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HomeMy WebLinkAbout; Carlsbad Research Center Lot 13; Soils Report; 1986-09-15GEOTECHNICAL INVESTIGATION FOR CARLSBAD RESEARCH CENTER, LOT13 SAN DIEGO, CALIFORNIA MISSION WEST PROPERTIES c/o CARL1 ARCHITECTURE SAN DIEGO, CALIFORNIA ENGINEERING DEPT. LIBRARY City of Carlsbad 2075 Las Palmas Drive Carkbad CA 92009-4859 BY GEOCON, INCORPORATED SAN DIEGO, CALIFORNIA SEPTEMBER, 1986 - - .I &otechnical Engineers and Engineering Geologists .- I 1 File No. D-3756-501 September 15, 1986 ‘1 1 .;-I "1 _ _- I Mission West Properties c/o Carli Architecture 2900 Fourth Avenue San Diego, California 92103 Attention: Mr. Gary Potter Subject: CARLSBAD RESEARCH CENTER, LOT 13 SAN DIEGO, CALIFORNIA GEOTECHNICAL INVESTIGATION Gentlemen: ‘1 We are pleased to submit the accompanying report which presents the results of OUT geotechnical investigation for the subject project. ,~jl !* # fl 1 The attached report presents the findings of our study and our conclusions and recommendations pertaining to site development as well as ihe results of our field exploration and laboratory tests. Based on the results of our study, it is our opinion that the site can be developed as proposed provided the recommendations of this report are followed. If you have questions'concerning this report or if we may be of further service, please contact the undersigned. very truly yours, GEOCON, INCORPORATED kZi$&h 4 Michael Hart RCE 38789 CEG 706 RRG:WS:lm (3) addressee (1) Carli Architecture (1) Mr. Doug Beetham 9530 Dowdy Drive s$9~~mw~ 9m9 uw - ,:&I - ;a - J - J - 1 ~J - IJ - J _. ,Y .- ;+J “51 _. s - $J :- TABLE OF CONTENTS GEOTECHNICAL INVESTIGATION Page Purpose and Scope. . . . . . . . . . Site and Project Description . . . . . . Soil and Geologic Conditions . . . . . Fill Soils . . . . . . . . . ~ . . . Santiago Formation . . . . . . . . . . Geologic Hazards . . . . . . Groundwater and Liquefaction Potential . . . . . . . . . . . . . . . . . . . . . . . CONCLUSIONS AND RECOMMENDATIONS General. . . . . . . . . . . . . . . . . Potential Geologic Hazards . . . . . Soil and Excavation Characteristics . . Grading. . . . . . . . . . . . . . Foundations. . . . . . . . . . . . Concrete Slabs-on-Grade. . . . . . . . Retaining Wall . . . . . . . . . . . Drainage . . . . . . . . . . Plan Review. . . . . . . . . . . . . LIMITATIONS AND UNIFORMITY OF CONDITIONS Figure 1, Site Plan Figure 2, Retaining Wall Drainage Detail APPENDIX A FIELD INVESTIGATION Figures A-l - A-5, Logs of Test Borings APPENDIX B LABORATORY TESTING. Table I, Moisture-Density & Direct Shear Test Results Table II, Compaction Test Results Table III, Expansion Index Test Results Table IV, Atterberg Limits Test Results APPENDIX C RECOMMENDED GRADING SPECIFICATIONS . . . . . . . . . . . . 5 5 6 6 7 8 9 10 10 File No. D-3756-501 September 15, 1986 - f - J s - ,1 - B GEOTECHNICAL INVESTIGATION purmse and Scow This report presents the results of our geotechnical investigation at the site of the proposed two-story office building in Carlsbad, California. The purpose of the investigation was to evaluate the surface and subsurface soil and geologic conditions at the site and, based on the conditions encountered, to provide recommendations pertaining to the geotechnical engineering aspects of developing the property as presently proposed. The investigation consisted of a site reconnaissance and the excavation of five exploratory borings. Laboratory tests were performed on selected representative samples obtained at various depths in the exploratory excavations to evaluate pertinent physical properties. Details of the field exploration and laboratory tests are presented in Appendices A and B, respectively, The conclusions and recommendations contained herein are based on an analysis of the data obtained in the various phases of the investigation and experience with similar soil and geologic conditions. Site and Proiect DescriDtion The project site is located on the west side of El Camino Real approxi- mately 2,000 feet to the north of the intersection with Palomar Airport Road in Carlsbad, California. The irregular-shaped, nearly level pad is bounded to the north and south by vacant lots and the east and west by El -l- i- File No. D-3756-501 September 15, 1986 Camino Real and La Place Court, respectively. The site is essentially a cut lot with shallow fills on the order of 5 feet at the southeast end (see Figure 1, Site Plan). It is our understanding that project development will consist of the construction of two two-story concrete office buildings. Each office building will be approximately 40,000 square feet in area. Foundation loads were not available for review at this time, however, anticipated foundations include isolated and/or continuous footings with concrete slabs-on-grade. Due to existing topography, very minor grading (in any) is expected. ii 1 l-l “I C II ;91 The locations and descriptions contained herein are based on our site reconnaissance and the as-built grading plans for Carlsbad Tract No. 81- 10, Carlsbad Research Center, prepared by Rick Engineering Company, dated September 23, 1981. If project details vary significantly from those . described, Geocon, Incorporated should be notified for review and possible revision of the conclusions and recommendations that follow. Soil and Geoloeic Conditions Two general soil types were encountered on the site, fill soils and formational soils of the Santiago Formation. Each of the soil conditions are described below. -2- f - b u u Y File No. D-3756-501 September 15, 1986 Fill Soils. Fill soils characterised as stiff, moist, mottled green- orange, very silty clays were encountered in the southeast end of the ,property in the vicinity of Boring 1. Santiaeo Formation. The Santiago Formation was found to underlie the fill soils and was encountered at existing grade within the remainder of the site. These soils extend to the maximum depth explored. This formation is characterised by very dense, moist, green to gray to olive- brown siltstones and sandstones with layers of very hard, olive green claystone. No faults or ancient landslides are known to exist at the site or in the immediate vicinity, and none were encountered during the course of our investigation. A trace of the potentially active Rose Canyon Fault zone has been mapped approximately 7 miles west of the site (Map No. 1, California Division of Mines and Geology). The nearest active faults are the Elsinore and San Jacinto Faults which lie approximately 24 miles and 48 miles, respectively, to the northeast. It is our opinion that the site could be subjected to moderate to severe ground shaking in the event of a major earthquake along any of the above- mentioned faults: however, the site is not considered to possess any greater seismic risk than that of the surrounding developments. -3- File No. D-3756-501 September 15, 1986 Groundwater and Liauefaction Potential In view of the relatively dense nature of the formational soils underlying the site and the lack of a near-surface groundwater table, it is our opinion that liquefaction does not present a significant geologic hazard to the proposed site development. im. - a - 3 File No. D-3756-501 September 15, 1986 CONCLUSIONS AND RECOMMENDATIONS General 1. It is our opinion that the site is suitable for development of the proposed two-story building provided that the recommendations of this report are carefully followed. 2. The majority of the site is underlain by dense soils of the Santiago Formation. In addition. stiff fill soils derived from the Santiago Formation were encountered at the southeast end of the lot. Potential Geoloeic Hazards 3. No faults or indications of faults were found on the site during the investigation. The site could be subjected to moderate to severe ground shaking in the event of a major earthquake along any of the active faults in the Southern California area. It is our opinion, however, that the seismic risk at the site is not significantly greater than that of nearby developments. 4. No landslides or indications of landslides were noted on the site. In our opinion, the potential for landslides is very low and should not be a constraint to development. -5- “J I -VI .-I 1 I -1 ,- _( 1 -1 -1 i-l 3 q -!J - I l-l rl - .I l-l File No. D-3756-501 September 15, 1986 Soil and Excavation Characteristics 5. The Santiago Formation possesses medium to highly expansive character- istics and good foundation support in either a dense undisturbed and/or properly compacted state. 6. It is our opinion that all soil materials on the site can be excavated with moderate effort by conventional heavy-duty grading equipment. Grading 7. All grading should be performed in accordance with the "Recommended Grading Specifications" contained in Appendix C and the City of Carlsbad Grading Ordinance. Where the recommendations of this section conflict with those of Appendix C, the recommendations presented herein shall take precedence. All earthwork should be observed by, and all compacted fill tested by, representatives of our firm. 8. No project grading'plans were available for review, however, based on the existing topography, it is anticipated that very minor grading with maximum cuts and fills on the order of 4 feet will be performed on the site. 9. All fill and backfill should be compacted to at least 90 percent of maximum dry density as determined by ASTM Test Procedure D1557-78, Method C or D. -6- - ai - ‘Lb - t 1 - u - t ;,a File No. D-3756-501 September 15, 1986 10. If imported soils are required to attain finish grade conditions, they should possess an expansion index of less than 50. 11. Although the majority of the site is underlain by dense soils of the Santiago Formation, the more easterly building may be partially founded within fill soils; therefore, we recommend that footings in this building be extended until dense formational soils are exposed. Foundations 12. The project is suitable for the use of continuous strip footings, isolated spread footings or appropriate combinations thereof. Continuous strip footings should be at least 12 inches wide and should extend at least 24 inches into dense formational soil. Isolated spread footings should be at least 2 feet square and extend at least 18 inches below adjacent pad grade into dense formational soil. 13. We recommend minimum reinforcement for continuous footings to consist of four No. 4 steel reinforcing bars placed horizontally in the footings, two near the top and two near the bottom. 14. The recommended reinforcement presented above is based on soil characteristics only and is not intended to be in lieu of reinforcement necessary to satisfy structural loading. -7- .- J - ‘J ..- J - i ,- J - I .- ‘J ,J - a .- 9 J - 3 - J !-J .-. t - ,J i :LJ File No. D-3756-501 September 15, 1986 15. The recommended allowable bearing capacity for foundations designed as recommended above is 2,500 psf. The above bearing capacity may be increased an additional 300 psf for each additional foot of depth and an additional 100 psf for each additional foot of width, to a maximum allowable bearing capacity of 3,500 psf. The values presented above are for dead plus live loads and may be increased by one-third when considering transient loads due to wind or seismic forces. 16. All foundations adjacent to slopes should possess a minimum horizontal distance of 7 feet from the low outside edge of the foundation to the face of the adjacent slope. 17. All footing excavations should be observed by a representative of Geocon, Incorporated prior to placing reinforcing steel or concrete. Concrete Slabs-on-Grade 18. Concrete slabs-on-grade should be at least 4 inches thick and should be underlain by 2 inches of clean sand. Where moisture sensitive floor coverings are planned, a visqueen moisture barrier should likewise be placed below the slab. At least 2 inches of the sand blanket should~ overlie the visqueen to allow for proper concrete curing. Minimal slab reinforcement should consist of No. 3 steel reinforcing bars placed at 18 inches on centers in both directions. The steel reinforcement should be placed in the middle of the slab. -8- J - 1 - J _.. .J J - J - Ll .- ~J 1 - 1 - iJ 3. - : I - I - L J CJ ‘I - il File No. D-3756-501 September 15, 1986 Retaininv Walls 19. Retaining wall foundations should conform to the recommendations under Items 12 through 17. The footings should be founded in dense formational material or properly compacted fill. 20. Lateral loads may be resisted by a passive pressure equivalent to that generated by a fluid weighing 350 pcf for foundations in dense formational soils. A coefficient of friction of 0.30 may be used to calculate the resistance to sliding along the concrete/soil interface. 21. Active earth pressures against walls will depend on the slope of backfill and degree of wall restraint. Unrestrained walls with horizontal, properly drained backfill should be designed to resist an active earth pressure equivalent to that generated by a fluid weighing 35 pcf. 22. The above recommendations assume level, properly drained granular backfill with no surcharge. For 2.0 horizontal to 1.0 vertical sloping backfill, an active pressure equivalent to that exerted by a fluid weighing 42 pcf should be assumed. 23. For restrained retaining walls, an additional uniform surcharge pressure of 7H psf should also be added to the loading diagram. If vehicles are to be parked or driven adjacent to the tops of retaining - “I P -9- d - --I 1 - LJ ‘II -9 - J .~J .r -1 I - -1 CJ File No. D-3756-501 September 15, 1986 walls, a surcharge equal to 2 feet of soil should be added to the design wall loads. 24. Retaining walls should be provided with gravel and perforated pipe drain systems to reduce potential for hydrostatic pressure buildup behind walls. Retaining walls should have the gravel drain for at least two- thirds the height of the wall. We recommend that the gravel be enclosed in a filter fabric envelope (see Figure 2 for details). Drainaee 25. Adequate site drainage is critical to future performance of the project. Under no circumstances should water be allowed to pond adjacent to footings. The site should be fine-graded such that irrigation excess and storm runoff drain away from structures and into swales or other controlled drainage devices. Roof downdrains, if used, should discharge onto splashblocks and the runoff should be directed into controlled drainage structures. Plan Review 26. Geocon, Incorporated should review grading and foundation plans prior to being finalized. Additional comments and recommendations can be determined at that time. J - I - ,: I e -lO- 1 1 7 1 File No. D-3756-501 September 15. 1986 LIMITATIONS AND UNIFORMITY OF CONDITIbNS 1. The recommendations of this report pertain only to the site investigated and are based upon the assumption that the soil conditions do not deviate from those disclosed in the investigation. If any variations or undesirable conditions are encountered during construction, or if the proposed construction will differ from that anticipated herein, Gqcon, Incorporated should be notified so that supplemental recommendations can be given. 2. This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project and incorporated into the plans, and the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. 3. The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. f T .f- ..,, - j r .~9 - jl j Le No. D-3756-501 )tember 15, 1986 - ,- PRESTLY 9 -I DRi ~ 4 B-[ggts *“+$* J: TS i me fl a, eJ S-4 \3 I- -- -- LEGEND 8 _______ APPROX. LOCATION OF TEST BORING ~~f~~~~~-~PREVlOUSLY PLACED FILL LEFT IN PLACE Ts -------SANTIAGO FORMATION SITE PLAN CARLSBAD RESEARCH CENTER. LOT 13 SAN DIEGO, CALIFORNIA - File No. D-3756-501 September 15; 1986 r i -, - ,~%J : :;c :Y. iY ; -? ,,\I f;- y i,- ;‘iz J -c ::-j J ‘,*-I i, ,g- ;,: J “7 ~~I ,.+c. NO SCALE :. ,~7, ’ RETAINING WALL DRAINAGE DETAIL CARLSBAD RESEARCH CENTER, LOT 13 SAN DIEGO, CALIFORNIA Figure 2 f PROPERLY COMPACTED BACKFILL 4” DIA. PERF6RATED ABS OR ADS PIPE NOTE: IF CLASS 2 PERYEA8LE MATERIAL ~(PER SEC,SB-1.02s CALTRANS STO. SPECS.1 IS USED THE FILTER FABRIC MAYBE OELETED (ELOPE _. .., . .~~,._ _.. ir :. 1 APPENDIX A GEOCON ,WCOIPO.A21D -- ~A. J - 9 i -. 1 - i - .A Y-J - J - J Y ,A B ,s - 1 - il - I - \J ?-J - ,. 1 - u hl File No. D-3756-501 September 15, 1986 APPENDIX A FIELD INVESTIGATION The field investigation was performed on August 15, 1986 and consisted of a site reconnaissance and the excavation of five exploratory borings. The borings were advanced to depths ranging from 10 to 20 feet below the .ll I 'ig using existing ground surface with a truck-mounted Mobile B-45 dri 6-inch-diameter continuous flight auger. The soil conditions encountered during trenching were visually classified and logged. Logs of the test borings are presented on Figures A-l through A-5. The approximate location of rhe borings is shown on Figure 1. As drilling proceeded, relatively undisturbed drive samples and disturbed bulk samples were obtained at various depths in the borings and returned to our laboratory for testing. The relatively undisturbed samples were obtained by driving a 3-inch O.D. split-tube sampler into the undisturbed soil mass with blows from a 140-pound hammer falling 30 inches. '56 1 L CH BORING 1 ELEVAllON 319 DATE DRILLED B/15/86 EQUIPMENT B45 Drill Rie /& [ ). ,jl I 1 / / ‘/ 4' 4 i, t iL ?-SC -- CL BORING TERMINATED AT 20.0 FEET MATERIAL DESCRIPTION FILL Medium dense, moist, motled green-orange, very Silty CLAY I SANTIAGO FORMATION Very dense, moist, green, Silty SANDSTONE Very hard, very moist, dark brown, Silty CLAY ,g of Boring 91 6 - '01 6.5 iO/ a 05. 08. 96, 98 - 18. 18. 25. 22. - SAMPLE SYMBOLS cl- UHPLlNG “NS”CCE!%sFUL q -STANDARD PENEII(AllON TEST I - ORNE UUPLE rUNoln”D*En q - OISnmBEOoaeAGsAMRE cl - CYUNI SIMPLE I. - - WATER TABLE 011 SEEPAGE .- *~~E~HEiOGOFS”BS”(IF*CECONo,T,ONSS~oWNWE~EONr\PPLIESONL”lTTnESPEClFlCsORlNGOR~ENC*LOC*TIONr\No ~~*EDI~E,NO,C*I~~,,T,~~,WIR.IW~~~~BEREPR~~N,*~EOF~“B5URF*CE~NoI,IONSLTO~ER~~~~N~*N~nu~~ 6 8 10 12 14 NO mbe J L) . D- r 15 - s !Y 2 ;: - - 2-u 2-1 2-2 2-3 2-4 2-5 ,375 6-501 986 - - 7 / 4 z ii: 2 $ LA ‘: I.;,: :.\::.I: ..‘j::C .j,;.;,, .t:7 h I I A-L - CH -- _-- -- SP CL BORING 2 iLEVATlON 317 DATE 3RILLED 8115186 IQUIPMENT B45 Drill Rig MATEAIAL DESCRIPTION SANTIAGO FORMATION Hard, moist, gray CLAYSTONE - becomes yellow, silty -- becomes olive-green Very dense, moist, olive-brown, very Silty very fine SANE Very hard, moist, dark gray-brown, Silty CLAY I BORING TEEINATED AT 20.0 FEET 5 -~ 'lgure A-2, Log of Test Boring 2 41 151 2 iO/ 8.5 io/ 7.5 i0 1.5 - ILK 19. 13. 19. 10. 30. - 12. 15. 18. 15. 23. - ile No. D-3756-501 198 - - .- BORING 3 zu. %I- 2:; iLE”ATION 317 DATE DRILLED 8115186 EG W,ZjO XXJIPMENT B45 Drill Rie $4 Lx= MATERIAL DESCRIPTION SANTIAGO FORMATION Hard, damp to moist, red, slightly Silty CLAY medium plasticity 37 -- becomes light blue-gray ' -- becomes green 501 - 7 - 501 7 BORING TERTINATED AT 15.0 FEET AWL 29.4 24.6 21.8 iigure A-3, Log of Test Boring 3 SAMPLE SYMBOLS u - SAUPUNG “NSUCCES E3 _ D,SNF!BED OR BIG u PARE q -CIIULIKsAMPLE x I - WATER ilee or) SEEPAGE I pi **~E~*~LOGOFSUBS~~FACEC~~~~~O~~~I(OWN~ERE~N*PP~IES~NL~~T~F~E~PE~~F~~BOR~NG~~TFYN~~LOCI~~~N~N~ ,I ~T*E*~~EI*o~UTEo.I,ISNOTWI..INIE*~sE~~PREYNT*TI”EOFSUBSU.FICECONoITIOUS*IOT)(ERL~DONSINOTlHES . . . y _.. I:,; Y-1 II - ,1 - I 1 - 1 - 1 - 1 .~. J - I .- I - I .- I - I - I I ..- I - File No. D-3756-501 I _--L-- ,c 10Q‘ sepremoer I>, 170~ s BORING 4 &7- g -" we 25s VJ ZL 52 ELEVATlON 315 DATE DRILLED R/l T/R6 g& i$ @ EO"IPME~JT B45 Drill Rig a= wwm * MATERIAL DESCRIPTION 50/ 109.6 18.9 - 10 22.8 11.6 '16 BORING TEFCXIh'ATED AT 15.0 FEET - -. rlgure A-4, Log of Test Boring 4 SAMPLE SYMBOLS _ SAUPLlNG “Ns”CCEs*FUL -STIND*I10 PENEwl.nON TEST I _ Dc?NE SAYPLE I”NDIST”rlBEDI -CH”NK SAMPLE $&le No. D-3657 septemt ,er 1 - "z Y 2 ;: 198 - G 0 ii E z - ;7; 2 I I 44 I. 7 I I / I I I ’ - - 5-1 5-2 5-3 - - CL ,-- - - BORING 5 iLE”ATlON 315 DATE DRILLED 8/15/86 tCXJIPMEN1 B45 Drill Rig MATERIAL DESCRIPTION SANTIAGO FORMATION Hard, very moist, olive-green, Silty CLAY -- becomes gray BORING TERMINATED AT 10.0 FEET of Test Boring 5 - 38 5Of 10.5 - - - t % ZLi g $ - ULK - WI - -’ I P $ .e ‘i ,i APPENDIX B 7 GEDCON I*COlPOl*TnD n n ,rn i p i I File No. D-3756-301 September 15, 1986 APPENDIX B LABORATORY TESTING Laboratory tests were performed in accordance with generally accepted test methods of the American Society for Testing and Materials (ASTM) or other suggested procedures. Selected relatively undisturbed samples were tested for their in-place moisture density and shear strength properties. In addition, selected bulk samples were tested for their maximum density, moisture content, expansive potential and Atterberg Limits character- istics. The results of the laboratory testing program are summarized on Tables I through IV. r _-_.___ _._~~, ~.~ .._,. ~... ~~ ~...d .- :J: :J ,- J J I -1 -1 -1 -1 1 1 1 1 1 1 1 ,1 ~1 - Pile No. D-3756-501 September 15, 1986 TABLE I Summarv of In-Place Moisture-Density and Direct Shear Test Results Angle of Dry Moisture Unit Shear Sample Depth Density content Cohesion Resistance NO. ft. Lxf % DSf Deerees 1-2 2 107.0 19.0 l-4 5 105.3 18.8 l-5 10 108.1 18.7 l-6 15 96.6 25.0 1-7 20 98.2 22.8 2-1 2 119.0 12.2 2-2 5 113.5 14.7 2-3 10 109.8 18.7 2-4 15 110.4 15.8 2-5 20 100.3 23.7 3-2 5 91.5 29.4 3-3 10 97.9 24.6 3-4 15 102.2 21.8 4-l 5 104.9 20.8 4-2 10 109.6 18.9 4-3 15 122.8 11.6 440 21 630 27 130 28 p b P File No. D-3756-501 September 15, 1986 TABLE II Summarv of Laboratory Compaction Test Results ASTM D1557-78 Maximum Dry Optimum SSlIDpl‘Z Density Moisture NO. Description ucf % Drv Wt. l-l Green, Silty CLAY 113.6 15.6 TABLE III Summarv of Laboratorv Expansion Index Test Results Moisture Content Before After Test Test Dry Sample No. 1-l l-3 2-IA 3-1 % 13.3 13.7 11.3 13.4 Density Expansion % DCf Index 36.4 97.2 112 37.4 96.2 132 25.1 105.1 76 29.4 97.4 42 TABLE IV ,%mmar?? of Atterberc Limits Test Results Samle No. l-3 Liquid Plastic Limit Limit 58 21 Plasticity Index 37 '1 1 7 7 ,7 ,7 '1 7 ""I "I :7 ?l 9 ,, '4 g( ,T '9 7 APPENDIX C File No. D-3756-501 September 15, 1986 1.2 1.3 2. 2.1 2.2 2.3 2.4 - RECOMMENDED GRADING SPECIFICATIONS General These specifications have been prepared for grading of the Carlsbad Research Center, Lot 13 located in San Diego, California. m=Y shall be used in conjunction with the Geotechnical Investigation report dated September 15, 1986 prepared by Geocon, Incorporated. The contractor shall be responsible for placing, spreading, watering) and compacting the fill in strict conformance with these specifications. All excavation and fill placement should be done under the observation of the Soil Engineer. The Soil Engineer should be consulted if the contractor or owner wishes to deviate from these specifications. The grading should consist of clearing, grubbing, and removing from the site all material the Soil Engineer designates as "unsuitable"; preparing areas to be filled; properly placing and compacting fill materials; and all other work necessary to conform with the lines, grades, and slopes shown on the approved plans. Preparation of Areas to be Graded All trees and shrubs not to be used for landscaping, structures, weeds, and rubbish should be removed from the site prior to commencing any excavating or filling operations. All buried structures (such as tanks, leach lines, and pipes) not designated to remain on the site should be removed, and the resulting depressions should be properly backfilled and compacted prior to any grading or filling operations. All water wells should be treated in accordance with the requirements of the San Diego County Health Department. The owner shall verify the requirements. All vegetation and soil designated as "unsuitable" by the Soil Engineer should be removed under his observation. The exposed surface should then be plowed or scarified to a depth of at least 12 inches until the surface is free from ruts, hummocks, or other uneven features that would prevent uniform compaction by the equipment used. 2.5 Where the slope ratio of the original ground is steeper thz.7 6.C horizontal to 1.0 vertical, or where recommended by the Scii Engineer, the bank should be benched in accordance with the folloving illustration. F,NlSH rmCE , NOTES (1) SLCWHING CR SLIDING ME5 NOT CCCJR REC%MNDED 3Y SOIL ENGINE:? (NOTE I) 2.6 3. 3.1 3.2 3.3 3.4 "8" should be 2' vider than the compaction equipment, and should be a minimum of 10' wide. The outside of the bottom key should be belov the topsoil or slopewash and at least 3' into dense forma- tional material. After the areas have been plowed or scarified, the surface should be disced or bladed until they are free from large clods: brought to the proper moisture content by adding water or aerating; and compacted as specified in Section 4 of these specifications. Materials Suitable for Use in Compacted Fill Material that is perishable, spongy, contains organic matter, or is otherwise unsuitable should not be used in compacted fill. Material' used for compacted fill should consist of at least 40 percent fines smaller than 3/4-inch diameter. The soil engineer should decide what materials, either imported to the site or excavated from on-site cut areas, are suitable for use in compacted fills; the Soil Engineer should approve any import material before it is delivered to the site. During grading, the contractor may encounter soil types other than those analysed for the soil investigation. The Soil Engineer should be consulted to evaluate the suitability of such soils. Any material containing rocks or hard lumps greater than 6 inches in diameter should be placed in accordance with Section 6 of these specifications. The Soil Engineer should perform laboratory tests on representative samples of material to be used in compacted fill. Such tests should be performed to evaluate the maximum dry density and moisture content of the samples. The tests should be performed in accordance with accepted test methods of the American Society of Testing and Materials (ASTM). 4. 4.1 4.2 4.3 4.4 4.5 4.6 4.7 5. 5.1 5.2 Placing, Spreading, and Compacting Fill Material Unless otherwise specified, fill material should be compacted while et a moisture content near the optimum moisture content and to a relative compaction of at least 90 percent as determined by accepted ASTM teet methods. Fill materials should be placed in layers that, when compacted, have a relative compaction in conformance vith the project specifications. Each layer should be spread evenly and mixed thoroughly to provide uniformity of materials in each layer. When the moisture content of the fill material is less than that recommended by the Soil Engineer, water should be added until the moisture content is as recommended. When the moisture content of the fill material is more than that recommended by the Soil Engineer, the fill material should be aerated by blading, mixing, or other methods until the moisture content is as recommended. After each layer is placed, mixed, and spread evenly, it should be thoroughly compacted to the recommended minimum relative compaction. The fill should be compacted by sheepsfoot rollers, multiple-wheel pheumatic-tired rollers, or other types of compacting rollers that are capable of compacting the fill at the recommended moisture content. Each layer should be rolled continuously over its entire area until the recommended minimum relative compaction is achieved throughout the fill. The fill operation should be continued in layers, as specified above, until the fill has been brought to the finished elopes and grades shown on the approved plans. Fill slopes should be compacted by sheepsfoot rollers, by track- walking with a dozer, or by other suitable equipment. Compaction operations should continue until the slopes are properly compacted (that is, in-place density tests indicate a relative compaction of at least 90 percent at a horizontal distance of 2 feet from the slope face). Observation of Grading Operations The Soil Engineer should make field observations and perform field and laboratory tests during the filling and compaction operations, so that he can express his opinion whether or not the grading has been performed in substantial compliance with project recommendations. The Soil Engineer should perform in-place density tests in accordance with accepted ASTM test methods; such density tests should be made in the compacted materials below the disturbed surface. When results of tests taken within any layer indicate a relative compaction below that recommended, that layer or portion thereof should be reworked until the recommended relative compaction is obtained. -’ .I ! p +- ,‘_I ‘i \;I ‘I -1 -1 -1 I 1 1 1 ,fl 1 1 1 1 .q ;r 6. 6.1 6.2 6.3 6.4 6.5 Oversize Rock Placement "Oversize" rock is defined as material that is greater than 6 incnes and less rhan 4 feet in maximum dimension. Material over 4 feet in maximum dimension should not be used in fills. "Soilfill" is defined as material containing no rock fragments over 6 inches in maximum dimension, and containing at least 40 percent (by weight) soil sizes passing a 3/4-inch sieve. Such "soilfill" should be compacted in accordance with specifications for structural fill. "Rockfill" is defined as material containing less than 40 percent (by weight) soil sizes passing a 3/4-inch sieve. Such "rockfill" can be placed in areas designated by the Soil Engineer and approved by the City Engineer. The Soil Engineer should continuously observe placement of oversize rock. Oversize rock should be placed in accordance with the following illustration. ZONE ZOHE LEGEND A: Compacted "soilfill." In public right-of-way areas and easements, ZONE A should be at least 10 feet thick and should extend at least 3 feet below proposed utility line depth. B: Rocks 2 to 4 feet in dimension placed in windrows in compacted "soilfill." ZONE B disposal not permitted for slopes steeper than 2 horizontal to 1 vertical. ZONE c: Rocks 6 inches to 2 feet in dimension, uniformly distributed in compacted "soilfill." 7. Protection of Work 7.1 During construction. the contractor should grade the site to provide positive drainage away from structures and to prevent water from pending adjacent to structures. Water should not be allowed to damage adjacent properties or finished work on the site. Positive drainage should be maintained by the contractor until permanent drainage and erosion control facilities are installed in accordance with project plans. 7.2 No additional grading shall be done, except under the observation of the Soil Engineer.