the project's architects and/or engineers so that they may be incorporated into plans. If conditions encountered during grading appear to differ from those described in this report, our office should be notified so that we may consider whether modifications are needed. No responsibility for construction compliance with design concepts, specifications or recommendations given in this report is assumed unless on-site review is performed during the course of construction. The subsurface conditions, excavation characteristics and geologic structure described herein are based on individual exploratory excavations made on the subject property. The subsurface conditions, excavation characteristics and geologic structure discussed should in no way be construed to reflect any variations which may occur among the exploratory excavations. Please note that fluctuations in the level of groundwater may occur due to variations in rainfall, temperature and other factors not evident at the time measurements were made and reported herein. Cardiff Geotechnical assumes no responsibility December 13, 1993 W.O. #P-121103 Page 15 for variations which may occur across the site. The conclusions and recommendations of this report apply as of the current date. In time, however, changes can occur on a property whether caused by acts of man or nature on this or adjoining properties. Additionally, changes in professional standards may be brought about by legislation or the expansion of knowledge. Consequently, the conclusions and recommendations of this report may be rendered wholly or partially invalid by events beyond our control. This report is therefore subject to review and should not be relied upon after the passage of three years. The professional judgments presented herein are founded partly on our assessment of the technical data gathered, partly on our understanding of the proposed construction and partly on our general experience in the geotechnical field. Our engineering work and the judgments given meet present professional standards. However, in no respect do we guarantee the outcome of the project. If you have any questions, please do not hesitate to contact our office at 753-3697. The opportunity to be of service is greatly appreciated. APPENDIX A APPENDIX "A" LABORATORY TEST RESULTS TABLE I Maximum Dry Density and Optimum Moisture Content (Laboratory Standard ASTM D-1557-78) Sample Max. Dry Optimum Location Density Moisture Content (pcf) T-1 @ 2'4' 119.0 14.0 (Mixture of clay and sand) TABLE!! Field Dry Density and Moisture Content Sample Field Dry Field Moisture Location Density Content (pcf) T-1@3.0' 104.0 16.2 T-1@5.0' 98.7 19.7 T-1 @ 7.0' 97.7 13.5 T-1 @ 10.0' 102.1 3.6 T-2@3.0' 105.5 17.9 (P-121103-1) TABLE II (Cont'd) Field Dr Density and Moisture Content Sample Field Dry Field Moisture Location Density Content (pcf) T-2@7.0' 112.7 17.3 T-2@9.0' 1.11.0 17.9 T-3 @ 3.0' 105.0 18.9 T-3 @ 5.5' 104.1 20.6 T-3@8.0' . 99.8 21.2 T-4 @ 3.0' 96.8 24.2 T-4@5.0' 114.9 16.9 T-4 @ 7.0' 115.7 7.5 T-5 @ 1.5' 115.6 9.7 T-5@3.5' 112.0 9.1 T-5@7.0' 111.1 8.9 T-5 @ 10.0' 115.6 4.9 T-6@1.0' 112.0 16.4 T-6@3.0' 118.6 15.2 T-6 @ 5.0' 107.8 10.7 T-6@8.0' 108.7 5.7 T-7@3.0' 104.3 22.1 T-7@4.5' 116.7 13.3 T-7 @ 6.5' 113.2 12.9 T-8@3.0' 106.3 21.2 (P-121103-2) TABLE S-i SEISMIC PARAMETERS FOR ACTIVE AND POTENTIALLY ACTIVE FAULTS Max. Max. Credible Probable Bedrock Design Earth- Earth- Accel- Accel- Fault Distance Quake Quake eration eration --Magnitude-- Rose Canyon 4 mi. S.W. 7.1 6.2 0.31g 0.20g j Coronado Banks 19 mi. S.W. 6.5 6.0 0.15g 0.10g Elisnore 25 mi. N.E. 7.5 7.3 019g 0.12g San Jacinto 50 mi. N.E. 7.5 7.3 0.19g 0.06g San Andreas 71 mi. N.E. 8.2 8.0 0.08g 0.05g The Rose Canyon fault has recently been designated as active (C.D.M.G.) Design acceleration is commonly considered to be about 65 percent of the maximum (peak) acceleration for the site within approximately 20 miles of the epicenter. F,~ SEISMIC MAP Total length of fu1t 2On reVe that baks c.N deposits or that has had seismic activity Fault segment with surface rupture during an ... historic earthquake, or with aseisajc fault \100,0 10 Approximate epicentrol area of earthquakes that occurred 1769 - 1933 (899 , S. as p Earthquake epicenters Since 1933 IGA 0 E. • N 1907 Ref; AEG Special Publication, Oct.1973 (by Richard J. Proctor - FISA a !1948 ---- -f RIVERSIDE 3'oN Cp I • 5ANuI BUJ çn.......UL (8 %918 (923 MG3, .v L_. R 899 INDIO%P 1866 E. 1910- .1937 I -. I Sea'z ..• 1954 • ? •..., 4N 'S A M 6.3 19C S.%NL GO (656 1915 1942 : SAN M6.3 1940 1M id IEGO .. \1 • \PRIE7p 1923 19 4 .111 •.. 1935 PIILC3 20 So •• __________________________________ 0 to ENSE4OA PTE S—i N • • • EXPLORATORY TRENCHES LOGS DEPTH DESCRIPTION Trench No. 1 0-2' FILL: Sand, clayey, tan to brown, pebbles, poorly mixed, moderately dense, moist, plastic and wire debris 2'-8' ALLUVIUM: Clay, slightly sandy, dark brown, damp, stiff, veins of tan sand 8'-10' ALLUVIUM(?): Sand, fine and medium- grained, slightly moist, loose, no cementation Trench No. 2 0-1' FILL: Sand, silty and fine-grained, tan to brown, dry, moderately dense 1 '-5.5' ALLUVIUM: Sand, clayey, mottled tan to brown, moist, dense 5.5'-10' ALLUVIUM: Clay, slightly sandy, dark brown, damp to very damp, stiff• 10!-14' TERRACE DEPOSITS(?): Sand, slightly clayey, tan to brown, moist, moderately dense Trench No. 3 0-2.5' FILL: Sand, clayey, tan to brown, moist, loose, plastic debris 2.5'-10.5' ALLUVIUM: Clay, slightly sandy, brown, caliche stringers, damp, soft in upper 4 feet (P-121103-1) 10.5'41.5' TERRACE DEPOSITS: Sand, fine and medium-grained, tan to reddish brown, moist, dense Trench No. 4 0-2' FILL: Sand, clayey, tan to brown, slightly moist, loose 2'-6' ALLUVIUM: Clay, slightly sandy, brown, caliche stringer, damp, soft in upper 3 feet 6'-8' TERRACE DEPOSITS: Sand, fine and medium-grained, slightly clayey, slightly moist, dense 8'-9.5' TERRACE DEPOSITS: Sand, fine and medium-grained, reddish brown to gray, slightly moist, dense Trench No. 5 Trench No. 6 0-1.5' SOIL: Sand, slightly clayey, tan to brown, slightly moist, loose, cultivated area 1.5'-2' SOIL: Sand, clayey, brown, caliche packets, moist, moderately dense 2'-9' TERRACE DEPOSITS: Sand, fine and medium-grained, reddish brown to gray, moist, moderately dense @ 8'-9 very moist, weakly cemented 0-1.5' SOIL: Sand, clayey, tan to brown, blocky, slightly moist, loose, cultivated area TERRACE DEPOSITS: Sand, fine and medium-grained, slightly clayey in upper 1.Y-2.5',moist, dense below 2.5 grades to weakly cemented reddish brown to gray sand (P-1211103-2) Trench No. 7 Trench No. 8 0-1' SOIL: Sand, clayey, tan to brown, blocky, slightly moist, loose, cultivated area 1 '-2.5' SOIL: Clay, slightly sandy, grey, very damp, soft 2.5'-5' TERRACE DEPOSITS: Weathered sand, slightly clayey, blocky, brown to slightly reddish brown, dense, slightly moist 5'-7' TERRACE DEPOSITS: Sand, slightly clayey, reddish brown, moist, dense 7'-8.5' TERRACE DEPOSITS: Sand, fine and medium-grained, very slightly clayey, moist, dense 0-2' SOIL: Sand, clayey, tan to brown, slightly moist, loose, cultivated area 2'-4' SOIL: Clay, slightly sandy, grey, very damp, soft 4'-6.5' TERRACE DEPOSITS: Sand, fine and medium-grained, moist dense (P-121103-3) I '4 20 WIDE STABILIZATION FILL H- VARIABLE 26' 2:1 4 NONPERFORATED PIPE LATERAL TO SLOPE FACE AT 100. INTERVALS 2' MINIMUM KEY DEPTH (into competent material) EQUIPMENT WIDTH KEY 20' MINIMUM TYPICAL STABILIZATION FILL DESIGN 63.0 \\ I I / 12-2- 55.29- 0-s% 7.0 \\\ 5 / I." 1:\~k kayms 19.0 I .kin \ J!\\\\ i \\ •\\ \ 1960 TOPOGRAPIC OVERLAY \ (showing drainage courses prior to development) ____1 w rrTTr fV1V1 IIIUURIII III.Ig1 IL CA APPENDIX B GRADING GUIDELINES Grading should be performed to at least the minimum requirements of the governing agencies, Chapter 70 of the Uniform Building Code and the guidelines presented below: Site Clearing Trees, dense vegetation, and other deleterious materials should be removed from the site. Non-organic debris or concrete may be placed in deeper fill areas under direction of the Soils engineer. Subdrainage During grading, the Geologist should evaluate the necessity of placing additional drains. All subdrainage systems should be observed by the Geologist and Soils Engineer during construction and prior to covering with compacted fill. Consideration should be given to having subdrains located by the project surveyors. Outlets should be located and protected. Treatment of Existing Ground All heavy vegetation, rubbish and other deleterious materials should be disposed of off site. All surf icial deposits of alluvium and colluvium should be removed unless otherwise indicated in the text of this report. Groundwater existing in the alluvial areas may make excavation difficult. Deeper removals than indicated in the text of the report may be necessary due to saturation during winter months. Subsequent to removals, the natural ground should be processed to a depth of six inches, moistened to near optimum moisture conditions and compacted to fill standards. Fill Placement All site soil and bedrock may be reused for compacted fill; however, some special processing or handling may be required (see report). Material used in the compacting process should be evenly spread, moisture conditioned, processed, and compacted in thin lifts not to exceed six inches in thickness to obtain a uniformly dense layer. The fill should be placed and compacted on a horizontal plane, unless otherwise found acceptable by the Soils Engineer. (1) 3. If the moisture content or relative density varies from that acceptable to the Soils engineer, the Contractor should rework the fill until it is in accordance with the following: Moisture content of the fill should be at or above optimum moisture. Moisture should be evenly distributed without wet and dry pockets. Pre-watering of cut or removal areas should be considered in addition to watering during fill placement, particularly in clay or dry surf icial soils. Each six inch layer should be compacted to at least 90 percent of the maximum density in compliance with the testing method specified by the controlling governmental agency. In this case, the testing method is ASTM Test Designation D-1557-91. 4. Side-hill fills should have an equipment-width key at their toe excavated through all surf icial soil and into competent material and tilted back into the hill (CG-1). As the fill is elevated, it should be benched through surf icial soil and slopewash, and into competent bedrock or other material deemed suitable by the Soils Engineer. 5. Rock fragments less than eight inches in diameter may be utilized in the fill, provided: They are not placed in concentrated pockets; There is a sufficient percentage of fine-grained material to surround the rocks; The distribution of the rocks is supervised by the Soils Engineer. 6. Rocks greater than eight inches in diameter should be taken off site, or placed in accordance with the recommendations of the Soils Engineer in areas designated as suitable for rock disposal. 7. In clay soil large chunks or blocks are common; if in excess of eight (8) inches minimum dimension then they are considered as oversized. Sheepsfoot compactors or other suitable methods should be used to break the up blocks. 8. The Contractor should be required to obtain a minimum relative compaction of 90 percent out to the finished slope face of fill slopes. This may be achieved by either overbuilding the slope and cutting back to the compacted core, or by direct compaction of the slope face with suitable equipment. (2) If fill slopes are built "at grade" using direct compaction methods then the slope construction should be performed so that a constant gradient is maintained throughout construction. Soil should not be "spilled" over the slope face nor should slopes be "Dushed out" to obtain arades. Compaction equipment should compact each lift along the immediate top of slope. Slopes should be back rolled approximately every 4 feet vertically as the slope is built. Density tests should be taken periodically during grading on the flat surface of the fill three to five feet horizontally from the face of the slope. In addition, if a method other than over building and cutting back to the compacted core is to be employed, slope compaction testing during construction should include testing the outer six inches to three feet in the slope face to determine if the required compaction is being achieved. Finish grade testing of the slope should be performed after construction is complete. Each day the Contractor should receive a copy of the Soils Engineer's "Daily Field Engineering Report" which would indicate the results of field density tests that day. 9. Fill over cut slopes should be constructed in the following manner: All surf icial soils and weathered rock materials should be removed at the cut-fill interface. A key at least 1 equipment width wide and tipped at least 1 foot into slope should be excavated into competent materials and observed by the Soils Engineer or his representative. The cut portion of the slope should be constructed prior to fill placement to evaluate if stabilization is necessary, the contractor should be responsible for any additional earthwork created by placing fill prior to cut excavation. 10. Transition lots (cut and fill) and lots above stabilization fills should be capped with a three foot thick compacted fill blanket. 11. Cut pads should be observed by the Geologist to evaluate the need for overexcavation and replacement with fill. This may be necessary to reduce water infiltration into highly fractured bedrock or other permeable zones,and/or due to differing expansive potential of materials beneath a structure. The overexcavation should be at least three feet. Deeper overexcavation may be recommended in some cases. (3) 12. Exploratory backhoe or dozer trenches still remaining after site removal should be excavated and filled with compacted fill if they can be located. Grading Observation and Testing Observation of the fill placement should be provided by the Soils Engineer during the progress of grading. In general, density tests would be made at intervals not exceeding two feet of fill height or every 1,000 cubic yards of fill placed. This criteria will vary depending on soil conditions and the size of the fill. In any event, an adequate number of field density tests should be made to evaluate if the required compaction and moisture content is generally being obtained. Density tests may be made on the surface material to receive fill, as required by the Soils Engineer. Cleanouts, processed ground to receive fill, key excavations,subdrains and rock disposal should be observed by the Soils Engineer prior to placing any fill. It will be the Contractor's responsibility to notify the Soils Engineer when such areas are ready for observation. A Geologist should observe subdrain construction. A Geologist should observe benching prior to and during placement of fill. Utility Trench Backfill Utility trench backfill should be placed to the following standards: Ninety percent of the laboratory standard if native material is used as backfill. As an alternative, clean sand may be utilized and flooded into place. No specific relative compaction would be required; however, observation, probing, and if deemed necessary, testing may be required. 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, until it is similar to the inpiace fill, should not be allowed in these trench backfill areas. Density testing along with probing should be accomplished to verify the desired results. (4) JOB SAFETY General: At Cardiff Geotechnical, getting the job done safely is of primary concern. The following is the company's safety considerations for use by all employees on multi-employer construction sites. On ground personnel are at highest risk of injury and possible fatality on grading construction projects. The company recognizes that construction activities will vary on each site and that job site safety is the contractor's responsibility. However, it is, imperative that all personnel be safety conscious to avoid accidents and potential injury. In an effort to minimize risks associated with geotechnical testing and observation, the following precautions are to be implemented for the safety of our field personnel on grading and construction projects. Safety Meetings: Our field personnel are directed to attend the contractor's regularly scheduled safety meetings. Safety Vests: Safety vests are provided for and are to be worn by our personnel where warranted. Test Pits Location. Orientation and Clearance The technician is responsible for selecting test pit locations. The primary concern is the technician's safety. However, it is necessary to take sufficient tests at various location to obtain a representative sampling of the fill. As such, efforts will be made to coordinate locations with the grading contractors authorized representatives (e.g. dump man, operator, supervisor, grade checker, etc.), and to select locations following or behind the established traffic pattern, preferable outside of current traffic. The contractors authorized representative should direct excavation of the pit and safety during the test period. Again, safety is the paramount concern. Test pits should be excavated so that the spoil pile is placed away from oncoming traffic. The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates that the fill be maintained in a driveable condition. Alternatively, the contractor may opt to park a piece of equipment in front of the test pits, particularly in small fill areas or those with limited access. A zone of non-encroachment should be established for all test pits. No grading equipment should enter this zone during the test procedure. The zone should extend approximately 50 feet outward from the center of the test pit. This zone is established both for safety and to avoid excessive ground vibration which typically decreases test results. (5) When taking slope tests, the technician should park their vehicle directly above or below the test location on the slope. The contractor's representative should effectively keep all equipment at a safe operation distance (e.g. 50 feet) away from the slope during testing. The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location. In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is directed to inform both the developer's and contractor's representatives. If the condition is not rectified, the technician is required, by company policy, to immediately withdraw and notify their supervisor. The grading contractors representative will then be contacted in an effort to effect a solution. No further testing will be performed until the situation is rectified. Any fill placed in the interim can be considered unacceptable and subject to reprocessing, recompaction or removal. In the event that the soil technician does not comply with the above or other established safety guidelines, we request that the contractor brings this to technicians attention and notify our the project manager or office. Effective communication and coordination between the contractors' representative and the field technician(s) is strongly encouraged in order to implement the above safety program and safety in general. The safety procedures outlined above should be discussed at the contractor's safety meetings. This will serve to inform and remind the equipment operators of these safety procedures particularly the zone of non-encroachment. Trench Safety It is the contractor's responsibility to provide safe access into trenches where compaction testing is needed. Our personnel are directed not to enter any excavation which 1) is 5 feet or deeper unless shored or laid back, 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench, or 3) displays any other evidence of any unsafe conditions regardless of depth. All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid back. Trench access should be provided in accordance with OSHA standards. Our personnel are directed not to enter any trench by being lowered or "riding down" on the equipment. (6) If the contractor fails to provide safe access to trenches for compaction testing, our company policy requires that the soil technician withdraw and notify their supervisor. The contractors representative will then be contacted in an effort to effect a solution. All backf ill not tested due to safety concerns or other reasons could be subject to reprocessing and/or removal. - (7) A I I c'ri crnw r C: AL ILS AL 3P ANOFETJ 1 ]D FaJ ) T'TJ IET X CD?I J!' ID W X ID E7 t ric / ft I I 1' / 1" = 200' / r i T ID On LQt _I r-zcm (approx. location) TR- 1 mi -r (approx. location) I I a Y?-AD I F F C3 IThI I /