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HomeMy WebLinkAboutGeotechInvestigation(Dec.16,1988)' ' I , I ' ' I~ ~ ~ ' Converse Consuitants Iniand Empire Consulting Enginee~s and Geologists 630 East Brier Drive, Suite 100 San Bemardino. Califomia 92408 Telephone 774 /889~8004 FAX 714 889-4830 ~- ^ V ~'~~lC'•j '~ ~~~ ~ D ~` OCT20 i989 Rlvt: .._ ~:OUNi't . JAD ~?FP; . P~Ai~; CHECI( GEOTECHNICAL INVESTIGATION TENTATIVE TRACT 24136 PLANNING AREA 8 PORTION OF THE MEADOWS RANCHO CALIFORNIA, CALIFORNIA PREPARED FOR Rancho California Development Company Post Office Box 755 28250 Ynez Road Rancho California, California 92390 CCIE Project No. 88-81-148-O1-B December 16, 1988 A Wholly Owned Subsidiary ol 1 ~ Converse Consultants Inland Empire Consulting Engineers and Geologisis , 1 ' ~ , ' , ~ ' ' , ' ~ 630 East Brier Drive. Suite ~00 San Bemartlino, Califomia 92408 Telephone 714 /889~8004 FAX 714 889-4830 ~ December 16, 1988 Rancho California Development Company Post Office Box 755 28250 Ynez Road Rancho California, California 92390 Attention: Mr. Csaba F. Ko Subject: GEOTECHNICAL INVESTIGATION Tentative Tract 24136 Planning Area 8 Western Portion of "The Meadows" Rancho California, California CCIE Project No. 88-81-148-O1-B Gentlemen: Enclosed are the findings of our geotechnical investigation performed for Planning Area 8 which is a portion of The Meadows Master Planned Community in Rancho California, California. A preliminary "Slope Stability Analysis" letter dated December 5, 1988 was written for this tract to expedite the County submittal process. Subsurface materials encountered in the exploratory excavdti0ns generally consisted of toose to medium dense granular sediments and soft sandstone bedrock of the Pauba Formation. Groundwater was not encountered in the exploratory borings. , Results of our investigation indicate that the site is suitable for the proposed residential development, provided that the recommendations contained herein are incorporated into final development plans. Development of the tract will involve ' conventional mass grading. Anticipated depths of overexcavation in proposed fill areas are indicated on the enclosed maps and ' ' ~I A Wholly Ownetl Subsitliary o~ The Converse Professonal Group ~ t Rancho California Development Company CCIE Project No. 88-81-148-O1-B December 16, 1988 ' Page 2 discussed in the appropriate sections of this report. Con- ' ventional 2:1 (horizontal to vertical) cut and fill fill slopes are proposed, with structure setbacks as recommended herein. , Spread footings may be used to support the proposed residential I structures. We appreciate this opportunity to be of service. If you have any ~ . questions, please feel free to contact the undersigned or Mr. David Simon. , Very truly yours, CONVERSE CONSULTANTS INLAND EMPIRE 1 ~~.~,~~,~~. obert M. P ide, E 697 , President RMP/DBS/TC6:88aa ' Dist: 5/Addressee 1/Robert Bein, William Frost and Associates ' 1/Dr. Roy J. Shlemon ~ , ' Converse Consultanls ~nland Empire ~ i , I' , ' ' , , `S'~~R£D Gfp O ~c,~~~B.s~~c ~ Q' N0.1400 0 ~ CERTIFIED 2 * ENGINEERING GEOLOGIST ' ~ ~9TF~F CAI~E~~~~ ~ • n . G~.t.-ZJ/ ' avi . Simon, G 1400 Senior 6eologist ' PROFESSIONAL REGISTRATION For: CCIE Project No. 88-81-148-O1-B Dated: December 16, 1988 This report has been prepared by the staff of Converse Consultants Inland Empire under the professionai direction of the Senior Geologist and Project Engineer whose seals and signatures appear hereon. The findings, recommendations, speci- fications or professional opinions are presented, within the limits prescribed by the client, after being prepared in accordance with generally accepted professional engineering and geologic practice. There is no other warranty, either express or implied. ~ Converse Consultants Inland Empire ~ Project Engineer , , TABLE OF CONTENTS GEOTECHNICAL INVESTIGATION ' PORTION OF THE MEADOWS RANCHO CALIFORNIA, CALIFORNIA CCIE PROJECT No. 88-81-148-O1-B ' Page , . 1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . 1 2.0 PROJECT DESCRIPTION . . . . . . . . . . . . . . . . . . . . 3 I ' 2.1 Existing Site Conditions : : . . . . . . . . . . . . . 3 2.2 Proposed Development . . . . . . . . . . . . . 3 ' 3.0 SCOPE OF INVESTIGATION . . . . . . . . . . . . . . . . . . . 4 3.1 Site Reconnaissance . . . . . . . . . . . . . . . . . . 4 3.2 Field Exploration . . . . . . . . . . . . . . . . . . . 4 ' 3.3 Laboratory Testing . . . . . : : : : : : : : : : : : 5 3.4 Research, Analyses and Report. 5 4.0 SITE GEOLOGY . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1 Earth Materials. . . . . . . . . . . 6 4.1.1 Pauba Formation (Map Symbol Qp) . . . . . . . . 6 4.1.2 Colluvium (Map Symbol Qcol) . . . . . . . . 6 4.1.3 Recent Alluvium (Map Symbol Qal). . . . . . . . 7 4.1.4 Topsoi 1 . . . . . . . . . . . . . . . . . . . . 7 4.2 Groundwater. . . . . . . . . . . . . . . . . 7 4.3 Faulting and Seismicity . . . . . . . . . . . . . . . . 7 4.4 Subsurface Variations . . . . . . . . . . . . . . . . . 9 5.0 CONCLUSIONS AND TRACT DEVELOPMENT CONSIDERATIONS. ..... 10 6.0 EARTHWORK/SITE GRADIN6 RECOMMENDATIONS. . . . . . . . . . . il 6.1 General. . . . . . . . . . . . . . . . . . . . . 11 6.2 Removals/Overexcavation . . . . . . . . . . . . . . . . 11 6.3 Subdrains. . . . . . . . . . . . . . . . . . . . 12 6.4 Permanent Cut Slopes . . . . . . . . . . . . . . . . . 13 6.5 Permanent Fill Slopes. . . . . . . . . . . . . . . 13 6.6 Temporary Sloped Excavations . . . . . . . . . . . . . 14 6.7 Utility Trench Backfill . . . . . . . . . . . . . . . . 14 6.8 Shrinkage and Subsidence . . . . . . . . . . . . . . . 15 6.9 Site Drainage. . . . . . . . . . . . . . . 15 6.10 Slope Protection and Maintenance . . . .~. . . . . . . 15 6.11 Asphalt Pavements . . . . . . . . . . . . . . . . . . . 16 7.0 STRUCTURAL DESI6N RECOMMENDATIONS . . . . . . . . . . . . . 18 7.1 Residential Foundation Design Criteria . . . . . . . . 18 7.2 Slabs-on-Grade . . . . . . . . . . . . . . . . . 19 7.3 Appurtenant Facilities . . . . . . . . . . . . . . . . 19 7.4 Corrosivity . . . . . . . . . . . . . . . . . . . . . . 19 Converse Consultants Inland Empire ~ , , Table of Contents CCIE Project No. 88-81-148-Oi-B Continued - ' Page ' 8.0 GEOTECHNICAL SER~ICES DURING CONSTRUCTION . . . . . . . . . 20 9.0 CLOSURE . . . . . . . . . . . . . . . . . . . . . . . . . . 21 ' REFERENCES ' Drawing 1 "Geologic Map" Drawing 2"Tentative Tract Geologic Map" ' Appendix A - Field Exploration Appendix B- Laboratory Test Program Appendix C- Recommended Earthwork Specifications ' Appendix D - Stability Analyses ~ ' ' ~ ~ ' ' ' ' ' ' Converse Consultants Inland Empire ~ 1.0 INTRODUCTION This report presents the findings of our geotechnical investigation applicable to tentative tract 24136 which is a portion of the western 707 acres that comprise The Meadows Master Planned Cortrtnunity at Rancho California. The 707 acres are located south of Pauba Road, north of California State Highway 79, east of Margarita Road and west of proposed Buecking Parkway. Tentative Tract 24136 encompasses approximately 99.8 acres of The Meadows project as shown on the site Location Map, Figure 1. The purpose of this investigation was to evaluate subsurface conditions and pertinent engineering properties of the encountered materials such that recommendations regarding general site grading, slope stability and pre- liminary foundation design criteria can be provided for submittal of eight Tentative Tract Maps to the County of Riverside. Converse Consultants Inland Empire (CCIE) performed a concurrent investigation to evaluate the lique- faction potential at the southerly portion of the tract (Converse, 1988). It is our understanding that the subject tract will be developed according to i' Specific Plan 219, The Meadows at Rancho California, dated September 6, 1988. We understand that the proposed development of "The Meadows" will consist of a ', ' combination of residential, commercial, schools, a neighborhood park, Day Care Center, greenbelt areas and an extensive circulation road network within the ' comprehensive plan. Vesting Tentative Tract Map 24136, addressed herein will be developed exclusively for residential use. Pertinent geologic and geotechnical data generated from this investigation of the 707 acre western portion of The Meadows project together with the location of explorations are shown on Drawing 1, titted "Geologic Map" (pocket). 1 Converse Consultants Inland Empire ' 7 _. `_._ __ _ .'( ' /~~~0 I ~~Y / ' ~ ~~~'~~~ .`-~ i\x°°~.~; D~`ti:11 N \ ~/~~ / ~~.~-ti°~ ~~ ~ ~~,%~ ~ ~fi ~•'~... ~/ ~~~ ~,J ~~( ~b !' ~'~~ ~~ j`JJ •l ~~~ til~. / ~~ I ° ~1 I'1/i I•iy ~ ~ A~ J i ~ (`I ~ ~ J/~ ~~ ' ~( ti~ ~~ f v~~~ ~~~r ~~"\ \%~ J/nr i~~ rL r ~ ~ r (~ r/ ~~~. ~~ o ~ui,.l~'.. 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'qc -' ~ ~ ~ ~1n ~ ~ i~ A . ~/ '~ ~ \ ~/~ \lMEN(~3~~~~ 1 4~9I~~~</\~~1`\~\~1~ ~ I 1 ~~_~_~ ~ •.~- \ ~ \ ^~` _'!.. / ~ 1 \~ ~ , a, ~--, ~ ~ ~,_ , , E;I ;a • ,~'' ~~x~i,=' ~~~,~ ~ ~;y; ~ ~ o ~ '~~ ``~" ~~~•_.>r; ~ ~ .= u,~~~~ ~ =~~ d U ell -N. ~y~ : ~ i (~ ~ ( il ~ ~ ~ )l ~ ~ ~ ; ~ ry ~ \ J ^ ~~(~ , ^ ~ ~ ~~ ~ l ~ (~~ '/~. % ~ _ ~ ~`~. .~ ~A AI ' 11/~ ~/ \~~~~ ~O/ O :.{~ / ~ \~\I\-~ ~\ 'BOI) \~-1' ~ T ~ ( ~ \~ y/ f •~ / ~~ ~/~ti' Y ~ L / ~ ' ~ ~ . ~'(~41~ r ' ' "I'n « `~ ~y~,,,~ ~._ y~.~'~ ~~ /~~_.~ ~.... ~ ~ ~~ : Wel1~ . /j~ ... ~ 1: _ . n ~ ~ ~ ~, ~ 'o REFERENCE: W ° Alquist-Priolo Special Studies Zone Map ~ Pechanga Quadrangle, California Division 0 2000 = of Mine and Geology, Janua 1 1980 ~ o ry r 3CALE IN FEET 0 ~ SITE LOCATION MAP WESTERN PORTION OF "THE MEADOWS" ProjeclNa. •' Rancho California, CalifoP"nia 88-81-148-O1 for: Rancho California Development Company .--..~ .__.-- .. _ . - ~ Fi9ure No. . d- =... _ ' ~' ' 'Converse C.onsuitants Inland Empire .. i 'b ~ ~-_ ~_ ,.~.. _ 0 ~JP.i ~ i .~ i " • ~ .~~~ ~ ,' ~ ~- - \,<, ~~----~. ~ ~ ` ^--'~ \ ~~~ ~~ ~ ~~~ f: ~ ~\ _ ` l _!~~ ~~~ ~ J~ ~ z?` ~'~-, <`~ Ja a r~~ '~b,~~~ ~\\/ 2.0 PROJECT DESCRIPTION 2.1 Existing Site Conditions Tentative Tract 24136 is located within the west-central region of The Meadows DeVelopment. The approximately 99.8-acre site is bounded on the north by the undeveloped Tentative Tract Nos. 24131, 24133, and 24135; on the east by an undeveloped hilly region scheduled to become Tentative Tract No. 24184; on the south by a south sloping region which is scheduled to become Tentative Tracts 24130, and 24137; and on the west by an existing residence and the proposed Joan F, Sparkman Elementary School, both of which are fronted on Margarita Road. Currently, the site is characterized by several hills, with a drainage running along the northwestern boundary of the tract draining southwest, and a minor "Y" shaped drainage draining south in the south-central region of the tract. In general, the site topography slopes down from the northeast to the southwest with as much as 170 feet of relief across the site. Site elevations range from approximately 1,237 feet (lot 33), to elevation 1,067 feet (lot 149). The site has a moderate growth of weeds, shrubs, and grasses, with occasional barbed wire fences traversing the site. In general, the site has not been previously developed. 2.2 Proposed Development Based upon Tentative Tract Map 24136, provided by Robert Bein, William Frost and Associates, dated December 4, 1988, (scale 1" = 200' ), site earthwork, exclusive of any potential overexcavations, is anticipated to consist of cuts on the order of 70 feet (Lot 33) and fills on the order of 32 feet in thickness (Lot 237). This map was used as the base map for Drawing 2, Tentative Tract Geologic Map (pocket). As depicted on Drawing 2, 400 residential lots are proposed. Slopes on the order of 30 feet in height are proposed. No retaining walls are anticipated. For the purposes of this report, it is assumed that the residential structures will consist of one to two story wood frame single family homes. All of the proposed homes are assumed to have concrete slabs-on-grade, without basements. ~ 88-81-148-O1-B 3 Converse Consultants Inland Empire 1~ ' 3.0 SCOPE OF INVESTI6ATION 3.1 Site Reconnaissance Our geologist performed a site reconnaissance of the property for mapping of geologic units and pertinent surficial features (Drawings 1 and 2). Aerial photographs of the site vicinity were examined stereoscopicaliy to assist the geologic reconnaissance. A set of aerial photographs was obtained from Riverside County Flood Control District taken in 1983 (see references). 3.2 Field Exploration A total of 23 exploratory boring and 55 exploratory trenches were excavated within the 707 acres that comprise the western portion of The Meadows investigated. Borings were drilled using a bucket auger drill rig and the trenches were excavated using a rubber-tired backhoe. All excavations were visually logged by our field personnel who carefully described the materials encountered. Selected borings were entered by a CCIE geologist who carefully observed and documented the exposed materials. ' Relatively undisturbed and bulk samples of representative materials i encountered were obtained from the borings. A description of the field ' , exploration and sampling program are presented in Appendix A. , Approximate locations of the exploratory borings and trenches excavated for the 707-acre por tion of The Meadows project are shown on Drawing 1. ' Approximate locations of the exploratory borings and tren ches within Tentative Tract 24136, as well as exploratory excavations within immediately adjacent , tracts utilized for this analysis of Tentative Tract 24136, are shown on Drawing 2. ' ' ' \O ~ 88-81-148-O1-B 4 Converse Consultants Inland Empire ' ! ' 3.3 Laboratory Testing Samples were tested in the laboratory to aid in the classification and to I' determine certain engineering properties of the site soils and bedrock. These tests include: I, o in-situ dry unit weight and moisture content; • maximum density and optimum moisture curves; • direct shear tests; ', ' . • moisture sensitivity (collapse) tests; • consolidation tests; • R-value test; and ' • pH, resistivity, and soluble sulfate and chloride testing. ' A description of the laboratory test methods and test results are presented in Appendix B, Moisture and density data are presented on the boring summary sheets of Appendix A. ' 3.4 Research, Analyses and Report In addition to pertinent published geologic literature concerning rock units of the area, unpublished geotechnical reports were also reviewed, particularly those of Pacific Soils Engineering, Inc. (1987a, 1987b, 1987c). Pertinent publications reviewed for this investigation are included in the list of references. This report was written to present the findings of this geotechnical investi- gation for the tentative tract, and to provide recommendations for the proposed development. Based upon the field and laboratory findings, slope stability analyses were performed, as presented in Appendix D. ~~ 88-81-148-O1-B 5 Converse Consultants Inland Empire 4.0 SITE GEOLOGY A general description of the subsurface conditions and various materials encountered at the site during field exploration is presented in this section. Also, a discussion of site specific geologic hazards is presented below. 4.1 Earth Materials The site is underlain by bedrock materials of the Pauba Formation, colluvium, and alluvium. These, in turn, are locally mantled by a thin veneer of topsoil. Areal distribution of the earth materials is shown on the geologic maps (Drawings 1 and 2), and these materials are described below from geologically oldest to youngest. 4.1.1 Pauba Formation (Map Symbol Qp): The Pauba Formation of late- Pleistocene age (Kennedy, 1977) underlies the site. In general, the formation consists of distal alluvial fan and braided channel deposits, with numerous intra-formation unconformities. Sedimentary features characteristic of the depositional environment such as channel lag, scour and fill and cross-bedding were observed in trench and boring exposures. Within the subject site, lithology of the Pauba Formation is highly variable, consisting of poorly interbedded to massive, moderately to well consolidated, fine to coarse sandstones. The sandstones are alluvial channel-type deposits with lenses of gravelly sandstone, siltstone and silty claystone. ' Bedrock structures within the Pauba Formation can vary over a relatively short distance. Bedding attitudes recorded at the site indicate strikes ' being roughly east-west, with dips to the south at 5° to 10°. Numerous horizontal and gradational bedding boundaries,were also observed. ' 4.1.2 Colluvium (Map Symbol Qcol): Colluvial materials were encountered ' within the northeastern region of the tract, as shown on Drawing 2. These materials were classified as silty sand with minor amounts of sandy ~v ' 88-81-148-O1-B 6 Converse Consultants Inland Empire silt. The colluvium was dry to slightly moist, loose to medium dense or firm, and contained numerous rootcasts and pinhole voids. 4.1.3 Recent Alluvium (Map Symbol Qal): Recent alluvium was encountered within the drainage channels as shown on Drawings 1 and 2. These materials were classified as silty sand, sand, and sandy silt. The alluvium was dry to moist, loose to medium dense, and contained numerous root casts and pinhole voids. 4.1.4 Topsoil: Topsoil materials mantled the majority of the site and ranged in thickness, where observed, from 1 to 1 1/2 feet. These soils, not differentiated on the geologic maps, consist of silty sands, are generally loose to medium dense and contain numerous root casts and pinhole voids. , 4.2 Groundwater Groundwater was not encountered in the exploratory borings drilled within Tentative Tract 24136. 4.3 Faulting and Seismicity A site-specific fault investigation (which included 4,000 feet of fault trenching) was performed for the 1,377 acres that comprise The Meadows project by Pacific Soils Engineering (1987b). Other faults or possible fault-related features in addition to those documented in the Pacific Soils Engineering Investigation (1987b) were not observed during field exploration, reconnaissance or analysis of aerial photographs. The findings of the Pacific Soils Engineering study (1987b) indicate that the faults within The Meadows project do not displace Holocene-age (about 11,000 years before present) sediments. As such, according to the California Division of Mines and Geology (CDMG), these faults, are not considered active, and building restrictions are not mandated. , In swmnary, there are no known active faults trending towards or through the site. Also, the subject tract is not situated within a currently designated State of California Alquist-Priolo Special Studies Zone (see Figure 1 for regional active fault). ~~ 88-81-148-O1-B 7 Converse Consultants Inland Empire , ' During our concurrent liquefaction investigation (Converse, 1988), major faults within a 100-km (62-mile) radius of the site were considered in regard ' to generating significant ground shaking at The Meadows project. The faults in Table 4-2 are those most likely to cause ground shaking at the site in case ' of a major earthquake [Richter magnitude (M) greater than 6.0]. Table 4-2 also summarizes important seismic characteristics for each causative fault. ' TABLE 4-2 ' SEISMIC CHARACTERISTICS OF RECIONAL FAULTS HORIZONTAL GROUND MOTION - PARAMETERS MINIMUM MAXIMUM* AXI U P D I t ' SITE CREDIBLE GROUND OF STRONG DISTANCE MACNITUDE ACCELERATION SHAKINC FAULT (mi) EARTHOUAKE (g) (seconds) Elsinore 7 1/2 7.5 0.63 25 - 35 ' (Wildomar Branch) San Jacinto 20 7.5 0.30 23 - 32 t Whittier 33 7.5 0.10 21 - 30 San Andreas (South) 36 7.5 0.17 20 - 25 ~~ ' E1 Modena 43 6.5 0.07 5- 10 San Andreas (Central) 43 8.25 0.21 18 - 25 !' Peralta Hills Sierra Madr (C amo a) 46 59 6.5 7 0 0.07 0 08 4- 8 7- e uc ng . . 11 Norwalk 55 6.5 0.05 c5 * From Greensfelder (1974). ** From Seed and Idriss (1982). t From 8olt (7973). As is the case for most regions of Southern California, groundshaking resulting from earthquakes along nearby and distant faults will occur. During the life of the project, seismic activity associated with active faults in the region (particularly the Elsinore, San Jacinto and San Andreas Fault Systems) may generate moderate to strong ground shaking at the site. The occurrences of ground acceleration during an average 100-year and 50-year period were calculated for the site area as part of the liquefaction 88-81-148-O1-B 8 ~ Converse Consultants Inland Empire investigation (Converse, 1988). Probable maximum horizontal ground accelera- tions are 0.29g once on the average every 100 years and 0.23g once on the average every 50 years. 4.4 Subsurface Variations Based on the results of our subsurface exploration and experience, variations in the continuity and depth of subsoil and bedrock deposits should be anticipated. Due to the nature and depositional characteristics of the natural soils at the site, care should be exercised in interpolating or extrapolating subsurface conditions between or beyond test borings and trenches. Variations in groundwater levels can be expected due to seasonal changes, or artificial changes such as variable regional irrigation, changes in groundwater pumping, and/or variations in the Vail Lake Reservoir downstream discharge. / ~~ 88-81-148-O1-B 9 Converse Consultants Inland Empire 5.0 CONCLUSIONS AND TRACT DEVELOPMENT CONSIDERATIONS The results of this investigation indicate that Tentative Tract 24136 is suitable for its intended usage and may be developed as planned. As depicted on Figure 2, lots with fill thickness of 32 feet are proposed, and lots which transition from cut to fill are also proposed. Of geotechnical concern for this project is the potential for differential settlement due to the variable fill thicknesses proposed to underly the various pads. Much of the residential distress which occurs in hillside graded lots is due to changes in moisture in the fill mass. Therefore subdrains should be installed as depicted on Figure 2. Also landscape irrigation and surface drainage should be controlled and provided such that the fill mass does not become excessively moist or wet. Any appurtenant structures such as swimming pools, retaining walls, grade changes and/or landscaping irrigation systems should be designed such that these changes do not adversely affect the graded lot stability or drainage. Therefore, it is strongly recommended that these changes be reviewed by CCIE or an experienced Geotechnical Engineer and/or Certified Engineering Geologist. These tract development considerations are described further in the following sections. ~, t Design recommendations are presented below for earthwork/site grading and structural design, for the development proposed on Drawing 2. Recommendations , for additional geotechnical services, to be performed after this report has been approved by appropriate governing agencies, are also provided. , ~ ~ ~ I _l ~~ , 88-81-148-O1-B 10 Converse ConsuMants Iniand Empire ' ' 6.0 EARTHWORK/SITE GRADING RECOMMENDATIONS ' ~ 6.1 General I' Site grading is expected to consist of cuts, removals and fill operations to _ prepare building pad areas. Cuts on the order of 70 feet (lot 33) are proposed. Maximum fills are expected to be on the order of about 32 feet (lot ' ' 237), based on site grade information as depicted on Drawing 2. Grading is also expected to include backfill for utility trenches. Loose backfill II ' exploratory trenches located throughout the site will require overexcavation and recompaction prior to the placement of structural fills. See Drawing 1 ' for approximate locations of trenches. All fill should be placed in accordance with the recommendations presented in Appendix C, titled ' "Recommended Earthwork Specifications". All structural fill should be compacted to at least 90% relative compaction (ASTM D1557-78). To reduce the potential for differential settlement across cut/fill transition lots, the cut portion of the lot should be overexcavated 3 feet below final grade. A fill zone "buffer" should then be backfilled to finish grade. All fill should be properly benched into firm and unyielding native bedrock materials, which are expected to consist solely of the Pauba Formation. In areas where fill is to be placed above cut slopes, the fill slope should be keyed into the firm and undisturbed bedrock, as discussed in Appendix C, and depicted on Drawing C-2, titled "Typical Fill Above Cut Slope". '~ Grading recommendations for removals, subdrains, permanent slopes, temporary sloped excavations, utility trench backfill, and site drainage are presented I~ below. Stability calculations for the anticipated slopes are presented in I Appendix D, "Stability Analyses". '- 6.2 Removals/Overexcavation I, All surface trash and vegetation (including, but not limited to, heavy weed growth, trees, stumps, logs, and roots) should be removed from the areas to be ~~ graded. Organic materials resulting from the clearing and grubbing operations ~ ~~ ' 88-81-148-O1-B 11 Converse Consultants Inland Empire ' ~i ' should be hauled off the site. Non-organic debris from site clearing may be hauled off site or stockpiled for crushing and/or placement by approved j~ methods in deeper fill areas. i' Removal of all topsoil, and loose shallow alluvium and/or disturbed bedrock (such as the shallow collapsible silty sands in ravines) will be necessary prior to placement of structural fills. Although not encountered in CCIE ' ' explorations, any existing fill should be excavated. Recommended removal depths are depicted on Drawing 2 in triangles adjacent to the explorations, ' and discussed below: ' • Ravine Areas: Removal depths will vary from 2 to 10 feet, with possible ocal-Tiie~areas of deeper removals. • Areas to Receive Fill Outside of Ravine Areas: Removal depths will , genera y vary rom 3 to 5 eet, wtt possib e ocatized areas of deeper colluvial removals. The topsoil/slopewash may be removed by stripping, heavy benching during grading, or a combination of both stripping and ' benching. • Ex loration Trenches: All exploratory trenches were loosely backfilled an wi require overexcavation and recompaction for new improvements I, support. Approximate locations of the trenches are shown on Drawing 1. ' The bottom of the excavated areas must be observed by a CCIE representative prior to placement of new fill. Soils removed during the overexcavation ' procedures may be utilized as compacted fill, provided they have been stripped of organics and other deleterious materials. All proposed fills should be placed on competent native materials as determined in the field by a CCIE , representative and in accordance with the specifications presented in Appendix C, titled "Recommended Earthwork Specifications". I , 6.3 Subdrains I, ' A subdrain should be installed within the northwesterly ravine area, sub- sequent to alluvial removals and prior to fill placement. Discharge from this ~, subdrain should be directed to the existing storm drain located along proposed Pio Pico Road. A typical subdrain detail is provided in Appendix C. Subdrains should generally be installed where shown on Drawing 2, but may be ,' modified by the Certified Engineering Geologist and project Civil Engineer, ~I ' 88-81-148-O1-B 12 ~ Converse Consultants Inland Empire based upon post removal observations. All subdrain devices should be accurately located by the project Land Surveyor. 6.4 Permanent Cut Slopes Permanent cut slopes up to 35 feet are anticipated (lot 277). As shown in Appendix D, cut slopes in the encountered materials not exceeding 35 feet in height and cut no steeper than 2:1 (horizontal:vertical) have a calculated factor-of-safety (FS) greater than 1.5. Cut slope ratios should not be steeper than 2:1 (horizontal:vertical). A primary concern for cut slopes on this site is the high potential for erosion of the sandy material, and the resultant surficial instability. Structures should be set back from slopes as shown on figure 29-1 of the 1988 Edition of the Uniform Building Code (UBC). ' Cut slopes should be observed during grading by a Certified Engineering Geologist (CEG) to determine if any adversely oriented planes of weakness ' (i.e., claystone or sittstone beds) are exposed. If these materials are exposed in a proposed cut slope during grading and are found to be adversely oriented, a buttress or stabilization fill may be required. 6.5 Permanent Fill Slopes Proposed fill slopes should be constructed with slope ratios no steeper than 2:1 (horizontal:vertical). fill slopes in excess of 35 feet in height are not anticipated. Fill slopes should be properly compacted out to the slope face. This may be achieved by either overbuilding and cutting back to the compacted core, or other methods which meet the intent of the project specifications. Assuming that fill slopes are properly compacted to the slope face, are graded no steeper than 2:1 (horizontal:vertical) and are no taller than 35 feet in height, the calculated factor-of-safety for compacted fill slopes is greater than 1.5. Fill slopes higher than 30 feet should be terraced as recommended in Section 7012 of the Uniform Building Code (1988 Edition). Structures should be set back from graded slopes in accordance with Chapter 29 (UBC Figure 29-1) of the Uniform Building Code (UCB), Where fill is proposed over cut slopes, fill should be benched into the bedrock as shown on Drawing C-2, in Appendix C. ~` 88-81-148-O1-B 13 Converse Consultants Inland Empire ' 6.6 Temporary Sloped Excavations The use of sloped excavations may be applicable where plan dimensions for ' excavation are not constrained by property lines, existing streets, or other structures. Where constraints exist, temporary shoring or e combination of ' slopes and shoring will be required. Recommendations for shoring design will be presented separately from this report, if requested. Excavations adjacent to existing roadways should not undercut the existing embankments. Based upon soils encountered in the test borings, it is our opinion that sloped temporary excavations may be made according to the slope ratios presented in the following table. TEMPORARY EXCAVATION SLOPES MAXIMUM DEPTH OF CUT MAXIMUM SLOPE RAT10* (ft) (horizontal:vertical) 0- 5 vertical to 1/2:7 5- 75 3/4:1 to 1 1/4:1 75 - SO 1.5:1 to 2:1 * Selection of temporary slape ratios should 6e made by the grading co~tractor based on act~al materials encountered during excavation. Slope ratios given above are assumed to be uniform from top to toe of slope. Sandy surfaces exposed in sloped excavations should be kept moist but not saturated to retard ravelling and sloughing during construction. Adequate provisions should be made to protect the slopes from erosion during periods of rainfall. Surcharge loads should not be permitted within 10 feet of the top of slope, or at least one-third the slope height. 6.7 Utility Trench Backfili Buried utility conduits should be bedded and backfilled around the conduit in accordance with the project specifications. Materials may be flooded/jetted_ around large-diameter pipelines, below the spring line. Care shouid be taken ' 88-81-?48-O1-B 14 ~ Converse Consultants Inland Empire not to move or damage utilities during compaction operations. Where conduit underlies concrete slabs-on-grade and pavement or is adjacent to proposed structures, the remaining trench backfill above the conduit should be placed and compacted in accordance with Appendik C. 6.8 Shrinkage and Subsidence Based on our test results, an average shrinkage value of 8% is considered appropriate to estimate the loss in volume during recompaction of existing loose shallow soils. However, shrinkage due to recompaction may vary from negligible to 17% by volume. Volume losses due to stripping of organics should be included during the calculations of earthwork quantities. Sub- sidence due to construction equipment activity will range from about 0.1 to 0.3 foot. These estimates are based upon the assumption that all removals and compaction is performed as recommended herein. 6.9 Site Drainage Adequate positive drainage should be provided away from structures to prevent ponding and to reduce percolation of water into the foundation soils. A desirable slope for surface drainage is 2% to 4% in landscaped areas and 1% to 2% in paved areas. Planters and landscaped areas adjacent to the building perimeter should be designed to minimize water infiltration into the subgrade soils. Gutters and downspouts should be installed on the roof, and runoff should be directed to the street through non-erosive devices. Surface drainage should be directed to suitable non-erosive devices. Slope drainage devices should be constructed in accordance with Chapter 70 of the Uniform Building Code (1988 Edition). Lot drainage should preclude the possibility of flow over slope faces, with the use of brow ditches, earth berms and other methads. 6.10 Slope Protection and Maintenance Proposed slopes should be planted as soon as possible after construction. Slopes will require maintenance through time to perform in a satisfactory manner. In most cases, lot and site maintenance can be provided along with normal care of the grounds and landscaping. Costs of maintenance is less expensive than repair resulting from neglect. 88-81-148-O1-B 15 ~ Converse Consultants Inland Empire Most hillside lot problems are associated with water. Uncontrolled water from a broken pipe, excess landscape watering, or exceptionally wet weather causes most damage. Drainage and erosion control are important aspects of slope stability and the provisions incorporated into the graded site must not be altered without competent professional advice. Terrace drains and brow ditches on the slopes should be periodically maintained and kept clear so that water will not overflow onto the slope, causing erosion. All subdrains should be kept open and clear of debris and soil which could block them. , Landscaping on the slopes should disturb the soil as little as possible and utilize drought resistant plants that require a minimum amount of landscape ' irrigation. Wet spots on or around the site should be noted and brought to the attention of the soils engineer. These may be natural seeps or an indication of broken water or sewer lines. , Watering should be limited or stopped altogether during the rainy season when ' little irrigation is required. Over-saturation of the ground can cause subsidence within subsurface soils. Slopes should not be over-irrigated. ' Ground cover and other vegetation will require moisture during the hot summer months; but, during the wet season, irrigation can cause ground cover to pull ' loose. This not only destroys the cover, but also starts serious erosion. It is suggested to consult a professional landscape architect for planting and _ irrigation recommendations. 6.11 Asphalt Pavements ' Asphalt pavement sections have been designed based on an R-value of 25. Final street structural sections should be provided by CCIE based on the actual soil ' conditions after grading. Based upon the CALTRANS Traffic Indexes (TI's) provided below, either full depth or composite ,asphalt and base pavement ' sections may be used as tabulated below: ASPHAIT PAVEMENT SECTIONS ' CALTRANS ASPHALT OVER BASE FULL DEPTH TRAFFIC INDEX in A P in ASPHALT (in) 4 4 2 1/2 5 , 5 6 3 6 1/2 6 7 4 7 1/2 7 11 4 9 ' 88-81-148-O1-B 16 Converse Consultants Inland Empire !~ In areas to support asphaltic pavement, the subgrade should be recompacted to a depth of at least one foot below the final subgrade as recommended in Appendix C. At the time of placing pavements, the subgrade should be firm and unyielding during proof rolling, and be within 2% to 3% of optimum moisture. All base material should be compacted to a minimum of 95% of the ASTM D1557-78 laboratory maximum dry density. Base course should consist of CALTRANS Class II aggregate base or equivalent. Placement of full depth asphalt will require that the compacted subgrade soils provide competent support for paving equipment. Clean cohesionless sands are subject to yielding under rubber tire and track loads from paving equipment. The paving contractor should confirm in writing the acceptability of the compacted subgrade prior to placement of full depth asphalt pavement. 88-81-148-O1-B 17 ~ Converse ConsuHants Inland Empire 7.0 STRUCTURAL DESIGN RECOMMENDATIONS 7.1 Residential foundation Desiqn Criteria Conventional spread footings, founded in properly compacted structural fill may be used to support the proposed residences. Footings should be set back at least 5 feet or one-third the slope height, whichever is greater, from the top-of-stope. Or footings may be embedded such that there is adequate setback between footings and the face of slopes. In any case, footings should have a minimum embedment of 12 and 18 inches below lowest adjacent grade for one and two stories, respectively. Residential footings should have a minimum width of 12 inches. Footings for one to two-story wood frame homes may be designed for an allowable bearing pressure of 1,500 pounds-per-square foot (psf). All continuous footings should be reinforced with at least #4 reinforcing bars top and bottom, along the full width of the footings to mitigate the potential for differential fill settlement. Additional reinforcement may be required by the project Structural Engineer. ' Structure settlement will be due to relatively light foundation loads, as well as long-term consolidation of fill soils and compressible native materials ' below the fill. Maximum anticipated structural load induced settlements of continuous residential footings, designed as recommended above, are 1/2 inch ' or less. Compacted fills will settle depending on the fill thickness and future changes in the "as-compacted" moisture conditions. For instance, 15 feet of properly compacted fill is expected to settle approximately an ' additional one to two inches if the soils are allowed to become saturated. These fill settlements should be considered in structural design. Residential structures lateral load resistance should be designed using Table 29-B of the 1988 Edition of the UBC, where residences are setback as recommended herein. Where reduced foundation setback is required, CCIE can evaluate structure specific cases, and provide appropriate passive resistance pressures for design. 88-81-148-O1-B lg ~ Converse Consultants Inland Empire 7.2 Slabs-on-Grade Conventional 4-inch minimum thickness slabs-on-grade may be constructed for support of nominal ground floor residential live loads. All slab subgrades should be moisture conditioned and compacted as recommended in Appendix C. Care should be taken to avoid slab curling if slabs are poured in hot weather. A mix design should also be provided to reduce the potential for shrinkage cracks. Slabs should be designed and constructed as promulgated by the Portland Cement Association (PCA). If non-expansive soils are imported (Expansion Index less-than 30), then the Structural Engineer need not design the slabs for expansive soils. Reinforcement should be provided as recommended by the Structural Engineer, and may include conventional, post-tensioned, or fiber reinforced slabs. ' If a moisture-sensitive floor covering sho ld b t t d b 6 il thi k (such as vinyl l th l tile) is used, slabs u e pro ec e y a -m c po ye y ene va por barrier. If the barrier is used, it should be protected with 2 inches of sand placed above and ' below to prevent punctures and to aid in the concrete cure. Vapor barrier seams should be lapped a minimum 6 incfies and sealed. 7.3 Appurtenant Facilities It is anticipated that residential lots will be customized, including home additions and construction of garden walls, pools, landscape ponds, retaining walls, general regrading, and modifications of landscaping. Any of these modifications may adversely change the foundation conditions, lot stability, and/or adversely affect adjacent lots. It is therefore strongly recommended that proposed lot modifications be reviewed by CCIE or an experienced Geotechnical Engineer and/or Certified Engineering Geologist. All homeowners should be made aware of the need for geotechnical evaluation of proposed foundation, grading, irrigation, and/or landscaping modifications. 7.4 Corrosivity , A bulk sample obtained from the exploration was tested for resistivity, pH, and soluble sulfate and chloride content. Relatively low sulfate con- centrations were measured, and therefore conventional Type I and II portland cements may be used. Relatively high resistivity and pH and low chloride content were also measured, which would indicate low corrosivity. Some variations over this large site should be anticipated. 88-81-148-O1-B 19 Converse Consultants Inland Empire ~~ ' , 8.0 GEOTECHNICAL SERVICES DURING CONSTRUCTION ' This report has been prepared to aid in evaluation of the site, to prepare ' site grading recommendations, and to assist the Structural Engineer in the design of the proposed structures. As indicated above, additional studies may be required for appurtenant structures. It is recommended that this office be , ' provided the opportunity to review the final design drawings and specifica- tions to determine if the recommendations of this report have been properly ' implemented. ' Recommendations presented herein are predicated upon the assumption that continuous earthwork monitoring will be provided by CCIE. Removal excavation ' bottoms should be observed by a CCIE representative. Structural fill and backfill should be placed and compacted during observation and testing by this office. Footing excavations should be observed prior to placement of ' steel and concrete to see that footings are founded on satisfactory soil and that excavations are free of loose and disturbed materials. ' ' ' ' ' ' ' ' ' ' 88-81-148-O1-B 20 Z~ Converse Consultants Inland Empire 9.0 CLOSURE The findings and recommendations of this report were prepared in accordance with generally accepted professional engineering and engineering geologic principles and practice. Our conclusions and recommendations are based on the results of the field and laboratory investigations, combined with an interpolation of subsurface conditions between and beyond exploration locations. Our continued consultation and construction monitoring will be necessary for the success of the project as the project evolves. CCIE should review plans and specifications to check if the recommendations presented herein have been appropriately interpreted, and that the design assumptions used in this study are valid. Where significant design changes occur, CCIE may be required to augment or modify the recommendations presented herein. Conditions may differ in some locations from those encountered in the explorations and may require additional analyses and possibly modified recommendations. This report was written for Rancho California Development Company, for the proposed development described herein, only. 88-81-148-O1-B 21 2~ Converse Consultants Inland Empire REFERENCES 88-81-148-O1-B ~ Converse Consultants Inland Empire ' PARTIAL LIST OF REFERENCES ' BOLT, B.A., 1973; "Duration of Strong Ground Motion," Proceedings on Fifth World Conference on Earthquake Engineering, V. 2, No. 292, p.10 , CALIFORNIA DIVISION ON MINES AND GEOLOGY, 1980; "Alquist-Priolo Special Studies Zone Map, Pechanga 7 1/2' Quadrangle". CONVERSE CONSULTANTS INLAND EMPIRE, December 9, 1988; "Liquefaction Investigation, The Meadows at Rancho California APN Nos. , 926-13-9, -10, -12, -13, and -14, Rancho California, California" (CCIE No. 88-81-148-02", ' DUNCAN, J.M., and Buchignani, A.L., March 1975; "An Engineering Manual for Slope Stability Studies", University of California, Berkeley, Department , of Civil Engineering. GREENSFELDER, R., 1974; "Maximum Credible Rock Accelerations from Earthquakes in California", California Division of Mines and Geology, Map Sheet 23. ' INTERNATIONAL CONfERENCE OF BUILDING OFFICIALS, 1988 Edition; "Uniform Building Code (UBC)". ' MARACHI, N.D., and DIXON, S.J., 1972; "A Method for Evaluation of Seismicity," Proceedings of the International Conference on Microzonation, Seattle, Washington. ' PACIFIC SOILS ENGINEERING, INC., May 5, 1987a; "6eotechnical Report for Environmental Impact Purposes, Butterfield Hills, Rancho California, ' County of Riverside, California" (WO #400082A). PACIFIC SOILS ENGINEERING, INC., August 1987b; "Fault Study, 1,400 acre, The !' Meadows at Rancho California, Rancho California" (WO #400082A). PACIFIC SOILS ENGINEERING, INC., September 30, 1987c; "Evaluation of Liquefaction Potential, A Portion of Vail Meadows Located North of ' Highway 79 and South of De Portola Road, between Margarita Road and future Butterfield Stage Road, Rancho California, California" (WO #400082A). Pl0E5SEL, M.R., and SLOSSON, J.E., 1974; "Repeatable High Ground Accelerations from Earthquakes," California Geology, September. 88-81-148-O1-B Z~ Converse Consultants Inland Empire DRAWINGS 88-81-148-O1-B ~ Converse Consultants Inland Empire APPENDIX A FIELD EXPLORATION 88-81-148-O1-B 3~ Converse Consultants Inland Empire _ __ APPENDIX A FIELD EXPLORATION ' Field exploration included a site reconnaissance and subsurface exploration program. During the site reconnaissance, the surface conditions were noted, and the locations of the test borings and trenches were determined. The ' exploratory borings and trenches were approximately located using existing ' . boundary and other features as a guide. Elevations shown on the logs were interpolated from the contours shown on the provided site topographic map. ' Exploratory borings were advanced using 18, 24, and 26 inch diameter bucket auger drilling equipment. Exploratory trenches were excavated by a backhoe equipped with a 24 inch width bucket. Soils were continuously logged by an ' experienced geologist and classified in the field by visual examination in accordance with the Unified Soil Classification system. Where deemed appropriate, the exploratory borings and trenches were entered by an engineering geologist who observed the exposed earth materials. Where appro- ' priate, field descriptions and classifications have been modified to reflect laboratory test results. Ring samptes of the subsurface materials were obtained at frequent intervals in the exploratory borings and trenches using a drive sampler (2.4-inch inside diameter, 3-inch outside diameter) lined with sample rings. The steel ring sampler was driven into the bottom of the borehole or trench with successive drops of a driving weight. Successive drops of telescoping kelly drove the samples in the bucket auger borings. The soil is retained in brass rings (2.4 inches inside diameter, 1.0 inch in height). The central portion of the sample was retained and carefully sealed in waterproof plastic containers for shipment to the laboratory. Bulk samples of typical soil types were also obtained. Calculated drive energies for each sample interval are presented on the boring logs. Logs of the exploratory borings and trenches are presented in the boring and trench summary sheets A-1 through A-87. Boring and trench summary sheets also include descriptions of the materials, pertinent field data and supplementary laboratory data. A key to soil symbols and terms is presented on the key sheet which is the last page in Appendix A. 88-81-148-O1-B ~ Converse Consultants Inland Empire APPENDIX B LABORATORY TEST PROGRAM 88-81-148-O1-B ~ Converse Consultants Inland Empire APPENDIX B LABORATORY TEST PROGRAM ' Laboratory tests were conducted in the Converse Consultants Pasadena (CCP) laboratory on representative samples for the purpose of evaluating their physical properties and engineering characteristics. Test results are presented on the exploration logs and in this appendix. A summary of the ' . various laboratory tests conducted is presented below. In-Situ Moisture Content and Dry Density ' Data obtained from these tests, performed on relatively undisturbed ring samples obtained from the field, were used to aid in the classification a~d correlation of the earth materials and to provide qualitative information , regarding strength and compressibility. The percent of moisture as a function of dry weight, and the encountered dry density in units of pounds-per-cubic- foot (pcf) are provided in the right-hand columns on the exploration logs. ' Laboratory Maximum Density and Optimum Moisture Tests Laboratory maximum density and optimum moisture tests were performed on ' representative bulk samples of the site materials. These tests were run in accordance with the ASTM D1557-78 laboratory procedure. Laboratory maximum density and optimum moisture curves are presented on Drawings B-1 and B-2. ' Shear Tests Direct shear tests were performed on both undisturbed ring and remolded ' samples. Individual rings were prepared, soaked and vertical surcharge applied. Each ring was then sheared at a constant rate of strain. A range of normal loads was applied and the shear strength envelope was determined. Results of the tests are presented on Drawings B-3 through B-8. ' Collapse Tests To evaluate the moisture sensitivity (collapsibility) of the encountered ,, soils, ring samples were loaded up to approximately 2 kips-per-square-foot (ksf), allowed to stabilize under load, and then submerged. The percent of consolidated measured after the sample was submerged is reported on the logs ' in the far right column as percent collapse. Consolidation Tests Data obtained from this test, performed on relatively undisturbed and remolded soil samples, were used to evaluate the settlement characteristics of on site soils and remolded soils under load. This test ~involved loading_specimens into the test apparatus which contained porous stones to accommodate vertical drainage during testing. Normal vertical axial loads were applied to one end of the sample through the porous stones, and the resulting vertical deflections were recorded at various time periods. The load was increased after the sample reached a reasonable state of equilibrium. 88-81-148-O1-B Z~ Converse Consultants Inland Empire B - 2 I' , Samples were loaded at field moisture and submerged for additional loading. Test results are shown on Drawings B-9 through B-19 entitled Consolidation Test, including a time-rate of consolidation plot. ' Resistance R-Value Test A selected bulk soil sample was tested in a Converse Consultants laboratory to determine the "R" value using the California "R" ~alue Test Method No. 301 , ' (ASTM D 2844-69). Results of the "R" value test is presented below: SAMPLE RESISTANCE 90RING SAMPLE DEPTH "R" No. No. (ft) SOIL DESCRIPTION VALUE* BH-2 ~B-2 70-11 SILTY SAND (SM)~ fine 26 * By exudation. Corrosivitv and Chemical Attack A bulk sample was sent to an analytical laboratory to test the soil pH, resistivity, and soluble sulfate and chloride content. These tests were performed to evaluate the corrosivity and chemical attack potential for the site soils. The results are as follows: SAMPIE BORING DEPTH No. (ft DESCRIPTION H~ BH-3 30-31 CLAYEY SILT (CL/MLj 7.9 RESISTIVITY SOLUBLE ( m) (ohm - cm) ~ 4,290 242 158 Sample Storage Soil samples presently stored in our laboratory will be discarded 30 days after the date of this report unless this office receives a specific request to retain the samples for a longer period. 88-81-148-Oi-B ~ Converse Consultants Inland Empire APPENDIX C RECOMMENDED EARTHWORK SPECIFICATIONS ' 88-81-148-O1-B Z~o Converse Consultants Inland Empire APPENDIX C RECOMMENDED EARTHWORK SPECIFICATIONS Grading Areas to organics, materials excavated All area prior to receive compacted fill shall be stripped of all vegetation, debris and existing structure remnants. Any existing fill shall be excavated. Any other unsuitable soils shall be as recommended by Converse Consultants Inland Empire (CCIE). s that are to receive compacted fill shall be observed by CCIE placement of fill. Subsequent to the removal of unsuitable materials, subgrade soil surfaces that will receive compacted fill shall be scarified to a depth of at least 6 inches. The scarified soil shall be moisture-conditioned to at or slightly above optimum moisture content. Scarified soil shall be compacted to at least a relative compaction of 90%. Relative compaction is defined as the ratio of the inplace soil density to the laboratory maximum dry density as determined by the ASTM D1557-78 test procedure. , , ' ' ' ' ~I , 3. Subdrains shall be installed in canyons and ravines as indicated by the project Certified Engineering Geologist (CEG). Subdrains shall be installed as depicted on the attached Drawings C-la and C-lb. 4. Fill shall be placed in suitable lifts, with lift thickness modified as necessary to achieve adequate compaction. A71 fill soils shall be compacted mechanically throughout to the specified density. Each layer shatl be compacted to at least a minimum relative compaction of 90%. Nowever, pavement base material shall be compacted to at least 95% of the ASTM D1557-78 laboratory maximum density. fills shall be benched into unyielding bedrock on slopes steeper than 4:1 (horizontal:vertical). Where fill is to be placed above cut slopes, fill shall be benched into bedrock as shown on Drawing C-2. The field density of the compacted soil shall be measured by the ASTM D1556-82 or D2922-81 test methods or equivalent. 5. Fill soils shall consist of excavated on site non-expansive soils essentially cleaned of organic and deleterious material or imported soils approved by CCIE. All imported fill shall be granular and non-expansive with an Expansion Index (EI) less than 30, as defined by the Uniform Buiiding Code (UBC) Standard 29-2. Rocks larger than 6 inches in diameter shall not be used unless they are sufficiently broken down. CCIE shall evaluate and/or test import materials for conformance with specifications prior to delivery to the site. The contractor shall notify CCIE at least two normal working days prior to importing fill to the site. 6. CCIE shall observe the placement of compacted fill and conduct inplace field density tests on the compacted fill to check for adequate moisture content and the required relative compaction. Where less than the specified relative compaction is indicated, additional compactive effort 88-81-148-O1-B Converse Consultants Inland Empire Z1 C-2 shall be applied and the soil moisture-conditioned as necessary until the specified relative compaction is attained. The contractor shall provide level testing pads for the soils engineer to conduct field density tests on. The contractor shall provide safe and timely access for CCIE personnel throughout the grading site, to allow continued monitoring and testing. , 7. Wherever, in the opinion of the Owner's or CCIE's Representatives, an unstable condition is being created, either by cutting or filling, the work shall not proceed in that area until an investigation has been made and the grading plan revised if found necessary. Erosion Control 1. Fill and cut slopes shall be graded and landscaped to reduce water-induced surficial erosion/sloughing. Permanent erosion control measures shall be initiated immediately after completion of slope construction. 2. All interceptor ditches, drainage terraces, down-drains and any other ' drainage devices shall be maintained and kept clear of d ebris. Runoff shall be directed to a suitable non-erosive drainage dev ice, and shall not flow uncontrolled offsite. -- ' 3. A suitable proportion of slope plantings shall have root systems which will develop well below 3 feet, such as drought-resistant shrubs a nd low ' trees, or equivalent. Intervening areas shall be lightweight surface plantings with shallower root systems. planted In any with event, lightweight, low-moisture planting shall be used. ' 4. Construction delays, climate/weather conditions, and plant growth rates may be such that additionai short-term, nonplant erosion control measures may be needed; including matting, netting, sprayed compounds, deep ' (5 feet) staking, etc. These measures shall be reviewed by CCIE. 5. Rodent burrowing, human trespass (footprints), small concentrations or ' uncontrolled surface/subsurface water, or poor compaction of utility trench backfill on slopes shall be repaired and controlled as soon as possible. I' 6. All possible precautions shall be taken to maintain moderate, uniform soil moisture. Slope irrigation systems shall be properly operated and maintained, and system controls shall be placed under continued contrnl ' by a landscape architect or similar qualified person. -~ 7. If completion of new slopes occurs during the rainy season, contingency ' plans shall be developed to provide prompt temporary protection against major erosion/sloughing. Offsite improvement shall be protected from site runoff. ' -- 8.-- Any erosion damage which occurs prior to the completion of the project shall be repaired by the Contractor. , 88-81-148-O1-B ~ Converse Consultanis Inland Empfre