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HomeMy WebLinkAboutCT 81-46; Carlsbad Airport Center Unit 2; Soils Report; 1988-07-29SUPPLmEnTAL GBOTECHBICAL IAVESTIGATION CARLSBAD AIRPORT CENTER, UNIT 2, AND OFF-SITE FILL AREA CARLSBAD, CALIFORUIA PREPARED FOR CENTRE DEVELOPMENT 21 1 1 PALOMAR AIRPORT ROAD CARLSBAD, CALIFORNIA 92009 PREPARED BY SAN DIEGO GEOTECHNICAL CONSULTANTS, INC. 6455 NANCY RIDGE DRIVE, SUITE 200 SAN DIEGO, CALIFORNIA 92121 JULY 29, 1988 JOB NO. 05-4879-011-00-00 LOG NO. 8-1797 . r Centre Development Carlsbad, California 92009 2111 Palomar Airport Road Attention: Mr. Joe Giedeman 7 - Job NO. 05-4879-011-00-00 Log NO. 8-1797 SUBJECT: SUPPLEMENTAL GEOTECHNICAL INVESTIGATION and Off-site Fill Area Carlsbad Airport Center, Unit 2, Carlsbad, California Gentlemen: As requested, San Diego Geotechnical Consultants has completed a supplemental geotechnical investigation for the proposed Unit 2 of the Carlsbad Airport Center in Carlsbad, California. Our work also covered a limited area of offsite fill that will be graded as part of the project. This report presents the re'sults of our investigation, as well as our conclusions and recommendations regarding your proposed development of this site. In general, the development will be feasible from a geotechnical standpoint. The major geotechnical constraints will be difficult excavation of volcanic rock in deeper cuts, the generation of oversize material from ripping or blasting of volcanic rock, the and the stability of proposed cut slopes. - - removal of compressible alluvium and colluvium in canyon bottoms, - We sincerely appreciate this opportunity to serve you . If you have any questions, please call us at your convenience. Very truly yours, SAN DIEGO GEOTECHNICAL CONSULTANTS, INC. c - - e7v1 Antho Vice President F. Bel ast, P.E. AFB/pb 974nTRAnF PI ACF SIIITF lon SAN nlFGn CAWI~R. IRIQI~?R.I~~?. FAY.I~~~Q! 6?~-17nfi A SUBSIDIARY OF THE IRVINE CONSULTING GROUP, INC. TABLE OF CONTENTS 1.0 INTRODUCTION...............................................l 1.1 Authorization.........................................l 1.2 Scope of Services.....................................l 2.0 PROPOSED DEVELOPMENT.......................................2 3.0 SITE DESCRIPTION.....................................-.....2 4.0 SITE INVESTIGATION.........................................3 4.1 General...............................................3 4.2 Field Exploration.....................................4 4.3 Laboratory Testing Program.. .......................... 5 5.0 GEOTECHNICAL SETTING AND SUBSURFACE CONDITIONS.............6 5.1 Regional Geology........... ........................... 6 5.2 Geologic Units........................................6 5.2.1 Santiago Peak Volcanics (Map Symbol Jsp)..... ..6 5.2.2 Santiago Formation (Map Symbol Tsa)............7 5.2.3 Alluvium (Map Symbol Qal>......................7 5.2.5 Topsoil................................. ....... 9 5.3 Groundwater...........................................g 5.4 Geologic Structure....................................9 6.0 SEISMICITY................................................lO 6.1 Earthquake Effects...................................lO 6.1.1 Surface Fault Rupture ......................... 10 6.1.2 Earthquake Accelerations......................ll 6.1.3 Seismically Induced Slope Failures............ll 6.1.4 Seismically Induced Settlement................12 6.1.5 Liquefaction..................................l2 6.1.6 Lurching and Shallow Ground Rupture...........lZ 6.1.7 Tsunamis, Seiches, and Reservoir Failures.....l2 7.0 GEOTECHNICAL EVALUATION AND RECOMMENDATIONS...............13 7.1 General..............................................l3 7.2 Grading and Earthwork................................l4 7.2.1 General.......................................l4 7.2.2 Geotechnical Observations.....................14 7.2.3 Site Preparation .............................. 15 7.2.4 Rippability ................................... 16 7.2.5 Fill Materials................................l7 7.2.6 Fill Compaction...... ......................... 19 5.2.4 Fill...........................................8 i TABLE OF CONTENlS (Continued) 7.2.7 Shrinkage and Bulking ......................... 20 7.2.8 Overexcavation of Bedrock.....................20 7.2.9 Cut-Fill Transitions..........................21 7.2.10 Trench and Wall Backfill......................21 7.2.11 Off-site Fill Area.......................... ..21 7.2.12 Existing Fills................................22 7.3.1 Bedrock and Soil Characteristics..............23 7.3.3 Stabilization and Buttress Fills..............26 7.3 Slope Stability. ..................................... 23 7.3.2 Cut and Fill Slopes ........................... 24 7.3.4 Fill-over-cut Slopes .......................... 28 7.3.5 Construction Slopes ........................... 28 7.3.6 Natural Slopes. ............................... 29 7.3.7 Slope Protection and Maintenance..............30 7.4 Settlement Considerations............................30 7.5 Surface and Subgrade Drainage... ..................... 32 7.6 Foundation Recommendations.. ........................ .34 7.7 Reactive Soils.......................................35 7.8 Pavements ............................................ 35 7.9 Review of Grading Plans..............................36 8.0 LIMITATIONS OF INVESTIGATION..............................^^ Figures 1 2 3 Appendices A B C 1 D ATTACWENTS Location Map Regional Fault Map Geologic Cross-sections References Field Exploration Program, Boring Logs, Figures B-2 through B-11 Test Pits, Figures B-12 through B-16 Seismic Traverses, B-17 and B-18 Laboratory Testing Program, Figures C-1 through C-8 Standard Guidelines for Grading Projects ii Plates 1 and 2 TABLE OF CONTENTS (Continued) Geotechnical Maps iii SUPPmEBrAL GEOTECHNICAL INVESTIGATION CARLSBAD AIRPORT CENTER, UNIT 2, CARLSBAD, CALIFORNIA AND OFF-SITE FILL AREA 1.0 INTRODUCTION This report presents results of a geotechnical investigation of a proposed commercial project in Carlsbad, California. The purpose of our investigation was to evaluate the surface and subsurface soils and geologic conditions at the site and, based on those conditions, to make recommendations regarding mass grading and other geotechnical aspects of the project. Because the project will create rough-graded lots that will be sold and developed separately, individual foundation investigations should be made for each lot when precise grading plans, building locations, and loading conditions are known. Our conclusions and recommendations are based on analysis of the data from our field exploration and laboratory tests, and from our experience with similar soils and geologic conditions in this area. 1.1 Authorization This investigation was authorized by Mr. Jim Morrissey of Centre Development on June 21, 1988. Our scope of services for this investigation generally conformed to that outlined in our Proposal No. SDP8-4833, dated June 3, 1988. 1.2 Scope of Services The scope of services for this investigation included the following tasks: a. Review of pertinent geotechnical literature, aerial photographs, and an 80-scale topographic map by Rick Engineering, Inc., dated June 7, 1988. Centr July .e Development 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 2 b. Geologic reconnaissance of the site; c. Subsurface exploration consisting of four 8-inch diameter hollow-stem auger drill holes, three 30-inch diameter bucket auger drill holes, nine test pits, and two seismic refraction traverses; d. Logging of the drillholes and test pits, with collection of bulk, disturbed, and relatively undisturbed samples for laboratory testing; e. Laboratory testing of samples obtained during the field exploration; f. Geologic and engineering analysis of the field and laboratory data to develop our conclusions and recommendations ; and g. Preparation of this report with its accompanying maps, figures, and other information to present our findings, conclusions, and recommendations. 2.0 PROPOSED DEVELOPMENT The proposed development is divided into about 22 separate commercial lots. We understand that the site will be rough graded during the initial phases of mass grading, after which each lot will be developed separately. Our review of the grading plans indicate that cut slopes to a maximum height of approximately 35 feet, and fill slopes to a maximum height of approximately 65 feet are proposed. 3.0 SITE DESCRIPTION Unit 2 of the Carlsbad Airport Center will occupy a land parcel of irregular shape located in Carlsbad, California. The site includes about 70 acres of hills and associated small drainage basins located east of the existing Carlsbad Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 3 Airport Center, Unit 1. The location and topography are shown on the attached Location Map (Figure 1). The site is bounded on the north and east by McClellan Palomar Airport, on the south by Palomar Airport Road, and on the west by Units 1 and 3 of the Carlsbad Airport Center. Topographically, the site includes both low- and high-relief areas. Steeply descending slopes lie near the western and eastern boundaries. Natural slopes within the project are approximately 1.5:l (horizonta1:vertical) or steeper on the canyon sidewalls in the western and eastern portions of the site. Maximum relief for the site is about 240 feet, with elevations ranging from about 190 to 330 feet above mean sea level. The site drains to east-west trending canyons in the northwestern and southeastern portions of the site and to several north-south trending tributary canyons. Access to the site is along improved roads from the existing Carlsbad Airport Center, Unit 1. An agricultural reservoir presently exists near the center of the site. 4.0 SITE INVESTIGATION 4.1 General A previous geotechnical report by H.V. Lawmaster and Company (Reference 1) includes Unit 2. In addition, the as-graded report for Unit 1 by Moore h Taber (Reference 2) describes offsite grading performed in Unit 2. We reviewed both reports as part of our work. Before starting field work, we studied aerial photos and topographic maps of the site to aid in determining the locations of our subsurface explorations. This information, combined with our field investigation, laboratory test results, seismicity reviews, and previous experience in the general area, forms the I FEET Centre Development J.uly 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 4 4.2 basis for the conclusions and recommendations in this report. The study methods used conform to generally accepted standards of practice for geotechnical investigations in southern California. Field Exploration Field work began on June 21, 1988. and was completed on June 30, 1988. During this period, seven borings were drilled through the surficial deposits and into the bedrock. Nine test pits were also excavated during this period. Two seismic traverses were performed to evaluate rippability in the area of proposed cuts in volcanic rock. The approximate locations of the test pits and boreholes are shown on the Geotechnical Map (Plate 1). These locations were made in the field by pacing and by inspection of available maps. Locations should not be considered more accurate than is implied by the methods of measurement used. The boreholes were drilled using an 8-inch diameter, continuous-flight, hollow-stem auger drill rig and a 30-inch bucket auger drill rig. Samples were obtained using a standard split spoon sampler and a 2.5-inch (inside diameter) Modified California sampler. In the hollow-stem auger drillholes, the drive weight was a 140-pound hammer falling 30 inches. The rig kelly bar was the drive weight in the bucket auger drillholes. For each drive sample, we recorded the number of blows needed to drive the sampler 12 inches into the soil. Three-inch (outside diameter) steel Shelby tubes were also hydraulically pushed to obtain samples from the hollow-stem auger drillholes. The test pits were excavated by a tracked backhoe. Bulk samples only were collected from the test pits. Each hole or pit was backfilled upon completion of logging and sampling. ... Centre Development July 29. 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 5 Our field geologist was present to supervise drilling and test pit excavation. Groundwater conditions were reported as they appeared to the geologist at the time of drilling. Each borehole and test pit was logged and sampled for laboratory tests. These logs are attached in Appendix B as Figures B-2 to B-16. The boundaries shown between soil types on the logs were interpolated between sample locations and are approximate only. Transitions between soil types actually may be either abrupt or gradual. Two seismic refraction traverses were made with a Bison 1570C signal-enhancement seismograph, using a 10-pound hammer as the energy source. Each traverse line was 100 feet long, with hammer stations at 10-foot spacings. The velocities of compressional waves were measured and interpreted on the basis of published charts and local experience to estimate the rippability characteristics of the bedrock. The results of the seismic survey are shown on Figures B-17 and B-18 in Appendix B. 4.3 Laboratory Testing Program Typical samples of the earth materials found during the field work were taken to our laboratory for testing. The testing program included particle-size, Atterberg limits, in-place density and water content. maximum density, direct shear, consolidation, expansion index, sulfate content, pH, and resistivity tests. Appendix C contains descriptions of the test methods and summaries of the results. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 6 5.0 GEOTECBNICAL SEYTING AND SUBSURFACE CONDITIONS 5.1 Regional Geolom The site is located in the Peninsular Ranges geomorphic province of California near the western margin of the Southern California Batholith. Along this margin, the terrain changes from the typically rugged landforms developed over granitic rocks to flatter, more subdued landforms underlain by sedimentary bedrock units of the coastal plain. Specifically, Jurassic metavolcanics and Eocene sedimentary rocks lie beneath the site. Alluvial sediments are present in the canyon bottoms. The distribution of the geologic units is shown on the attached Geotechnical Map (Plate 1). 5.2 Geologic hits 5.2.1 Santiago Peak Volcanics (Map Symbol Jsp) The Jurassic-age Santiago Peak Volcanics lie under the western part of the site. This is a series of mildly metamorphosed volcanic rocks. Regionally, the Santiago Peak Volcanics vary in composition from basalt to rhyolite. On the site, they are predominantly andesite. The Santiago Peak Volcanics are moderately to highly jointed. Joint spacings are variable; clay fillings are usually present. The Santiago Peak Volcanics are weathered to depths varying from of about two feet on top of the volcanic peaks to about 12 feet on lower slopes. Excavation in the Santiago Peak Volcanics will be difficult. The highly weathered rock within about five feet of the existing ground surface can generally be excavated with conventional heavy earthmoving equipment. Below that depth heavy ripping and Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log No. 8-1797 Page 7 blasting should be expected. Heavy ripping or blasting will generally produce oversize materials. The difficulty of handling and placing these materials in fills will tend to increase the cost of grading the site. 5.2.2 Santiago Formation (Map Symbol Tsa) The Eocene-age Santiago Formation underlies about two-thirds to three-fourths of the site. As observed, the unit is massive to thick-bedded silty to clayey sandstone with interbedded sandy claystone and siltstone. Santiago Formation rocks probably can be excavated by conventional earth moving equipment. The claystones and some siltstones are moderately to highly expansive. 5.2.3 Alluvium (Map Symbol Qal) Alluvium is present in the east-west and north- south trending drainage courses As mapped for this project, the alluvium includes variable deposits of colluvium on canyon side slopes. Most alluvium and colluvium consists of dry to moist, porous, soft, silty and sandy clay. Alluvium was observed to a maximum depth of about 20 feet at the location of the proposed off site fill and was, on the average, about six feet deep. As observed, the alluvium appeared to be deepest near the center of the drainage courses, with shallower depths observed along the margins. The colluvium was observed to a maximum depth of about five feet and averaged about three feet deep on canyon side slopes. The primary concern with regard to alluvium and Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 8 colluvium is their potential for settlement in response to loads imposed by fills or struc- tures. Unacceptable settlement may occur after construction, especially if these soils become saturated at a later date. Recommendations to reduce settlement potential are presented in later sections. 5.2.4 Fill - A small part of the site is overlain by uncompacted fill and debris. The uncompacted fill exists in the northern and southeastern areas of the property. In the northern area, the material consists of sandy clay used to construct an agricultural reservoir. At the southeastern edge of the site. the fill is the result of a prior landfill operation. The fill consists of rocky soil which may contain some oversized materials. trash, or debris. In their present condition, these materials are not suitable to support either fill or structural loads. The expansion potential of the fill soils is expected to be low to medium. Existing fill materials may be reused as fill material for grading if they are properly processed before use. Much larger areas along Camino Vida Robles were filled during the grading of Unit 1 in 1985 and 1986. These are mostly canyon fills with maximum depths of 20 to more than 50 feet. According to the as-graded soils report (Reference 2) these were placed as engineered, compacted fills in accordance with the local Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 9 standards of practice for such fills. We did not investigate or test the fill for this report, and we relied on Reference 2 for all information relating to the nature and quality of the site preparation and grading. 5.2.5 Topsoil The topsoil seen on the site consisted of loose, dry, fine-grained silty sand. Fills or structures should not be founded directly on topsoil due to its limited strength and potential for settlement and seepage. Topsoil should have low to moderate expansion potential and may be used in compacted fills if vegetation and organic material is removed. The topsoil was not mapped and is not shown on Plate 1. 5.3 Groundwater Groundwater was found in test pits TP-1 and TP-2 and in drillholes BW-1, BW-2 and BW-3 at the contact between alluvium and bedrock. This is probably a localized, "perched" water table and does not reflect the regional water table. Groundwater conditions may fluctuate with seasonal rainfall conditions, and will probably change in response to development of the site. 5.4 Geologic Structure Most of the dominant structural features in the area are associated with pre-Tertiary folding along north- south axes. The post-Cretaceous sequences have been gently folded and tilted generally to the west. Dips ranging from 4 to 15 degrees to the southwest were measured on bedding planes in the Santiago Formation. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 10 Discontinuous northeast-trending faulting is associated with the post-Cretaceous folding. Although no faults were found within the site during our investigation, faulting has been mapped in adjacent areas. However, the closest known active fault is the Elsinore Fault. about 25 miles to the northeast. 6.0 SEISICITY As with all of southern California. this site lies in a seismically active area. There are, however, no known active faults either on or adjacent to the site. Figure 2 shows the known active faults and earthquake epicenters (M > 5.0) in the region and their relationship to the site. Because the active faults lie at some distance, the seismic risk at this site is thought. to be only low to moderate in comparison with many other areas of southern California. Seismic hazards at the site are the result of ground shaking caused by earthquakes on distant, active faults. The hazard level is sufficient to place the area in seismic risk zone 3 as defined in the Uniform Building Code. Table 1 lists the known major active and potentially active faults within a 100-kilometer radius and the estimated bedrock accelerations resulting from the maximum probable earthquakes on those faults. By definition, the maximum probable earthquake is the largest event likely to occur in a 100-year interval, but is in no case smaller than the largest historic earthquake (Reference 6). 6.1 Earthquake Effects 6.1.1 Surface Fault Rupture Because active or potentially active faults do not cross the site, the probability of surface fault rupture is very low. TABLK I SEISMICITY FOR MAJOR FAULTS MAXIMLM ESTIMATED DISTANCE PROMJ3LE PEAKBEDROCK REPEAUBLE HIQI FAUIX FRa4 SITE wmwu~~~1 ACCEIERATI~~ BEDROCK ACCELERATLONS~ Ia Nacion4 35 Miles SE 6.0 0.05g 0.05g =Canyon4 10 Miles SW 6.0 0.22g 0.14g Elsinore 25 Miles NE 7.0 0.1 7g 0.17g Coranado Banks 40 Miles SSW 6.0 0.048 0.04g Newport- San Jacinto 48 Miles NE 7.5 0.089 0.08g San Clemente 57 Miles SW 7.3 0.07g 0.07g Inglm 40 Miles W 6.5 0.06 0.06 1. 2. 3. 4. Values are local magnitudes. Maximun probable earthquake estimates taken frm Seismic Safety Study for the City of San Mego (1 974). employing the method of Banilla (1 970). From attenuation chart in Seed and Idriss (1982). After Ploessel h Slosson (1 974). 'Ihe earthquake capability of the Ia Nacion and Rose Canyon Faults has not been established. Although the faults are classed as only potentially active, they are included for information purposes due to their proximity to the site. Centre Development July 29. 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 11 6.1.2 Earthquake Accelerations In our opinion, based on the information now available, the most significant event likely to affect this project will be an earthquake on the Elsinore Fault. While a maximum probable event on the Rose Canyon Fault would generate high accelerations at the site, the capability of the Rose Canyon Fault to generate such an earthquake has not been demonstrated. We therefore recommend that earthquakes associated with the Elsinore Fault be used for design and evaluation purposes at this project. For Elsinore events, we estimate a peak bedrock acceleration at the site of about 0.17g for a maximum probabie earthquake of magnitude 7.0. We do not expect surface accelerations at this site to differ significantly from the bedrock accelerations. The repeatable high bedrock acceleration is about 65 percent of the peak acceleration and is used as a design value for events occurring within 20 miles of a site. Beyond 20 miles, the peak acceleration is the recommended design value (Reference 5). Because the Elsinore Fault is about 25 miles from the site, we recommend use of the peak bedrock acceleration for the structures at this site. 6.1.3 Seismically Induced Slope Failures Seismically-induced slope failures are not likely to occur at this site under the design earthquake loading, provided that proper grading and construction practices are used. Centre Develomnent July 29, 1988' 6.1.4 6.1.5 6.1.6 6.1.7 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 12 Seismically Induced Settlement The bedrock under this site should not undergo significant settlement as a result of seismic shaking. However, the thicker alluvial soils may experience small settlements. Any measures taken to mitigate the compressibility of the alluvium during grading should also decrease the potential for seismically induced ;ettlement. Recompaction of those soils should reduce the potential for seismically induced settlement to insignificant levels. Liquefaction Liquefaction is unlikely at this site due to the absence of saturation, the fines present in the soils, and the density of the soil. Lurching and Shallow Ground Rupture Shallow ground rupture should not be a hazard, given the apparent absence of active faults in the area. Ground cracking also should not be a major hazard. However, it is possible that some cracking may occur at any site during a major earthquake. Tsunamis, Seiches. and Reservoir Failures The site is not subject to inundation by tsunamis or seiches because of its elevation above sea level and its distance inland from a major body of water. No reservoirs exist that are capable of flooding the property. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 13 7.0 GEOTECHNICAL EVALUATlOU AND REC(MMEIYDATI0NS 7.1 General We did not identify any geotechnical conditions during our investigation that would prevent development of the Carlsbad Airport Center, Unit 2, essentially as now planned. However, the recommendations in this report should be followed to minimize delay, inconvenience, or loss that might arise from the geotechnical conditions that do exist. To reduce the potential for damaging settlements, the existing surficial soil, colluvium, and alluvium should be removed prior to fill placement, and the resulting overexcavation should be made as uniform as practical beneath the building areas. If areas can be identified where buildings will not be constructed, such as roads or parking lots, it may be possible to limit removal of alluvium to shallower depths. This determination can be made upon review of the grading plans. Many or most of the required excavations can be made by conventional heavy grading equipment; however, blasting may be necessary in volcanic rocks. Hard rock affects grading not only as it is excavated (rippability), but also when it is reused as fill (oversized rock disposal or rockf ill) . If practical, soils having significant potentials for expansion should be buried at least five feet beneath finish grade. The use of expansive soils at shallower depths will require that specially designed foundations or special site preparation be used. Specific foundation recommendations should be made when details of the buildings to be constructed are known. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 14 However, shallow footing foundations should be suitable if (a) all footings in a building will bear entirely on bedrock or entirely on compacted fill, (b) the pads are overexcavated so that fills will have relatively uniform thicknesses under individual buildings, and (c) compressible soils are removed prior to placing fill. The remainder of this report explains our geotechnical recommendations in more detail. These recommendations are based on empirical and analytical methods typical of the state of practice in Southern California. If these recommendations appear to not cover any specific feature of the proposed development, please contact San Diego Geotechnical Consultants at once for revisions or additions to our recommendations. 7.2 Grading and Earthwork 7.2.1 General The proposed development will use cut and fill grading to produce building pads, slopes and street improvements. This grading and earthwork should be done in accordance with the "Standard Guidelines for Grading Projects" attached to this report as Appendix D, and with Chapter 70 of the Uniform Building Code. Where special recommendations in the body of this report conflict with the guidelines in Appendix D, the recommendations in the report should govern. 7.2.2 Geotechnical Observation San Diego Geotechnical Consultants personnel should continuously observe the grading and earthwork operations for this project. Such Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 15 observations are essential to identify field conditions that differ from those predicted by preliminary investigations, to adjust designs to actual field conditions, and to determine that the grading is in general accordance with the recommendations of this report. Our personnel should perform sufficient testing of fill during grading to support the geotechnical consultant's professional opinion as to compliance of the fill with compaction requirements. 7.2.3 Site Preparation The ground should be stripped and prepared to receive fill as recommended in Appendix D. In addition, the existing colluvium and alluvium in building areas should be removed to the depth at which bedrock is encountered. Removals should extend beyond the building footprint a minimum of five feet or to an imaginary one-to-one plane extending down and out from the building's outer edge, whichever is greater. Our personnel in the field should observe the depth and lateral extent of this removal. In drainageways where groundwater is present, full removal of alluvium may not be practical. Removals in these areas should extend to depths at which water inflows or the onset of surface "pumping" make further removals unfeasible. The resulting subgrade may be loose and saturated. Such subgrades may require stabilization prior to placing fill. A heavy geofabric intended for stabilization use, such as Mirafi 500X, Propex 2002, or Typar 3341, should be installed on the Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 16 exposed subgrade. The geofabric should then be covered with a minimum of 12 inches of coarse- grained gravel or crushed rock. If substantial thicknesses of alluvium are left in place under fills. settlement monuments should be installed and monitored during fill placement. 7.2.4 Rippability The proposed grading may involve cuts up to 35 feet high in the Santiago Peak Volcanics rock. Excavability of this rock will probably be a significant factor in site development. Data from the test pits were used with the seismic refraction data to estimate the rippability of the rock. The velocity of a compressional wave can be correlated to rock hardness and used as a indicator of rock behavior during excavation. The seismic traverses provide useful data down to depths of about 20 to 30 feet. Figures B-16 and B-17 in Appendix B summarize the seismic data and our interpretation of it. Reference reports seismic data from previous studies. From the data available, the uppermost two to five feet in the Santiago Peak Volcanics outcrop area appears rippable with relative ease by a Caterpillar D-9 bulldozer fitted with a,single- shank ripper. A layer of weathered bedrock, rippable with moderate difficulty, exists in places to depths of five to 15 feet below the present ground surface. This layer is, however, discontinuous. In many areas, the easily-ripped surficial layer rests directly on less-weathered rock that is rippable only with much difficulty, .. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 17 if at all. This layer, which lies at depths of about four to 15 feet below the present surface, will probably require a combination of blasting and hard ripping. Blasting may also be needed where solid boulders ("floaters") are found in otherwise rippable material. Once excavated, many of the rock fragments may be too large for use in normal compacted soil fills without special placement techniques (see Appendix D) or placement as rockfill. The size of rock fragments may be controlled somewhat by careful design of blasting patterns. 7.2.5 Fill Materials Any soil imported or excavated from cuts may be reused for compacted fill if, in the opinion of the geotechnical engineer, it is suitable for such use. Debris and organic matter should be removed from the soil before it is placed. The criteria governing placement of fills depend on the size of material present. In general, fills can be divided into "soil", "soil-rock", and "rock" fills : a. "Soil" fills are fills containing no rocks or hard lumps larger than 12 inches in maximum dimension and containing at least 60 percent (by weight) of material passing the 314 inch U.S. Standard sieve. b. "Soil-rock'' fills are fills that contain no rocks larger than four feet in maximum dimension and that have a matrix of soil fill. Rocks larger than 12 inches may be placed in windrows and by using the other Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 18 techniques described in Appendix D. Some boulders too large for windrowing will require special handling during grading. c. "Rock" fills are fills containing rock fragments no larger than 2 feet in maximum dimension, with no appreciable fine-grained soil matrix. Rock fills require special testing to monitor compaction as recommended in Section 7.2.6. Cuts in Santiago Peak Volcanics (Jsp) may quite likely generate materials suitable for placement in rock fills. Fill placed within three feet of finish grade should be select finish-grade soil that contains no rocks or hard lumps greater than six inches in maximum dimension. For landscaping purposes, the uppermost four inches of fill should contain no rocks or hard lumps greater than two inches in maximum dimension. Soils with an expansion index of 21 or higher should not be used within . three feet of finish grade if practical. Typical samples of soil to be used for soil fill should be tested by the geotechnical engineer to evaluate their maximum density, optimum moisture content and, where appropriate, shear strength and expansion characteristics. During grading operations, the contractor may encounter soil types other than those tested for this report. The geotechnical engineer should be consulted to evaluate the suitability of these soils for use as fill and finish-grade soils. Imported soils should, if practical, be relatively well-graded, granular, nonexpansive soils containing small to moderate amounts of silty and clayey fines. The Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 19 geotechnical engineer should be contacted at least two working days before the first use of an imported soil to assess its desirability as a fill soil. 7.2.6 Fill Compaction Soil and soil-rock fills should be placed as described in the standard guidelines of Appendix D, except where those guidelines are superseded by recommendations in this report. The minimum compaction for fills is 90 percent of modified Proctor maximum dry density (ASRI D 1557-78). The water content at placement should be at, or slightly above the optimum water content. Rock fill requires special placement methods. The general placement technique is to place a relatively thin lift of rock, water the lift, and then compact the lift with heavy compaction equipment. Heavy vibratory rollers yield the best results. The actual thickness of each lift depends on the gradation of the rock. However, the lifts will probably be about two to three feet thick. After each lift has been uniformly spread, it should be sprayed with water to wash fines through the rock material and to lubricate the rock mass. Water spraying should continue throughout the compaction process. The watering operation is essential to adequate compaction of the fill. The volume of water used should be at least 15 percent of the rock fill volume. At the start of rock fill construction, a test fill should be built so that placement and compaction procedures can be evaluated by the geotechnical Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 20 engineer. Once an acceptable procedure has been established, it may be used throughout the fill. The rock fill should be brought to finish grade by placement of a compacted soil fill cap. This cap should meet the criteria for finish-grade fill stated in Section 7.2.5. The gradation of the rock fill should be assessed during grading by the geotechnical consultant to determine if a filter is needed between the rock fill and the soil cap. If needed, this filter may be either graded aggregate or a geofabric. The purpose of the filter is to minimize piping of the earth fill cap into the voids within the underlying rock fills. However. local experience indicates that a filter may not be needed. 7.2.7 Shrinkage and Bulking Removal and recompaction of the surficial soil, alluvial deposits, and other cut materials will probably result in shrinkage of about 5 to 10 percent. Bulking in dense alluvium, weathered rock, and rippable volcanic rock can be expected to be about 5 to 10 percent. Blasting or hard ripping of solid rock will probably result in bulking of 15 to 20 percent. 7.2.8 Overexcavation of Bedrock Where bedrock is exposed at finish grade, it is recommended that an overexcavation of at least three feet be made, and that compacted fill be placed up to finish grade. This will permit the economical excavation of utility and foundation trenches, and will improve the drainage of the Centr July 'e Development 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 21 lots. If deeper utility trenches will be cut, the overexcavation depth should be increased accordingly. 7.2.9 Cut-Fill Transitions Buildings should not be located over cut/fill transitions because of differential settlement that may occur between bedrock and compacted fill. In addition, large changes in fill depth below structures may cause damaging differential settlements. The potential for such conditions should be evaluated during review of the grading plans. Mitigation of differential settlements usually includes overexcavation of the rock to produce near-uniform fill thicknesses under the pads, with or without special foundation design. 7.2.10 Trench and Wall Backfill Unless we recommend otherwise in specific cases, backfill in trenches and behind retaining walls should be compacted to at least 90 percent of modified Proctor maximum density (ASTM D1557). The backfill should be placed in uniform lifts of six to eight inches. Mechanical compactors normally should be used to achieve the required density; water-flooding should not be used. When specified, strict attention should be given to special requirements for bedding or hand compaction around pipes and conduits. 7.2.11 Off-site Fill Area Excess soil and rock generated from cuts will be placed in an off-site fill. The fill area is in Centre Development Job NO. 05-4879-01 1-00-00 July 29, 1988- 7.2.12 Log NO. 8-1797 Page 22 a canyon west of Carlsbad Airport Center, Unit 1, as shown on Plate 2. In general, off-site fill should be placed in the same way, and to the same standards, as mass fill for Unit 2. The canyon does, however, contain at least 15 feet of uncompacted agricultural fill and 10 feet of alluvium. Both materials are highly compressible and should be completely removed before the off-site fill is placed. Existing Fills Two classes of existing fill are present on the site. The first of these is agricultural fill, including that placed for land-levelling and that placed for dams and stock ponds. This fill is entirely undocumented and is probably of poor quality. All agricultural and undocumented fill should be completely removed during grading. The second class of fill is off-site fill placed during grading of Carlsbad Airport Center, Unit 1. This fill mostly adjoins Camino Vida Roble along the south edge of Unit 2. For the most part, it consists of canyon fills varying from less than 20 to more than 50 feet thick. This fill was observed and tested by Moore h Taber of Anaheim, California, in 1985 and 1986. Their as-graded report (Reference 2) states that the fill was properly placed and compacted on a correctly prepared surface. Because San Diego Geotechnical Consultants did not observe any of this grading, and because our scope of services did not include subsurface exploration of the canyon fills, our recommendations for further Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 23 grading rely on Moore & Taber's representations regarding fill quality. We therefore recommend that the surface of this fill be stripped of any loose, dry, or otherwise unsuitable soil. The stripped fill surface should then be scarified, moistened, and compacted in the same way as the native soil surface prior to receiving fill. 7.3 Slope Stability 7.3.1 Bedrock and Soil Characteristics Slope stability conditions vary greatly over the site. Although most of the soil and rock have moderately high shear strength, weaker rock is present also. This weaker rock often includes low-strength discontinuities. Nevertheless, both the natural and man-made slopes should be stable over the life of the project if proper care, prudence, and skill are applied to their construction and maintenance. The current absence of free groundwater over most of the site enhances the stability of slopes. Care should be taken, though, to prevent or minimize the development of groundwater seepage during the post-construction period. Soil strength parameters used in analysis were based on laboratory test results, on data from other local projects, and on our experience and judgement. For silty sandstone and similar weak rocks (mostly Santiago Formation), a cohesion of 100 psf and an effective friction angle of 31 degrees was chosen. For clayey sandstone and claystone, a cohesion of 400 psf and a friction angle of 26 degrees was used. Fills built from Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 24 mixtures of these rocks were assumed to have a cohesion of 200 psf and a friction angle of 29 degrees. For pre-sheared clay seams in the bedrock. a residual friction angle of 12 degrees was assumed, with no cohesion. Cut slopes in the Santiago Peak Volcanics were not analyzed for stability in the usual way. The stability of hard rock slopes is controlled by jointing. the nature of fracture fillings, and the prsence of seepage. Analyses based on mass strength parameters are usually misleading because they do not account for the geometry or mechanisms of rock failure. Accordingly, the stability of the rock slopes was judged on the basis of experience and local practice. 7.3.2 Cut and Fill Slopes The proposed fill and cut slopes will mostly be built to maximum heights of about 40 feet. We assume that they will be built at slope ratios of 2.0 (horizontal) to 1.0 (vertical), will have level surfaces behind their crests, will not be subject to significant surcharge loads, and will not become saturated. Under these assumptions, the slopes may be built to the following maximum heights : Slope Type and Material Slope Height, Feet Cut; Silty Sandstone (Tsa) 51 Cut; Clayey Rocks (Tsa) 83 Fill; Mixed Soils 72 These heights are based on Taylor's charts, with static factors of 1.5. They therefore should meet local state-of-practice standards for slope Centre Development July 29. 1988 Job No. 05-4879-01 1-00-00 Page 25 Log NO. 8-1797 stability. Slopes not conforming to the stated assumptions should be individually studied prior to construction of the buildings. Cut slopes in Santiago Peak Volcanic rocks should be stable to heights of at least 35 to 40 feet. As discussed above, though, the stability of these hard rock slopes will depend heavily on structural factors that must be assessed during grading. Two atypical slopes have been planned for the site. In the eastern part of the tract, along Palomar Airport Road, a fill slope will rise up to about 65 to 70 feet above the valley floor. In its highest section. the slope gradient will be 3:l (horizonta1:vertical). with an eight-foot bench at a height of 40 feet. This slope should have a factor of safety of at least 1.5, subject to the assumptions stated above. However, the factor of safety against a toe failure should be reassessed during grading if high groundwater levels will prevent full removal of alluvium or saturate the toe. The second atypical slope is in the eastern part of the site, where the north property line abuts the developed part of the airport. A planned slope about 30 to 32 feet high will be cut down from the property line, just below an existing fill slope. This cut slope should be stable if no presheared clay seams are present and if the other assumptions stated above are met. If not, though, mitigation measures may be needed. Despite the overall stability of the slopes, some erosion, ravelling, or thin surficial Centre Development July 29, I988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 26 sliding may occur on otherwise stable slopes if they are not well vegetated or maintained after construction. Groundwater seepage, fractures and other unfavorable geologic structures, or variations in soil and rock properties may lower the stability of cuts greatly. Such conditions usually can be assessed only when soil and rock is exposed during grading. For this reason, San Diego Geotechnical Consultants personnel should observe all slopes during grading to evaluate the geologic conditions. In particular, cut slopes in clayey rocks of the Santiago Formation are very likely to contain weak seams of soft, pre-sheared clay. Multiple seams were found in our drillholes B-1 and B-3, in the center of Unit 2 (Figure 3). Similar conditions were reported throughout Unit 1, and stabilization or buttress fills were constructed on most of the larger cut slopes in that unit. The diversity of slope heights and orientations, and the unknown number, Location, and attitudes of the clay seams present, require an assumption that most cut slopes in Santiago Formation rock will require stabilization or buttressing. 7.3.3 Stabilization and Buttress Fills Given the information now known, stabilization or buttress fills probably will be needed on most of the cut slopes in Santiago Formation rocks. Moore h Taber noted that the slopes cut along Camino Vida Roble during the grading of Unit 1 would need stabilization (Reference 2). Observations in drillholes B-1 and B-3 indicate Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 27 that almost any cut slope in the central part of the site may need stabilization as well. Clay seams in Santiago Formation rocks may be less common in the east part of the site. However, observations during grading may identify such seams in that area as well. For planning purposes, it should be assumed that stabilization fills at least 15 feet wide will be required at all significant cut slopes in the Santiago Formation. Typical details of buttress and stabilization fills can be found in Appendix D. The actual size and extent of stabilization fills and buttresses should be designed during grading, when geologic conditions are adequately exposed. We recommend that false cuts be used to construct the cut slopes. so that geologic conditions can be mapped and assessed before the final cuts are made. If the presence or nature of the clay seams cannot be properly assessed from the false cuts, large-diameter boreholes should be drilled and logged at critical points. Careful planning and coordination between the contractor and the geotechnical engineer will be needed so that this work can be done without undue expense and delay. In the case of slopes along the north property line, very little room exists in which to build buttresses and slope failures might damage airport facilities. We recommend that contingency plans for modifying the grading in this area be made in advance, in the event that stabilization is needed. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 28 7.3.4 Fill-over-cut Slopes Where fill-over-cut slopes are proposed, the cut portion should be finished before fill placement begins. A keyway, at least one equipment-width wide (about 12 to 15 feet), should be built at the cut/fill contact. Also, a subsurface drain should be placed along the rear of the keyway. The drain may consist of perforated PVC pipe surounded by gravel or crushed rock and wrapped with geofabric. This drain should lap up onto the rear of the keyway at least six inches above the cut/fill contact. Alternative drain designs should be submitted to San Diego Geotechnical Consultants for review prior to use. 7.3.5 Construction Slopes In the absence of surcharge loads, groundwater seepage, or presheared clay seams, temporary excavations and slopes may be cut to the slope ratios and heights listed below: Slope Ratio Height of Slope, Feet (Horiz. :Vert .) - Fill Qal Jsp Vertical 4 3 4 4 0.75: 1 .O 26 7 15 10 1 .oo: 1 .o 44 11 26 20 1.25: 1.0 " 20 48 -- Slopes higher than those listed above should be built on the basis of specific recommendations made by the geotechnical engineer. If surcharge loads (such as equipment, material stockpiles, or spoil banks) are placed along the edges of excavations or slopes, the slope ratios should be flattened from those given above. For Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 29 planning purposes, we recommend flattening when surcharge loads fall within a zone defined by a 1:l plane rising from the nearest bottom corner of the excavation or slope. Contact San Diego Geotechnical Consultants if such surcharges will exist for specific recommendations. Water should not be allowed to flow freely over the tops of temporary slopes. Workmen should be protected from the local ravelling and surficial sliding that may still occur at the slope ratios listed above. Temporary slopes and excavations subjected to severe vibratory loads should be analyzed for dynamic stability. All temporary excavations should meet at least the minimum requirements of applicable occupational safety and health standards. San Diego Geotechnical Consultants should be contacted for further recommendations if soil conditions are found that deviate from those assumed or if evidence of instability appears at the site. 7.3.6 Natural Slopes With the existing slope ratios and groundwater conditions. the natural slopes on and near this site presently appear stable. If drainage is provided and the grading recommendations in this report are observed, development of this tract or adjoining properties should not cause these slopes to become unstable. However, we should review this conclusion when grading plans are complete and during the grading operation. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 30 7.3.7 Slope Protection and Maintenance Although graded slopes on this site should be grossly stable if built in accordance with the recommendations in this report, the soils will be somewhat erodible. For this reason, the finished slopes should be planted as soon as practical after the end of construction. Preferably, deep-rooted plants adapted to semi arid climates should be used. In addition, runoff water should not be permitted to drain over the edges of slopes unless the water is confined to properly designed and constructed drainage facilities. 7.4 Settlement Considerations Both the weight of the new fill and the loads imposed by buildings and structures will produce settlement. Some degree of settlement will occur in compacted fill and in the underlying native soil and rock. However, settlements within rock of the Santiago Formation and the Santiago Peak Volcanics should be negligible. If compressible soils are properly removed and replaced with compacted fill, settlements within the native materials should not be significant. If groundwater prevents the full removal of alluvium or other compressible soils from beneath fills, buildings or other settlement-sensitive structures should not be built until primary settlement of both the alluvium and the fill is essentially complete. Settlement monuments should be installed at the base of fills and surveyed at intervals during and after fill placement if more than five feet of alluvium will remain in place. San Diego Geotechnical Consultants can then review the Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 31 survey data to evaluate the progress of settlement. Our experience in the area is that settlementls, buildings or other settlement-sensitive structures should not be built until primary settlement of both the alluvium and the fill is essentially complete. Settlement monuments should be installed at the base of fills and surveyed at intervals during and after fill placement if more than five feet of alluvium will remain in place. San Diego Geotechnical Consultants can then review the survey data to evaluate the progress of settlement. Our experience in the area is that settlement is largely complete within three to four months after completion of the fill. Compacted fills normally settle under their own weight by approximately 114 percent to 112 percent of their original height following construction. Although much of this settlement occurs during the construction period, the structures planned for this site should be designed to withstand settlements of this magnitude. Compaction of the fill at water contents above optimum should minimize the potential for future settlements if the fill later becomes saturated. If the settlement of the fill under its own weight is not tolerable, the total amount of settlement affecting structures can be reduced by delaying construction of buildings until the settlement is largely complete. This will require that settlement monuments. like those described above, be installed and monitored. Settlement monuments may also be used if there is any question as to the ability of the fill placed during grading of Unit 1 to support new fill without excessive settlement. Estimates of settlement due to building loads depends on the design of the building and on the foundation Centr July 'e Development 29. 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 32 system selected for use. Reliable estimates therefore cannot be made until foundation investigations are made for individual buildings. If designed for appropriate bearing pressures, though, shallow foundations should generate total and differential settlements that fall within limits generally considered acceptable. 7.5 Surface and Subgrade Drainage Foundation and slab performance depends greatly on how well the runoff waters drain from the site. This is true both during construction and over the entire life of the structure. The ground surface around structures should be graded so that water flows rapidly away from the structures without ponding. The surface gradient needed to achieve this depends on landscaping type. Pavements or lawns within five feet of buildings should slope away at gradients of at least 2 percent. Densely vegetated areas should have minimum gradients of 5 percent away from buildings in the first five feet if it is practical to do so. Terrace drains should be constructed on fill slopes at intervals not exceeding 30 to 40 vertical feet. The benches for terrace drains should be at least six feet wide. Drainage facilities should be regularly maintained, cleaned, and repaired so that they will function properly. Planters should be built so that water from them will not seep into the foundation areas or beneath slabs and pavements. Maintenance personnel should be instructed to limit irrigation to the minimum actually necessary to properly sustain the landscaping plants. Should excessive irrigation, waterline breaks, or unusually high rainfall occur. saturated zones and "perched" groundwater may develop in the soils. Consequently, Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 33 the site should be graded so that water drains away readily without saturating foundation or landscaping areas. Potential water sources, such as water mains, drains, and pools, should be frequently examined for signs of leakage or damage. Any such leakage or damage should be repaired promptly. Subdrains should be installed at the base of fills placed in drainageways or over areas of actual or potential seepage. The general locations of subdrains should be indicated on the grading plans. Specific locations should be determined in the field during grading, with installations being reviewed by San Diego Geotechnical Consultants prior to the fill placement. Appendix'D includes typical details of subdrains. Subdrain pipes may be of coated metal, plastic, or other corrosion-resistant materials. The pipe should have adequate structural strength to withstand the loads imposed by fills, structures, and live loads. The recommended subdrain type consists of a perforated pipe surrounded by free-draining gravel or crushed rock. The rock, in turn, is wrapped with geofabric. We recommend the following pipe sizes for the drains: Total Run Length Pipe Diameter 0 - 400 ft. 4 in. 400 - 800 ft. 6 in. More than 800 ft. 8 in. About nine cubic feet of rock should be used for each lineal foot of subdrain. The gravel or crushed rock should be a nondegrading, durable, open-graded material with a maximum grain diameter of 1.0 to 1.5 inches. It should not have more than three percent (by weight) of fines passing the No. 200 U.S. Standard sieve, as Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 34 placed. The fines should not have a plasticity index (ASTM D 4318-84) greater than 4.0. The geofabric should be a high-permeability, nonwoven fabric such as Mirafi 140N. Propex 4545, or Typar 3201. The outlets of subdrains should be mapped at the end of grading and accurately shown on the as-built plans. Thereafter. the outlets should be cleaned and repaired at frequent intervals to prevent burial or blockage. 7.6 Foundation Recommendations Bearing capacities, foundation dimensions, pressures on retaining walls, and other foundation recommendations depend on structural details of the specific buildings to be constructed and on economic and constructability concerns. As the individual lots in Unit 2 will be marketed for ultimate development by others, detailed recommendations are premature at this point. Separate foundation investigations should be made for each lot when it is developed. The foundation recommendations can then be guided by the specific requirements of each building and structure. In general, the building pads should be suitable for the support of moderate foundation loads typical of one- and two-story concrete tilt-up structures. The allowable bearing capacities for conventional spread footings and strip footings should be at least 2000 psf. Foundation costs can be minimized if (1) the lots are capped with at least 3 feet of nonexpansive or low- expansive soil, and (2) buildings are not located over transitions from bedrock to fill or over areas where large changes in fill depth occur across the building footprint. Both of these provisions are incorporated into the recommendations of this report. Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 35 7.7 Reactive Soils Based on chemical tests and our experience with similar soils, either Type I or Type 11 Portland cement may be used for concrete in contact with the soil. However, the absence of water-soluble sulfates in the soil and rock should be confirmed at the completion of grading. 7.8 Pavements R-value tests were not made because the soil types in the subgrades of streets and parking areas will not be known until grading is complete. It is conservative to assume, however, that relatively poor subgrades and thick pavement sections will be needed. For traffic indices of 7.0, 8.0, and 8.5 which are typical for the street areas, the following pavement sections can be used for planning purposes: Traffic Index 7.0 8.0 8.5 R-value 10.0 10.0 10.0 Pavement Thickness 4" 4" 5 " Aggregate Base 14.5" 1 8" 18" Total Thickness 18.5" 22" 23" These sections indicate that streets should be kept about two feet low during rough grading to accommodate the pavement sections. Please note that these pavement sections may not be the final ones used and that actual sections will vary across the site. R-value tests should be performed after grading for final design of pavement sections. The pavement subgrades should be prepared as recommended in Section 7.2.3 and compacted to at least 90 percent of the Modified Proctor maximum dry density (ASTM D 1557-78). Aggregate base course should conform to the CALTRANS Standard Specifications Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 36 for Class I1 base. and should be compacted to a minimum relative compaction of 95 percent. If rigid pavements are required at loading docks or trash enclosures. we recommend a full-depth Portland cement concrete section with a minimum thickness of six inches. The concrete should be durable and resistant to scaling, with a modulus of rupture equal to at least 600 pounds per square foot. We further recommend that #3 deformed steel reinforcement bars be placed on 18- inch centers in both directions for crack control. Steel dowels should be installed at all cold joints, and contraction joints should be placed at spacings of 25 feet. 7.9 Review of Grading Plans San Diego Geotechnical Consultants should review the grading plans for the proposed development prior to construction. This review will allow us to assess the compatibility of those plans with the recommendations in this report. If the final plans differ materially from our present understanding of the project, further investigation and analysis or recommendations for design changes may be necessary. 8.0 LIMITATIONS OF INVESTIGATION Our investigation was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable soils engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. Centre Development July 29, 1988 Job NO. 05-4879-011-00-00 Log NO. 8-1797 Page 37 The samples taken and used for testing and the observations made are believed typical of the entire project. However, soil and geologic conditions can vary significantly between drillholes, test pits, or other exploration locations. As in most projects involving earthwork, the conditions revealed by excavation during construction may vary from those predicted in our preliminary findings. If such changed conditions are found, they should be evaluated by the project soils engineer and geologist. It may then be necessary to adjust the project designs or to recommend alternate designs. This report is issued with the understanding that the owner, or his representative, is responsible for bringing the information and recommendations contained herein to the attention of the architects and engineers involved in the project. The owner or his representative is also responsible for assuring that the information and recommendations are incorporated into the plans, and that the necessary steps are taken to see that the contractor and subcontractors carry out the recommendations in the field. This firm does not practice or consult in the field of safety engineering. We do not direct the contractor's operations, and we cannot be responsible for anyone other than our own personnel on the jobsite. Therefore, the safety of other persons at the jobsite is the responsibility of the contractor. The contractor should notify the owner promptly if he considers any of the recommendations in this letter to be unsafe. Our findings in this report are valid as of the date of issue. However, changes in the condition of a site can occur with the passage of time, due either to natural processes or the works of man on this or adjacent Centre Development July 29, 1988 Job NO. 05-4879-01 1-00-00 Log NO. 8-1797 Page 38 properties. In addition, changes to the applicable or appropriate laws, regulations, and standards of practice may occur as a result of either new legislation or the broadening of knowledge. Our findings may be invalidated wholly or in part by such changes, over which we have no control. The validity of this report therefore should not be relied upon after a period of three years without a comprehensive review by San Diego Geotechnical Consultants. *** - SAN DIEGO GEOTECHNICAL CONSULTANTS, INC. - k e, d- Patrick A. Thomas - Staff Geologist P.E. C 43422, Registration Expires: 6-30-92 C.E.G. 1355, Registration Expires: 6-30-90 Senior Engineer " .. No. 1355 CERTIFIED GEOLOGIST Anthony F. Belfast, P.E. Principal Engineer ENGINEERING PAT/RNM/AFB/rm/pb APPEUDIX A References References 1. H. V. Lawmaster h Company, Inc., 1980, Preliminary Geotechnical Investigation, Proposed Palomar Business Park, North San Diego County, California: Unpublished report no. 79-939416546 to Palomar Business Park, January 15, 1980 (includes grading plan review letters dated June 8. 1982 and September 27, 1982). 2. Moore h Taber, 1987, Report of Geotechnical Services, Carlsbad Tract No. 81-46, Airport Business Center, Unit No. 1, City of Carlsbad, California: Unpublished report to Centre Development Company, February 25, 1987. 3. Bonilla, M. G., 1970, Surface Faulting and Related Effects, - in Wiegel, R. L. (ed.), Earthquake Engineering: Engle- wood Cliffs, New Jersey, Prentice-Hall, p. 47-74. 4. Seed, H. B., and Idriss, I. M., 1982, Ground motions and soil liquefaction during earthquakes, Earthquake Engineering Research Institute, Monograph Series. 5. Ploessel, M. R., and Slosson, J. E., 1974, Repeatable high ground accelerations from earthquakes, California Geology, September. 6. California Division of Mines and Geology, 1975, Recommended Guidelines for Determining the Maximum Credible and the Maximum Probable Earthquakes: California Division of Mines and Geology Notes, Number 43. APPEBDIX B Field Exploration .. . DEFINITION OF TERMS SILTS AND CLAYS LIQUID LIMIT IS LESS THAN SO% GRAIN SIZES ILTS AND CLAYS SAND I QAAVEL FINE I MEDIUM I COARSE I FINE I COARSE COBBLES BOULDERS 200 40 10 4 314' 3' 12. u.a STANDARD SERIES SIEVE CLEAR SQUARE SIEVE OPENINQE p QROUNDWATER LEVEL AT TIME OF DRILLINQ. QROUNDWATER LEVEL MEASURED LATER IN STANDPIPE. LOCATION OF SAMPLE TAKEN USINQ A STANDARD SPLIT TUBE SAMPLER. 2-INCH O.D.. 1-318-lNCH I.D. DRIVEN WITH'A 14O.POUND HAMMER FALLINQ 30-INCHEB. LOCATtQN OF SAMPLE tAKEN.USlNQ A MODIFIED CALIFORNIA SAMPLER. 3-118-INCH O.D.. WITH 2-112-INCH I.D. LINER RINQS. DRIVEN USINQ THE WEIQHT OF KELLY BAR (LARQE DIAMETER BORINQS) OR USINQ A 140 POUND HAMMER FALLlNQ 30-tNCHES (SMALL DIAMETER BORINQ): LOCATION OF SAMPLE TAKEN USINQ A 3-INCH 0.0. THIN-WALLED TUBE SAMPLER (SHELBY TUBE) HYDRAULICALLY PUSHED. LOCATION OF BULK SAMPLE TAKEN FROM AUQER CUTTINQS. m LOG OF BORING NO. 1 Sheet 1 of 2 DESCRIPTION TOPSOIL: Medium brown clayey SAND, dry to damo. loose, fine grained SANTIAGO FORMATION ITsak Light brown silty SANDSTONE, damp to moist, dense, orange iron oxide staining (mottled), fine grained, laminated, moderately weathered, friable, N20E/2OE @ 6' remolded clay seam about 3" thick, some caliche, clay is dark olive-gray, moist, soft to firm, NSOE/3S, wavey @ 8' sandstone becomes light grey with yellow sulfide stain, changes to sandy silt CONTACT: N4OW/9S I Olive-grey sandy CLAYSTONE, damp to staining and yellow sulfide staining moist, firm to stiff, orange-red iron oxide CONTACT: N80E/10 NW 1 )ATE OBSERVED: 6-30-88 METHOD OF DRILLING: 30" Bucket A I ELEVATIOM298.0' LOCATION: See Geotechn 0'-24':2218 1I: i I ! i - " k - - - - - 1 " n - - R Diego Geotechnical Consultants, Inc. I B-: Medium brown clayey SANDSTONE, damp to moist, medium dense, fine grained, some @I 15.5 joint fracture, N25W 55 SW gypsum in fractures @ 19.0' Remolded clay seam about 3" thick, olive-gray sandy clay with iron (oxide stain, N5OW 5 I Light grey silty SANDSTONE, damp to thin bedded to laminated, moderately moist, dense to very dense, fine grained, @I 25' becomes medium brown to light weathered, well indurated, sulfide staining grey, cross laminae N90E 5 S @ 28.5' gypsum seam, 1/2" thick, continuous, horizontal @I 30' less brown coloration; mostly light olive-grey, cross lamiiae (sulfide and iron oxide stained) N80E 10 NW @ 35' dark grey sandy CLAY, damp to moist, very dense to hard, very fine ,grained, some yellow sulfide stain, fracture N5OE 80 W. drilling becomes more unoxidized, slab fracture during drilling, uxer 6 24'-44'31358 lb lcal Mao SOIL TEST herberg Limits 5xpansion Index LOG OF BORING NO. 1 Sheet 2 of 2 DISCRIPTION \Minor seepage at 39' Total Depth: 40' Minor seepage at 39' No Caving Geologically logged to 39' Backfilled 6-30-88 I umx lical MaD 24'-44':1358 Ib SOIL TEST &E 00 5 LOG OF BORING NO. 2 !L Sheet 1 of 1 DESCRIPTION moist, soft to stiff 10.0 SANTIAGO FORMATION ITsaI: Light olive-gray to medium brown sandy silty CLAYSTONE, moist, firm to Stiff, massive, orange iron oxide staining, some cobbles and gravel, mottled, slightly fractured - weathered to about 9' @ 9' joint set N23W 50 N to N90W 75 SE ,CONTACT: Horizontal I Light brown silty SANDSTONE, damp, dense to very dense, fine grained, fossiliferous @ 11' fossiliferous. zone @ 12' crossbedded sandstone dipping 5 degrees to SW, S I5 W @ 13' clay seam horizontal CONTACT: N60W, 15 S, gypsum filling I I @ 16' Olive-gray sandy CLAYSTONE, moist, stiff, some brown color @ 20' some iron oxide and sulfide staining and gypsum concretion ~~ ]thick, gypsum at contact @ 25' fossiliferous cemented zone about 6" I ~~ ~~~ Dark grey sandy CLAYSTONE, damp to fracture during drilling, unoxidized, well moist, very hard, fossiliferous, slab indurated Drilling becomes more difficuic near refusal Total Depth 30' No Water No Caving Geologically logged to 30' Backfilled 6-30-88 uger b: 24'-44':1358 Ib. ~Cal Mao SOIL TEST >irect Shear, Sieve inalysis, Atterberg .imits iulfate Expansion Index L DATE OBSERVED: 6-30" METHOD OF DRILLING 30" Bucket A1 ELEVATION280' LOCATION See Geotechn 0'-24':2218 Ib L LOG OF BORING NO. 3 Sheet 1 of 1 DESCRIPTION TOPSOIL. Medium brown to dark olive gray CLAY, damp to very moist, soft, to firm CONTACT: gradational, caliche infilled, N70W 10 S I SANTIAGO FORMATION (Tsal: Light olive gray white to light brown silty SANDSTONE, damp to moist, dense, fine to medium grained, orange iron oxide stainiig. moderately weathered, massive, friable, cross bedded @ 9' cross laminae, iron oxide stained, N-S 15 E, fracture, caliche infilled, N-S 73 E @ 14' clay seam about 2"-3" thick, caliche infiied, slightly undulating CONTACT: generally horizontal I Olive-gray clayey SANDSTONE, damp to moist, very dense, fine-grained, iron oxide mottling, well indurated @ 18' clay seam, 2"-3" thick, remolded, wet, generally horizontal @ 20.5' clay seam slightly remolded at sandstone contact, horizontal @ 23' clay bed @ 30' gypsum concretions, dark charcoal brown with caliche infilled fractures and iron oxide borders Total Depth 35' Geologically Logged to 35' No Caving No Seepage " user ical Ma0 .: 24'-44':1358 lb. SOIL TEST Xrect Shear, Sieve lnalysis LOGGED BY: LOG OF BORING NO. 4 Sheet 1 of 2 DESCRIPTION mL: Medium brown SAND, dry to damp, loose to medium dense, fine grained DATE OBSERVED: 6-28-88 METHOD OF DRILLING: 8" Hollow SI 1 ELEVATION:= LOCATION: See Geotech 140 Ib. Ham I -. ALLUVIUM lOalk Medium brown clayey SAND, moist, stiff Medium brown clayey SAND, damp, medium dense, fine grained "_"""-""""""""" Sampler bouncing on quartz gravel clast 55"38' tem Auzer mer. 30" Fall nical MaD SOIL TEST Consolidation, Sieve Analysis, Atterberg Limits iANTIAGO FORMATION ITsak - PA DATE OBSERVED 6-28-88 METHOD OF DRILLING: 8" Hollow Stem Auger OUND ELEVATI0N:m LOCATION: See Geotechn 140 Ib. Hammer: 30" Fall . gc I 02 LOG OF BORING NO. 4 i - w" . n; i jE I Zfi Sheet 2 of 2 DESCRIPTION damp to moist, very dense, fine grained, I micaceous I Total Depth' 42' Backfilled 6-28-88 No Water ical Ma0 SOIL TEST DATE OBSERVED: 6-28-88 METHOD OF DRILLING 8" Hollow LOGGED BY:& L I 140 Ib. H LEVATION232LT LOCATION See Geote LOG OF BORING NO. BW-1 Sheet I of 2 DESCRIPTION COLLUVIUM. dry to damp, loose. fine grained . Medium brown SAND, I SANTIAGO FORMATION (Ts& Light brown SANDSTONE, damp, dense, fine grained, some silt Dark gray CLAYSTONE, damp to moist, firm to stiff @ 36' Medium brown CLAYSTONE, moist to wet, soft to firm Dark grey CLAYSTONE, moist, very dense lieno Geotechnical Consultants. em Auger mer: 30" Fall niCd Mao SOIL TEST " San ;EVATION2$0.0' LOCATION See Geote 140 Ib. Hr LOG OF BORING NO. BW-1 Sheet 2 of 2 DESCRIPTION Total Depth: 51' No Caving Seepage @ 36' Well Installed 6-28-88 by Hydrotech. All samples by Hydrotech. SOIL TEST " - - iesro Geotechnical Consultants, Inc. LoGGl t LOG OF BORING NO. BW-2 Sheet 1 of I DESCRIPTION FILL: Medium brown SAND, dry to damp, loose, fine grained DATE OBSERVED: 6-28-88 METHOD OF DRILLING: 8" Hollow Ste 140 Ib. Hamn ALLUYIUM IOalk Dark brown sandy CLAY, moist to wet, soft, strong petroleum odor SANTIAGO FORMATION [Tsa): Olive-gray CLAYSTONE, moist, soft to firm, some yellow staining Total Depth 16.5 No Water Well installed 6-28-88 by Hydrotech :m Auger lex 30" Fall ical Ma0 SOIL TEST DATE OBSERVED: 6-28-88 METHOD OF DRILLING 8" Holloa 140 Ib. H LEVATION238.0' LOCATION See Geotc LOG OF BORING NO. BW-3 Sheet 1 of 1 DESCRIPTION ____ FILL: Medium brown SAND, dry to damp, loose, some roots and organic debris, fine grained ALLUVIUM (Oalk Medium gray to medium brown clayey SAND, moist, loose, some gravel, fine grained 7 'SANTIAGO FORMATION (Tsal: Medium brown to medium grey SANDSTONE, moist to wet, medium dense, some orange staining, fine grained Total Depth' 15' Water @ 11' Well installed 6-28-88 by Hydrotech !go Geotechnical Consultants, I :m Auaer ner: 30" Fall ucal Mao SOIL TEST FATE OBSERVED: 6-21-88 DRILLIN& Kubota KH 170L Tracked Hoe ,OQQED BY: PAT - LOQQED BY: QROUND E TEST PIT NO. 1 DESCRIPTION WWIUM (Qal) : Light brown SAND, damp, loose, fine grained, some rip- ~ rap and debris on surface Dark grey sandy CLAY, wet, soft, som seepage at 2-3', strong petroleum odor "" . ~" .. ~ SANTIAGO FORMATION (Tsa) : Olive-gray sandy CLAYSTONE, mist to wet, soft to firm, some yellow-oranqe staining " Total Depth: 8' No Caving Seepage at 2' Backfilled 6-21-88 . son TEST 2' , 240' 2 See Geotechnical Map LEVATION:. 01 1-01 - TEST PIT NO. 2 ALLWIUM (Qal): Medium brown clayey SAND, damp to wet, loose, fine grained Seepage at 6'-13' SANTIAGO FORMATION (Tsa) : Olive-gray sandy CLAYSTONE, damp, soft to firm \ Total Depth: 13' Seepage at 6-13' Expansion Index Backfilled 6-21-88 Caving 00 ILOG OF TEST PIT IFlQUW%B- 12. 1 DESCRIPTION ALLUVIUM (Qal): Medium brown silty SAND, dry to damp. loose, some roots and organic debris, fine grained SANTIAGO FORMATION (Tsa): Light brown SANDSTONE, damp to moist, medium dense to dense, fine grained, some orange staining Total Depth: 9' No Water No Caving :a1 Map SOIL TEST TEST PIT NO.4 A~LWIUM (Qal): Medium brown silty SAND, dry to damp, loose, fine grained SANTIAGO FORMATION (Tsa): Medium brown silty SANDSTONE, damp, medium dense to dense, fine grained, some orange staining T cal Map Total Depth: 9.5' NO Water No Caving TOPSOIL: Dark brown sandy CLAY, damp to moist, soft SANTIAGO FORMATION (Tsa): Light brown silty SANDSTONE, damp to mist, . medium dense to dense, some orange staining, fine grained Total Depth: 9' No Water No Caving OQQED BY: QROUND ELEVATION "" LOCATION: See Geotechnical Map t TEST PIT NO.& ALLUVIUM (Qal) : Dark brown clayey SAND, damp to wet, loose to firm, fine grained SANTIAGO FORMATION (Tsa): Light brown SANDSTONE, damp to mist, dense to very dense, fine grained, some orange staining Total Depth: 8' No Water Backfilled 6-21-88 No Caving Maxim density, Direct Shear, Sieve Analysis DATE OBSERVED: 6-21-88 6 10 16 sc TEST PIT NO.", son TEST DESCRIPTION I ALLWIUM (Qal): Medium brown sandy CLAY, damp to mist, soft to stiff SANTIAGO FORMATION (Tsa) : Light brown SANDSTONE. damp, dense to very dense, fine grained Total Depth: 5' I No Water No Caving LOQQED BY:& QROUND ELEVATION 288' f LOCATION See Geotechnical Map I I TEST PIT NO. 8 - - . CLAY, damp to moist, soft to firm, sc ALLWIUM (Qal): Medium brown sandy - some gravel - - 6- - SANTIAGO FORMATION (Tsa): Light brown SM to gray SANDSTONE, damp to moist, dense to very dense, some orange - - staining, fine grained IO- - - - Total Depth: 7' - No Water 16- No Caving - - 'OB N0-:05-4879-0 1 I -00-00 I LOG OF TEST PIT IF- 8-16. WWIUM (Qal): Medium brown silty CLAY, damp to moist, soft to film SANTIAGO FORMATION (Tsa) : Medium brown SANDSTONE. dam^ to mist. densc I\ to very dense, fine grained I’ Total Depth: 6.5’ No Water No Caving Backfilled 6-21-88 IVATION LOCATION: TEST PIT NO. 0 0 h m 0 0 I F 0 c 0 t OD -1 14 m 3 0 m r a W -1 t W 0 < L 0 -1 W m r a t W > 0 0 0 -1 W > W t a a c U 0 m n L w W LL Y 2 0 c < 0. 0 -I W - m 0 I- ~. a W s APPENDIX C Laboratory Testing Program Laboratory Testing Program Typical soil samples from the site were tested to determine their engineering properties. The test methods used conform generally to those of the American Society for Testing and Materials (ASTM) or those of other recognized standard-setting organizations. The following section describes the testing program. Classification During fieldwork, the soil and rock was classified by the Unified Soil Classification System (visual-manual procedure) of ASTM D 2488-84. These classifications were checked and, if necessary, modified on the basis of laboratory test results (ASTM D 2487- 85). The logs in Appendix B show the classifications. Atterberg Limits ASTM D 4318-84 was used to determine the liquid limit, plastic limit. and plasticity index of three selected clayey samples. Figure C-1 shows the results. Particle Size Analysis Mechanical analyses of particle-size distribution, as described in ASTM D 422-63, were made on four selected samples. Figures C- 2 through C-5 show the results. Direct Shear Consolidated, drained, direct shear tests (ASTM D 3080-72) were made on two relatively undisturbed samples of Santiago Formation rocks from drillholes B-2 and B-3. The test results are plotted on Figure C-6. Tests were also made on a Santiago Formation sample from test pit TP-6 that had been remolded to 90 percent of the modified Proctor maximum dry density. The results of these tests are shown on Figure C-7. All three tests were made under saturated conditions and were carried out to measure ultimate strength values. Laboratory Testing Program (Continued) Consolidation Tests To assess its compressibility when loaded and wetted, a sample of alluvium from drillhole B-4 was subjected to a consolidation test (ASTM D 2435-80). Figure C-8 shows the results. Maximum Density/Optimum Moisture Content The moisture - density relationship for one sample of Santiago Formation rock from test pit TP-6 was determined using AS" D 1557-78. Table C-1 lists the test results. Expans ion The expansion potential of two samples of Santiago Formation rock from drillholes B-1 and B-3. and of one sample of surficial soil from test pit TP-6, was tested using the UBC 29-2 expansion index method. Table C-2 lists the results. Sulfate Content A sample of Santiago Formation rock from drillhole B-2 was tested for water-soluble sulfate minerals with CALTRANS Method 417 (Part I). The results are listed in Table C-3. PLASTICITY CHART LIQUID LIMIT (%I UNIFIED No. *O0 INDEX CLASS+ SYMBOL SIEVE FlCATlON 68.0 -0.1 e CL ATTERBERG LIMITS IB NO: OS-4879-Ot1-00-00 DATE: FIQURE: C- 1 - PERCENT PASSINQ PERCENT PASSINQ NO.: i-4879-011-00-00 PARTICLE SIZE ANALYSIS FIQURE: c-2 PERCENT PA881NQ PERCENT PA881NO 36 NO.: 95-4870 - 011 " QO OQ PARTICLE SIZE ANALYSIS FIBURE - PERCENT PASSINQ PERCENT PASSINO PERCENT PA881NQ PERCENT PA881NQ JOB NO.: 06-4879-011-00-00 PARTICLE SIZE ANALYSIS FIQURE: c-6 I I 1 I I 1000 2000 3000 4000 6000 NORMAL LOAD (PSn . Doa 18 NO.: - 79-~~1-~0-~0 FIQURE: SHEARING STRENGTH TEST c-6 NORMAL LOAD (PSn OB NO.: os-4870-011 - 00 - 00 I SHEARING STRENGTH TEST FIOURE: - INITIAL DENSITY (PCF) 10.8 INITIAL MOISTURE (%I EXPLANATION 80.7 FIELD MOISTURE FINAL MOISTURE (%) I 19.8 INITIAL VOID RATIO 10.710 """"" SAMPLE SATURATED I I I REBOUND 4.0 2.0 4.0 0.0 CI s z c 0 P m 10.0 g 12.0 0 20.00 I 0 a 0 0 00 2 1 1 8 000 0 00 0 0 00 ru o*o NORMAL LOAD (PSn DB NO.: 06-4879-011-00-00 I LOAD CONSOLIDATION TEST FIQURE: - TABLE C-1 MAXIMUM DENSITY/OPTIMUM MOISTURE RELATIONSHIPS (ASTM D 1557-78) Sample Optimum Moisture Maximum Dry Location Content (%) Density (pcf) TP-6 @ 5.0-6.0 13.7 113.8 TABLE c-2 RESULTS OF EXPANSION TESTS (UBC Method 29-2) Sample Potential Index Location Expansion Expansion B-1 @ 20.0"21.0' Medium 85 TP-6 @ 1.0"2.0' Low 24 B-2 @ 30.0'-31.0' Low 30 TABLE C-3 RESULTS OF SOLUBLE SULFATE TESTS (EPA 300) Sample Location Soluble Sulfates (X) B-2 @ 20.0'-21.0' 0.0797 APPJIHDIX D Standard Guidelines for Grading Projects - STANDARD GUIDELINES FOR GRADING PROJECTS - 1. GENERAL 1.1 1.2 1.3 1.4 - - 1.5 1.6 - Representatives of the Geotechnical Consultant should be present on-site during grading operations in order to make observations and perform tests so that professional opinions can be developed. The opinion will address whether grading has proceeded in accordance with the Geotechnical Consultant's recommendations and applicable project specifications; if the site soil and geologic conditions are as anticipated in the preliminary investigation: and if unexpected site conditions. Services do not include additional recommendations are warranted by any supervision or direction of the actual work of the contractor, his employees or agents. The guidelines contained herein and the standard details attached hereto represent this firm's standard recommendations for grading and other associated operations on construction projects. These guidelines should be considered a portion of the report to which they are appended. All plates attached hereto shall be considered as part of these guidelines. without prior recommendation by the Geotechnical The Contractor should not vary from these guidelines Consultant and the approval of the Client or his authorized representative. These Standard Grading Guidelines and Standard Details may be modified and/or superseded by recommendations contained in the text of the preliminary geotechnical report and/or subsequent reports. If disputes arise out of the interpretation of these grading guidelines or standard details, the Geotech- nical Consultant should determine the appropriate interpretation. - 2. DEFINITIONS OF TERMS 2.1 ALLUVIUM -- Unconsolidated detrital deposits resulting - from flow of water, including sediments deposited in river beds, canyons, flood plains, lakes, fans at the foot of slopes and estuaries. - Standard Guidelines for Grading Projects Page 2 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 AS-GRADED (AS-BUILT) -- The surface and subsurface conditions at completion of grading. BACKCUT -- A temporary construction slope at the rear of earth retaining structures such as buttresses, shear keys, stabilization fills or retaining walls. BACKDRAIN -- Generally a pipe and gravel or similar drainage system placed behind earth retaining structures such buttresses, stabilization fills, and retaining walls. BEDROCK -- A more or Less solid, relatively undis- turbed rock in place either at the surface or beneath superficial deposits of soil. BENCH -- A relatively level step and near vertical be placed. rise excavated into sloping ground on which fill is to BORROW (Import) -- Any fill material hauled to the project site from off-site areas. BUTTRESS FILL -- A fill mass, the configuration of which is designed by engineering calculations to retain slope conditions containing adverse geologic minimum key width and depth and by maximum backcut features. A buttress is generally specified by angle. A buttress normally contains a backdrainage system. CIVIL ENGINEER -- The Registered Civil Engineer or consulting firm responsible for preparation of the grading plans, surveying and verifying as-graded topographic conditions. COLLUVIUM -- Generally loose deposits usually found near the base of slopes and brought there chiefly by gravity through slope continuous downhill creep (also see Slope Wash). COMPACTION -- Is the densification of a fill by mechanical means. CONTRACTOR -- A person or company under contract or otherwise retained by the Client to perform demolation. grading and other site improvements. ." Standard Guidelines for Grading Projects Page 3 - 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 DEBRIS -- All products of clearing, grubbing, demolition, contaminated soil material unsuitable for reuse as compacted fill and/or any other material so designated by the Geotechnical Consultant. ENGINEERING GEOLOGIST -- A Geologist holding a valid certificate of registration in the specialty of Engineering Geology. ENGINEERED FILL -- A fill of which the Geotechnical Consultant or his representative, during grading, has made sufficient tests to enable him to conclude that the fill has been placed in substantial compliance with the recommendations of the Geotechnical Consultant and the governing agency requirements. result of the movement of wind, water, and/or ice. EROSION -- The wearing away of the ground surface as a EXCAVATION -- The mechanical removal of earth materials. EXISTING GRADE -- The ground surface configuration prior to grading. or other similar materials placed by man. FILL -- Any deposits of soil, rock, soil-rock blends which time the surface elevations conform to the FINISH GRADE -- The ground surface configuration at approved plan. GEOFABRIC -- Any engineering textile utilized in geotechnical applications including subgrade stabilization and filtering. GEOLOGIST -- A representative of the Geotechnical Consultant educated and trained in the field of geology. GEOTECHNICAL CONSULTANT -- The Geotechnical Engineer- ing and Engineering Geology consulting firm retained to provide technical services for the project. For the purpose of these guidelines, observations by the Geotechnical Consultant include observations by the Geotechnical Engineer, Engineering Geologist and those performed by persons employed by and responsible to the Geotechnical Consultants. - Standard Guidelines for Grading Projects - Page 4 2.24 2.25 2.26 2.27 2.28 2.29 2.30 2.31 2.32 2.33 2.34 GEOTECHNICAL ENGINEER -- A licensed Civil Engineer who applies scientific methods, engineering principles and professional experience to the acquisition, inter- pretation and use of knowledge of materials of the earth's crust for the evaluation of engineering problems. Geotechnical Engineering encompasses many of the engineering aspects of soil mechanics, rock mechanics, geology, geophysics, hydrology and related sciences. GRADING -- Any operation consisting of excavation, filling or combinations thereof and associated operations. LANDSLIDE DEBRIS -- Material, generally porous and of low density, produced from instability of natural of man-made slopes. MAXIMUM DENSITY -- Standard laboratory test for maximum dry unit weight. Unless otherwise specified, accordance with ASTM Method of Test D1557. the maximum dry unit weight shall be determined in OPTIMUM MOISTURE -- Test moisture content at the maximum density. RELATIVE COMPACTION -- The degree of compaction material as compared to the maximum dry unit weight of (expressed as a percentage) of dry unit weight of a the material. ROUGH GRADE -- The ground surface configuration at which time the surface elevations approximately conform to the approved plan. SITE -- The particular parcel of land where grading is being performed. generally constructed by excavating a slot within a SHEAR KEY -- Similar to buttress, however, it is natural slope in order to stabilize the upper portion of the slope without grading encroaching into the lower portion of the slope. of which is generally specified as a ratio of SLOPE -- Is an inclined ground surface the steepness horizonta1:vertical (e.g.. 2:l). SLOPE WASH -- Soil and/or rock material that has been transported down a slope by mass wasting assisted by Colluvium). runoff water not confined by channels (also see -. Standard Guidelines for Grading Projects Page 5 2.35 - 2.36 2.37 - 2.38 2.39 2.40 2.41 - 2.42 - 2.43 SOIL -- Naturally occurring deposits of sand, silt, clay, etc., or combinations thereof. SOIL ENGINEER -- Licensed Civil Engineer experienced in soil mechanics (also see Geotechnical Engineer). STABILIZATION FILL -- A fill mass, the configuration of which is typically related to slope height and is specified by the standards of practice for enhancing the stability of locally adverse conditions. A key width and depth and by maximum backcut angle. A stabilization fill is normally specified by minimum stabilization fill may or may not have a backdrainage system specified. SUBDRAIN -- Generally a pipe and gravel or similar drainage system placed beneath a fill in the alignment of canyons or former drainage channels. during grading operations. SLOUGH -- Loose, noncompacted fill material generated TAILINGS -- Nonengineered fill which accumulates on or adjacent to equipment haul-roads. TERRACE -- Relatively level step constructed in the face of graded slope surface for drainage control and maintenance purposes. TOPSOIL -- The presumably fertile upper zone of soil which is usually darker in color and loose. WINDROW -- A string of large rock buried within engineered fill in accordance with guidelines set forth by the Geotechnical Consultant. 3. SITE PREPARATION 3.1 Clearing and grubbing should consist of the removal of vegetation such as brush, grass, woods, stumps, trees, materials from the areas to be graded. Clearing and roots to trees and otherwise deleterious natural grubbing should extend to the outside of all proposed excavation and fill areas. .- 3.2 Demolition should include removal of buildings, struc- underground pipelines, septic tanks, leach fields, tures, foundations, reservoirs, utilities (including seepage pits, cisterns, mining shafts, tunnels, etc.) and other man-made surface and subsurface improvements - Standard Guidelines for Grading Projects -. Page 6 from the areas to be graded. Demolition of utilities of wells in accordance with the requirements of the lines at the project perimeter and cutoff and capping governing authorities and the recommendations of the Geotechnical Consultant at the time of demolition. " should include proper capping andfor re-routing pipe- - 3.3 Debris generated during clearing, grubbing andfor be graded and disposed off-site. Clearing, grubbing demolition operations should be wasted from areas to and demolition operations should be performed under . the observation of the Geotechnical Consultant. 4. SITE PROTECTION 4.3 4.4 4.5 The Contractor should be responsible for the stability Geotechnical Consultant pertaining to temporary of all temporary excavations. Recommendations by the of stability of the completed project and, therefore. excavations (e.g.. backcuts) are made in consideration should not be considered to preclude the responsibil- Geotechnical Consultant should not be considered to ities of the Contractor. Recommendations by the preclude more restrictive requirements by the regulating agencies. Precautions should be taken during the performance of work site from flooding. ponding or inundation by poor site clearing, excavations and grading to protect the or improper surface drainage. Temporary provisions should be made during the rainy season to adequately direct surface drainage away from and off the work site. During periods of rainfall, the Geotechnical as to the nature of remedial or preventative work Consultant should be kept informed by the Contractor being performed (e.g., pumping. placement of sandbags or plastic sheeting. other labor, dozing, etc.). Following periods of rainfall. the Contractor should contact the Geotechnical Consultant and arrange a review of the site in order to visually assess rain related damage. The Geotechnical Consultant may also recommend excavations and testing in order to aid in his assessments. Rain related damage should be considered to include, but may not be limited to, erosion, silting. saturation, swelling, structural distress and other adverse conditions identified by the Geotechnical - Standard Guidelines for Grading Projects - Page 7 Consultant. Soil adversely affected should be classified as Unsuitable Materials and should be subject to overexcavation and replacement with compacted fill or other remedial grading as recommended by the Geotechnical Consultant. 5. EXCAVATIONS - 5.1 UNSUITABLE MATERIALS 5.1.1 Materials which are unsuitable should be of the Geotechnical Consultant. Unsuitable excavated under observation and recommendations materials include, but may not be limited to, dry, loose, soft, wet, organic compressible natural soils and fractured, weathered, soft bedrock and nonengineered or otherwise deleterious fill materials. 5.1.2 Material identified by the Geotechnical Consultant as unsatisfactory due to its moisture conditions should be overexcavated. blended to a uniform near optimum moisture watered or dried. as needed, and thoroughly prior to placement as compacted fill. condition (as per guidelines reference 7.2.1) 5.2 CUT SLOPES 5.2.1 Unless otherwise recommended by the Geotech- nical Consultant and approved by the regulating agencies, permanent cut slopes should not be steeper than 2:l (horizonta1:vertical). 5.2.2 If excavations for cut slopes expose loose. cohesionless, significantly fractured or otherwise unsuitable material, overexcavation with a compacted stabilization fill should be and replacement of the unsuitable materials accomplished as recommended by the Geotechnical Consultant. Unless otherwise specified by the Geotechnical Consultant, stabilization fill construction should conform to the requirements of the Standard Details. 5.2.3 The Geotechnical Consultant should review cut Consultant should be notified by the contractor slopes during excavation. The Geotechnical prior to beginning slope excavations. - Standard Guidelines for Grading Projects Page 8 5.2.4 If, during the course of grading, adverse or .. potentially adverse geotechnical conditions are preliminary report, the Geotechnical Consultant encountered which were not anticipated in the should explore, analyze and make recommen- dations to treat these problems. - 6. COMPACTED FILL _- All fill materials should be compacted to at least 90 percent of maximum density (AS" D1557) unless otherwise recommended by the Geotechnical Consultant. 6.1 PLACEMENT 6.1.1 6.1.2 6.1.3 Prior to placement of compacted fill, the Contractor should request a review by the Geotechnical Consultant of the exposed ground surface. Unless otherwise recommended, the exposed ground surface should then be scarified (6-inches minimum), watered or dried as needed, thoroughly blended to achieve near optimum moisture conditions, then thoroughly compacted to a minimum of 90 percent of the maximum density . Compacted fill should be placed in thin horizontal lifts. Each lift should be watered optimum moisture conditions then compacted by or dried as needed, blended to achieve near mechanical methods to a minimum of 90 percent of laboratory maximum dry density. Each lift should be treated in a like manner until the desired finished grades are achieved. When placing fill in horizontal lifts adjacent vertical), horizontal keys and vertical benches to areas sloping steeper than 5:l (horizontal: area. Keying and benching should be sufficient should be excavated into the adjacent slope to provide at least 6-foot wide benches and a minimum of 4-feet of vertical bench height within the firm natural ground, firm bedrock or engineered compacted fill. No compacted fill keying and benching until the area has been should be placed in an area subsequent to reviewed by the Geotechnical Consultant. Material generated by the benching operation should be moved sufficiently away from the bench area to allow for the recommended review of the horizontal bench prior to placement - Standard Guidelines for Grading Projects Page 9 6.1.4 6.1.5 6.1.6 6.1.7 fill. Typical keying and benching details have been included within the accompanying Standard Details. Within a single fill area where grading procedures dictate two or more separate fills, temporary slopes (false slopes) may be created. When placing fill adjacent to a false slope, benching should be conducted in the same manner as above described. At least a 3-foot vertical bench should be established within the firm core adjacent approved compacted fill prior to placement of additional fill. Benching should proceed in at least 3-foot vertical increments until the desired finished grades are achieved. Fill should be tested for compliance with the recommended relative compaction and moisture conditions. Field density testing should conform to accepted test methods. Density testing frequency should be adequate for the geotechnical consultant to provide professional opinions regardings fill compaction and adherence to recommendations. Fill found not to be in conformance with the grading recommendation should be removed or otherwise handled as recommended by the Geotechnical Consultant. The Contractor should assist the Geotechnical Consultant and/or his representative by digging test pits for removal determinations andlor for testing compacted fill. As recommended by the Geotechnical Consultant, the Contractor may need to remove grading personnel safety is considered to be a problem. equipment from an area being tested if 6.2 MOISTURE 6.2.1 For field testing purposes "near optimum" moisture will vary with material type and other optimum" may be specifically recommended in factors including compaction procedure. "Near evaluated during grading. Preliminary Investigation Reports andlor may be 6.2.2 Prior to placement of additional compacted fill following an overnight or other grading delay, the exposed surface or previously compacted - Standard Guidelines for Grading Projects Page 10 watered or dried as needed, thoroughly blended fill should be processed by scarification, to near-optimum moisture conditions, then recompacted to a minimum of 90 percent of laboratory maximum dry density. Where wet, dry, or other unsuitable materials exist to materials should be overexcavated. depths of greater than one foot, the unsuitable - 6.2.3 Following a period of flooding, rainfall or overwatering by other means, no additional fill should be placed until damage assessments have been made and remedial grading performed as described under Section 5.6 herein. 6.3 FILL MATERIAL 6.3.1 6.3.2 6.3.3 6.3.4 Excavated on-site materials which are considered suitable to the Geotechnical Consultant may be utilized as compacted fill, provided trash, vegetation and other deleterious materials are removed prior to placement. Where import fill materials are required for use on-site, the Geotechnical Consultant should be notified in advance of importing, in order borrow sites. No import fill materials should to sample and test materials from proposed be delivered for use on-site without prior sampling and testing notification by Geotechnical Consultant. Where oversized rock or similar irreducible material is generated during grading, it is material off-site or on-site in areas recommended, where practical, to waste such designated as "nonstructural rock disposal be placed with sufficient fines to fill areas". Rock placed in disposal areas should voids. The rock should be compacted in lifts to an unyielding condition. The disposal area should be covered with at least three feet of material. The upper three feet should be compacted fill which is free of oversized placed in accordance with the guidelines for compacted fill herein. Rocks 12 inches in maximum dimension and smaller may be utilized within the compacted fill, provided they are placed in such a manner Standard Guidelines for Grading Projects Page 11 that nesting of the rock is avoided. Fill should be placed and thoroughly compacted over not exceed 40 percent by dry weight passing the and around all rock. The amount of rock should 3/4-inch sieve size. The 12-inch and 40 percent recommendations herein may vary as field conditions dictate. 6.3.5 Where rocks or similar irreducible materials of greater than 12 inches but less than four feet of maximum dimension are generated during within an engineered fill, special handling in grading, or otherwise desired to be placed accordance with the accompanying Standard Details is recommended. Rocks greater than four feet should be broken down or disposed off-site. Rocks up to four feet maximum dimension should be placed below the upper 10 feet of any fill and should not be closer than 20-feet to any slope face. These recommen- dations could vary as locations of improvements dictate. Where practical, oversized material should not be placed below areas where structures or deep utilities are proposed. Oversized material should be placed in windrows on a clean, overexcavated or unyielding compacted fill or firm natural ground surface. Select native or imported pranular soil (S.E. 30 or higher) should be placed and thoroughly flooded over. and around ill windrowed rock, such that voids are filled. Windrows of oversized material should be staggered so that successive strata of oversized material are not in the same vertical plane. 6.3.6 It may be possible to dispose of individual larger rock as field conditions dictate and as recommended by the Geotechnical Consultant at the time of placement. 6.3.7 The construction of a "rock fill" consisting primarily of rock fragments up to two feet in maximum dimension with little soil material may be feasible. Such material is typically generated on sites where extensive blasting is required. Recommendations fo'r construction of rock fills should be provided by the bas is. Geotechnical Consultant on a site-specific Standard Guidelines for Grading Projects Page 12 6.3.8 During grading operations, placing and mixing the materials from the cut and/or borrow areas may result in soil mixtures which possess unique physical properties. Testing may be required of samples obtained directly from the fill areas in order to determine conformance with the specifications. Processing of these additional samples may take two or more working operation to other areas within the project, or days. The Contractor may elect to move the may continue placing compacted fill pending laboratory and field test results. Should he elect the second alternative, fill placed is done so at the Contractor's risk. 6.3.9 Any fill placed in areas not previously reviewed and evaluated by the Geotechnical Consultant may require removal and recom- paction. Determination of overexcavations should be made upon review of field conditions by the Geotechnical Consultant. 6.4 FILL SLOPES 6.4.1 Permanent fill slopes should not be constructed steeper than 2:l (horizontal to vertical). unless otherwise recommended by the Geotech- nical Consultant and approved by the regulating agencies. 6.4.2 Fill slopes should be compacted in accordance with these grading guidelines and specific compaction are typically utilized in mass report recommendations. Two methods of slope grading, lateral over-building and cutting back, and mechanical compaction to grade (i.e. sheepsfoot roller backrolling). Constraints such as height of slope, fill soil type, access, property lines, and available equipment will influence the method of slope construction and be notified by the contractor what method will compaction. The geotechnical consultant should be employed prior to slope construction. Slopes utilizing over-building and cutting back should be constructed utilizing horizontal fill lifts (reference Section 6) with compaction equipment working as close to the edge as prac- tical. The amount of lateral over-building will vary as field conditions dictiate. Compaction testing of slope faces will be required and - Standard Guidelines for Grading Projects Page 13 6.4.3 6.4.4 reconstruction of the slope may result if testing does not meet our recommendations. Mechanical compaction of the slope to grade during construction should utilize two types of compactive effort. First, horizontal fill lifts should be compacted during fill placement. This equipment should provide compactive effort to the outer edge of the fill slope. Sloughing of fill soils should not be permitted to drift down the slope. Secondly, at intervals not exceeding four feet in vertical slope height or the capability of available equipment, whichever is less, fill slopes should be backrolled with a sheepsfoot-type roller. Moisture conditions of the slope fill soils should be maintained throughout the compaction process. Generally upon slope completion, the entire slope should be compacted utilizing typical methods, (i.e. sheepsfoot rolling, bulldozer tracking, or rolling with rubber-tired heavy equipment). Slope construction grade staking should be removed as soon as possible in the slope compaction process. Final slope compaction should be performed without grade sakes on the slope face. In order to monitor slope construction procedures, moisture and density tests will be taken at regular intervals. Failure to achieve the desired results will likely result in a recommendation by the Geotechnical Consultant to overexcavate the slope surfaces followed by reconstruction of the slopes utilizing over- filling and cutting back procedures or further backrolling approach. Other recommendations compactive effort with the conventional may also be provided which would be commensurate with field conditions. Where placement of fill above a natural slope or above a cut slope is proposed, the fill accompanying Standard Details should be slope configuration as presented in the adopted. For pad areas above fill slopes, positive drainage should be established away from the top-of-slope, as designed by the project civil engineer. - Standard Guidelines for Grading Projects Page 14 6.5 OFF-SITE FILL 6.5.1 6.5.2 6.5.3 Off-site fill should be treated in the same manner as recommended in the specifications for site preparation, excavation, drains, compaction, etc. Off-site canyon fill should be placed in preparation for future additional fill, as shown in the accompanying Standard Details. Off-site fill subdrains temporarily terminated (up canyon) should be surveyed for future relocation and connection. 6.6 TRENCH BACKFILL 6.6.1 6.6.2 6.6.3 6.6.4 Utility trench backfill should, unless other- wise recommended, be compacted by mechanical means. Unless otherwise recommended, the degree of compaction should be a minimum of 90 percent of maximum density (ASTM D1557). Backfill of exterior and interior trenches extending below a 1:l projection from the outer edge of foundations should be mechanically compacted to a minimum of 90 percent of the laboratory maximum density. Within slab areas, but outside the influence of foundations, trenches up to one foot wide and two feet deep may be backfilled with sand (S.E. > 30), and consolidated by jetting, flooding or by mechanical means. If on-site materials are utilized, they should be wheel-rolled, tamped For minor interior trenches, density testing or otherwise compacted to a firm condition. may be deleted or spot testing may be elected if deemed necessary, based on review of backfill operations during construction. If utility contractors indicate that it is undesirable to use compaction equipment in close proximity to a buried conduit, the Contractor may elect the utilization of light weight mechanical compaction equipment and/or material, (S.E. > 30) which should be shading of the conduit with clean, granular thoroughly moistened in the trench, prior to Standard Guidelines for Grading Projects Page 15 Other methods of utility trench compaction may initiating mechanical compaction procedures. also be appropriate, upon review of the Geotechnical Consultant at the time of construction. 6.6.5 In cases where clean granular materials are where flooding or jetting is proposed, the proposed for use in lieu of native materials or procedures should be considered subject to review by the Geotechnical Consultant. 6.6.6 Clean granular backfill and/or bedding are not recommended in slope areas unless provisions are made for a drainage system to mitigate the potential build-up of seepage forces and piping. 7. DRAINAGE 1 7.1 Canyon subdrain systems recommended by the Geotechnical Consultant should be installed in accordance with the Standard Details. 7.2 Typical subdrains for compacted fill buttresses, slope stabilizations or sidehill masses, should be installed in accordance with the specifications of the .accompanying Standard Details. 7.3 Roof, pad and slope drainage should be directed away via suitable devices designed by the project civil from slopes and areas of structures to disposal areas area drains, earth swales, etc.). engineer (i.e., gutters, downspouts, concrete swales, 7.4 Drainage patterns established at the time of fine grading should be maintained throughout the life of the project. Property owners should be made aware slope stability and foundation performance. that altering drainage patterns can be detrimental to a. SLOPE MAINTENANCE 8.1 LANDSCAPE PLANTS problems, slope planting should be accomplished at the In order to decrease erosion surficial slope stability completion of grading. Slope planting should consist of deep-rooting vegetation requiring little watering. A Landscape Architect would be the test party to configuration. consult regarding actual types of plants and planting - Standard Guidelines for Grading Projects 8.2 IRRIGATION Page 16 8.2.1 Slope irrigation should be minimized. If automatic timing devices are utilized on irrigation systems, provisions should be made for interrupting normal irrigation during periods of rainfall. 8.2.2 Property owners should be made aware that overwatering of slopes is detrimental to slope stability and may contribute to slope seepage, erosion and siltation problems in the subdivision. Rev 5/88 1s' MINIMUM 4. DIAMETER PERFORATED PIPE BACKDRAIN 4' DIAMETER NON-PERFORATED PIPE LATERAL DRAIN ELOPE PER PLAN BENCHINQ 1-t PROVIDE BACK DRAIN PER BACKDRAIN DETAIL. AN ADDITIONAL BACKDRAIN AT MID-ELOPE WILL BE REQUIRED FOR ELOPE IN EXCESS OF 40 FEET HIQH. (QENERALLY 112 ELOPE HEIQHT. 1s' KEY-DIMENSION PER SOIL8 ENQINEER MINIMUM) TYPICAL STABILIZATION FILL DETAIL OB NO.: - DATE: - - .. -< JULY *-',, FIQURE: 1 4' DIAMETER PERFORATED PIPE BACKDRAIN \ 4' DIAMETER NON-PERFORATED PIPE LATERAL DRAIN SLOPE PER PLAN- BENCHINQ \ LPROVIDE BACKDRAIN PER BACKDRAIN DETAIL. AN ADDITIONAL BACKDRAIN AT MID-SLOPE WILL BE REQUIRED FOR ELOPE IN EXCESS OF 40 FEET-HIQH. -KEY-DIMENSION PER SOILS ENQINEER TYPICAL BUTTRESS FILL DETAIL ~ ~~ ~~ OS NO.: DATE: - 0-1 1-00*00' FIQURE: JULY" tOdM 2 r NATURAL QROUND PROPOSED QRADINQ " COMPACTED FILL PROVIDE BACKDRAIN PER BACKDRAIN DETAIL. AN ADDITIONAL BACKDRAIN AT MID-SLOPE WILL BE REQUIRED FOR BACK SLOPES IN EXCESS OF BASE WIDTH .W. DETERMINED 40 FEET HIQH. LOCA- BY SOILS ENQINEER AND OUTLETS PER SOILS TIONS OF BACKDRAINS ENQINEER ANDIOR EN- QlNEERlNQ QEOLOQIST DURINQ QRADINQ. )B NO.: 06-487Q-Qll - DATE: JULY 1.0881 FIGURE: 3 FINAL I EXCA .IM VA OVEREXCAVATE Ill OF TlON DAYLIQHT /- FINISH PAD DAYLIGHT SHEAR KEY DETAIL OB no.: DATE: .. FIGURE: 06-48?@-01 ?-OO-OQ- JULY 1988.: 4 BENCHING FILL OVER NATURAL SURFACE OF FIRM EARTH MATERIAL 7 / -10' MIN. (INCLINED 2% MIN. INTO SLOPE) BENCHING FILL OVER CUT SURFACE OF FIRM FINISH FILL SLOPE EARTH MATERIAL TYPICAL 16' MIN. OR STABILITY EQUIVALENT PER SOIL ENQlNEERlNQ (INCLINED 2% MIN. INTO SLOPE) BENCHING FOR COMPACTED FILL DETAIL B NO.: DATE: Q5-48?SdWt-00-00: FIQURE: JULY 1988'1 6 " FINISH SURFACE SLOPE - 3 FT3 MINIMUM PER LINEAL FOOT APPROVED FILTER ROCK* ~ _- COMPACTED FILL - 4. MINIMUM APPROVED PERFORATED PIPE** (PERFORATION8 DOWN) MINIMUM 2% QRADIENT 4. MINIMUM DIAMETER SOLID OUTLET PIPE TO OUTLET ENQINEER REQUIRE- DRAIN MENTS DURINQ QRADINQ TYPICAL BENCHINQ - SPACED PER SOIL BENCH INCLINED TOWARD I- DETAIL A-A /TEMPORARY FILL LEVEL I- - / ! COMPACTED 4. MINIMUM DIAMETER APPROVED SOLID 1- OUTLET PIPE ~ 12' MINIMUM COVER - .- I i 1- 12. MINIMUM F *FILTER ROCK TO MEET FOLLOWINQ SPECIFICATIONS OR APPROVED EQUAL - SIEVE PERCENTAQE PASSINQ - 'APPROVED PIPE TYPE: 1' 100 SCHEDULE 40 POLYVINYL CHLORIDE MINIMUM CRUSH STRENQTH 1000 PSI. 314. 80-100 318. 40-100 N0.4 2s-40 N0.30 N0.60 s-1s 0-7 N0.200 0-3 - (P.V.C.) OR APPROVED EQUAL. - - TYPICAL BACKDRAIN DETAIL JOB NO.: DATE: 06-4879-011-40-0@! FIQURE: JULY t08W. 6 FINISH SURFACE SLOPE MINIMUM 3 FT3 PER LINEAL FOOT OPEN QRADED AQQREQATE* TAPE AND SEAL AT CONTACT COMPACTED FILL SUPAC 8-P FABRIC OR APPROVED EQUAL 4. MINIMUM APPROVED PERFORATED PIPE 4. MINIMUM DIAMETER (PERFORATIONS DOWN) SOLID OUTLET PIPE MINIMUM 2% QRADIENT SPACED PER SOIL TO OUTLET ENQINEER REQUIREMENTS TOWARD DRAIN BENCH INCLINED BENCHING DETAIL A-A r TEMPORARY FILL LEVEL I 1 / MINIMUM BACKFILL COMPACTED 12" COVER MINIMUM 4. DIAMETER APPROVED SOLID OUTLET PIPE ktZUd *NOTE: AQQREQATE TO MEET FOLLOWINQ SPECIFICATIONS OR APPROVED EQUAL: SIEVE SIZE PERCENTAQE PASSINQ 1 112' 100 1. 314' 0-17 5-40 918" NO. 200 0-7 0-3 BACKDRAIN DETAIL (GEOFABRIC) OB NO.: DATE: - FIQURE: - " JULY lQ88, 7 f- SURFACE OF FIRM EARTH MATERIAL \ \ TYPICAL BENCHING REMOVE UNSUITABLE BEE DETAIL BELOW INCLINE TOWARD DRAIN """"" \ / MINIMUM 4. DIAMETER APPROVED PERFORATED PIPE (PERFORATIONS DOWN) MNIMUM e FT~PER LINEAR FOOT )F APPROVED FILTER MATERIAL 8. FILTER MATERIAL BEDDlNa :ILTER MATERIAL TO MEET FOLLOWINQ IPEClFlCATlON OR APPROVED EQUAL: llEVE SIZE 1. 314. 318' N0.4 N0.30 NO.60 N0.200 PERCENTAQE 100 80-100 40- 100 26-40 6-15 0-7 0-3 APPROVED PIPE TO BE SCHEDULE 40 POLY-VINYL-CHLORIDE (P.V.C.) OR APPROVED EQUAL. MINIMUM CRUSH STRENQTH 1000 pal PIPE DIAMETER TO MEET THE FOLLOWINQ CRITERIA. SUBJECT TO FIELD REVIEW BASED ON ACTUAL QEOTECHNICAL CONDITIONS ENCOUNTERED DURING QRADINQ LENQTH OF RUN PIPE DIAMETER UPPER 600' 4. NEXT 1000' 8. > 1600' 8. TYPICAL CANYON SUBDRAIN DETAIL OB NO.: os-4879-011-00-00 DATE: JULY 1988 FIQURE: 8 CANYON SUBDRAIN DETAILS SURFACE OF FIRM EARTH """" f / / TYPICAL BENCHINQ REMOVE UNSUITABLE MATERIAL INCLINE TOWARD DRAIN 8EE DETAIL8 BELOW TRENCH DETAIL 8' MINIMUM OVERLAP > OPTIONAL V-DITCH DETAIL rMlNlMUM 0 FT3 PER LINEAL , FOOT OF APPROVED DRAIN MATERIAL 8UPAC 8-P FABRIC BUPAC 5-P FABRIC OR APPROVED EQUAL """ 8. MINIMUM OVERLAP MINIMUM MINIMUM 0 FT3 PER LINEAL FOOT OF APPROVED DRAIN MATERIAL 8PECIFICATION OR APPROVED EQUAL: DRAIN MATERIAL TO MEET FOLLOWINQ ADD MINIMUM 4. DIAMETER SIEVE SIZE PERCENTAQE PA881NQ LE88 THAN 2% APPROVED PERFORATED PIPE WHEN QRADIENT I8 1 112' 88- 100 1. 314' 318' N0.200 5-40 0-17 0-7 0-3 APPROVED PIPE TO BE SCHEDULE 40 POLY-VINYL- CHLORIDE (P.V.C.) OR CRU8H BTRENQTH 1000 pal. APPROVED EQUAL. MINIMUM GEOFABRIC SUBDRAIN OB NO.: O6-487@-0t~-80-00 . DATE: JULY teae 4 9 FIQURE: FINAL NATURAL SLOPE LIMITS OF FINAL EXCAVATION TOE OF SLOPE SHOWN ON QRADINQ PLAN COMPETENT EARTH MATERIAL MINIMUM DOWNBLOPE KEY DEPTH PROVIDE SACKDRAIN AS MENDATIONS OF SOILS REQUIRED PER RECOM- ENQINEER DURINQ QRADINQ WHERE NATURAL SLOPE QRADIENT 18 6:1 OR LESS. BENCHING 18 NOT NECESSARY. HOWEVER. FILL IS NOT TO BE PLACED ON COMPRESSIBLE OR UNSUIT- ABLE MATERIAL. GENERAL GRADING RECOMMENDATIONS CUT LOT ,,-"ORIQINAL QROUND TOPSOIL, COLLUVIUM AND WEATHERED BEDROCK,,/.. LOVEREXCAVATE AND UNWEATHERED BEDROCK REQRADE CUTlFlLL LOT (TRANSITION) LOVEREXCAVATE AND /COLLUVIUM AND , TOPSOIL. REQRADE WEATHERED 00 UNWEATHERED BEDROCK BEDROCK 0 TRANSITION LOT DETAIL DATE: OB NO.: 06-4879-011-00-00 JULY lO88: FIQURE: 12 BUILDING FINISHED QRADE CLEAR AREA FOR FOUNDATION. UTILITIES. AND SWIMMINQ POOLS 0 0 Ow0 WINDROW So OR BELOW DEPTH OF (WHICHEVER QREATER) DEEPEBT UTILITY TRENCH TYPICAL WINDROW DETAIL (EDGE VIEW) QRANULAR SOIL FLOODED TO FILL VOIDS \ HORIZONTALLY PLACED COMPACTION FILL / I .' / / / / / / / / / PROFILE VIEW ROCK DISPOSAL DETAIL OB NO.: DATE: - ste-011-00-00 JULY leea >'>, FIQURE: 13