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001695 (OFC) Soil Foundation Investigation., Al' LEIGHTON and ASSOCIATES INCORPORATED /vw r SOIL ENGINEERING GEOLOGY GEOPHYSICS GROUND WATER HAZARDOUS WASTES SOIL AND FOUNDATION INVESTIGATION - PROPOSED OFFICE- BUILDING------.— LOTS-3, UILDING------ —LOTS 3, 4, AND 5, DESERT CLUB.TRACT NORTH OF CALLE ESTADO, BETWEEN AVENIDA BERMUDAS AND DESERT CLUB DRIVE LA QUINTA, CALIFORNIA June 6, 1985 Project No. 5850844-01 Prepared for: ROBERT H. RICCIARDI, AIA & ASSOCIATES 45-275 Prickly Pear Lane ' Palm Desert, California.92260 74-240 HIGHWAY 111, PALM DESERT, CALIFORNIA 92260 (619) 568-0993 • (800) 253-4567 IRVINE • WESTLAKE/VENTURA • DIAMOND BAR/WALNUT • SAN BERNARDINO/RIVERSIDE • SAN DIEGO PALM DESERT 0 SANTA CLARITA/VALENCIA I * * 17 ` z LEIGHTON and ASSOCIATES /1 INCORPORATED SOIL ENGINEERING GEOLOGY GEOPHYSICS T0: GROUND WATER HAZARDOUS WASTES June 6, 1985 , Project No. 5850844-01 Robert H. Ricciardi, AIA & Associates 45-275 Prickly Pear Lane Palm Desert, California 92260 _ SUBJECT: Soil and Foundation Investigation, Proposed Office Building, Lots 3, 4, and 5, Desert Club Tract, North of -Calle -Estado, - Between Avenida Bermudas and Desert Club Drive, La Quinta, California . Introduction In accordance with your authorization we have conducted a geotechnical investi- gation of the subject -property: The scope of work included -(1) site-reconnaissancp; (2) excavation; logging, sampling and backfill of three exploratory trenches up to 17 feet in depth; (3) laboratory testing of representative soil samples;, (4) analysis of field and laboratory test data; and (5) preparation of this report presenting our findings, conclusions and recommendations. The approximate locations of the Boundary and Topo Map of lots 3, Haver and Associates, dated March H. Ricciardi, A.I.A. & Associates erences for this investigation. Accompanying Maps and Appendices Index Map - Page 2 exploratory trenches are shown on Plate 1. A 4 and 5, Desert Club Tract, prepared by Charles 12, 1985, and a Site Plan prepared by Robert of Palm Desert, California, were used as ref - Plate 1 - Location of Trenches - End of Text Appendix A - Sampling and Testing Procedures Appendix B - Geotechnical Trench Logs Appendix C - Laboratory Test Results Appendix D - General Earthwork and Grading Specifications Appendix E - References 74-240 HIGHWAY 111, PALM DESERT, CALIFORNIA 92260 (619) 568-0993 • (800) 253-4567 IRVINE • WESTLAKE/VENTURA • DIAMOND BAR/WALNUT • SAN BERNARDINO/RIVERSIDE • SAN DIEGO PALM DESERT • SANTA CLARITA/VALENCIA I �J \ ..water ;•vI - 6V jIII"`... ••. F� :. ' --��•L��n �1, `Water -i• • �; ::�:::_:__... • �;•-. ��•: ? :.••• 'I� •` f+ eAVEAYJE 50 `. \,water Well ' . •� 2 3 p x o h __ 398�j :�aooaop� OD aa00 �C.1• D000aOo 0�6 � ' : a�O�OQ� :: � �0�0 a � • - 38 W �_ \ i •oao�R,w_�� EDE* ti OR HO�c ,.•�aoo n a m u' ta� .-� ! A • 000 • ON • zo �`�I��J�� 40 0 scale INDEX MAP OF PROPOSED OFFICE BUILDING LOTS 3, 4 & 5, DESERT CLUB TRACT NORTH SIDE OF CALLE ESTADO LA QUINTA, CALIFORNIA Base Map: USGA 71' Quadrangle, !;La Quinta, California" TT;ag LEIGHTON and ASSOCIATES INCORPORATED 5850844-01 SITE CONDITIONS AND PROPOSED DEVELOPMENT ' Site Conditions The site is located on the -south side of the Coachella Valley, California in ' the La Quinta cove, surrounded on the east, west and south by the Santa Rosa Mountains. The site covers approximately one-third acre.in the city of La Quinta. No buildings or evidence of man-made structures were observed on ' the site at the.time of our field investigation. The site was flat, sloping - slightly to the -northeast and was essentially free,of surficial trash and debris. Silty and sandy soils were exposed at the ground surface and the site ' supported sparse, low brush and herbaceous vegetation. Undeveloped, vacant land bordered the site on the north, east and"west sides, with Calle Estado on the south and an unnamed alley to the north. Proposed Development It is our understanding. that the site will be developed to support a one and two ' story office structure with parking and landscape areas. No structural load in formation or grading.plans were available at the time of this report. ' FIELD AND LABORATORY INVESTIGATION ' Our subsurface exploration program was conducted on May 23, 1985. -The sub- surface soils were examined by means of three exploratory trenches located as shown on Plate 1. The trenches were excavated to depths of 16 and 17 feet using .a rubber tired backhoe.. In-place soil density and moisture tests were performed- ' and bulk samples taken in the trenches. Laboratory testing of soil samples taken from the trenches included determination of maximum dry density, optimum moisture content, in-situ moisture content and density, sieve analysis and sand equivalent tests. Testing procedures are described in Appendix A. Test results are included in Appendix C and on the trench logs of Appendix B. 1 ' -3 - LEIGHTON and ASSOCIATES INCORPORATED 5850844-01 SUMMARY OF GEOTECHNICAL.CONDITIONS IEarth Materials ' The earth materials encountered in the trenches consisted, in. general, of natural silty sand and sandy silt soils, light -gray in color., dry to slightly moist, medium dense -and medium.stiff in consistency. Sieve analysis of two samples tested indicated -that the .soil fraction passing the -#200 sieve ranged -- from 21 to 46 percent. Based on their classification, the expansion potential of the on-site soils is expected to be low. Ground Water No free ground water or seepage -was encountered in--any-of the trenches during - "- our investigation.--Based�on information from the Coachella Valley Water District, the depth to ground water.in wells nearby the site is on -the -order of 80 feet- - or more. Seismicity ' The nearest active or potentially active fault to the site is .the San Andreas fault zone, 10 miles northeast of the site and the San Jacinto fault which is 13 miles to the southwest. Regional maps show no known faults to be present or ' adjacent to the site. The site is not included in the California Special Studies Zone. Liquefaction, a phenomenum involving total or substantial loss of shear strength ' in saturated soil, is caused by the buildup of excess hydrostatic pressure in saturated cohesionless soils as a result of cyclic stresses generated by g"round motions. The Riverside County Seismicity and'Safety Element (1976) indicates that the liquefaction potential at the site is minimal. Our investigation con- firms these findings for the site. . 4 op LEIGHTON and ASSOCIATES INCORPORATED 5850844-01 r CONCLUSIONS AND RECOMMENDATIONS. Based on the results of our field exploration, laboratory testing and our experience and judgement, the site is suitable for the proposed development. Some overexcavation, scarification and reworking of soils as compacted fill ' is recommended for areas to-support.structures or pavements and..to_provide . adequate and uniform bearing and reduce the potential for excessive differ- ential settlement. 'Recommendations ' 1. Site Preparation The site should be stripped and cleared of any debris or vegetation: After clearing, the existing ground should be excavated to a depth of 18 inches, extending a minimum of5 feet beyond the building footing Iines on the foundation plan._ The exposed excavation should be scarified, thoroughly ' soaked to moisten, the dry silty and sandy soils, and recompacted to 90 percent relative -compaction to a depth of 18 inches prior to place- ment of fill. ' In driveway and parking subgrade areas, the upper 12 inches of existing -ground should be scarified and recompacted to 90 percent relative -compaction prior -.- "to placement of soils as compacted fills. The base course and upper six inches ' of .subgrade soils should be compacted to 95 percent relative compaction. The trenches excavated for our subsurface exploration were up to 17 feet deep, ' approximately 15 feet long, and 3 feet wide.- After logging and sampling, they were loosely backfilled. Where structures are planned at these locations, the trenches should be re -excavated to a depth of 3 feet below existing grade and backfilled with properly controlled compacted fill. A11 grading.should be performed in accordance with the General Earthwork and Grading Specifications (Appendix D) except as modified in the text of this report. 2. Compacted Fills The on-site soils, free of organic material, are suitable for use in compacted fills. The fill materials should be placed in thin lifts, moisture -conditioned ' and compacted to at least,90 percent relative compaction according to ASTM D1557-78.- Thorough watering and the use of heavy rubber-tired/vibratory equipment should provide good results. ' 3. Shrinkage -Subsidence Based on test results, scarification and recompaction of the upper foundation soils should result in a shrinkage of approximately 10 percent. Furthermore, a subsidence of -0.15 feet should also be considered due to preparation of areas to receive fill and equipment operations. _. 5 - • LEIGHTON and ASSOCIATES INCORPORATED ' 5850844-01 r ^ 4. Foundation Design • Footings After site preparation as recommended, the use of shallow continuous footings or isolated pad footings is feasible. The .footings should be at least 18 inches deep and 15 inches wide. The depth of the footings should be measured from the -lowest adjacent final grade. For this depth, an allowable bearing value of 1500 psf is recommended. This value may be increased by one-third for wind or seismic loads. Reinforcement of footings with at least two No. 4 bars at the top and two No. 4 bars at the bottom will reduce the potential for foundation cracking as a result of deep, ' localized ground saturation. While the potential for this may not be high, this or an equivalent level of reinforcement is recommended as a cost- effective precautionary measure. • Lateral Design Static design of permanent cantilevered retaining walls which can be con- sidered to yield and which support horizontal granular backfill may be based on an equivalent fluid density of 35 pounds per cubic foot. This pressure assumes no water pressure buildup behind the walls. Therefore, drainage devices must be properly designed and maintained. A uniform lateral pressure due to backfill surcharge if any, should be computed using a co- efficient of 0.35 times the vertical surcharge load. For walls restrained ' from rotating such as basement walls, an equivalent fluid density of 55 pounds per cubic foot may be used. A maximum value of 200 psf per foot of depth may be used in calculating ' the resistance of properly compacted fill to lateral forces. A coefficient.of friction of 0.3 may be utilized in calculating the re- sistance to sliding at the base of foundations. • Slabs -on -Grade Slabs -on grade should.be at least 4 inches thick. A moisture barrier consisting of Visqueen, properly protected with sand above and below, should be provided where moisture -sensitive floor covering is planned. Light wire mesh reinforcement may be provided to minimize distress due to.hydroconsolidation, temperature and shrinkage stresses. ' • Concrete The slab subgrade and footing excavations should be properly moistened prior to placing of concrete. Low slump concrete (preferably 4 inches) when properly vibrated and cured will have a very low potential for shrinkage cracking. The sulfate content of the soils exposed in the sub - grades and footing excavations should be tested before pouring slabs and footings, and -based on the test results the need for sulfate resistant (Type V) concrete can be evaluated. 0 - 6 - • LEIGHTON and ASSOCIATES INCORPORATED ' 5850844-01 r 5. Based on the classification, we expect the 'R' value of on-site soils to be on the order of 30 or more. With an assumed R -value of 30 for imported fill (to be verified after grading), a tentative structural pavement section con- sisting of 22 inches AC over 5 inches of aggregate base should satisfy an assumed Traffic Index of 4. This Traffic Index -is generally assumed for pavement design of parking stalls and light service conditions. A Traffic ' Index of 5 or more, generally assumed .for travelled lanes, would result in a thicker structural section. Asphaltic concrete should conform to Section 203 of the "Standard Specification ' for Public Works Construction", 1982 edition (SSPWC). Base course should be a Crushed Aggregate Base or Processed Miscellaneous Base conforming with -- Sections 200-2.4 of the SSPWC. The base course and AC should be placed in accordance with Sections 301-2 and 302-5 of the SSPWC. The recommended pavement sections may be supported by properly compacted fill prepared as described in the "Site Preparation" section of this report. 6. Drainage Surface drainage should -be directed and maintained away from the foundation ' towards the street or approved drainage devices. Ponding of water adjacent to,the foundations should be avoided. Minimum drainage gradients of 2 percent in landscaped areas and 1 percent in paved areas are recommended. Planters and landscaped areas adjacent to the building -perimeter should be designed to minimize water infiltration into the.foundation_soils. Consideration should be given to the use of planters with closed bottoms.' ' 7. Seismic Considerations ' Seismic design considerations for structures in the Southern California area are critical because of high regional seismic activity. Seismic design should be in'accordance with provision of applicable codes. ' 8. Excavations The dry on-site soils may be subject to caving. Laying back of deep utility excavations (or shoring) may be a consideration. Temporary excavations during construction should be.designed in accordance with the applicable safety codes. Sandy soils exposed in temporary construction excavations should be kept moist but not saturated to retard ravelling and sloughing during construction. 9. Construction Observations and Testing Grading plans and construction plans should be reviewed by Leighton and Associates, Inc., prior to grading. Construction should be observed by this office at the following stages: ' a. Upon completion of clearing and during excavation of building and pavement areas. b. During all 'stages of grading and earthwork operations including scarifi- cation, precompaction, and while utility trench backfilling. c. Prior to paving or other construction overfill or backfill, d. Whenever any unusual soil conditions are encountered during construction. A final report should be prepared upon completion of rough grading, summarizing the compliance with this report and geotechnical observations made during the grading work. -7- 5850844-01 Should you have any questions concerning this report, please contact this office. We appreciate the opportunity to be of service. Respectfully submitted, LEIG3jjTON & ASSOCIATES, INC.. Brent J. In hram Senior Engineer - BJI/DW/mt Distribution 0 0 - Reviewed By: Don K'. Westphal,. RCE 13921 Senior.Project 'Engiheer (6) Addressee i 0 8 LEIGHTON and ASSOCIATES INCORPORATED • 1 11 i- I l BLOCK 10 0 1 . V 1 �+ z I i. W = a� VN 1 �I i 1 z I I w. 1 1 v I `� i- 1 VJ e' i a Ij1 COO �I F- v u 1 ��I• 1 1. KEY T-0 indicates number and approximate location'of exploratory trenches WI �G QI f1�14 Z I _. A - q1 6 - - CALLS rl Sl •l EX/fT. f' 9Tl�L /lirlR Lin'E� 0) /.P T lrr i� JiLriw . 1, �-�Sf T NAit 1 5 T4,0 ir ROBERT H: RICCIARDI A. I. A. & ASSOCIATES WENDELL W. VEITH ARCHITECT 'ASSOCIATE 45-276 PRICKLY PEAR LANE PALM DESERT CALIFORNIA 9226 260 TELEPHONE 6'19-346-2223 ' Ol sir i'•i/iiaa I I LEGAL DESCRIPTION LOTS 3,485 DI � WI �G QI f1�14 Z I _. A - q1 6 - - CALLS rl Sl •l EX/fT. f' 9Tl�L /lirlR Lin'E� 0) /.P T lrr i� JiLriw . 1, �-�Sf T NAit 1 5 T4,0 ir ROBERT H: RICCIARDI A. I. A. & ASSOCIATES WENDELL W. VEITH ARCHITECT 'ASSOCIATE 45-276 PRICKLY PEAR LANE PALM DESERT CALIFORNIA 9226 260 TELEPHONE 6'19-346-2223 ' Ol sir i'•i/iiaa I I LEGAL DESCRIPTION LOTS 3,485 l BLOCK 10 0 5 T4,0 ir ROBERT H: RICCIARDI A. I. A. & ASSOCIATES WENDELL W. VEITH ARCHITECT 'ASSOCIATE 45-276 PRICKLY PEAR LANE PALM DESERT CALIFORNIA 9226 260 TELEPHONE 6'19-346-2223 ' Ol sir i'•i/iiaa I I LEGAL DESCRIPTION LOTS 3,485 l BLOCK 10 0 In 00 DESERT CLUB TRACT UNIT NO. 1 .a Iat V C!S �+ z W = a� VN - C0 z N O v `� �O^ VJ e' _ a COO F- v O°' I d� ° oo= NOR TN Q r/ PNOJtCI W t lal Z m J 00 ` W l►3yb �tP � 0 sowvii I � I� A TYP/to 4j �i4 W r 1• I SITE PLAN a UA1/ SKI' NO OFM BI SCAT( APD�IIQViF�D Of APPENDIX A 1 f] -JL Q • LEIGHTON and ASSOCIATES INCORPORATED ' 5850844-01 APPENDIX A ' SAMPLING AND TESTING PROCEDURES Sampling Procedures Backhoe Trenches: Bulk samples were obtained from the trenches and returned to our laboratory for testing. In-place density and moisture tests were performed at various depths in the trenches as well as selected locations outside the ' trenches on the existing ground surface. In-place densities and moisture con- tents were determined in accordance with the sand cone method, ASTM D1556-64. The exploratory trenches were logged by our field representative concurrent with their excavation. Representative samples were bagged and transported to our laboratory for testing. Laboratory Testing Procedures ' Classification Tests: Typical materials were subjected to mechanical grain -size analysis by wet sieving with U. S'. Standard brass screens. The data was ' evaluated in determining the classification of the materials. A graphical presentation of the grain -size distribution is presented in the test data and the Unified Soil Classification is presented in both the test data and the Boring Logs. ' Maximum Density Tests: The maximum dry density and optimum moisture content of typical materials were determined in accordance with ASTM D1557-78. This ' test procedure uses 25 blows of a 10 -pound hammer falling a height of 18 inches on each of five layers in a 1/30 cubic foot cylinder. ' Sand Equivalents: The sand equivalents of typical samples were determined in accordance with ASTM D2419-74. �00 LEIGHTON and ASSOCIATES INCORPORATED APPENDIX B n 11 1!1;gft LEIGHTON and ASSOCIATES INCORPORATED ULUI tUH1141LAL 1 t-MINUM LVO ' Trench No: Date: 1444 23 /M8S_ Q ro j ec,t : Z4 al Vr4 e xEWMF 0*/Ce Job No : S8S084*-0/ 's DE Equi rit Company Vi¢LLEY /dAU�NoE Equipment Type: ��D .SS 1��cxH ''Equipment Elevation: ¢3.�� + Ref. or Datum9^1M/7oP0MAP Logged By: �G LEIGHTON and ASSOCIATES, INC. SO _ � s'0p►ah .— d +-) •r ap v H N E Ry L a� 4- o N C au L 4-3 =3 r r GEOTECHNICAL DESCRIPTION dQ)' v-0 r- F Q4-3 F 0: Cl) -1-j CL (A in 4- >-,U 4-J O N+-) •r i N r U rN a1 41 pLL. > > co 2-1 rt3 01 Nm >, (IJ F- F- L a C O O U C :D N� sM n 5r�7Y Sava v. tic �a �% ie ,j;ned� AUd. d&48, drl, �;q�i ,ras, Growh LA) ; S94 dy %,JSIT+ 843 3.0 S an ,�-•� �o 1S vTr0M oic1113 /l0 r&E GM0Un/1> it/,4/-M FfVCoUn/TD�rD LEIGHTON and ASSOCIATES, INC. SO _ � s'0p►ah GEOTECHNICAL TRENCH LUU Trench No: Date: t4AY 23 1995 Projectt: CA OUTAJra &F,-UTi✓EDPAIer /306. Job No: SErSo F4• -D/ Equipment Type: ro12D Equipment Company Vi4��EY ,Qi4ckNaE Gi oa t,+; nn • Lq n + Ref. or Datum b100 MSP Logged By: DG LEIGHTON and ASSOCIATES) INC. Uj r CL 4..) a F v N N F s- w 4- o (A a) s- +3 :3C +j C r0 r U^ N GEOTECHNICAL DESCRIPTION QU — F F n. CL CA U '.r C rN U U CD LL. =3 :3 m Z ro pt (/) N I— I— i Q. ' J!n O O O ZD 0 SM 'Si LV SAND ' IV f; Ax - f rre gialne� !? ismg6:1 3.0 Md. C&OS2, dr l9�f ray - !rows, UE►�m 2.3 2 ,?l% asst' skgo s;e✓e eo M Wf of T,eEA/0 /6 �Er' A o -r2EF CAWAID IiI 47EX C�/toUMrtKE7� LEIGHTON and ASSOCIATES) INC. GEOTECHNICAL TRENCH LOG ' Trench No: 3 Date: /-1AY �23, l9� Project: LYUWTA FeFW7-IVF DAFick- 13tD6. Job No: SeS 08¢, -61 Equipment Type: r2b SY6' .-kNoE Equipment Company VOLI-EY Elevation: ¢¢,D �+ Ref. or Datum &W&4A) °"bAW Logged By: /✓V LEIGHTON and ASSOCIATES, INQ, Ud n �. rn t E r6 a) s 4- o C a) a -- L +� v o o r cn GEOTECHNICAL DESCRIPTION d () -0 E d 41 E Q a) 4J c -N 4- >1U Ln 4J .r C � U rN C) a) p li 0 7 fn Z rp a) V) in a) F- i 0 O O U Ci-) N S� SILTY 57AMD AN S 4AIDY S c r D&4say 92.2 1.Ir MC very �%,,e - '►� Jrayhed, dry � /:� � l' gray - brow� 1%SITY 967 4-.2 5 46% f aSs'J 4"20 Sieve S Equ; vale t-� = /% l D i U'M •�r�t 1310T7oM or FriEver 17reFr- AV 4 Fge�F 6tUdA D WIUM F1V60VNrC: *n LEIGHTON and ASSOCIATES, INQ, f] I . I APPENDIX C 1 1 F 1!lLij;oft LEIGHTON and ASSOCIATES INCORPORATED SOIL TYPE OR LOCATION 0 MAXIMUM DENSITY TEST RESULTS* SOIL DESCRIPTION T-3 at 4' Silty sand and sandy silt (SM/ML) OPTIMUM MOISTURE (%) 15.5 * Test performed in accordance with ASTM D1557-78. SAND EQUIVALENT TESTS ** SAMPLE LOCATION DESCRIPTION T-3 at 4 feet Silty sand and sandy silt (SM/ML) ** Tests performed in accordance with ASTM.D2419-74- MAXIMUM DRY DENSITY (PFC) 107.0 SAND EQUIVALENT 17 Project No. 5850844-01 LEIGHTON & ASSOCIATES Plate No. C-1 APPENDIX D ILil;oft 0 LEIGHTON and ASSOCIATES INCORPORATED .5820756-01 APPENDIX D ' GENERAL EARTHWOI;I< AI,JD GR/01111G SPECIFICATIONS 1.0 General Intent These specifications present general procedures and requirements for grading and earthwork as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdroins, and excavations. The recommendations contoined in the geotechnical report are a part of the earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case.of conflict. Evaluations performed by the consultant during the course of grading may result in new recommendations which could supersede these specifications or the recommendations of the geotechnical report. 2.0 Earthwork Observation and Testing Prior to the commencement of grading, a qualified geotechnical consultant (soils engineer and engineering geologist, and their representatives) shall be employed for the pirpose of observing earthwork procedures and testing the fills for conformance with the recommendations of the geotechnical report and these specifications. It will be necessary -that the consultant provide adequate testing and observation so that he may determine that the work was accomplished as specified. It shall be the responsibility of the contractor to assist the consultant and keep him apprised of work schedules and changes so that he may schedule his personnel accordingly. It shall be the sole responsibility of the contractor to provide adequate equipment and methods to accomplish the work in accordance with applicable grading codes or agency ordinances, these specifications and the approved grading plans. If, in the opinion of the consultant, unsatisfactory conditions, such as questionable soil, poor moisture condition, inadequate compaction, adverse weather, etc., are resulting in a quality of work less than required in these specifications, the consultant will be empowered to reject the work and recommend that construction be stopped until the conditions are rectified. Maximum dry density tests used to determine the degree of compaction will be performed in accordance with the American Society for Testing ani: Materials test method ASTM D1557-78. 3.0 Preparation of Areas to be Filled 3.1 Clearina and Grubbing: All brush, vegetation and debris shall be removed or piled and otherwise disposed of. _ 3.2 Processing: The existing groun support of fill shall be scarified ground which is not. satisfactor following section. Scarification and free of Jorge clay lumps reasonably uniform and free of compaction. d which is determined to be satisfactory for to a minimum depth of 6 inches. Existing y shall be overexcovoted as specified in the shall continue until the soils are bro<<en down or clods and until the working surface is uneven features which would inhibit uniform D 4 1 3.3 OvcrexcavaI icon: Soft, dry, spongy, highly fractured or otherwise unsuitable ground, extending to such a depth 1hot surface processing cannot be adequately improve the condition, shall.be-overexcovated down to firm ground, ' approved by the consultant. 3.4 Moisture Conditioning: Overexcovated and processed soils shall be watered, dried -back, blended, and/or mixed, as required to attain a uniform moisture content near optimum. I3.5 Recompoction: Overexcavated and processed soils which have been properly mixed and moisture -conditioned shall be recompacted to a minimum relative compaction of 90 percent. ' 3.6 Benching: Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical units), the ground shall be'stepped or benched. The ' lowest bench shall be a minimum of 15 feet wide, shall be at least 2 feet deep, shall expose firm material, and shall be approved by the consultant. Other benches shall be excavated in firm material for a' minimum width of 4 feet. Ground sloping flatter than 5:1 shall be benched or otherwise overexcovated t when considered necessary by the consultant. 3.7 Approval: All areas to receive fill, including processed .areas, removal areas and toe -of -fill benches shall be approved by the c,_)nsultont prior - to fill placement. 4.0 Fill Material ' 4.1 General: Material to be placed as fill shall be free of organic matter end other deleterious substances, and shall be approved by the consultant. Soils of poor gradation, expansion, or strength characteristics shall be placed in areas designated by the consultant or shall be mixed with other soils to serve as satisfactory fill material. 4.2 Oversize: Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 12 inches, shall not be buried or placed in 'fills, unless the location, materials, and disposal methods are specifically approved by the consultant. Oversize disposal operations shall be such that nesting of oversize material does not occur, and such that the oversize- material is completely surrounded by compacted or densified fill. Oversize material shall not be placed within 10 feet vertically of finish grade or within the range of future utilities or underground construction, unless specifically approved by the consultant. 4.3 Import: If importing of fill material is required for grading, the import material shall meet the requirements of Section 4.I. 5.0 Fill Placement and Compaction 5.1 Fill Lifts: Approved fill material shall be placed in areas prepared to receive fill in neon -horizontal layers not exceeding 6 inches in compacted thickness. The consultant may approve thicker lifts if testing indicates the grading procedures ore such thot adequate compaction is being achieved with lifts of greater thickness. Each layer shall be spread evenly and shall be 1horOLIghly mixed during spreading to attain uniformity of material and moisture in each layer. J 5.2 Fill Moisture: Fill layers at a moisture content less than optimum shall be ' watered and mired, and wet fill layers shall be aerated by scarification or shall be blended with drier material. Moisture -conditioning and mixing of fill ' layers shall continue until the fill material is at a uniform moisture content at or near optimum. ' 5.3 Compaction of Fill: After each layer has been evenly spread, moisture - conditioned, and mixed, it ' shall be uniformly compacted to not less than 90 percent of maximum dry density. Compaction equipment shall be adequately sized and shall be either specifically designed for soil compaction or of proven reliability, to efficiently achieve the specified degree of compact ion. ' 5.4 Fill Slopes: Compacting of slopes shall be accomplished, in addition to normal compocting procedures, by backrolling of slopes with sheepsfoot rollers at frequent increments of 2 to 3 feet in fill elevation' gain, or by other methods ' producing satisfactory results. At the completion of. grading, the relative compaction of the slope out to the slope face -shall be at least 90 percent. ' 5.5 Compaction Testing: Field tests to check the fill moisture and degree of compaction will be performed by the consultant. The location and frequency of tests shall be at the consultant's discretion. In general, the tests will be taken at an interval not exceeding 2 feet in vertical rise and/or 1,000 cubic ' yards of embankment. ' 6.0 Subdrain Installation Subdrain systems, if required, shall be.installed in approved ground to conform to ' the approximate alignment and details shown on the plans or herein. The subdrain location or materials shall not be changed or modified without the approval of the consultant. The consultant, 'however, may recommend and upon approval, direct ' changes in subdrain line, grade or material. All subdrains should be surveyed for line and grade after installation and sufficient time shah be allowed for the surveys, prior to commencement of filling over the subdrains. ' 7.0 Excavation I Excavations and cut slopes will be examined during grading. if directed by the consultant, further excavation or overexcavation and refilling of cut areas shall. be performed, and/or remedial grading of cut slopes shall be performed. Wher-e fill - over -cut slopes are to be graded, unless otherwise approved, the cut portion of the slope shall be made and approved by the consultant prior to placement of materials for construction of the fill portion of the slope. APPENDIX E PFfl;o! LJLI LEIGHTON and ASSOCIATES INCORPORATED 1,1io 5850844-01 APPENDIX E REFERENCES Envicom Corporation. and the County of Riverside Planning Department, 1976, Seismic Safety and Safety General Plan Elements (Technical Report) for the County of Riverside, report dated September 1976. Leighton and Associates,'Inc., 1984, Geotechnical Investigation, Residential Complex, Southeast of Dr. Carreon Boulevard and Monroe Street, Indio, California, report dated October 29, 1984, Project No. 5841190-01. Leighton.and'Associates, Inc., 1985, Geotechnical Investigation, Proposed Office Building, Southeast corner of Fred Waring Drive and Monterey Avenue, Palm Desert, California, report dated January 16, 1985, Project No.. 5841471-01. Riverside County Planning Department, June 1978, County of Riverside Seismic/ Safety Element. Policy Report. E-1