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HomeMy WebLinkAboutCT 90-14; Aldea; Soils Report - Site Grading Plans; 1991-03-25- EBERHART 8 STONE, INC. GEOTECHNICAL CONSULTANTS 733 WEST TAFT AVENUE - ORANGE, CA 92685 . (714) 9214810 Tic2.P/,lI DAN R. EBERHART, CEG GERALD L. STONE, RCE pKm ?x?l-UC W.O. 158800.24 March 25, 1991 Bramalea California, Inc. One Park Plaza, Suite 1100 Irvine, California 92714 Attention: Mr. Jack Reimer Subject: Geotechnical review of 20-scale model site grading plans, ALDEA-CT 90- 14, Carlsbad, California. References: 20-scale Model Site Grading Plans, ALDEA-CT 90-l 4, Sheets 1 through 4, by Crosby Mead Benton & Associates, dated March 20, 1991 (J.N. 135-8). - 20-scale Revised Site Plan, Aviara Planing Area 16, Lot 90, Sheets 1 through 7, by Crosby Mead Benton & Associates, dated February 9, 1991 (J.N. 135-8). Geotechnical review of 40-scale site plans, Aviara Planning Area 16, Lot 90, Carlsbad, California, by Eberhart & Stone, Inc., dated April 13, 1990 (W.O. 158600.24). 40-scale Site Plans, Aviara Planning Area 16, Lot 90, Sheets 1 through 3, by Crosby Mead Benton & Associates, dated April 2, 1990 (J.N. 135- 8). As-Graded Geotechnical Report, Units A through E, Aviara, Carlsbad, California, by I.C.G. Incorporated, dated January 18, 1990 (Job No. 04 3179-007-02-10). Interim As-Graded Geotechnical Report, Pacific Rim Country Club and Resort, Preliminary Grading and Improvement, Alga Road, Carlsbad, California, by San Diego Geotechnical Consultants, Inc., dated December 30, 1988 (Job No. 05-3179-003-06-10). Supplemental Geotechnical Investigation, Pacific Rim Country Club and Resort, Units A, 8, C and Alga Road Corridor, Carlsbad, California, by San Diego Soils Engineering, Inc., dated March 25, 1988 (Job No. 04-3179- 003-00-00). - I - - - - - r Brarnalea California, Inc. -2- W.O. 158600.24 Preliminary Geotechnical Investigation, The Pacific Rim Country Club and Resort, Phase I, Carlsbad, California, by San Diego Soils Engineering, Inc., dated January 29, 1986 (Job No. SD1400-01). Gentlemen: This firm has completed a geotechnical review of the 20-scale model site grading plans for the subject site. This review was performed in order to evaluate the proposed grading and how it relates to existing mass-graded conditions and the referenced geotechnical reports. The scope of this review consisted of the following: 0 Site reconnaissance 0 Review of the referenced geotechnicaf reports 0 Review of the 20-scale model site grading plans 0 Review of the 40-scale site plans ‘0 Preparation of this correspondence. REPORT ON REVIEW EXISTING SITE CONDITIONS The site was originally mass graded in 1989 and 1990. This grading created a large nearly level pad and a 2:l (horizontal:verticalj fill slope. The slope has a maximum height of 6 feet and descends to the pad, adjacent Alga Road. A descending 2:1, 20 foot high fill slope was also constructed adjacent the eastern site boundary. A bedrock to compacted fill transition exists within the central portion of the pad, and is shown on the enclosed geologic map. Previous site grading is discussed in detail in the referenced geotechnical reports. PROPOSFD G@,DlNG AND SITE DEVEl OPMFNT The referenced 20-scale model site grading plans are similar to the referenced 4D-scale site plans previously reviewed by this firm. Cut-and-fill grading is proposed to develop a model site complex consisting of a building pad for a multi-family structure, associated private roadways, and a temporary parking area and desilting basin. EBERHART P STONE, INC. - I Bramalea California, Inc. -3- W.O. 158600.24 Grading is proposed to consist of cuts from 0.5 foot to 16 feet and fills from 9.5 foot to 10 feet. Cut and fill slopes are proposed at a 2:l (horizontal:verticalj slope ratio to maximum heights of 19 feet and 10 feet, respectively. A retaining wall is proposed adjacentthe northwest property boundary with a maximum height of 5 feet. Retaining wall design parameters will be presented upon completion of rough grading. EBERHART P STONE, INC. Bramalea California, Inc. -4- W.O. 158600.24 - - ,- r- I-- - r- - - OPINIONS AND RECOMMENDATIONS Recommendations in this review are opinions based upon the referenced reports, site plans, site observations, experience with other projects in the area, and professional judgment. Opinions and recommendations are applicable to the d~evelopment proposed under the scope of this review, and should be incorporated into project design and construction practice. Based upon this review, the subject site may be developed for its intended use. Grading for the proposed development should be conducted in accordance with local codes, this firm’s standard grading specifications, and the recommendations presented herein. Dbservation and Testing Prior to the start of grading, a meeting should be held at the site with the developer, grading contractor, civil engineer, and geotechnical consultant to discuss the work schedule and geotechnical aspects of the grading. All grading, including ground preparation and fill placement, shall be accomplished under the full-time observation and testing of the geotechnical consultant. Clearing All vegetation, trash, or other deleterious materials present on the subject site should be removed from areas to be graded and wasted from the site. It was noted that several irrigation lines, a concrete paved v-ditch, and a catch basin were present within the subject site. These manmade improvements should be removed and wasted from the site prior to the commencement of grading. Ground Preoarm Prior to fill placement, areas to be graded should be scarified to a depth of six inches to twelve inches, moisture-conditioned to near optimum, and compacted to 90% or more of the laboratory maximum density. WI Placemem Subsequent to clearing and ground preparation, fill placement may proceed. Fill should be placed in loose lifts restricted to about six inches in thickness. Each lift should be EBERHART it STONE. INC. Bramalea California, Inc. -5- W.O. 158600.24 - -- - r moisture-conditioned as needed to obtain near-optimum conditions, then compacted to 90% or more of the laboratory maximum .density. Each lift should be treated in a like manner until the desired rough grades are achieved. &&g&g&Rock Placement Oversized rock, greater than 12 inches, may be generated during grading within bedrock cut areas and overexcavations. Oversized rocks greater than 12 inches, but less than 3 feet, may be placed in the deeper fill areas in accordance with Plate GD-6. Rocks larger than 3 feet should be reduced in size or removed from the site. Fill slopes should be constructed at a ratio of 2:l (horizontal:vertical) or flatter. Fill slopes of up to about 25 feet are anticipated to be grossly and surficially stable. All proposed cut slopes greater than 10 feet should be replaced with stabilization fill slopes. Fill slopes should be keyed into competent compacted fill or bedrock. Details for fill keys are presented on Plate GD-4. . . . Stabilization fill slopes are recommended where proposed cut slopes are anticipated to expose highly erodible or cohesionless sandstone bedrock. The locations of proposed stabilization fill keys are presented on the Geologic Maps, Plates 1 and 2. Details for stabilization fills are presented on Plate GD-3. A backdrain system will be required within each stabilization fill constructed. Details for backdrains are presented on Plate GD-2. n Areas The proposed mass grading will create shallow fills and/or transitions from bedrock to compacted fill in the temporary parking lot, opposite the model site. Overexcavation of this area (a future building site) to provide a minimum of 3 feet of compacted fill is recommended. This compacted fill blanket is intended to provide uniform bearing conditions for future foundations. The proposed future building area is shown on the enclosed Geologic Map, Plate 1. EBERHART P STONE. INC. - ,- r r Bramalea California, Inc. -6- ARY W.O. 158600.24 Based upon a review of the enclosed 20-scale model site grading plans, it is this firm’s opinion that the subject site can be developed for its intended use, provided that the opinions and recommendations presented herein, and those within the referenced reports, are incorporated into design and construction practice. The findings contained in this review are based upon the proposed grades as shown on the 20-scale model site grading plans and the 20-scale revised site plans. The opinions and recommendations contained herein have been further based upon experience with similar projects, geotechnical evaluations, and professional judgment. No warrant is expressed nor implied. Should you have any questions regarding the information contained herein, please do not hesitate to call. Respectfully submitted, EBERHART 81 STONE, INC. Project Geologist President CEG 965 JML:RJF:DRE:GLS:sw (15860024.001 j Enclosures: Standard Grading Specifications - Pages l-6 Grading Details - Plates GD-2 thru GD-6 Geologic Maps - Plates 1 and 2 Distribution: (21 Addressee (4) Crosby Mead Benton 8 Assoc. Attn: Mr. Ed Huntington EBERHART 8 STONE, INC. - 1 - - - - - r 1.0 The specifications contained herein and the standard details attached hereto represent minimum requirements for grading operations on construction projects. Variance from these specifications will not be permitted unless specifically approved by the soil engineer. These recommendations should not be considered to preclude more restrictive requirements of the regulating agencies. 2.0 2.1 DEFINITION OF TERMS BEDROCK - a relatively solid undisturbed or in-place rock existing at either the ground surface or beneath surficial deposits of soil. Bedrock will be identified in the field by the project engineering geologist. 2.2 ENGINEERED FILL - a fill of which the soil engineer or his representative during grading has made sufficient observations and taken sufficient tests to enable him to conclude that the fill has been placed in substantial compliance with the governing specifications. 2.3 ENGINEERING GEOLOGIST - a geologist holding a valid certificate of registration in the specialty of engineering geology. 2.4 FILL - any deposits of soil, rock, soil-rock blends or other similar materials placed by man. 2.5 GEOTECHNICAL CONSULTANT - the soil engineering and engineering geology consulting firm(s) retained to provide technical services for the project. For the purpose of these specifications, observations by the soil engineer and engineering geologist include those performed by persons employed by and responsible to the geotechnical consultant. 2.6 GRADING - any operation consisting of excavation, filling or combinations thereof. 2.7 IMPORTED OR BORROW MATERIAL - any fill material hauled to the project site from off-site areas. 2.8 RELATIVE COMPACTION - the degree of compaction (expressed as' a percentage) of'dry density of a material as compared to the maximum dry density of the material. Unless otherwise specified, the maximum dry density shall be determined in accordance with ASTM method of test D1557-70. 2.9 SOIL ENGINEER - a licensed civil engineer experienced in soil mechanics. -l- STANDARD GRADING SPECIFICATIONS ERERHART R STONE, INC. - - - 3.0 3.1 3.2 3.3 3.4 4.0 4.la 4.lb 4.2a - 4.2b - - 4.3a - -2- SITE PREPARATION Clearing and grubbing shall consist of the removing of all vegetation such as brush, grass, woods, stumps, trees, roots of trees and all otherwise deleterious natural materials from the areas to be graded. Clearinq and grubbing shall extend to the outside of all proposed excavation and fill areas. Demolition shall include removal of all buildings, structures, utilities and all other manmade surface and subsurface improvements from the areas to be graded. Trees, plants or manmade improvements not planned to be removed or demo- lished shall be protected by the contractor from damage or injury. All deleterious material generated during clearing, grubbing and demoli- tion operations shall be wasted from areas to be graded. All clearing, grubbing and demolition operations shall be performed under the observation of the soil engineer. EXCAVATIONS Unsuitable Materials: Material which is unsuitable shall be excavated as dlrected by the soil engineer. Unsuitable materials include, but may not be limited to dry, loose, soft, wet, compressible and non-engineered or otherwise non-approved fill materials. Material identified by the soil engineer as unsatisfactory due to its~ moisture conditions shall be overexcavated, watered or dried as needed and thoroughly blended to a uniform near-optimum moisture condition prior to placement as compacted fill. Site Protection: The contractor shall be responsible for the stability of all temporary excavations. Recormnendations by the soil engineer shall not be considered to preclude those requirements of the regulating agencies. Precautions shall be taken during the performance of all slte clearing earthwork, excavations and grading to orotect the work site from flooding, ponding or inundation by poor or improper surface drainage. Temporary provisions should be made during the rainy season to ade- quately direct surface drainage from all sources away from and off the work site. Slopes: Unless otherwise recoasaended by the geotechnical consultant and approved by the regulating agencies, permanent cut slopes shall not be steeper than 2:l (horizontal to vertical). EBERHART & STONE,INC. 4.3b - - 4.3c - - - 4.3d 4.3e 5.0 5.1 5.2a - 5.2b - -3- If excavations for cut slopes expose loose. significantly fractured or otherwise unsuitable material, overexcavation and replacement of the unsuitable materials with a compacted stabilization fill will be required as directed by the soil engineer or engineering geologist. Unless otherwise specified by the soil engineer, stabiliration fill construction shall conform to the requirements of Grading Oetail GO-3. All lot pad areas, including side-yard terraces, above stabilization fills or buttresses shall be overexcavated to provide for a minimum of three feet of compacted fill over the entire pad area. Pad areas with both fill and cut materials,exposed and pad areas containing both very shallow (less than three feet) and deeper fill shall be overexcavated to provide for a uniform compacted fill blanket a minimum of three feet in thickness. Cut areas exposing significantly varying material types shall also be overexcavated to provide for a minimum three-foot thick compacted fill blanket. For cut slopes made in the direction of the prevailing drainage above the cut, a diversion swale (brow ditch) should be provided at the top of cut. The diversion swale configuration should conform to the applicable code requirements and should be reviewed by the soil engineer prior to installation. For pad areas created above cut or natural slopes, positive drainage' shall be established away from the top of slope. This may be accomplished utilizing a berm and/or an appropriate pad gradient. COMPACTED FILL Compaction: All fill materials shall be compacted as specified below or by other methods specifically approved by the soil engineer. Unless otherwise specified, the minimum degree of compaction (relative compac- tion) shall be 90% of the laboratory maximum density. Placement: Prior to placement of compacted fill, the ground surface approved by the soil engineer shall be scarified, watered or dried as needed, thoroughly blended to achieve near-optimum moisture conditions, then thoroughly compacted to a minimum of 90% of the laboratory maximum dry density. Compacted fill shall be placed in thin horizontal lifts not exceeding eight inches in thickness prior to compaction. Each lift shall be watered or dried as needed, thoroughly blended to achieve near-optimum moisture conditions, then thoroughly compacted by mechanical methods to a minimum of 90% of the laboratory maximum dry density. Each lift shall be treated in a like manner until the desired finished grades are achieved. EDERHART R STONE, INC. - - - - - - 5.2~ 5.2d 5.3a - 5.3b - 5.3c - 5.4a - 5.4b - -4- When placing fill in horizontal lifts adjacent to areas sloping steeper than 5:1 (hori,rontal to vertical), horizontal keys and vertical benches shall be excavated into the adjacent slope area. Keying and benching shall be sufficient to provide a minimum of four feet of vertical bench height within firm natural ground or approved compacted fill. All keys and benches shall be approved by the soil engineer or engineerinq geolo- gist at the time of grading. No compacted fill shall be placed in an area subsequent to keying and benching until the area has been approved by the soil engineer or engineering geolopist. Typical keying and benching details have been included on the accompanying Grading Oetails- GO-3, GO-4, and GO-5. Within a single fill area where grading procedures dictate two or more separate fills, temporary slopes (false slooes) will be created. When placing fill adjacent to a false slope, benching shall be conducted in the same manner as the above described. A minimum four-foot vertical bench shall be established within the adjacent approved compacted fill (i.e., the material underlying the surface loose material) prior to placement of additional fill. Benching shall proceed in approximately four-foot increments until the desired finished,grades are achieved. For field control purposes, "near-optimum" moisture shall be considered to mean optimum plus-or-minus two percent unless otherwise approved by the soil engineer at the time of grading. Prior to placement of additional compacted fill following an overnight or ,other grading delay, the exposed surface of previously compacted fill shall be processed by scarification, watered or dried as needed, thoroughly blended to near-optimum moisture conditions, then recompacted to a minimum of 90% of the laboratory maximum dry density. Following a period of flooding, rainfall or overwatering by other means, no additional fill shall be placed until the existing ground surface is thoroughly scarified, aerated, overexcavated if directed by the soil engineer, blended to achieve near-optimum moisture conditions, then thoroughly compacted to a minimum of 90% of the laboratory maximum dry density. Fill Material: Excavated onsite materials which are approved by the soil engineer may be utilized as compacted fill provided all trash, vegetation and other deleterious materials are removed prior to placement. Where import materials are required for use onsite, the soil engineer shall be notified at least 72 hours in advance of importing in order to sample, test and approve or disapprove materials from proposed borrow sites. No import materials shall be delivered for use onsite without prior approval of the soil engineer. EBERHART R STONE, INC. - - - - 5.4c 5.4d 5.4e 5.5a 5.5b - - - 5.5c 5.5d .- -5- Rocks 12 inches in maximum dimension and smaller may be utilized within the compacted fill, provided they are placed in such a manner that nestinq of the rock is avoided. Fill shall be placed and thoroughly compacted to the minimum requirement over and around all rock. Rocks greater than 12 inches, but less than 3 feet, maximum dimension (oversized rock) require special.placement procedures if they are to be utilired within compacted fills. Rocks greater than 3 feet should be broken down or disposed of offsite. Oversized rock should not be placed within the upper 10 feet of any fill and no closer than 15 feet to any slope face. Where practical, over- sized 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 granular soil (S.E.=30 or better) should be placed and/or thoroughly flooded over and around all windrowed rock, such that no voids remain. Windrows of oversized material should be staggered so that successive strata of oversized material are not in the same vertical plane. Oetails,for oversized rock placement are presented on Grading Detail GD-6. Slooes: Unless otherwise reconsnended by the soil engineer and approved by regulating agency, compacted fill slopes shall be limited to a slope ratio of no steeper than 2:I (horizontal to vertical). All compacted fill slooes shall be overbuilt and cut back to grade exposing the firm compacted fill innercore. The actualamount of over- building may vary as field conditions dictate. If the desired results are not achieved, the existing slopes should be overexcavated and reconstructed. The degree of overbuilding shall be increased until the desired compacted slooe surface condition is achieved. Care should be taken by the contractor to provide thorough mechanical compaction to the outer edge of the overbuilt slope surface. As fill slope construction proceeds, the slope surface shall be thoroughly backrolled with a sheepsfoot roller at vertical height intervals not exceeding four feet. Following the attainment of the desired slope height, the outer surface of overbuilt slopes should be cut back to a desired finished surface contour. Care should be taken by the contractor not to excavate beyond the desired finished slope surface. In lieu of overbuilding and cutting back, alternative construction pro- cedures may be attempted where specifically approved by the soil engineer prior to grading. Prior to such approval, the contractor shall submit to the soil engineer a detailed written description of the proce- dure he proposes to utilire. Within such a description, the following guidelines may be included: Unless slopes are overfilled and cut back to grade, the outer faces of all fill slopes shall be backrolled uti- lizing a sheepsfoot roller at intervals not exceeding four feet of ver- tical slope height. Vibratory methods may be required. ERERHART R STONE. INC. -6- c - 5.5e - 5.5f - 5.59 - / tr During construction of the fill slopes, care should be taken to maintain near-optimum moisture conditions over the entire slope height. Following achievement of the desired slope height, the entire slope face should be thoroughly compacted utiliring a vibratory sheepsfoot roller. Upon completionof the above procedures, the faces of all fill slopes should be grid-rolled over the entire slope height with standard grid-rolling type of equipment. Prior to grid-rolling, care should be taken to main- tain near-optimum moisture conditions. Following slope construction in the manner described above, if the required uniformly compacted fill slope condition is not achieved, over- filling and cutting back should be adopted. Completed slopes not approved by the soil engineer should be overexcavated. a minimum of 12 feet (horizontal) and replaced by the overfilling and cutting back pro- cedure described above. Where placement of fill above a natural slope or above a,cut slope is proposed, the fill slope configuration should conform to the applicable requirements as indicated on Grading Detail GO-4. For pad areas above fill slopes, positive drainage shall be established away from the top of slope. This~ may be accomplished'utilizing a berm and/or an appropriate pad gradient. ERERHARTR fTONE.INC. TYPICAL SUBDRAIN FOR BUTTRESS , STABILIZATION I OR SIDEWILL FILL MASSES %552@z?~~& 7/d- T 1 .v&.v J/c Wd. ---w-v-- I hT 1. FliwR #yA7CRI*L -LD dI l ?-*7a OF CA FO”,v,” Y CLASS 2 prm+*- E/A-, CALTRANI aA-cnon Cd-/.oas% 2. p&e/ CCH -7 PlRl P-0 u - wvzu couPAc*m -s+zc so/L. I 4. Twr NR.UIIlry pr dudDHy/Iv *t YILL on dlc=edn- dAlyI collll-- an-..f -La aa “--*$&y4$” - rv -zacyNKIL 5. c.ec4 .sffe suano 2wIpvo me - UAIVU w= mv4rADc,dvM a= MU- cJrabvs .n- GRADING DETAlL m TYPICAL STABIUZATION FILL FIG. I TYPICAL BUTTRESS FILL FIG. 2 1. A+p -aT- u.uIY-~uQen LIO Aad- ‘Ip*r-T*w-11(poa -a x(y). 2. nf- t4c.w .c rrr, .45a..AeNa w -MML -(.w~nuu*OIAf3W4*-Q-. 3. a- rurnvorAa7r7rar 4. Ma Drrrr, ocxlr-.7 - 5. wkw A.vD -Pvw arsvrnrrvAa)ru -.zdF,aD ,” axor@z,dhv,~ *a- 6. forw.w- -7&,&s -1 /x471 60-2. GRADING DETAIL EBERHART 8 STONE. INC. CEmcMNlcu. cousuL,~ nl-lmwu.mnN.u-.~m~ .; . . . STANDARD GRADING SPECIFICATIONS Im=63-3 TYPICAL FILL OVER NATURAL SLOPE WFKAL FILL OVER CUT SLOPE -: -am@& -1pyAmud nmma4f:..va! do- OF llCIar =+ruorrmw&T.wci nowr - SJDd. - w47xRaa -- ?D -ZISHN,aL CoIw&?-4wr GRADlNG DETAIL I EBEICHART I STONE. INC. GEOnxnw ConslJLTum ?amr*-.-a-.(rr- I STANDARD GRADING SPECIFICATIONS TYPICAL REMOVAL OF TRANSITION LOTS -A.-w - MeA- - - -1 CUT flLL LOT I GRADING DETAIL EBERHART I STONE. INC. (yglEQ**uLconsuL1m ln-,YIAmnm.OU*ILUI.mm STANDARD GRADING SPECIFICATICNS pl.ATR~p-~ ,- c - - Y - I - C Z)‘.’ -c f I.,:, -4 p: .3 TYPICAL ROCK WINDROW I w*- r(yrz*r Pm= e WM. I rwv.ypvo - ClLL - A--- --om-tr--&-, =z- ir= 0 0 0 0 0 0 ~&;;(-;;~~ \ TYPICAL WINDROW DETAIL (edge view) PROFILE VIEW --d.aY Y.=BDWDrnWD EEERHART I; STONE. INC. o?zs: iv7 rwr.so !. P*~wIAIo 7.. so.ymnon, OF mm rdort mc7.m - OEOTSCHWUL Con~T~TS 7D -.w.Ms Y,T” 4-m FaL.br(L* --II -.kzvc-csrr. F-9 T-Hz Lu*#=AcL. m011.m.-.~UI.~~*4m nu CO.vRAcIoLI se.& riwln *x) 7-P sucucw I cwzr[Nmw.ury-. , ppw.-wwT LotiT-- oc bvRI0 -. D/--L /A- LIRYT R a+.. 4 -am w-Y)?uc- STANI~RD GRADING SPE~IFIC~\TI~NS v LLY HPze a= //7,&z-,*. lPulE LiP-G