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Home My WebLink AboutCT 04-21; CARLSBAD VILLAGE TOWNHOMES; PRELIMINARY GEOTECHNICAL INVESTIGATION; 2004-03-20COAST GEOTECHNICAL CONSULTING ENGINEERS AND GEOLOGISTS September 20, 2004 Bob Enright 31499 Lake Vista Circle Bonsall, CA 92003 RE: PRELIMINARY GEOTECHNTCAL INVESTIGATION Proposed Nine (9) Townhomes 2685 and 2687 Roosevelt Carlsbad, California Dear Mr. Enright: In response to your request and in accordance with our Proposal and Agreement dated May 17, 2004, we have performed a preliminary geotechnical investigation on the subject site for the proposed nine townhomes' project. The findings of the investigation, laboratory test results and recommendations for foundation design are presented in this report. From a geologic and soils engineering point of view, it is our opinion that the site is suitable for the proposed development, provided the recommendations in this report are implemented during the design and construction phases. If you have any questions, please do not hesitate to contact us at (858) 755-8622. This opportunity to be of service is appreciated. Respectfully COAST GE( YA144&-14 Mark Burwell, C.E. Engineering Geolol Vithaya inghanet, Geotechnical En2in\ 782 Exp. 12-31-05 779 ACADEMY DRIVE • SOLANA BEACH, CALIFORNIA 92075 (858) 755-8622 • FAX (858) 755-9126 PRELIMINARY GEOTECHNICAL INVESTIGATION p Proposed Nine (9) Townhomes 2685 and 2687 Roosevelt Carlsbad, California Prepared For: Bob Enright 31499 Lake Vista Circle Bonsall, CA 92003 September 20, 2004 W.O. P-426064 Prepared By: COAST GEOTECHNICAL 779 Academy Drive Solana Beach, California 92075 TABLE OF CONTENTS VICINITY MAP 4 INTRODUCTION 5 SITE CONDITIONS 5 PROPOSED DEVELOPMENT 5 SITE INVESTIGATION 6 LABORATORY TESTING 6 GEOLOGIC CONDITIONS 7 CONCLUSIONS 10 RECOMMENDATIONS 11 GRADING-REMOVALS/RECOMPACTION 11 TEMPORARY SLOPES/EXCAVATION CHARACTERISTICS 12 C. FOUNDATIONS 13 SLABS ON GRADE (INTERIOR AND EXTERIOR) 13 RETAINING WALLS 14 F. SETTLEMENT CHARACTERISTICS 15 G. SEISMIC CONSIDERATIONS 15 H. SEISMIC DESIGN PARAMETERS 15 I. PRELIMINARY PAVEMENT DESIGN 16 J. UTILITY TRENCH 16 K. DRAINAGE 17 L. GEOTECHNICAL OBSERVATIONS 17 M. PLAN REVIEW 18 LIMITATIONS 18 REFERENCES 20 APPENDICES APPENDIX A LABORATORY TEST RESULTS EXPLORATORY BORING LOGS CROSS SECTION A-A' TOPOGRAPHIC MAP APPENDIX B REGIONAL FAULT MAP SEISMIC DESIGN PARAMETERS DESIGN RESPONSE SPECTRUM APPENDIX C GRADING GUIDELINES www.delorme.com V 1"= 466.7 ft Data Zoom 15-0 Coast Geotechnical September 20, 2004 W.O. P-426064 Page 5 INTRODUCTION This report presents the results of our geotechnical investigation on the subject property. The purpose of this study is to evaluate the nature and characteristics of the earth materials underlying the property, the engineering properties of the surficial deposits and their influence on the proposed residential project. SITE CONDITIONS The subject property is located north of Grand Avenue, along the west side of Roosevelt Street, in the city of Carlsbad. The subject property consists of approximately 0.46 acres of very gently west sloping terrain. The property is occupied by three (3) separate residential structures. Relief on the site is approximately 2.0 vertical feet. The subject property is bounded by developed residential and commercial lots on the north, south and west. Vegetation includes grass and several palm trees adjacent to the street. Most of the rest of the site, with the exception of planters, is generally void of significant vegetation. Drainage is generally by sheet flow to the southwest. PROPOSED DEVELOPMENT Preliminary plans for the development of the site were prepared by David Soanes, Architect. The * Coast Geotechnical September 20, 2004 W.O. P-426064 Page 6 project includes demolition of existing structures and the construction of nine (9) townhomes. The attached two story units will be constructed over a subterranean garage/basement located approximately 4.0 feet below the existing grade. SITE INVESTIGATION Site exploration included four (4) exploratory borings drilled to a maximum depth of 12 feet. Boring No. 4 was converted to a groundwater monitoring well (piezometer). Earth materials encountered were visually classified and logged by our field engineering geologist. Undisturbed, representative samples of 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. Standard penetration tests were performed in Boring Nos. 3 and 4. 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. Coast Geotechnical September 20, 2004 W.O. P-426064 Page 7 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 Laboratory Tests Results and Exploratory Logs. Maximum Dry Density and 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-1557-91. The results of the tests are presented in the Laboratory Test Results. Expansion Index Tests Expansion Tests were performed on selected samples. Test procedures were conducted in accordance with the Uniform Building Code, Standard No. 29-2. The classification of expansive soil, based on the expansion index, are as indicated in Table 29-C of the Uniform Building Code. The test results are shown on the enclosed Laboratory Test Results. GEOLOGIC CONDITIONS The subject property is located in the Coastal Plains Physiographic Province of San Diego. The Coast Geotechnical September 20, 2004 W.O. P-426064 Page 8 property is underlain at relatively shallow depths by Pleistocene terrace deposits. The terrace deposits are underlain at depth by Eocene-age sedimentary rocks which have commonly been designated as the Santiago Formation on published geologic maps. The terrace deposits are covered by soil deposits and, in part, by fill deposits. A brief description of the earth materials encountered on the site follows. Artificial Fill No evidence of significant fill deposits were observed on the site. Minor fill deposits, up to 2.5 feet, appear to be located along the northwestern portion of the property. Additional minor fill deposits are present in and around the existing structures and driveway areas. The fill is composed of tan to reddish brown silty, fine and medium-grained sand in a dry and hard condition. Residual Soil Site exploration suggests the underlying terrace deposits are blanketed by approximately 6.0 to 12 inches of brown clayey sand to sandy clay. The soil is generally damp and stiff. The contact with the underlying terrace deposits is gradational and may vary across the site. Terrace Deposits Underlying the surficial materials, poorly consolidated Pleistocene terrace deposits are present. The upper 4.5 to 6.0 feet of the terrace deposits are composed of tan to brown clayey, fine and medium- I Coast Geotechnical September 20, 2004 W.O. P-426064 Page 9 grained sand in a soft and near saturated condition. The sediments grade to weakly cemented, tan, fine and medium-grained sand with pebbles and cobbles. Regionally, the Pleistocene sands are considered flat-lying and are underlain at depth by Eocene-age sedimentary rock units. Expansive Soil Based on our experience in the area and laboratory testing of selected samples, the residual soil and clayey Pleistocene terrace deposits reflect an expansion potential in the low range but approaching the medium range. Groundwater Groundwater was encountered in all four exploratory borings below the upper clayey deposits, in the sandy cobble zone, at an approximate depth of 8.0 feet below the existing grade. Tectonic Setting The site is located within the seismically active southern California region which is generally characterized by northwest trending Quaternary-age fault zones. Several of these fault zones and fault segments are classified as active by the California Division of Mines and Geology (Alquist- Priolo Earthquake Fault Zoning Act). Based on a review of published geologic maps, no known faults transverse the site. The nearest active fault is the offshore Newport-Inglewood Fault Zone located approximately 4.6 miles west of Coast Geotechnical September 20, 2004 W.O. P-426064 Page 10 the site. It should also be noted that the offshore Rose Canyon Fault is not a continuous well-defined feature, but rather a zone of right stepping en echelon faults. The complex series of faults has been referred to as the Offshore Zone of Deformation (Woodward-Clyde, 1979) and is not fully understood. Several studies suggest that the Newport-Inglewood and the Rose Canyon faults are a continuous zone of en echelon faults (Treiman, 1984). Further studies along the complex offshore zone of faulting may indicate a potentially greater seismic risk than current data suggests. Other faults which could affect the site include the Coronado Bank, Elsinore, San Jacinto and San Andreas Faults. The proximity of major faults to the site and site parameters are shown on the enclosed Seismic Design Parameters. Liquefaction Potential Liquefaction is a process by which a sand mass loses its shearing strength completely and flows. The temporary transformation of the material into a fluid mass is often associated with ground motion resulting from an earthquake. Owing to the moderately dense nature of the Pleistocene terrace deposits and the age of the sediments, the potential for seismically induced liquefaction and soil instability is considered low. CONCLUSIONS 1) The proposed townhouses will be constructed over a subterranean parking structure, located approximately 4.0 feet below the existing grade. Coast Geotechnical September 20, 2004 W.O. P-426064 Page 11 It is anticipated that relatively soft clayey terrace deposits will be exposed along the base of the parking excavation. A minimum of 3.0 feet of the terrace deposits should be removed and replaced as properly compacted fill, in order to support proposed footings and slabs on grade. Groundwater was encountered approximately 8.0 feet below the existing grade. It should be noted that fluctuations in the groundwater level can occur. Some degree of difficulty should be anticipated in compaction of the clayey terrace deposits, due to the high groundwater conditions and soil characteristics. It is suggested that where sandy deposits are encountered in the garage excavation, that they be stockpiled and mixed with the underlying clayey terrace deposits. Such an approach will aid in compaction characteristics and reduce potential expansion. RECOMMENDATIONS Grading-Removals/Recomaction If structural footings or slabs on grade are planned outside the proposed subterranean walls, the existing fill, soil and weathered terrace deposits should be removed and replaced as properly compacted fill. As previously indicated, granular deposits encountered during the subterranean excavation should be stockpiled for latter mixing with clayey terrace deposits. Removals should Coast Geotechnical September 20, 2004 W.O. P-426064 Page 12 include the entire building pad, extending a minimum of 5.0 feet beyond the building footprint, where applicable. The depth of removals are anticipated to be on the order of 3.0 feet below the proposed garage grade. However, deeper removals may be necessary based on conditions revealed during grading. Most of the existing earth deposits are generally suitable for reuse, provided they are cleared of all vegetation, debris and thoroughly mixed. Prior to placement of fill, the base of the removal should be observed by a representative of this firm. Additional recommendations may be necessary, at that time. The exposed bottom should be scarified to a minimum depth of 6.0 inches, moistened as required and compacted to a minimum of 92 percent of the laboratory maximum dry density. Fill should be placed in 6.0 to 8.0 inch lifts, moistened or aerated to approximately 1.0-2.0 percent above optimum moisture content and compacted to a minimum of 90 percent of the laboratory maximum dry density. Fill, soil and weathered terrace deposits in areas of proposed concrete flatwork and driveways should be removed and replaced as properly compacted fill. Imported fill, if necessary, should consist of non-expansive granular deposits approved by the geotecimical engineer. Temporary Slopes/Excavation Characteristics Temporary excavations should be trimmed to a gradient of 3/4:1 (horizontal to vertical) or less depending upon conditions encountered during grading. The Pleistocene terrace deposits are generally weakly cemented but may contain hard concretion layers. Based on our experience in the area, the terrace deposits are easily rippable with conventional earth moving equipment in good working order. All excavations should be constructed in accordance with Cal-OSHA requirements. Coast Geotechnical September 20, 2004 W.O. P-426064 Page 13 Foundations The following design parameters are based on footings founded into approved compacted fill deposits with an expansion potential in the low range. Footings for the proposed residences should be founded a minimum of 18 inches below the lower most adjacent subgrade, at the time of foundation construction for single-story and two-story structures. A 12 inch by 12 inch grade beam should be placed across the garage opening. Footings should be reinforced in accordance with the project structural engineer's recommendations. For design purposes, an allowable bearing value of 2000 pounds per square foot may be used for foundations at the recommended footing depths. The bearing value indicated above is for the total dead and frequently applied live loads. This value may be increased by 33 percent for short durations of loading, including the effects of wind and seismic forces. Resistance to lateral load may be provided by friction acting at the base of foundations and by passive earth pressure. A coefficient of friction of 0.35 may be used with dead-load forces. A passive earth pressure of 300 pounds per square foot, per foot of depth of fill penetrated to a maximum of 2000 pounds per square foot may be used. Slabs on Grade (Interior and Exterior) Slabs on grade should be a minimum of 5.0 inches thick and reinforced, as recommended by the Coast Geotechnical September 20, 2004- W.O. P-426064 Page 14 project structural engineer. Slabs should be designed in accordance with structural considerations, anticipated settlement and an expansion approaching the medium range. The slab should be underlain by a minimum 2.0-inch sand blanket. Where moisture sensitive floors are used, a minimum 6.0-mil Visqueen or equivalent moisture barrier should be placed over the sand blanket and covered by an additional two inches of sand. Utility trenches underlying the slab may be backfihled with on-site materials, compacted to a minimum of 90 percent of the laboratory maximum dry density. Slabs including exterior concrete flatwork should be reinforced and provided with saw cuts/expansion joints, as recommended by the project structural engineer. All slabs should be cast over dense compacted subgrades. Retaining Walls Cantilever walls (yielding) retaining nonexpansive granular soils may be designed for an active- equivalent fluid pressure of 35 pounds per cubic foot. Restrained walls (nonyielding) should be designed for an "at-rest" equivalent fluid pressure of 58 pounds per cubic foot. Wall footings should be designed in accordance with the foundation design recommendations. All retaining walls should be provided with an adequate backdrainage system (Miradrain 6000 or equivalent is suggested). The soil parameters assume a level granular backfill compacted to a minimum of 90 percent of the laboratory maximum dry density. Coast Geotechnical September 20, 2004 W.O. P-426064 Page 15 Settlement Characteristics Estimated total and differential settlement over a horizontal distance of 30 feet is expected to be on the order of 1.0 inch and 3/4 inch, respectively. It should also be noted that long term secondary settlement due to irrigation and loads imposed by structures is anticipated to be 1/4 inch. Seismic Considerations Although the likelihood of ground rupture on the site is remote, the property will be exposed to moderate to high levels of ground motion resulting from the release of energy should an earthquake occur along the numerous known and unknown faults in the region. The Newport-Inglewood Fault Zone located approximately 4.6 miles west of the property is the nearest known active fault and is considered the design earthquake for the site. A maximum probable event along the offshore fault segment is expected to produce a peak bedrock horizontal acceleration of 0.38g and a repeatable ground acceleration of 0.25g. Seismic Design Parameters (1997 Uniform Building Code) Soil Profile Type - SD Seismic Zone - 4 Seismic Source - Type B Near Source Factor (NJ - 1.1 Near source Acceleration Factor (Na) - 1.0 Seismic Coefficients Ca = 0.44 C= 0.71 Coast Geotechnical September 20, 2004 W.O. P-426064 Page 16 Design Response Spectrum T=O.645 T0 =O.129 Nearest Type B Fault - 4.6 miles Preliminary Pavement Design The following pavement section is recommended for proposed driveways: 4.0 inches of asphaltic paving or 5.0 inches of concrete on 6.0 inches of select base (Class 2) on 12 inches of compacted subgrade soils Subgrade soils should be compacted to the thickness indicated in the structural section and left in a condition to receive base materials. Class 2 base materials should have a minimum R-value of 78 and a minimum sand equivalent of 30. Subgrade soils and base materials should be compacted to a minimum of 95 percent of their laboratory maximum dry density. The pavement section should be protected from water sources. Migration of water into subgrade deposits and base materials could result in pavement failure. Utility Trench We recommend that all utilities be bedded in clean sand to at least one foot above the top of the conduit. The bedding should be flooded in place to fill all the voids around the conduit. Imported Coast Geotechnical September 20, 2004 W.O. P-426064 Page 17 or on-site granular material compacted to at least 90 percent relative compaction may be utilized for backfill above the bedding. The invert of subsurface utility excavations paralleling footings should be located above the zone of influence of these adjacent footings. This zone of influence is defined as the area below a 45 degree plane projected down from the nearest bottom edge of an adjacent footing. This can be accomplished by either deepening the footing, raising the invert elevation of the utility, or moving the utility or the footing away from one another. Drainage Specific drainage patterns should be designed by the project architect or engineer. However, in general, pad water should be directed away from foundations and around the structure to the street. Roof water should be collected and conducted to the street, via non-erodible devices. Pad water should not be allowed to pond. Vegetation adjacent to foundations should be avoided. If vegetation in these areas is desired, sealed planter boxes or drought resistant plants should be considered. Other alternatives may be available, however, the intent is to reduce moisture from migrating into foundation subsoils. Irrigation should be limited to that amount necessary to sustain plant life. All drainage systems should be inspected and cleaned annually, prior to winter rains. Geotechnical Observations Structural footing excavations should be observed by a representative of this firm, prior to the Coast Geotechnical September 20, 2004 W.O. P-426064 Page 18 placement of steel and forms. All fill should be placed while a representative of the geotechnical engineer is present to observe and test. Plan Review A copy of the final plans should be submitted to this office for review prior to the initiation of construction. Additional recommendations may be necessary at that time. 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 construction 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. Coast Geotechnical September 20, 2004 W.O. P-426064 Page 19 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. Coast 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 two 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. However, in no respect do we guarantee the outcome of the project. This study has been provided solely for the benefit of the client and is in no way intended to benefit or extend any right or interest to any third party. This study is not to be used on other projects or extensions to this project except by agreement in writing with Coast Geotechnical. r Coast Geotechnical September 20, 2004 W.O. P-426064 Page 20 REFERENCES Hays, Walter W., 1980, Procedures for Estimating Earthquake Ground Motions, Geological Survey Professional Paper 1114, 77 pages. Seed, H.B., and Idriss, I.M., 1970, A Simplified Procedure for Evaluating Soil Liquefaction Potential: Earthquake Engineering Research Center. Tan, S.S., and Giffen, D.G., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San Diego County, Plate 35A, Open-File Report 95-04, Map Scale 1:24,000. Treiman, J.A., 1984, The Rose Canyon Fault Zone, A Review and Analysis, California Division of Mines and Geology. MAPS/AERIAL PHOTOGRAPHS Aerial Photograph, 1982, Foto-Map D-7, Scale 1"=2000'. California Division of Mines and Geology, 1994, Fault Activity Map of California, Scale 1"=750,000'. Geologic Map of the Oceanside, San Luis Rey and San Marcos 7.5' Quadrangles, 1996, DMG Open File Report 96-02. Pasco Engineering, 2004, Topographic Map 2685 and 2687 Roosevelt Street, Carlsbad, CA, Scale 1"=10'. U.S.G.S., 7.5 Minute Quadrangle Topographic Map, Digitized, Scale Variable. H I, APPENDIX A LABORATORY TEST RESULTS TABLE I Maximum Dry Density and Optimum Moisture Content (Laboratory Standard ASTM D-1557-91) Sample Max. Dry Optimum Location Density Moisture Content (pcf) B-i @ 1.0'-4.0' 120.5 12 .8 TABLE II Field Dry Density and Moisture Content Sample Field Dry Field Moisture Location Density Content (pcf) B-i @ 2.0' 98.8 23.6 B-i @ 4.0' 104.2 18.9 B-i @ 6.0' 85.4 31.5 B-i @ 8.0' 107.4 19.0 B-2 @ 2.0' 100.1 10.6 B-2 @ 4.0' 95.2 28.0 B-2 @ 6.0' 96.4 25.4 B-2 @ 8.0' Sample Disturbed 12.1 TABLE III Expansion Index Test Results Sample Expansion Location Potential B-i @ 3.01 -4.0' 48 (low) P-426064 LOG OF EXPLORATORY BORING NO. 1 DRILL RIG: PORTABLE BUCKET AUGER PROJECT NO. P-426064 BORING DIAMETER: 3.5" DATE DRILLED: 07-08-04 SURFACE ELEV.: 98' (Approximate) LOGGED BY: MB OZ 0 1D 0 r.i o 1D GEOLOGIC DESCRIPTION 98.00 0.00 SC SOIL (Qs): Brown clayey sand, damp, stiff - - - - -97.00 - 1.00 -"' sc TERRACE DEPOSITS (QE): Tan to brn. clayey sand, v.moist. - RE 98.8 23.6 9 96600' E 0! VRL - - - - 95.00 . ,• - T - 3.00 L..- - - - - - 94.0 104.2 18.9 - 4.00 II - i . - 93.00 Olt- - 5. - 85.4 31.5 0 2.0 .00 6 From 6', soft, saturated clayey sand - 91.00 7.00 GM TERRACE DEPOSITS (Qt): Tan to Whitish tan, fine and med.-grained sand, 9000 pebbles/cobbles 107.4 19.0 Groundwater@ 8' - 8.00 : End of Boring @ 9' due to cobble - 89.00 _ SHEET IOF 1 COAST GEOTECHNICAL LOG OF EXPLORATORY BORING NO. 2 ir DRILL RIG: PORTABLE BUCKET AUGER PROJECT NO. P-426064 BORING DIAMETER: 3.5" DATE DRILLED: 07-08-04 SURFACE ELEV.: 98' (Approximate) LOGGED BY: MB ZO n.. ZO rID rID rID rID GEOLOGIC DESCRIPTION 98.00 - 0.00 SM FILL (af):Tan to Reddish brn., silty fine and medium-grained sand, dense - - 97.00 1.e4eze 1.00 : - 96.00 - 2.00 100.1 10.6 - SC SOIL (Qs): Brown clayey sand, damp, stiff MMM — 95.00.& - 3.00 SC TERRACE DEPOSITS (Qt): Tan to brn. clayey sand, v.moist. - 95.2 28.0 - 94.00. From 4', soft, saturated clayey sand - 4.00 - 93.00 - 5.00 - - - - 92.00 - 96.4 25.4 6.00 - 91.00 - 7.00 - .- - --; GM TERRACE DEPOSITS (Qt): Grey to Whitish tan, fine and med.-grained sand, : pebbles/cobbles - 90.00 :: :: Distrubed 12.1 Groundwater @ 8' - 8.00 IIJL .1 :: End of Boring @ 8.5' due to cobble COAST GEOTECHNICAL SHEET IOF I 'LOG OF EXPLORATORY BORING NO. 3 DRILL RIG: HOLLOW STEM AUGER PROJECT NO. P426064 BORING DIAMETER: 6.0" DATE DRILLED: 09-13-04 SURFACE ELEV.: 98' (Approximate) LOGGED BY: MB 140 Pound Hammer, 30 Inch Drop 0 0 U 0 rID i.1 - 0 . rID rID rID -.. - DESCRIPTION 98.00 0.00 FILL (al): Tan to bm. silty sand, with gravel Driveway Sc soi (Qs): Brown clayey sand, damp, stiff 97.00 1.00 VR - - - 96.00 Graditional Contact 2.00 sc TERRACE DEPOSITS (Qt): Tan to brn. clayey sand, v.moist. It 95.00 - 3.00 - 94.00 MEK in Medium dense 4.00 R = 16 - 93.00. - 5.00 - 92.00 - 6.00 - - rn - 91.00. - 7.00 ' GM TERRACE DEPOSITS (Qt): Tan to Whitish tan, fine and med.-grained s 90.00 :._..... pebbles/cobbles . Groundwater @ 8 - - 8.00 - 89.00; - 9.00 88.00.. - 10.00.wa!& 87.00 - - 11.00. End of Boring @ 12' 86.00_i:: - 12.00 SHEET IOFI COAST GEOTECHNICAL LOG OF EXPLORATORY BORING NO. 4 DRILL RIG: HOLLOW STEM AUGER PROJECT NO. P-426064 BORING DIAMETER: 6.0" DATE DRILLED: 09-15-04 SURFACE ELEV.: 98' (Approximate) LOGGED BY: MB 140 Pound Hammer, 30 Inch Drop ZO CIO 0 0 41 - . ( Q rID -I ID rID - 0 0 rID S rID rID DESCRIPTION 9800 - 0.00 cU' FILL (al): Tan to brn. silty sand, with gravel - Driveway SC SOIL (Qs): Brown clayey sand, damp, stiff - 97.00 gg 1.00 ft - - 96.00 Graditional Contact 2.00 - SC TERRACE DEPOSITS (Qt): Tan to brn. clayey sand, v.moist. 95.00': - 3.00 - 94.00 Medium dense 4.00 12 93.00 - - 5.00" - 92.00 .. 6.00 91.00 .. :- 7.00 - GM TERRACE DEPOSITS (Qt): Tan to Whitish tan, fine and med.-grained s - 90.00 pebbles/cobbles Groundwater @ 8 - - 8.00 89.004 - 9.00 88.00 Note: Boring converted to monitoring well Bentonite seal from 4 ft. to 7 ft. 10.00 - 87.00 - 11.00.. - End of Boring @ 12' 86.00 - 12.00 SHEET I OF 1 COAST GEOTECHNICAL CROSS SECTION A-A' (SHOWING GENERAL SUBSURFACE CONDITIONS) SCALE I"=lO' ------------ 0 - I I I ----( I I I I I PROPOSED RESIDENCES I I PROPOSED RESIDENCES I I I I I I 1 —110 I I I __L --------- I I EXISTING GRADE I - 100 PROPOSED GARAGE_( af Qt (clayey) -( -------------------------'---- .---2 ---------- GW (Groundwater) 90 6W : Qt (sandy w/pebbles) GEOLOGIC UNITS af ARTIFICIAL FILL Qs RESIDUAL SOIL Qt TERRACE DEPOSITS COAST GEOTECHNICAL P-426064 TOPOGRAPHIC SURVEY - SEWER MA OLE BENCHMARK ASSUMED R ooIèVeft----S.tree SEW STMP—~/~ MAIL BOX SEW STMP SEW STMP N31~4aj:~~ 106, W. DRIVE WAX~ 0) BUILDING / DASHED LINE REPRE EXISTING I RESIDENCE GROUND CONTOURS 7 EXISTING I RESIDENCE "g'-./ CONC BLOCK I INTERLINK I DIN -101-05 SURFACE 101.36FF . ______ 101. 67FF Fr~t 1 —4 00 -98378W 98 7OFF (covered by af/Qs) 0 L DECK NDPEKONE WALL -98.278W B 00 99.05FF—.. INTERLINK U. SURFACE 203-101-18 [----------------- cn / gAY r -to - TEMP\SHEO in — — — — m 98.97FF— / \.s 77 in 97.946W it, i8-3" WOOD TRACTOR SHED It Qt EXISTING f (covered by tflQs) 'i' \\\\ EE 9.1 98. 328W SHED tj F ' HIGH FREESTANDING . GRASSY LOCK WALL WITH 3 HIGH ..- o: FENCE ABOVE •B2 ' B-1 YARD GRASSY YARD DIRT AND GRAVEL yA: 4/ I EXISTING CHAIN EXISTING WOOD FENCE LINK FENCE S ' --- GRASSY CONCRETE SWALE YARD EXISTING BUILDING 203-101-01,03 LEGEND SCALE: I"=20' SYMBOLS 4. BORING LOCATION (approx.) —-- CONTACT (approx.) GEOLOGIC UNITS af ARTIFICIAL FILL Qs RESIDUAL SOIL Qt TERRACE DEPOSITS COAST GEOTECHNICAL P-426064 APPENDIX B REGIONAL FAULT MAP EXPLANATION Foil l,e, on toni j,4,c..S by 0.114 hon. .bat tell aaed. by d Ii... .bat .ppatlnloly t..e.d infatet 04 by 4004b— .4... onled by y net.w by nba b.y.. F..b bone. qoneled the.. .oninn.bon e. ne1n in oO. C. foil, in do Ge.l, V.Iley no. b-ed on .4 .ekO.ed non. koni. be.0., nbote oeq,cneoneno .,dy.,, c etob.4,..bmne04 ythl. toned. no. boon .ol.d nit, o.1ooe 04 &r..& oba. inboeed..ed - FAULT CLASSIFICATION COLOR CODE (indicating Recency of Movement) Fn.ohioneg nbicb blOono (ln0 0(4,. bolooIy1 onaod by g,00nd 40ki doing . d.qoioa. e.g. noino geoned be.N.ga = wdoWbft oonod bydobarnVT. byi.nhq&eo( I952l.Tbe0(do.n40n - dolatod. What ngo0od toO... n.pt.on on do Etlioeeon.,nly do0(do 10.0 .no.neto toy be CSV apneinily 0 toll,, ..n — .S 4 - m .4 gtoeod baSs (bl l.on anep slippng. - aS grnetd di.pbaunon. nelod)y - llldi%pbcod 000.007 ll-. .4400 ben.y00000 ion db.ss000 48 SPECIAL NOTATIONS S-28 AB tnu DaotooSb A I V / bo ab b 40 04 ye. bog C Li..... . .,L .1o4. ' •—--J I DL. 1.sh,,olscslook000n .atl..Ioo.nep417ngobaba040.atod.ndtoo.404 I nep gononoitw . VVVVVV .VVç V I /\; / ' ' 4._i. ' (I ,00.leon000ytlnLnooJ1 0010000n0001.n.ne.boni000doaS S.poee,nongyslehS \ e•Vnoo/ h j, . \\'7,I/ . *oni000000.oipe.o.bol...,00o0bbe..bn..dloo.n,.nboo i s'W .. p 'II . \ IF" , f 000o.onaoataee.bel.00nlf000.dgn.ne.I CDGto ' \ p 1 0 12 24mi1es V S GRAPHIC SCALE MEXICO COAST GEOTECHNICAL *********************** * * * U B C S E I S * * * * Version 1.03 * * * * *** * * **** * * *********** COMPUTATION OF 1997 UNIFORM BUILDING CODE SEISMIC DESIGN PARAMETERS e JOB NUMBER: P-426064 JOB NAME: ENRIGHT FAULT-DATA-FILE NAME: CDMGUBCR.DAT SITE COORDINATES: SITE LATITUDE: 33.1634 SITE LONGITUDE: 117.3507 UBC SEISMIC ZONE: 0.4 UBC SOIL PROFILE TYPE: SD NEAREST TYPE A FAULT: NAME: ELSINORE-JULIAN DISTANCE: 39.4 km NEAREST TYPE B FAULT: NAME: NEWPORT-INGLEWOOD (Offshore) DISTANCE: 7.3 km NEAREST TYPE C FAULT: NAME: DISTANCE: 99999.0 km SELECTED UBC SEISMIC COEFFICIENTS: Na: 1.0 Nv: 1.1 Ca: 0.44 Cv: 0.71 Ts: 0.645 To: 0.129 DATE: 03-20-2004 --------------------------- SUMMARY OF FAULT PARAMETERS --------------------------- Page 1 ------------------------------------------------------------------------------- APPROX. SOURCE I MAX. I SLIP I FAULT DISTANCE1 TYPE I MAG. I RATE I TYPE (km) I (A,B,C) I (MW) I (mm/yr) I (SS, DS, BT) I B I 6.9 1.50 SS 7.6 B 6.9 1.50 SS 33.7 B 7.4 I 3.00 SS 38.9 B 6.8 5.00 SS 39.4 A 7.1 j 5.00 SS 53.3 B 6.8 I 5.00 SS 56.2 B 7.1 3.00 j SS 71.6 B 6.5 2.00 SS 72.5 B 6.9 1.00 SS 75.1 B 6.7 1.00 DS 75.1 j A 7.2 12.00 SS 75.8 B 6.9 12.00 SS 81.3 B 6.8 2.50 SS 85.0 B 6.8 4.00 SS 94.6 B 6.8 4.00 SS 95.3 B 6.7 12.00 SS 104.1 A 7.4 24.00 SS 107.7 B 6.6 4.00 SS 108.4 B 6.5 0.50 DS 112.6 A 7.0 5.00 DS 112.7 B 7.0 3.00 DS 115.4 B 7.0 2.50 SS 121.9 B 7.0 1.00 DS 123.8 B 6.5 3.00 SS 125.6 B 6.5 0.60 SS 127.1 B 6.5 0.50 DS 127.7 B 6.5 0.50 DS 128.6 A j 7.8 34.00 SS 130.1 B 6.5 0.60 SS 130.7 B 6.7 0.50 DS 131.0 B 6.7 0.50 DS 134.2 B 6.5 1.00 DS 134.3 B 6.6 5.00 SS 140.1 B j 6.6 1.00 SS 141.1 B 7.3 0.60 SS 141.5 B 7.1 0.60 SS 141.8 B 6.6 I 4.00 SS 141.8 B 6.6 1.00 DS 145.1 B 7.0 3.50 SS 146.3 B 6.7 0.30 DS 148.2 B 7.3 0.60 SS 151.9 B 6.7 2.00 DS 153.5 B 6.7 0.60 SS 154.4 j B 6.5 25.00 SS 154.5 B 6.9 j 0.60 SS 154.8 B 7.0 1.00 SS ABBREVIATED FAULT NAME NEWPORT- INGLEWOOD (Offshore) ROSE CANYON CORONADO BANK ELS INORE - TEMECULA ELSINORE-JULIAN ELSINORE-GLEN IVY PALOS VERDES EARTHQUAKE VALLEY NEWPORT-INGLEWOOD (L.A. Basin) CHINO-CENTRAL AVE. (Elsinore) SAN JACINTO-ANZA SAN JACINTO-SAN JACINTO VALLEY ELSINORE-WHITTIER SAN JACINTO-COYOTE CREEK ELS INORE - COYOTE MOUNTAIN SAN JACINTO-SAN BERNARDINO SAN ANDREAS - Southern SAN JACINTO - BORREGO SAN JOSE CUCAMONGA SIERRA MADRE (Central) PINTO MOUNTAIN NORTH FRONTAL FAULT ZONE (West) CLEGHORN BURNT MTN. RAYMOND CLAMSHELL- SAWPIT SAN ANDREAS - 1857 Rupture EUREKA PEAK NORTH FRONTAL FAULT ZONE (East) VERDUGO HOLLYWOOD SUPERSTITION MTN. (San Jacinto) ELMORE RANCH LANDERS HELENDALE - S. LOCKHARDT SUPERSTITION HILLS (San Jacinto) SANTA MONICA ELSINORE-LAGUNA SALADA MALIBU COAST LENWOOD-LOCKHART-OLD WOMAN SPRGS SIERRA MADRE (San Fernando) JOHNSON VALLEY (Northern) BRAWLEY SEISMIC ZONE EMERSON So. - COPPER MTN. SAN GABRIEL SUMMARY OF FAULT PARAMETERS --------------------------- Page 2 ------------------------------------------------------------------------------- APPROX. ISOURCE I MAX. I SLIP I FAULT ABBREVIATED IDISTANCEI TYPE I MAG. I RATE I TYPE FAULT NAME I (km) I (A,B,C) I (MW) I I (mm/yr) I (SS.DS,BT) ANACAPA-DUME 154.9 I ====== B 7.3 3.00 DS PISGAH-BULLION MTN.-MESQUITE LK 165.1 B 7.1 0.60 SS CALICO - HIDALGO 167.0 B 7.1 0.60 SS SANTA SUSANA 167.3 B I 6.6 5.00 DS IMPERIAL 168.1 A I 7.0 20.00 I Ss HOLSER 176.3 B 6.5 I 0.40 DS SIMI-SANTA ROSA 184.0 B 6.7 1.00 DS OAK RIDGE (Onshore) 184.7 B I 6.9 4.00 DS SAN CAYETANO 193.1 B I 6.8 J 6.00 I DS GRAVEL HILLS - HARPER LAKE 194.2 B I 6.9 0.60 SS BLACKWATER 209.2 B 6.9 0.60 SS VENTURA - PITAS POINT 212.2 B 6.8 I 1.00 DS SANTA YNEZ (East) 212.9 B 7.0 2.00 SS SANTA CRUZ ISLAND 221.5 B 6.8 1.00 I DS M.RIDGE-ARROYO PARIDA-SANTA ANA 222.8 B 6.7 0.40 DS RED MOUNTAIN 226.3 B I 6.8 2.00 DS GARLOCK (West) 229.1 A 7.1 6.00 I SS PLEITO THRUST 234.4 B 6.8 2.00 DS BIG PINE 240.3 B 6.7 0.80 SS GARLOCK (East) 244.1 A 7.3 7.00 SS WHITE WOLF 255.0 B 7.2 2.00 DS SANTA ROSA ISLAND 256.4 B 6.9 1.00 I DS SANTA YNEZ (West) 258.3 B I 6.9 2.00 SS So. SIERRA NEVADA 268.6 B 7.1 0.10 DS LITTLE LAKE 273.5 B I 6.7 I 0.70 SS OWL LAKE 275.2 B 6.5 2.00 SS PANAMINT VALLEY 275.4 B I 7.2 2.50 SS TANK CANYON 275.7 B 6.5 I 1.00 DS DEATH VALLEY (South) 285.0 B 6.9 4.00 SS LOS ALAMOS-W. BASELINE 300.6 B 6.8 0.70 DS LIONS HEAD 318.1 B I 6.6 0.02 DS DEATH VALLEY (Graben) 325.5 B 6.9 4.00 I DS SAN LUIS RANGE (S. Margin) 327.7 B 7.0 I 0.20 DS SAN JUAN 328.2 B 7.0 1.00 SS CASMALIA (Orcutt Frontal Fault) 336.1 B 6.5 0.25 DS OWENS VALLEY 341.7 I B 7.6 1.50 I ss LOS OSOS 357.7 B 6.8 0.50 DS HOSGRI 363.9 B 7.3 2.50 SS HUNTER MTN. - SALINE VALLEY 368.5 B 7.0 2.50 I Ss INDEPENDENCE I 377.5 B I 6.9 0.20 DS RINCONADA 378.5 B 7.3 1.00 SS DEATH VALLEY (Northern) j 378.8 A 7.2 5.00 SS BIRCH CREEK I 433.8 B 6.5 0.70 DS SAN ANDREAS (Creeping) 434.6 B 5.0 I 34.00 SS WHITE MOUNTAINS 438.4 B 7.1 I 1.00 I SS DEEP SPRINGS 457.0 I B 6.6 0.80 I DS SUMMARY OF FAULT PARAMETERS --------------------------- Page 3 ------------------------------------------------------------------------------- APPROX. ISOURCE I MAX. I SLIP I FAULT ABBREVIATED IDISTANCEI TYPE I MAG. I RATE I TYPE FAULT NAME I (km) I (A,B,C) I (Mw) I (mm/yr) (SS,DS,BT) DEATH VALLEY (N. of Cucamongo) 462.4 A 7.0 5.00 SS ROUND VALLEY (E. of S.N.Mtns.) 468.8 B 6.8 I 1.00 DS FISH SLOUGH 476.7 B 6.6 0.20 DS HILTON CREEK I494.9 B 6.7 2.50 DS ORTIGALITA 518.9 B I 6.9 I 1.00 SS HARTLEY SPRINGS 519.1 B I 6.6 0.50 DS CALAVERAS (So.of Calaveras Res) 524.5 B 6.2 15.00 SS MONTEREY BAY - TULARCITOS 527.2 B 7.1 0.50 DS PALO COLORADO - SUP. 528.3 B 7.0 3.00 I SS QUIEN SABE I537.7 B 6.5 1.00 SS MONO LAKE 555.1 B 6.6 I 2.50 DS ZAYANTE-VERGELES 556.3 B 6.8 0.10 SS SAN ANDREAS (1906) 561.5 A 7.9 24.00 SS SARGENT 561.6 B 6.8 3.00 SS ROBINSON CREEK 586.3 B 6.5 0.50 DS SAN GREGORIO 602.6 A I 7.3 I 5.00 SS GREENVILLE 611.3 B 6.9 2.00 SS MONTE VISTA - SHANNON 611.7 B I 6.5 0.40 DS HAYWARD (SE Extension) J 611.7 B 6.5 I 3.00 SS ANTELOPE VALLEY 626.6 B I 6.7 0.80 DS HAYWARD (Total Length) 631.5 A 7.1 I 9.00 I Ss CALAVERAS (No.of Calaveras Res) 631.5 B I 6.8 6.00 SS GENOA 651.9 I B 6.9 1.00 DS CONCORD - GREEN VALLEY 679.2 B I 6.9 6.00 SS RODGERS CREEK I 718.0 A 7.0 I 9.00 SS WEST NAPA 718.8 B 6.5 1.00 SS POINT REYES I 736.9 B 6.8 j 0.30 DS HUNTING CREEK - BERRYESSA I 741.3 B 6.9 6.00 SS MAACANA (South) 780.7 I B 6.9 I 9.00 SS COLLAYOMI 797.6 B 6.5 I 0.60 I SS BARTLETT SPRINGS 801.1 A 7.1 I 6.00 I SS MAACAMA (Central) 822.3 I A I 7•1 9.00 I ss MAACAMA (North) 881.8 A I 7.1 I 9.00 SS ROUND VALLEY (N. S.F.Bay) I 888.0 B 6.8 6.00 SS BATTLE CREEK 911.6 B I 6.5 I 0.50 I DS LAKE MOUNTAIN 946.4 B I 6.7 6.00 I SS GARBERVILLE-BRICELAND 963.5 B I 6.9 9.00 SS MENDOCINO FAULT ZONE I 1019.8 A 7.4 35.00 DS LITTLE SALMON (Onshore) I 1026.5 A I 7.0 I 5.00 DS MAD RIVER 1029.3 B I 7.1 I 0.70 DS CASCADIA SUBDUCTION ZONE 1033.5 A 8.3 I 35.00 I DS McKINLEYVILLE 1039.7 I B I 7.0 I 0.60 DS TRINIDAD I 1041.2 I B 7.3 2.50 I DS FICKLE HILL 1041.7 B 6.9 I 0.60 I DS TABLE BLUFF 1047.1 B I 7.0 I 0.60 DS LITTLE SALMON (Offshore) 1060.4 B I 7.1 I 1.00 DS 2.5 0.0 DESIGN RESPONSE SPECTRUM Seismic Zone: 0.4 Soil Profile: SD 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Period Seconds 1 APPENDIX C GRADING GUIDELINES Grading should be performed to at least the minimum requirements of the governing agencies, Chapter 33 of the Uniform Building Code, the geotechnical report and the guidelines presented below. All of the guidelines may not apply to a specific site and additional recommendations may be necessary during the grading phase. 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. Su bdrainage During grading, the Geologist and Soils Engineer 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 surficial deposits including 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 1. Most site soil and bedrock may be reused for compacted fill; however, some special processing or handling may be required (see report). Highly organic or contaminated soil should not be used for compacted fill. 4 (1) 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-1 557-91. 4. Side-hill fills should have a minimum equipment-width key at their toe excavated through all surficial soil and into competent material (see report) and tilted back into the hill. As the fill is elevated, it should be benched through surficial deposits and into competent bedrock or other material deemed suitable by the Soils Engineer. 5. Rock fragments less than six 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 six 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 six (6) 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 "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 surficial soils and weathered rock materials should be removed at the cut-fill interface. A key at least 1 equipment width wide (see report) 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 four foot thick compacted fill blanket (or as indicated in the report). 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. 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. (3) 10 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 maybe 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, unless 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. (4)