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HomeMy WebLinkAboutCT 74-21; Carlsbad Oaks East; Soils Report; 1988-08-01ENGINEERIN0 DEPT. LIBRARY City of Carlsbad 2075 Las Palmas Drive Carlsbad CA 92009-4859 GEOTECHNICAL INVESTIGATION LOT 36 CARLSBAD OAKS EAST FOR THE PROPOSED CARLSBAD, CALIFORNIA Prepared for: T&G Investments 3575 Kenyon Street San Diego, California 92110 b.~ Woodward=Clyde Consultants w n - .I/" 1550 Hotel Circle North San Dlego. California 92108 619-294-9400 Fax: (619) 293-7920 August 1,1988 Project No. 8851091J-SI01 T&G Investments 3575 Kenyon Street San Diego, California 921 10 Attention: Mr. Paul Tchang GEOTECHNICAL INVESTIGATION LOT 36 CARLSBAD OAKS EAST CARLSBAD, CALIFORNIA Gentlemen: WoodwardGlyde Consultants Woodward-Clyde Consultants (WCC) is pleased to provide the accompanying report, performed in accordance with our proposal dated March 3,1988. which presents the results of our geotechnical investigation for the project. This study was This report presents our conclusions and recommendations pertaining to the project, as well as the results of our field explorations and laboratory tests. very auly yours,- WOODWARD-CLYDE CONSULTANTS Joseph G. Kocherhans G.E. 480 JGWrlg Consulting Engineers. Gmlwlsts and Env~ronmenlal Sc~enl~sts Onlces In Olher Prtnclaal Citles Project No. 8851091J-SI01 PURPOSE AND SCOPE OF INVESTIGATION DESCRIPTION OF THE PROJECT 1 FIELD AND LABORATORY INVESTIGATIONS 2 SITE CONDITIONS 2 Geologic Settings Subsurface Conditions Ground Water 2 3 3 DISCUSSIONS, CONCLUSIONS, AND RECOMMENDATIONS 3 Slopes Floor Slabs Foundations Trench Excavations Grading Drainage UNCERTAINTY AND LIhaATIONS 7 - A. Field Investigation B . Laboratory Tests C. Guide Specifications for Earthwork i Project No. 8851091J-SI01 GEOTECHNICAL INVESTIGATION FOR THE PROPOSED LOT 36 CARLSBAD OAKS EAST CARLSBAD, CALIFORNIA PURPOSE AND SCOPE OF INVESTIGATION This report presents the results of our geotechnical investigation at the site of the proposed Lot 36 of Carlsbad Oaks East in Carlsbad, California. The site is located on the west side of Loker Avenue East approximately 420 feet north of Palomar Airport Road. This report has been prepared exclusively for T&G Investments and their consultants for use in evaluating the property and in project design. This report presents our conclusions and/or recommendations regarding: . The geologic setting of the site; . General subsurface soil conditions; . General extent of existing fill soils; . Presence and effect of expansive soils; . Grading and earthwork; . Types and depths of foundations; and . Allowable soil bearing pressures. DESCRIPTION OF THE PROJECT For our study, we have discussed the project with Mr. Ted Tchang. We have also been provided with a Site Plan indicating a proposed building location and property limits, prepared by KrommenhoeklMcKeown & Associates.A.1.A.. dated January 11, 1988. We Project No. 8851091J-SI01 understand that the proposed project will include the construction of a one or two-story concrete tilt-up structure on an essentially flat graded pad. We understand, funher, that fill soil has been placed, compacted and tested by others on the south portion of the site. The fill could be up to 5 feet thick at the south property line and thins to zero about 100 feet north in the eastern end of the proposed building of this south line. The approximate limits of the fill, the site and proposed building locations are shown on the Site Plan (Figure 1). FIELD AND LABORATORY INVESTIGATIONS Our field investigation included making a visual reconnaissance of the existing surface conditions, making eight test pits on March 4, 1988, and obtaining soil samples. The test pits were advanced to depths ranging form 2 to 16 feet. The location of the test pits are shown on Figure 1. I A Key to Logs is presented in Appendix A as Figure A-1. Final logs of the test pits are presented in Appendix A as Figures A-2 through A-9. The descriptions on &e logs are based on field logs, sample inspection, and laboratory test results. Results of laboratory tests are shown at the corresponding sample locations of the logs and in Appendix B. The field investigation and laboratory testing programs are discussed in Appendices A and B. SITE CONDITIONS Geoloeic Setting The site is located roughly five miles form the Pacific Ocean in Carlsbad California. the elevation across the site varies from about 425 to 432 feet above Mean Sea Level. The geologic setting of the vicinity is characterized by Eocene age marine sediments that were deposited on the Cretaceous age granitic bedrock and are overlain by eroded remnants of Pleistocene Terrace deposits. The study area is underlain entirely by Eocene age deposits of the Delmar Formation that consist of interbedded siltstone, sandstone and claystone. Structurally the Delmar 4gk -2- Project No. 8851091J-SI01 Formation is relatively flat-lying with shallow dips of two to three degrees. Faults have were not observed on the site during our field investigation. Since the site has been graded flat the majority of the site has been cut with the formational soils exposed at existing grade. A small portion of the south property line area has been filed, which may be up to 15 feet thick, there is a scattering of weeds and grassed on the surface. The cut slope along the sites west side has been planted and street improvements have also been constructed. Subsurface Conditions The test pits indicate that the site is essentially all cut, except for a zone along the south property line, where up to 15 feet of fill was placed. These fill soils generally consist of silty and sandy silt with siltstone fragments. the test pits indicate that fill soils may be less than 5 feet thick under the proposed building. The soils underlying the remainder of the site are composed of deposits within the Delmar Formation. These soils are interbedded silty to clayey sandstone, siltstone and claystone with concretions and local cemented layers. The equipment used for excavating the test pits encountered refusal and near refusal on cemented layers at depths of one and two feet in Test Pits 5 and 6, respectively. Ground Water - No ground water was encountered in the test pits at the time of excavation. DISCUSSIONS, CONCLUSIONS, AND RECOMMENDATIONS The discussions, conclusions, and recommendations presented in this report are based on the information provided to us, results of our field and laboratory studies, analyses, and professional judgment. -3- Project No. 8851091J-SI01 The existing slope along the western property line appears to be essentially a cut slope having a maximum height of less than 20 feet with a slope inclination of about 1.75 to 1 (horizontal to vertical). Since the slope was designed by others, we assume its design has been verified. Our experience has shown that, typically, cut slopes in these formational materials are grossly stable: nevertheless there is a finite possibility that such slops could become unstable. In our opinion, the probability of this slope becoming unstable is low. Foundations A layout of the proposed building footprint on a 1 inch equal 200 feet scale plan with the original topography superimposed indicates that up to 10 feet of fill could exist under the south comer area of the building. This fill was placed during the mass grading of the area. The test pits, however, indicate that the fill may be only as deep as 5 feet under the building. It is recommended that existing formational soils within the proposed building footprint plus a minimum distance of 5 feet horizontally outside the building be excavated to a minimum depth of 3 feet below the bottom of planned footing depth. We also recommend that all existing fill soils under the building as described above be removed and be replace as part of undercut grading operation. The recommended minimum lateral removal is 2 feet out side of footings and downward and outward at a slope of 1 to 1. We recommend that these soils be treated and compacted as outlined in the Grading section. An alternate would be to replace the on-site soils with select compacted import soils. It is our opinion that the proposed structure run be supported on conventional spread footings placed on properly completed fill soils as described above. We recommend a maximum allowable soil bearing pressure of 2,000 psf (dead plus line load) be used for design and that the footing be a minimum 12 inches wide and a minimum of 18 inches deep measured from the lowest adjacent rough pad grade. In our opinion, this bearing pressure can be increased by no more than one-thud for loads that include wind or seismic forces. We recommend that all footings be reinforced top and bottom with at least one No. 4 reinforcing bar. The actual reinforcing should be evaluated by the smctural engineer. Project No. 8851091J-SI01 Footings should not be located within 8 feet of the top of a slope. Footings located closer than 8 feet from the top of a slope should be extended in depth until the outer bottom edge of the footing is the required distance (8 feet) horizontally from the outside face of the slope. Floor Slab We recommend that slab-on-grade floors have a minimum thickness of 4 inches and that they be properly reinforced. Slabs should be designed by the structural engineer for appropriate loading and usage. Concrete slabs should be underlain by 4 inches of sand and a plastic vapor banier in those areas where floor coverings are sensitive to moisture. We also recommend the installation of perimeter cutoff drains at the outside edge of exterior wall footings in areas where planters or landscaping may extend up to the building or where the adjacent ground surface is higher than the floor slab. Trench Excavations Utility trench excavations may encounter different excavation conditions. The efficiently of such excavation is heavily dependent upon the condition of contractor equipment and contractor capability. The surface of trench backfiil frequently settles even when backfill is placed under optimum conditions. We recommend that any slab or StNcture placed over a trench be designed to accommodate such settlement. We recommend that all earthwork be done in accordance with the attached "Guide Specifications for Site Grading" (Appendix C). We also recommend that Woodward- Clyde Consultants review the grading plans prior to final design and observe the grading and test compacted fills. We funher recommend that a pre-grading conference be held at the site with the owner, civil engineer, contractor, and the soil engineer in attendance. Soil conditions, processing methods, and the grading schedule can be discussed at that time. Project No. 8851091J-SI01 The grading operations to create the existing flat pad, to our knowledge, did not require blasting to achieve grade. Cemented zones were encounter in our investigation with small equipment in confined areas. It is anticipated, however, that all of the recommended undercut materials within the proposed excavation depths can be excavated with heavy ripping using heavy duty excavation and grading equipment. Large pieces of concretions, over 2 feet in maximum dimension should be removed form the site, unless broken into pieces of less than 2 feet If it is decided to excavate the native soils and replace them as compacted fill, it is recommended that the formational materials be thoroughly broken into soils, not chunks, moisturized, and mixed prior to replacing. The recommended moisture for compaction is 3 to 5 percent over the optimum for the soil mixture. We recommend that this soil mixture have a maximum UBC expansion index of less than 50, should the onsite mixture exceed this value impomng of select soils may be required. We recommend that the soils within 3 feet of final rough grade be select soils which have an expansion index value of 30 or less when tested in accordance with UBC Standard 29-2. More expansive soils may be placed in the deeper undercut. We recommend’that the entire site be cleared of all vegetation and any other debris or rubble. Any unsuitable material generated should be disposed of offsite prior to initiation of the undercutting operation. Drainage We recommend that positive measures be taken to properly finish grade the pad so theat drainage waters form the pads directed off the pad and away form foundations, floor slabs, and slope tops. Even when these measures have been. taken, experience has shown that a shallow ground water or surface water condition can and may develop in areas where no such water condition existed prior to site development; this is particularly me where a substantial increase in surface water infiltration results from landscape irrigation. Project No. 8851091J-SI01 TO further reduce the possibility of moisture related problems, we recommend that all landscaping and irrigation be kept as far away form the building perimeter as possible. Irrigation water, especially close to the building, should be kept to the minimum required level. We recommend that the ground surface in all areas be graded to slope away form the building foundations and floor slabs and that all runoff water be directed to proper drainage areas and not be allowed to pond. A minimum ground slope of 2 percent is recommended We recommend that planter areas placed adjacent the saucture be provided with a positive drainage system to remove any excess irrigation water. UNCERTAINTY AND LIMITATIONS We have observed only a very small portion of the pertinent soil and groundwater conditions. The recommendations made herein are based on the assumption theat soil conditions do not deviate appreciably from those found during our field investigations. We recommend that Woodward-Clyde Consultants review the foundation and grading plans to verify that the intent of the recommendations presented herein has been properly interpreted and incorporated into the contract documents. We further recommend that Woodward-Clyde Consultants observe the site grading, subgrade preparation under paved areas, and foundation excavations to verify that site conditions are as anticipated or to provide revised recommendations if necessary. If the plans for site development are changed, or if v&iations of geotechnical conditions are encountered during construction, we should be consulted for further recommendations. This report is intended for design purposed only and may not be sufficient to prepare an accurate bid. California, including Carlsbad, is an area of high seismic risk. It is generally considered economically unfeasible to build a totally earthquake-resistant project; it is, therefore, possible that a large or nearby earthquake could cause damage at the site. Geotechnical engineering and the geologic sciences are characterized by uncertainty. Professional judgements presented herein are based partly on our understanding of the proposed construction, and partly on our general experience. Our engineering work and -7- Project No. 8851091J-SI01 judgements rendered meet current professional standards; we do not guarantee the performance of the project in any respect. Inspection services allow the testing of only a small percentage of the fill placed at the site. contractual arrangements with the grading contractor should contain the provision theat he is responsible for excavating, placing, and compacting fill in accordance with project specifications. Inspection by the geotechnical engineer during grading should not relieve the grading contractor of his primary responsibility to perform all work in accordance with the specifications. This fii does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we can not be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if he considers any of the recommended actions presented herein to be unsafe. r -8- Project No. 8851091J-SI01 APPENDIX A FIELD INVESTIGATION woodward-clydecolrsuttants . Eight exploratory test pits were advanced at the approximate locations shown on the Site Plan (Figure 1). The excavations were made on April 4, 1988, under the direction of a geologist from our fm, using a Case 580E backhoe. Bag and sack samples of the subsurface materials were obtained from the excavated material in the test pits. The locations and elevations of all test pits are approximate. The location of each and the prepared by KrommenhoeWMcKeown & Associates, A.1.A. dated January 11,1988. elevation of the ground surface at each location were estimated by use of the Site Plan I A- 1 Project: LOT 36 - CARLSBAD OAKS EAST Type of Excavation: Type of Drill Rig: Date Drilled: Water Depth: Measured KEY TO LOGS Surface Elevation: _______ - DISTURBED SAMPLE LOCATDN Obtained by collecting the auger cuttings in a plastic bag. Fill Sand Clay Silt SikSand SandIClay - GS -Grain Size Distribution Analysis PI - Plasticity Index LC - Laboratory Compaction Test _. -gum: A-1 Project: LOT 36 - CARLSBAD OAKS EAS~p~eotTest Pit No: 1 Date Drilled: 4-4-88 Water Depth: - - Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 Measured: -- * see Key to Logs, Fig. A-1 5- - % g= n a Material Description 0 5. x= f a, " >; L. zgs *.% 'ij 53 ngn m * ._ v) O+ n SS Surface Elevation: Approximately 431' MSL Moist. light gray, clayey fine silty sand with olive siltstone fragments FILL Moist, brown. clayey sand Moist. liaht brown. siltv sand and sandv clav \ FILL / Dense, moist, olive brown. sandy silt (ML) . Very dense, moist. light brown. silh sand (SMI DELMAR FORMATION ~ ~~~ / Bottom of Pit at 7 feet 'iura: A-2 Project: LOT 36 - CARLSBAD OAKS EAST Log of Test Pit No: 2 Date Drilled: 4-4-88 Water Depth: - - Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 Measured: - - Surface Elevation: Approximately 431' MSL Moist, light olive brown, silty sand and sandy siltFlLL I Moist, dark brown. clayey sand FILL / Moist, light brown, silty sand / dark brown, clayey sand light brown, silty sand FILL FILL / FILL / Very dense, moist, dark brown, sandy clay (CL) to clayey sand (SM) TOPSOIL / Hard, moist. olive brown, siltstone and sandstone (ML-SM) DELMAR FORMATION / Bottom of Pit at 16 feet JI 'roject No: 8851091J-SlO1 Woodward-Clyde Consultants e Foure: A-3 Project: LOT 36 - CARLSBAD OAKS EAST Log of Test Pit No: 3 Date Drilled: 44-88 Water Depth ~ - Measured: -- Type of Excavation: Backhoe pa Type of Drill Rig: Case 580 Bottom of Pt at 5 feet ~ 7 Hard, dry to moist, olive. lean clay (CL) DELMAR FORMAW Hard, moist. olive brown, sandy siitstone (ML) wah silty sandstone DELMAR FORMATION II 'roject No: 8851091J-S101 I Woodward-Clyde Consultants Faure: A4 Project: LOT 36 - CARLSBAD OAKS EAST Log of Test Pit No: 4 Date Drilled: 4-4-88 Measured: ~ - Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 * see Key to Logs, Fig. A-1 nzy 5- oc 0 2: F6= 5s os0 m* F.5 5 Z+$ .- Material Description 2 m $% 5 - I a. i -. 0 In Surface Elevation: Appmximately 429' MSL Very dense. dry. reddish brown. siitv sand (SM) Hard, moist, olive, fat clay (CH) DELMAR FORMATION 0 j! :I (SM) and sandy siltstone (ML) I: I! DELMAR FORMATION Very dense, moist, interbedded olive brown, silty sandstone 'roject No: 8851091J-SI01 Woodward-Clyde Consultants 3 Bottom of Pa at 5 feet L Figure: A-5 Project: LOT 36 - CARLSBAD OAKS EAST Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 Date Drilled: 4-4-88 Water Depth: - - Measured: - - Log of Test Pit No: 5 Surface Elevation: Aooroximateiv 427 MSL Very dense, moist, light brown, silty sandstone (ML) cemented ~ ~~ ~ \ DELMAR FORMTADN Refusal at 1 foot Figure: A-6 Project: LOT 36 - CARLSBAD OAKS EAST Log of Test Pit No: 6 Date Drilled: 4-4-88 Water Depth: - - Measured: - - Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 5- a. 0 reject No: 8851 091 J L .SIC - Surface Elevation: Approximately 429’ MSL Hard. moist, olive brown and oiive gray sikstone (ML) with cementation DELMAR FORMATION Near Refusal at 2 foot Figure: A-7 ~~ Project: LOT 36 - CARLSBAD OAKS EAST ~~ Date Drilled: 4-4-88 Water Depth: - - Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 Measured: - - Surface Elevation: Approximately 430' MSL Dry, light gray brown. silty sand Dense, moist, dark brown, silty to clayey fine sand (SM) Very dense, moist. reddish brown, line sand (SM) Bottom of Pit at 2 feet FILL DELMAR FORMATDN DELMAR FORMATDN - GS Project: LOT 36 - CARLSBAD OAKS EAST Log of Test Pit No: 8 Date Drilled: 4-4-88 Water Depth: - ~ Measured: .- Type of Excavation: Backhoe pit Type of Drill Rig: Case 580 Surface Elevation: Approximately 429’ MSL Hard, moist, light brown, fine sandy lean clay (CL) ~~ DELMAR FORMATION Boltom of Pa at 2 feet rgure: A-9 ‘ Project No. 8851091J-SI01 APPENDIX B LABORATORY TESTS The materials observed in the test pits were visually classified and evaluated with respect to strength, swelling, and compressibility characteristics; dry density; and moisture content. The classifications were substantiated by performing grain size analyses and evaluating plasticity characteristics of samples of the soils. Fill suitability tests, including compaction tests, expansibility tests, and grain size analyses, were performed on samples of the probable fill soils. The strength of the soils was evaluated by composition of grain size distribution and plasticity characteristics as well as excavation characteristics of those materials in the test pits, by considering the density and moisture content of the samples and the penetration resistance of the sampler. Swelling characteristics were estimated by performing UBC Expansion Index tests on recompacted samples. The grain size distribution curves are shown in Figures B-1 and B-2. The results of the suitability test are presented on Figure B-3. .” B-1 SYMBOL BORING "p &- _&F DESCRIPTION 0 1-1 34 18 CLAYEY FINE UNO (sc) 0 3-2 A 4-2 0 7-2 Remark : 8510915 SI01 LOT 36 CARISBAD OAKS EAST Voodward Clyde hnsultants GRAIN SIZE DISTRIBUTION ngme NO. 6-1 3a.n Diego, CA UNIFIED SOIL CLASSIFICATION COBBLES - I RY GRAVEL SAND - FlwE SILT OR CUY 0 8-1 37 19 FINE SANDY LEAN CLAY (U) Remark : 5851091J SI01 Woodward Clvde I LOT 36 CARISBAD OAKS EAST Consultants I GRAIN SIZE DISTRIBUTION Ngure No. 8-2 san Diego. CA - ~~ DIRECT SHEAR TEST DATA I I 1 I I Dry Density. pct I I I 1 I FILL SUITABILITY TESTS LOT 36 - CARLSBAD OAKS EAST DRAWN By: & I CHECKED BY: I PROJECTNO 8851091J-S101[ DATE:7-22-88 I FIQURENO: B-3 . WOOOWARO-CLYOE CONSULTANTS Project No. 8851091J-SI01 APPENDIX C GUJDE SPECIFICATIONS FOR EARTHWORK L-36 CARLSBAD OAKS NORTH NOTE: These specijications are provided as a guide for preparation of the final grading specifications for the project, which with the plans consritute the project documents. These guide specifcations are not intended for use as final grading specificatons. 1. GENERAL 1.1 1.2 1.3 The work of the Contractor covered by these specifications consists of furnishing labor and equipment and performing all operations necessary to prepare areas to receive till, and to excavate and fill to the lines and grades remove deleterious and undesirable materials from areas of grading, to properly shown on the plans or as directed in writing by the Owner. The Contractor shall perform the work in strict accordance with these specifications and the Contractor shall be responsible for the quality of the finished product notwithstanding the fact that the earthwork may be observed and tests made by a Geotechnical Engineer. Deviations from these specifications will be permitted only upon written authorization from the Owner. The data contained in the geotechnical report and in any following addenda indicating subsurface conditions are not intended as representations or warranties of the accuracy or continuity of subsurface conditions between soils borings. It shall be expressly understocd that the interpretations or conclusions drawn from such data are the responsibility of the Contractor. 2. DEFINlTlONS 2.1 2.2 2.3 2.4 Qontractol: shall mean the contractor performing the earthwork. Owner shall mean the owner of the property or the party on whose behalf the earthwork is being performed and who has contracted with the Contractor to have the earthwork performed. Lrepared the grading plans and who is the Owner's representative concerning Civil Engineer) (Architectl shall mean the (engineer) (architect) who has the configuration, quantities and dimensions of the earthwork and who usually sets basic surveying data at the site for the Contractor's conformance. title "Geotechnical Engineer" in accordance with Section 6736.1, Chapter 7, -shall mean a licensed civil engineer authorized to use the Division 3, State of California Business and Professions Code. The c- 1 Project No. 88510911-SI01 Geotechnical Engineer shall be responsible for having representatives on site to observe and test the Contractor's work for conformance with these specifications. 2.5 Green Book shall mean the most recent edition of the Standard Specifications for Public Works Construction, prepared by the Joint Cooperative Committee of the Southem California Chapter, American Public Works Association, and Southern California Districts, Associated Contractors of California. 2.6 Standard Soecial Provision% shall mean the most recent edition of the Standard Works. Special Provisions, prepared by County of San Diego, Department of Public 3. OBSERVING AND TESTING 3.1 The Geotechnical Engineer shall be the Owner's representative to observe and operations. make tests during the foundation preparation, filling, and compacting 3.2 The Geotechnical Engineer shall make field density tests in the compacted fill to provide a basis for expressing an opinion as to whether the fill material has been compacted to at least the minimum relative compaction specified. The basis for relative compaction of less than that specified. Density tests shall be made in this opinion shall be that no tests in compacted or recompacted areas indicate a the compacted material below any disturbed surface. When these tests indicate that the density of any layer of fill, or portion thereof, is below the specified density, the particular layer or area representative by the test shall be reworked until the specified density has been achieved. 3.3 Testing shdl conform to the following standards as pertinent: ASTM D2922-81, "Density of Soil and Soil-Aggregate in place by Nuclear Methods (Shallow Depth)" ASTM D3017-78, "Moisture Content of Soil and Soil-Aggregate in place by Nuclear Methods (Shallow Depth)" ASTM D1556-82, "Density of Soil in place by the Sand-Cone Method" ASTM D1557-78, "Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using a 10-lb. (4.54 kg) Rammer and 18-in. (457-mm) Drop," Methods A, B, and C. AASHTO T 224-86, "Correction for Coarse Particles in the Soil Compaction Test." c-2 Project No. 8851091J-SI01 4. CLEARING AND PREPARING AREAS TO BE FILLED 4.1 Clearing and grubbing shall be in accordance with Section 300-1 of the Green Book and, in addition, all trees, brush, grass, and other objectionable material commencement of any earth moving so as to leave the areas that have been shall be collected from areas to receive fill and disposed of off-site prior to cleared with a neat and fmished appearance free from debris. 4.2 All loose or porous soils shall be removed or compacted as specified for fill. The depth of removal and recompaction shall be approved in the field by the Geotechnical Engineer. Prior to placing fill, the surface to be filled shall be free from uneven features that would tend to prevent uniform compaction by the equipment to be used. It shall then be plowed or scarified to a depth as required and in no case less than a minimum depth of 6 inches. 4.3 Where the exposed slope is steeper than 6 horizontal to 1 vertical, or where which the fill is to be placed shall be stepped or keyed by the Contractor as specified by the Geotechnical Engineer, the slope of the original ground on shown on the figure below. The steps shall extend completely into the underlying formational materials or, where formational materid is not present, into previously compacted fill. The outside edge of bottom key "A" shall be not less than 2 feet in depth into formational soil or no less than 5 feet into previously compacted fill. The minimum width of benches "B" shall be at least 1-1/2 times the width of the compaction equipment, and not less than 10 feet. Project No. 8851091J-SI01 4.4 After the foundation for the fill has been cleared, plowed or scarified, it shall be disked or bladed by the Contactor until it is uniform and free from large clods, brought to the specified moisture content, and compacted as specified for fill. 5. SUBGRADE PREPARATION IN PAVEMENT. AREAS 5.1 Subgrade preparation shall be in accordance with Section 301-1 of the Green Book, except that relative compaction of subgrade shall be in accordance with Section 12 of these specifications. Scarification and recompaction requirements may be waived by the Geotechnical Engineer in subgrade areas with naturally cemented formational soils. 5.2 All areas to be paved shall be proofrolled in accordance with Section 301-1.3 of the Standard Special Provisions. 6. MATEFULS - GENERAL FILL 6.1 6.2 6.3 6.4 Materials for compacted fill shall contain no rocks or hard lumps greater than 24 inches in maximum dimension and shall contain at least 40% of material smaller than 1/4 inch in size. Material of a perishable, spongy, or otherwise improper nature shall not be used in fills. Select soil, to be used at finish grade to the depths and at the locations specified on the grading plans, shall consist of material that contains no rocks or hard lumps greater than 6 inches in maximum dimension and that has an Expansion Index of 30 or less when tested in accordance with UBC Standard 29-2. Samples of materials to be used for fill shall be tested in the laboratory by the Geotechnical Engineer in order to evaluate the maximum density, optimum moisture content, classification of the soil, and expansion index, as required of the geotechnical investigation may be encountered by the Contractor. The During earthwork operations, soil types other than those analyzed in the report Geotechnical Engineer shall be consulted to determine the suitability of these soils. 7. MATERIALS - PAVEMENT SUBGRADE 7.1 Pavement subgrade shall be defined as the top 12 inches of soil, excluding aggregate base, in areas to be paved with asphalt concrete or Portland cement concrete. 7.2 Materials for pavement subgrade shall contain no rocks or hard lumps greater than 6 inches in maximum dimension, shall contain at least 40 percent of or less when tested in accordance with UBC Standard 29-2. Material of a material smaller than 1/4 inch in size, and shall have an Expansion Index of 30 perishable, spongy or otherwise improper nature shall not be used in fills. C-4 Project No. 8851091J-SI01 8. MATERIALS - TRENCH BACKFILL 8.1 Trench backfill materials above pipe bedding shall be in accordance with Section 306-1.3 of the Green Book. 8.2 As an alternative, cement slurry may be used to bacW111 trenches. The slurry building limits and zone of influence of foundations and other settlement- shall have a minimum cement content of two sacks per cubic yard within the elsewhere. sensitive smctures. A minimum one sack per cubic yard sluny shall be used 9. MATERIALS -WALL BACKFILL 9.1 Wall backtidl materials shall be in accordance with Section 300-3.5 of the Green Book. 10. COMPACITON EQUIPMENT 10.1 Compaction shall be accomplished by sheepsfoot rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of compaction equipment made specifically for the purpose of compacting soils. Equipment shall be of such a design that it will be capable of compacting the fill to the specified density at the specified moisture content. 11. PLACING, SPREADING, AND COMPACIWG GENERAL FILL MATERIAL 11.1 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted by the Contractor to a relative compaction that is indicated by test to be not less than 90 percent. Relative compaction is defined as the ratio (expressed in percent) of the in-place dry density of the compacted fJl divided by the maximum laboratory dry density evaluated in accordance with the ASTM D15.57-78. Unless otherwise specified, fill material shall be compacted by the Contractor while at a moisture content at or above the optimum moisture content determined in accordance with the above test method. 11.2 The fill material shall be placed by the Contractor in layers that, when compacted, shall not exceed 6 inches. Each layer shall be spread evenly and shall be thoroughly mixed during the spreading to obtain uniformity of moisture and material in each layer. The entire fill shall be consmcted as a unit, in nearly continuous over the entire area, and the equipment shall make sufficient uniform level lifts starting up from the lowest area to receive fill. Compaction shall be mps so that the desired density has been obtained throughout the entire fill. Rock materials greater than 6 inches in maximum dimension shall be dismbuted in such a manner that they are completely surrounded by compacted fines; nesting of rocks shall not be permitted. 11.3 When the moisture content of the fill material is helow that specified by the Geotechnical Engineer, water shall be added by the Contractor until the moisture content is as specified. c-5 . Project No. 8851091J-SI01 11.4 When the moisture content of the fill material is above that specified by the Geotechnical Engineer or too wet to achieve proper compaction, the fill material methods until the moisture content is as required to permit compaction. shall be aerated by the Contractor by blading, mixing, or other satisfactory 11.5 Properly compacted fill shall extend to the design surfaces of fill slopes. The these specifications. surface of fill slopes shall be compacted in accordance with Section 11.1 of 12. PLACING, SPREADING, AND COMPACTING PAVEMENT SUBGRADE 12.1 Subgrade materials shall be placed, spread, and compacted in accordance with material shall be compacted to a relative compaction that is indicated by test to Section 11 of these specifications, except that the top 6 inches of subgrade be not less than 95 percent. 13. PLACING AND COMPACTING TRENCH BACKFILL 13.1 Backfiiling and compacting shall be in accordance with Section 306-1.3 of the Green Book, except that jetting or flooding shall not be allowed and that all backfii shall be compacted to a relative compaction that is indicated by test to be not less than 90 percent. 13.2 All trenches 5 feet or more in depth shall be sloped or shored in accordance with OSHA safety requirements. Trenches less than 5 feet in depth shall also be so guarded when examination indicates hazardous ground movement may be expected. 13.3 No compaction testing shall be required for portions of trenches backfilled with cement slurry. 14. PLACING AND COMPACTING WALL BACKFILL 14.1 Backfiiling and compacting shall be in accordance with Section 300-3.5 of the Green Book, except that jetting or flooding shall not be allowed. 14.2 The Contractor shall be responsible for using equipment capable of compacting the backfill to the specified relative compaction without damaging adjacent walls or other existing improvements. C-6 Project No. 8851091J-SI01 15. PROTECTION OF WORK 15.1 During consmction, the Contractor shall properly grade all excavated surfaces to provide positive drainage and prevent ponding of water. When earthwork operations are interrupted, the Conuactor shall reestablish specified compaction to the depth necessary before placing new fill. The Contractor shall control surface water to avoid damage to adjoining properties or to fmished work on the site. The Contractor shall take remedial measures to prevent erosion of freshly graded areas and until such time as permanent drainage and erosion control features have been installed. 15.2 After completion of the earthwork and when the Geotechnical Engineer has finished observation of the work, no funher excavation or fiUing shall be done except under the observation of the Geotechnical Engineer. -. c-7