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HomeMy WebLinkAboutCT 00-13; Tabata Property; Soil and Geologic Reconnaissance; 2000-06-01i GEOTE :cir-ioij o I () I IHMCA .TAM E 5 D SOIL AND GEOLOGIC RECONNAISSANCE TABATA CARLSBAD, CALIFORNIA PREPARED FOR THE BREHM COMPANIES SAN DIEGO, CALIFORNIA cro JUNE 2000 GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS ProjectNo. 06542-52-01 June 28, 2000 The Brehm Companies 5770 Oberiin Drive San Diego, Cahfomia 92121-1723 Attention: Ms. Paula Lombardi Subject: TABATA CARLSBAD, CALIFORNIA SOIL AND GEOLOGIC RECONN/USSANCE Dear Ms. Lombardi: In accordance with your authorization of our proposal (LG-00384) dated June 22, 2000, we have performed a soil and geologic reconnaissance of the subject project. The study was conducted to assess the site soil and geologic conditions, and to identify potential geologic hazards that may impact the property with respect to future development. The accompanying report presents preliminary findings of our study with respect to the geotechnical aspects of site development. No soil or geologic conditions were encountered that would preclude development of the property. Should you have questions regarding this report, or if we may be of fiirther service, please contact the undersigned at your convenience. Very tmly yours, GEOCON INCORPORATED Hoobs 1524 KPA:JH:lek (6/del) Addressee 6960 Flanders Drive • San Diego, California 92121-2974 • Telephone (858) 558-6900 • Fax (858) 558-6159 TABLE OF CONTENTS 1. PURPOSE AND SCOPE 1 2. SITE AND PROJECT DESCRIPTION 1 3. SOIL AND GEOLOGIC CONDITIONS 2 3.1 Topsoil (Unmapped) 2 3.2 Lindavista Formation (Qln) 2 4. GEOLOGIC STRUCTURE 2 5. GROUNDWATER 2 6. GEOLOGIC HAZARDS 3 6.1 Faulting and Seismicity 3 6.2 Liquefaction 3 7. CONCLUSIONS AND RECOMMENDATIONS 4 7.1 General 4 7.2 Grading 4 7.3 Future Proj ect Plans 5 LBVlITAnONS AND UNIFORMITY OF CONDITIONS MAPS AND ILLUSTRATIONS Figure 1, Vicinity Map Figure 2, Geologic Map APPENDIX A RECOMMENDED GRADING SPECIFICATIONS REFERENCES SOIL AND GEOLOGIC RECONNAISSANCE 1. PURPOSE AND SCOPE The purpose of this recormaissance was to identify the soil and geologic conditions at the site, evaluate potential geologic hazards (if any), and provide preliminary geotechnical recommendations with respect to development of the property for initial land use studies. Additional studies, including subsurface exploration and laboratory testing should be performed prior to approval of the site grading plans. The scope of this study consisted of a review of published geologic literature and in- house geotechnical reports and performing a site reconnaissance. Specifically, our study included the following: • Field mapping by an engineering geologist to identify the soil and geologic units and to map their approximate areal extent. • Review of stereoscopic aerial photographs. • Review of Conceptual Site Plan for Tabata, Study No. 12, scale 1 inch equals 40 feet, prepared by O'Day Consultants, progress print date May 30, 2000. 2. SITE AND PROJECT DESCRIPTION The rectangular-shaped property consists of approximately 5 acres of imdeveloped land located east of Black Rail Road and west of proposed Cabela Place in the City of Carlsbad, Califomia (see Vicinity Map, Figure 1). Presently, the property is undeveloped and is covered with grasses. Topographically, the site slopes to the west and northeast with a north-trending ridge located near the eastem portion ofthe property. Elevations range fi-om a high of approximately 383 feet Mean Sea Level (MSL) along the southem margin of the site to a low of approximately 346 feet MSL at the southwest comer of the property. Surface drainage for the overall property flows both northeast and west from the ridge. A review of the referenced site plan indicates that proposed development of the property will consist of grading the site to constmct 17 single-family residential lots with three roadways. In addition, several retaining walls are proposed on the property. Cut and fill slopes are proposed at inclinations of 2:1 (horizontahvertical) with maximum heights on the order of 15 feet. Project No. 06542-52-01 - 1 - June 28, 2000 3. SOIL AND GEOLOGIC CONDITIONS One surficial soil deposit and one geologic formation were observed at the site. The surficial deposit includes topsoil. The geologic formation includes the Quatemary-age Lindavista Formation. The surficial deposit and formational unit is discussed below in order of increasing age. Their estimated areal extent, as determined by field mapping, is depicted on the Geologic Map (Figure 2). 3.1 Topsoil (Unmapped) Topsoil generally blankets the site and typically consists of reddish-brown to dark brown clayey sands to sandy clays. Topsoil overlying the Lindavista Formation is generally low to medium expansive with an estimated thickness varying fi-om 2 to 4 feet. The topsoil is highly compressible which will require removal and compaction. 3.2 Lindavista Formation (Qln) Dense to very dense, reddish brown, silty, fine to medium sandstone of the Quatemary-age Lindavista Formation occurs across the site (Figure 2). This formation typically possesses adequate shear strength and low expansion characteristics in either a natural or properly compacted state. However, it is not unusual to encounter partially to well cemented zones within this formation that will require very heavy effort to excavate. 4. GEOLOGIC STRUCTURE The geologic formation generally consists of massive sandstone with bedding attitudes that are typically not discemable. The regional dip is estimated to be 2 to 5 degrees toward the south and west, but can vary locally several degrees in other directions. 5. GROUNDWATER No seeps, springs or groundwater conditions were observed during the site recormaissance. However, it is likely that during the rainy season, shallow perched groundwater conditions can develop within the topsoil and could seasonally impact proposed remedial grading. Groundwater is not anticipated to adversely impact the proposed project development. Proj ect No. 06542-52-01 - 2 - June 28,2000 6. GEOLOGIC HAZARDS 6.1 Faulting and Seismicity Based upon a review of published geologic literature and observations during the site recormaissance, it is the opinion of Geocon Incorporated that no known active or potentially active faults exist on the site. The active Rose Canyon Fault lies approximately 8 miles west of the property. A summary of the closest known active faults within 62 miles (100 kilometers) of the site with deterministic site parameters are indicated in Table 6.1. The listed peak site accelerations were calculated using the attention relationships of Geomatrix (1994) for sites underlain by soil. TABLE 6.1 DETERMINISTIC SITE PARAMETERS FOR SELECTED FAULTS Fault Name Distance From Site (miles) Maximum Credible Event Maximum Probable Event Fault Name Distance From Site (miles) Magnitude Event (mag) Peak Site Acceleration (g) Magnitude Event (mag) Peak Site Acceleration (g) Rose Canyon 8 6.9 0.27 5.7 0.13 Newport-Inglewood (offshore) 17 6.9 0.15 5.8 0.07 Coronado Bank 22 7.4 0.16 6.3 0.07 Elsinore - Julian 25 7.1 0.12 6.4 0.07 Earthquake Valley 36 6.5 0.05 5.7 0.02 The site could be subjected to moderate to severe ground shaking in the event of an earthquake along any of the faults listed in Table 6.1 or other faults in the southem Califomia/northem Baja Califomia region. However, the site is not considered to possess any greater risk than that of the surrounding developments. While listing of peak accelerations is useful for comparison of potential effects of fault activity in a region, other considerations are unportant in seismic design, including the fi-equency and duration of motion and the soil conditions underlying the site. The seismic design of stmctures should be performed in accordance with the Uniform Building Code (UBC) guidelines currently adopted by the City of Carlsbad. 6.2 Liquefaction The potential for liquefaction during a strong earthquake is limited to those soils which are in a relatively loose, unconsolidated condition and located below the groundwater table. The occurrence of such conditions are nonexistent on the site; therefore, the potential for liquefaction is considered to be very low. Project No. 06542-52-01 June 28,2000 7. CONCLUSIONS AND RECOMMENDATIONS 7.1 General 7.1.1 In our opinion, no soil or geologic conditions exist at the site that would preclude the development of the property as presently planned. Preliminary grading recommendations are presented herein for planning purposes. Detailed recommendations can be provided in future geotechnical studies based upon site specific mformation obtained fi-om field subsurface studies. 7.1.2 The site is underlain by a thin veneer of topsoil. This material is unsuitable in its present condition for support of fill and/or stmctural loading and will require remedial grading. 7.1.3 The Lindavista Formation may contain highly cemented zones which may be difficult to excavate. Oversize concretions that may be generated during excavation of these cemented zones will requke special placement techniques for incorporation into the fill. 7.2 Grading 7.2.1 It is recommended that as grading and improvement plans are developed, a supplemental site investigation be performed to further delineate and evaluate the site geology and to test for the engineering characteristics of the site soil materials. 7.2.2 The surficial soils within areas of planned development will require removal and compaction. 7.2.3 Oversize cemented chunks may be generated during excavations within the formational unit. Oversize rock should be kept at least 10 feet below proposed finish grade elevations and placed in accordance with the recommendations in the Recommended Grading Specifications in Appendix A. 7.2.4 All fill (including scarified ground surfaces and backfill) should be compacted to at least 90 percent of laboratory maximum dry density as determined by ASTM Test Procedure D-1557-91; at or slightly above optimum moisture content. 7.2.5 In general, cut or fill slopes constmcted at inclinations of 2:1 (horizontahvertical) constmcted of sandy materials derived fi-om the formational units should have adequate factors of safety against both deep seated and surficial instability for the proposed slope ProjectNo. 06542-52-01 -4- June 28,2000 heights. Cut slopes should be observed during grading by an engineering geologist to determine if adverse conditions exist. 7.3 Future Project Plans 7.3.1 Prior to finalizing of the grading plans for the property, a geotechnical investigation addressing the specific grading plans should be performed. The investigation should provide site specific grading recommendations, recommendations for mitigation of adverse soil conditions and preliminary foundation design criteria. ProjectNo. 06542-52-01 -5 - June 28,2000 LIMITATIONS AND UNIFORMITY OF CONDITIONS 1. The recommendations of this report pertain only to the site investigated and are based upon the assumption that the soil conditions do not deviate fi-om those disclosed in the investigation. If any variations or undesirable conditions are encountered during constmction, or if the proposed constmction will differ fi-om that anticipated herein, Geocon Incorporated should be notified so that supplemental recommendations can be given. The evaluation or identification of the potential presence of hazardous or corrosive materials was not part of the scope of services provided by Geocon Incorporated. 2. This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project and incorporated into the plans, and the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. 3. The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result firom legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our contiol. Therefore, this report is subject to review and should not be relied upon after a period of three years. Project No. 06542-52-01 June 28, 2000 SOURCE: 2000 THOMAS BROTHERS MAP SAN DIEGO COUNTY, CALIFORNIA REPRODUCED WITH PERMISSION GRANTED BY THOMAS BROTHERS MAPS. THIS MAP IS COPYRIGHTED BY THOMAS BROS. MAPS. IT IS UNLAWFUL TO COPY OR REPRODUCE ALL OR ANY PART THEREOF, WHETHER FOR PERSONAL USE OR RESALE, WITHOUT PERMISSION 4 NO SCALE GEOCON ^ INCORPORATED ^^fw GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858 558-6900 - FAX 858 558-6159 VICINITY MAP GEOCON ^ INCORPORATED ^^fw GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858 558-6900 - FAX 858 558-6159 TABATA CARLSBAD, CALIFORNIA JH/TA DSK/EOOOD DATE 06-28-2000 PROJECT NO. 06542 - 52 - 01 FIG. 1 IVICMAP 5A!fi7 / OF 1 SHEET GEOCON LEGEND Qln ..LINDAVISTA FORMATION GEOLOGIC MAP TABATA CARLSBAD, CALIFORNIA GEOCON iS SCALE >„ _ iOATE 1 = 40 1 06-28-S »990 GEOCON iS """-^-06542 - 52 - 01 FIGURE 2 CaUnUNCM CONSUTANR l»W flANns DIM - SM CCOO, CAUOMA 72B1.»7i IHOMta • MX M SSmOt """-^-06542 - 52 - 01 FIGURE 2 CaUnUNCM CONSUTANR l»W flANns DIM - SM CCOO, CAUOMA 72B1.»7i IHOMta • MX M SSmOt SHEET 1 OF 1 FIGURE 2 PRCPMSO IMY W. 2000 [©2000 O'Day Consultonts, Inc. 0^04^ DESIGNED BY: KR.. A.a DATF: IHY 2000 DRAWN BY? T.a. Oil. SCAIF. f • 40' PROJECT MGR.: T.C JOB NO.: 00-1003 CONSULT A/N T S 3900 PMMIT Court CMI Ewgiw—ring SwM* 100 PIgnning C4vfeAcHJ« CoMomis 92000 PTOCSMM^ 7«>-93t-7700 Sorv.ving Fw; TBo-ut-aeao ENGINEER OF WORK: DATE: TMOmr 0. OWROO. JR RCE: 5S381 APPENDIX APPENDIX A RECOMMENDED GRADING SPECIFICATIONS for TABATA CARLSBAD, CALIFORNIA PROJECT NO: 06542-52-01 RECOMMENDED GRADING SPECIFiCATIONS 1. GENERAL 1.1. These Recommended Grading Specifications shall be used in conjunction with the Geotechnical Report for the project prepared by Geocon Incorporated. The recom- mendations contained in the text of the Geotechnical Report are a part of the earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case of conflict. 1.2. Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be employed for the purpose of observing earthwork procedures and testing the fills for substantial conformance with the recommendations of the Geotechnical Report and these specifications. It will be necessary that the Consultant provide adequate testing and observation services so that he may determine that, in his opinion, the work was performed in substantial conformance with these specifications. It shall be the responsibility of the Contractor to assist the Consultant and keep him apprised of work schedules and changes so that personnel may be scheduled accordingly. 1.3. It shall be the sole responsibility of the Contractor to provide adequate equipment and methods to accomplish the work in accordance with applicable gradmg codes or agency ordinances, these specifications and the approved grading plans. If, in the opinion of the Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture condition, inadequate compaction, adverse weather, and so forth, result in a quality of work not in conformance with these specifications, the Consultant will be empowered to reject the work and recommend to the Owner that constmction be stopped until the unacceptable conditions are corrected. 2. DEFINITIONS 2.1. Owner shall refer to the owner of the property or the entity on whose behalf the grading work is being performed and who has contracted with the Contractor to have grading performed. 2.2. Contractor shall refer to the Contractor performing the site grading work. 2.3. Civil Engineer or Engineer of Work shall refer to the Califomia licensed Civil Engineer or consulting firm responsible for preparation of the grading plans, surveying and verifying as-graded topography. GI rev. 8/98 2.4. Consultant shall refer to the soil engineering and engineering geology consulting firm retained to provide geotechnical services for the project. 2.5. Soil Engineer shall refer to a Califomia licensed Civil Engineer retained by the Owner, who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be responsible for having qualified representatives on-site to observe and test the Contractor's woric for conformance with these specifications. 2.6. Engineering Geologist shall refer to a California licensed Engineering Geologist retained by the Owner to provide geologic observations and recommendations during the site grading. 2.7. Geotechnical Report shall refer to a soil report (including all addenda) which may include a geologic recormaissance or geologic investigation that was prepared specifically for the development of the project for which these Recommended Grading Specifications are intended to apply. 3. MATERIALS 3.1. Materials for compacted fill shall consist of any soil excavated from the cut areas or imported to the site that, in the opinion of the Consultant, is suitable for use in constmction of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as defined below. 3.1.1. Soil fills are defined as fills containing no rocks or hard lumps greater than 12 inches in maximum dimension and containing at least 40 percent by weight of material smaller than 3/4 inch in size. 3.1.2. Soil-rock fills are defined as fills containing no rocks or hard lumps larger than 4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow for proper compaction of soil fill around the rock fi-agments or hard lumps as specified in Paragraph 6.2. Oversize rock is defined as material greater than 12 inches. 3.1.3. Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet in maximum dimension and containing little or no fines. Fmes are defined as material smaller than 3/4 inch in maximum dimension. The quantity of fines shall be less than approximately 20 percent of the rock fill quantity. GI rev. 8/98 3.2. Material of a perishable, spongy, or otherwise unsuitable nature as detennined by the Consultant shall not be used in fills. 3.3. Materials used for fill, either imported or on-site, shall not contain hazardous materials as defined by the Califomia Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9 and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall not be responsibie for the identification or analysis of the potential presence of hazardous materials. However, if observations, odors or soil discoloration cause Consultant to suspect the presence of hazardous materials, the Consultant may request fi-om the Owner the termination of grading operations within the affected area. Prior to resuming grading operations, the Owner shall provide a written report to the Consultant indicating that the suspected materials are not hazardous as defined by applicable laws and regulations. 3.4. The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of properly compacted soil fill materials approved by the Consultant. Rock fill may extend to the slope face, provided that the slope is not steeper than 2:1 (horizontahvertical) and a soil layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This procedure may be utilized, provided it is acceptable to the goveming agency. Owner and Consultant. 3.5. Representative samples of soil materials to be used for fill shall be tested in the laboratory by the Consultant to determine the maximum density, optimum moisture content, and, where appropriate, shear strength, expansion, and gradation characteristics of the soil. 3.6. During grading, soil or groundwater conditions other than those identified in the Geotechnical Report may be encountered by the Contractor. The Consultant shall be notified immediately to evaluate the significance of the unanticipated condition 4. CLEARING AND PREPARING AREAS TO BE FILLED 4.1. Areas to be excavated and filled shall be cleared and gmbbed. Clearing shall consist of complete removal above the ground surface of trees, stumps, bmsh, vegetation, man-made stmctures and similar debris. Gmbbing shall consist of removal of stumps, roots, buried logs and other unsuitable material and shall be performed in areas to be graded. Roots and other projections exceeding 1-1/2 inches in diameter shall be removed to a depth of 3 feet below the surface of the ground. Borrow areas shall be gmbbed to the extent necessary to provide suitable fill materials. GI rev. 8/98 4.2. Any asphalt pavement material removed during clearing operations should be properiy disposed at an approved off-site facility. Concrete fi-agments which are fi-ee of reinforcing steel may be placed in fills, provided tiiey are placed in accordance with Section 6.2 or 6.3 of this document. 4.3. After clearing and grabbing of organic matter or other unsuitable material, loose or porous soils shall be removed to the depth recommended in the Geotechnical Report. The depth of removal and compaction shall be observed and approved by a representative of the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth of 6 inches and until the surface is fi-ee fi-om uneven features tiiat would tend to prevent uniform compaction by the equipment to be used. 4.4. Where tiie slope ratio ofthe original ground is steeper tiian 6:1 (horizontahvertical), or where recommended by tiie Consultant, tiie origmal ground should be benched in accordance with the following illustration. TYPICAL BENCHING DETAIL Rnish Grade Original Ground Finish Slope Surface Remove All Unsuitable Material As Recommended By Soil Engineer Slope To Be Such That Sloughing Or Sliding Does Not Occur B' See Note 1 See Note 2 No Scale DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet wide, or sufficiently wide to permit complete coverage with the compaction equipment used. The base ofthe key should be graded horizontal, or inclined slightly into the natural slope. (2) The outside ofthe bottom key should be below the topsoil or unsuitable surficial material and at least 2 feet into dense formational material. Where hard rock is exposed in the bottom ofthe key, the depth and configuration ofthe key may be modified as approved by the Consultant. GI rev. 8/98 4.5. After areas to receive fill have been cleared, plowed or scarified, the surface should be disced or biaded by the Contractor until it is uniform and free from large clods. The area should then be moisture conditioned to achieve the proper moisture content, and compacted as recommended in Section 6.0 of these specifications. 5. COMPACTION EQUIPMENT 5.1. Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of acceptable compaction equipment Equipment shall be of such a design that it will be capable of compacting the soil or soil-rock fill to the specified relative compaction at the specified moisture content. 5.2. Compaction of rock fills shall be performed in accordance with Section 6.3. 6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL 6.1. Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with the following recommendations: 6.1.1. Soil fill shall be placed by the Contractor in layers that, when compacted, should generally not exceed 8 inches. Each layer shall be spread evenly and shall be thoroughly mixed during spreading to obtain uniformity of material and moisture in each layer. The entire fill shall be constmcted as a unit in nearly level lifts. Rock materials greater than 12 mches in maximum dimension shall be placed in accordance with Section 62 or 6.3 of these specifications. 6.1.2. In general, the so/7 fill shall be compacted at a moisture content at or above the optimum moisture content as detennined by ASTM D1557-91. 6.1.3. When the moisture content of soil fill is below that specified by the Consultant, water shall be added by tiie Contractor until the moisture content is in the range specified. 6.1.4. When the moisture content of the soil fill is above the range specified by the Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by the Contractor by blading/mixing, or other satisfactory methods until the moisture content is within the range specified. GI rev. 8/98 6.1.5. After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted by the Contractor to a relative compaction of at least 90 percent. Relative compaction is defined as the ratio (expressed in percent) of the in-place dry density of the compacted fill to the maximum laboratory dry density as determined in accordance with ASTM Dl 557-91. Compaction shall be continuous over the entire area, and compaction equipment shall make sufficient passes so that the specified minimum relative compaction has been achieved throughout the entire fill. 6.1.6. Soils having an Expansion Index of greater than 50 may be used in fills if placed at least 3 feet below finish pad grade and should be compacted at a moisture content generally 2 to 4 percent greater than the optimum moisture content for the material. 6.1.7. Properly compacted soil fill shall extend to the design surface of fill slopes. To achieve proper compaction, it is recommended that fill slopes be over-built by at least 3 feet and then cut to the design grade. This procedure is considered preferable to track-walking of slopes, as described in the following paragraph. 6.1.8. As an altemative to over-buildmg of slopes, slope faces may be back-rolled with a heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height intervals. Upon completion, slopes should then be track-walked with a D-8 dozer or similar equipment, such that a dozer track covers all slope surfaces at least twice. 6.2. Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance with the following recommendations: 6.2.1. Rocks larger than 12 inches but less than 4 feet in maximum dimension may be incorporated into the compacted soil fill, but shall be limited to the area measured 15 feet minimum horizontally from the slope face and 5 feet below finish grade or 3 feet below the deepest utility, whichever is deeper. 6.2.2. Rocks or rock fragments up to 4 feet in maximum dimension may either be individually placed or placed in windrows. Under certain conditions, rocks or rock fragments up to 10 feet in maximum dimension may be placed using similar methods. The acceptability of placing rock materials greater than 4 feet in maximum dimension shall be evaluated during grading as specific cases arise and shall be approved by the Consultant prior to placement. GI rev. 8/98 6.2.3. For individual placement, sufficient space shall be provided between rocks to allow for passage of compaction equipment. 6.2.4. For windrow placement, the rocks should be placed in trenches excavated in properly compacted soil fill. Trenches should be approximately 5 feet wide and 4 feet deep in maximum dimension. The voids around and beneath rocks should be filled with approved granular soil having a Sand Equivalent of 30 or greater and should be compacted by flooding. Windrows may also be placed utilizing an "open-face" method in lieu of the trench procedure, however, this method should first be approved by the Consultant. 6.2.5. Wmdrows should generally be parallel to each other and may be placed either parallel to or perpendicular to the face of the slope depending on the site geometry. The minimum horizontal spacing for windrows shall be 12 feet center-to-center with a 5-foot stagger or offset from lower courses to next overlying course. The mmimum vertical spacing between windrow courses shall be 2 feet firom the top of a lower windrow to the bottom of the next higher windrow. 6.2.6. All rock placement, fill placement and flooding of approved granular soil in the windrows must be continuously observed by the Consultant or his representative. 6.3. Rock fills, as defined in Section 3.1.3., shall be placed by the Contractor in accordance with the following recommendations: 6.3.1. The base of the rock fill shall be placed on a sloping surface (minimum slope of 2 percent, maxunum slope of 5 percent). The surface shall slope toward suitable subdrainage outlet facilities. The rock fills shall be provided with subdrains during constmction so that a hydrostatic pressure buildup does not develop. The subdrains shall be permanently connected to controlled drainage facilities to control post-constmction infiltration of water. 6.3.2. Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock tmcks traversing previously placed lifts and dumping at the edge of the currently placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the rock. The rock fill shall be watered heavily during placement. Watering shall consist of water tmcks traversing in front of the current rock lift face and spraying water continuously during rock placement. Compaction equipment with compactive energy comparable to or greater than that of a 20-ton steel vibratory roller or other compaction equipment providing suitable energy to achieve the GI rev. 8/98 required compaction or deflection as recommended in Paragraph 6.3.3 shall be utilized. The number of passes to be made will be determined as described in Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional rock fill lifts will be permitted over the so/7 fill. 6.3.3. Plate bearing tests, in accordance with ASTM D1196-64, may be performed in both the compacted soil fill and in the roc^ fill to aid in determining the number of passes of the compaction equipment to be performed. If performed, a minimum of three plate bearing tests shall be performed in the properly compacted soil fill (minimum relative compaction of 90 percent). Plate bearing tests shall then be performed on areas of roc^^ fill having two passes, four passes and six passes of the compaction equipment, respectively. The number of passes required for the rock fill shall be detennined by comparing the results of the plate bearing tests for the soil fill and the rock fill and by evaluating the deflection variation with number of passes. The requued number of passes of the compaction equipment will be performed as necessary until the plate bearing deflections are equal to or less than that determined for the properly compacted soil fill. In no case will the required number of passes be less than two. 6.3.4. A representative of the Consultant shall be present during rock fill operations to verify that the minimum number of "passes" have been obtained, that water is being properly applied and that specified procedures are being followed. The actual number of plate bearing tests will be determmed by the Consultant during grading. In general, at least one test should be performed for each approximately 5,000 to 10,000 cubic yards of root fill placed. 6.3.5. Test pits shall be excavated by the Contractor so that the Consultant can state that, in his opinion, sufficient water is present and that voids between large rocks are properly filled with smaller rock material. In-place density testing will not be required in the roc^ fills. 6.3.6. To reduce the potential for "piping" of fines into the rock fill fi-om overlying so/7 fill material, a 2-foot layer of graded filter material shall be placed above the uppermost lift of rock fill. The need to place graded filter material below the rock should be determined by the Consultant prior to commencing grading. The gradation of the graded filter material will be determined at the time the rock fill is being excavated. Materials typical of the rock fill should be submitted to the Consultant in a timely manner, to allow design of the graded filter prior to the commencement of rock fill placement. GI rev. 8/98 6.3.7. All rock fill placement shall be continuously observed during placement by representatives of the Consultant. 7. OBSERVATION AND TESTING 7.1. The Consultant shall be the Owners representative to observe and perform tests during clearing, gmbbing, filling and compaction operations. In general, no more tiian 2 feet in vertical elevation of so/7 or soil-rock fill shall be placed without at least one field density test being performed within that interval. In addition, a minimum of one field density test shall be performed for every 2,000 cubic yards of so/7 or soil-rock fill placed and compacted. 7.2. The Consultant shall perform random field density tests of the compacted so/7 or soil-rock fill to provide a basis for expressing an opinion as to whether the fill material is compacted as specified. Density tests shall be performed in the compacted materials below any disturbed surface. When these tests indicate that the density of any layer of fill or portion thereof is below that specified, the particular layer or areas represented by the test shall be reworked until the specified density has been achieved. 7.3. During placement of roc* fill, tiie Consultant shall verify that the minimum number of passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant shall request the excavation of observation pits and may perform plate bearing tests on the placed rock fills. The observation pits will be excavated to provide a basis for expressing an opinion as to whether the roc* fill is properly seated and sufficient moisture has been applied to the material. If performed, plate bearing tests will be performed randomly on the surface of the most-recentiy placed lift. Plate bearing tests will be performed to provide a basis for expressing an opinion as to whether the rock fill is adequately seated. The maximum deflection ui the roc* fill determined in Section 6.3.3 shall be less than the maximum deflection of the properly compacted so/7 fill. When any of the above criteria indicate that a layer of roc* fill or any portion thereof is below that specified, the affected layer or area shall be reworked until the roc* fill has been adequately seated and sufficient moisture applied. 7.4. A settlement monitoring program designed by the Consultant may be conducted in areas of roc* fill placement. The specific design of the monitoring program shall be as recommended in the Conclusions and Recommendations section of the project Geotechnical Report or in the final report of testing and observation services performed during grading. GI rev. 8/98 7.5. The Consultant shall observe the placement of subdrains, to verify that the drainage devices have been placed and constructed in substantial conformance with project specifications. 7.6. Testing procedures shall conform to the following Standards as appropriate: 7.6.1. Soil and Soil-Rock Fills: 7.6.1.1. Field Density Test, ASTM D1556-82, Density of Soil In-Place By the Sand-Cone Method. 7.6.1.2. Field Density Test, Nuclear Metiiod, ASTM D2922-81, Density of Soil and Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth). 7.6.1.3. Laboratory Compaction Test, ASTM D1557-91, Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound Hammer and 18-Inch Drop. 7.6.1.4. Expansion Index Test, Unifonn Building Code Standard 29-2, Expansion Index Test. 7.6.2. Rock Fills 7.6.2.1. Field Plate Bearing Test, ASTM Dl 196-64 (Reapproved 1977) Standard Method for Nonrepresentative Static Plate Load Tests of Soils and Flexible Pavement Components, For Use in Evaluation and Design of Airport and Highway Pavements. 8. PROTECTION OF WORK 8.1. During constmction, the Contractor shall properly grade all excavated surfaces to provide positive drainage and prevent ponding of water. Drainage of surface water shall be controlled to avoid damage to adjoining properties or to finished work on the site. The Contractor shall take remedial measures to prevent erosion of fi-eshly graded areas until such time as permanent drainage and erosion control features have been installed. Areas subjected to erosion or sedimentation shall be properly prepared in accordance with the Specifications prior to placing additional fill or stmctures. 8.2. After completion of grading as observed and tested by the Consultant, no fiirther excavation or filling shall be conducted except in conjunction with the services of the Consultant. GI rev. 8/98 9. CERTIFICATIONS AND FINAL REPORTS 9.1. Upon completion of the work. Contractor shall fumish Owner a certification by the Civil Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot horizontally of the positions shown on the grading plans. After installation of a section of subdrain, the project Civil Engineer should survey its location and prepare an as-built plan of the subdrain location. The im>ject Civil Engineer should verify die proper outlet for the subdrains and the Contractor should ensure that the drain system is fi%e of obstmctions. 9.2. The Owner is responsible for fiimishing a final as-graded soil and geologic report satisfactory to the appro[niate governing or accepting agencies. The as-graded report should be prepared and signed by a Califomia licensed Civil Engineer experienced m geotechnical engineering and by a Califomia Certified Engineering Geologist, indicating that the geotechnical aspects of the grading were performed in substantial conformance with the Specifications or approved changes to the Specifications. GI rev. 8/98 REFERENCES Anderson, J. G., Synthesis of Seismicity and Geologic Data in Califomia, U.S. Geologic Survey Open-File Report 84-424,1984, pp. 1-186. Blake, T. F., EQFAULT, A Computer Program for the Deterministic Prediction of Peak Honzontal Acceleration from Digitized Califomia Faults, User's Manual. 1989a, p. 79. , EQSEARCH, A Computer Program for the Estimation of Peak Horizontal Acceleration from Southem Califomia Historical Earthquake Catalogs, User's Manual. 1989b, p. 94. Jennings, C. W., Fault Map of Califomia with locations of Volcanoes, Thermal Springs and Thermal Wells, Califomia Division of Mines and Geology, 1975 (revised 1987). Tan, S. S., and Kermedy, M. P., Geologic Map of the Encinitas and Rancho Santa Fe 7.5' Quadrangles, San Diego County, Califomia, Cahfomia Division of Mines, Open-File Report 96-02.1996. Unpublished reports, aerial photographs, and maps on file with Geocon Incorporated. Wesnousky, S. G., Earthquakes, Quatemary Faults, and Seismic Hazard in Califomia, Joumal of Geophvsical Research. Vol. 91. No. B12.1986, pp. 12, 587, 631. Project No. 06542-52-01 June 28,2000