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CT 02-15; BRESSI RANCH INDUSTRIAL; GEOTECHNICAL UPDATE INVESTIGATION; 2014-01-21
croz_gc5 r 55 __54• I GEOTECHNICAL UPDATE. INVESTIGATION,,,': LOTS 19 TO 22 OF CARLSBAD TRACT CT-02-15 BRESSI RANCH, CARLSBAD, CALIFORNIA I r U 4 - Prepared For • Shea Properties Management Company, Inc --- 130 Vantis, Suite 200 U ' - Aliso Viejo, California 92656 U 4 S55 4 S - -• -' 4 S ' r - I) Project No. 10570.001., • January 21, 2014 • RECEIVED I Ad APR172015 I CITY OFCARLSBAD • - - PLANNING DIVISION ç I Leighton and Associ ates, 106., A LEIGHTON GROUP COMPANY - • I 1 I , • 5, S • - • T.-- I. Leighton and Associates, I nc. ,. A LEIGHTON GROUP COMPANY U January 21, 2014 -I Project No. 10570.001 U - Shea Properties Management Company, Inc. .. 130 Vantis, Suite 200 U Aliso Viejo, C.A.92656 Attention Mr. Jim Peterson I . . •- Subject: Geotechnical Update Investigation Lots 19 to 22 of Carlsbad Tract CT-02-15 Bressi Ranch, Carlsbad, California . .' In accordance with your request and authorization, we have conducted a geotèchnical I ..- update investigation for the proposed Lots 19 to 22-of Carlsbad Tract CT-02-15 in the ;.-.; Bressi Ranch area.of Carlsbad, California. Based on the results of our study, it is our professional opinion that the site is suitable for the proposed commercial development U . and associated improvements. The accompanying report presents a summary of our, update investigation and provides preliminary geotechnical conclusions and . recommendations relative to the proposed site development: -. U • If 'you have any questions regarding our report, please donot hesitate to contact this h,.: ::::1:z:::. opportunity to be of service. Z NO. 2457 I /1 CERTIFIED LEIGHTON AND ASSO, 1 41 ENGINEERING CIATES William D. Olson, RCE 45283 EXp.______ ' Mike Jensen, CEG 2457. Associate Engineer' e v1s. Project Geologist doon(jeihtonqroup corn .. O,c:t. rnienseneiqhtonqroup corn I Distribution: (4) Addressee U I P - - . 3934 Murphy Canyon Road, Suite B205 San Diego, CA 92123-4425 . 858.292.8030 Fax 858.292.0771 www.leightongroup.com -• I--. Geotechnical UDdate Investigation, Bressi RanchCarIsbad, California 10570.001 TABLE OF CONTENTS I Section Page 1.0 INTRODUCTION ...................................................................................................... I I 1.2 SITE LOCATION AND DESCRIPTION............................................................................2 1.3 PROPOSED DEVELOPMENT ......................................................................................2 I 2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING ..........................4 3.0 SUMMARY OF GEOTECHNICAL CONDITIONS ............................ ......................... 5 3.1 GEOLOGIC SETTING ................................................................................................5 3.2 AS-GRADED GEOLOGIC CONDITIONS ........................................................................5 3.3 SITE-SPECIFIC GEOLOGY ........................................................................................5 3.3.1 Artificial Documented Fill (Map Symbol-Af) ...................................................5 3.3.2 Santiago Formation (Map Symbol-Tsa) ......................................................... 6 3.4 SURFACE AND GROUND WATER ...............................................................................7 3.4.1 Infiltration.......................................................................................................7 3.5 GRADED SLOPES ....................................................................................................8. 3.6 SOIL CORROSIVITY..................................................................................................8 4.0 FAULTING AND SEISMICITY.................................................................................9 5.0 CONCLUSIONS .................................................................... . --------------------- ----------- 11 6.0 RECOMMENDATIONS..........................................................................................13 6.1 EARTHWORK .......................................................................................................... 13 6.1.1 Site Preparation...........................................................................................13 6.1.2 Mitigation of Cut/Fill Transition Conditions ..................................................14 6.1.3 Mitigation of High to Very High Expansive Soils at Finish Grade ................14 6.1.4 Excavations .................................................................................................. 14 6.1.5 Fill Placement and Compaction ................................................................... 15 6.2 FOUNDATION AND SLAB DESIGN CONSIDERATIONS ..................................................15 6.2.1 Moisture Conditioning...................................................................................17 6.2.2 Foundation Setback ....................................................................................18 6.2.3 Anticipated Settlement.................................................................................18 6.3 LATERAL EARTH PRESSURES ..............................................................................19 6.4 FENCES AND FREESTANDING WALLS ................................................ . ................... 21 6.5 CONCRETE FLATWORK .......................................................................................22 6.6 GEOCHEMICAL CONSIDERATIONS.........................................................................23 6.7 PRELIMINARY PAVEMENT DESIGN ........................................................................23 6.8 CONTROL OF SURFACE WATER AND DRAINAGE ....................................................25 6.9 SLOPE MAINTENANCE GUIDELINES ......................................................................26 6.10 LANDSCAPING AND POST-CONSTRUCTION ............................................................27 6.11 CONSTRUCTION OBSERVATION AND TESTING .......................................................28 Leighton Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 TABLE OF CONTENTS Section Page 7.0 LIMITATIONS ........................................................................................................29 Tables TABLE I - CBC MAPPED SPECTRAL ACCELERATION PARAMETERS - PAGE 10 TABLE 2- PRESATURATION RECOMMENDATIONS BASED ON FINISH GRADE SOIL EXPANSION POTENTIAL - PAGE 17 TABLE 3-MINIMUM FOUNDATION SETBACK FROM DESCENDING SLOPE FACES - PAGE 18 TABLE 4- LATERAL EARTH PRESSURES - PAGE 20 TABLE 5- PRELIMINARY PAVEMENT SECTION DESIGNS - PAGE 24 FIGURE FIGURE 1 - SITE LOCATION MAP - AT END OF TEXT PLATE PLATE 1 - GEOTECHNICAL MAP - IN POCKET - APPENDICES APPENDIX A - REFERENCES APPENDIX B - TEST PIT LOGS AND FIELD PERCOLATION TESTS APPENDIX C - LABORATORY TESTING PROCEDURES AND TEST RESULTS APPENDIX D - GENERAL EARTHWORK AND GRADING SPECIFICATIONS APPENDIX E -ASFE €4 -ii- . Leighton Geotechnical Update Report, Bressi Ranch, Carlsbad. California . 10570.001 1.0 INTRODUCTION 1.1 Purpose and Scope This. report presents the results of our geotechnical update investigation for Lots 19 to 22 of Carlsbad Tract CT-02-15 in the Bressi Ranch area of Carlsbad, California (Figure 1). The purpose of our geotechnical update investigation was to evaluate existing geotechnical conditions present at the site and to provide preliminary geotéchnical conclusions and recommendations relative to the proposed commercial development. As part of our update investigation of the site, we performed the following: Review of available pertinent, published, and unpublished geotechnical reports, geologic literature, and maps (Appendix A). Field reconnaissance of the existing onsite geotechnical conditions. Coordination with Underground Services Alert (USA) to locate potential underground utilities on or adjacent to the site. Subsurface exploration consisting of eight (8) test pits and two field percolation tests. The approximate boring and field percolation test locations are shown on the Geotechnical Map (Plate 1). The logs of the borings are presented in Appendix B. I . • Laboratory testing of representative soil samples obtained from the subsurface exploration. Results of these tests are presented in Appendix C, with the exception of moisture/density determinations, which are provided on I the boring logs (included in Appendix B) Compilation and analysis of the geotechnical data obtained from the field I investigation and laboratory testing. . I • Preparation of this report presenting our findings, conclusions, and geotechnical recommendations (including General Earthwork and Grading I . . 4 1 :. •1 . Leighton I Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 Specifications presented as Appendix D) with respect to the proposed design, I site grading, and general construction considerations. -. 1.2 Site Location and Description The site consists of a square shaped property bordered on the north by elevated I vacant commercial lots, on the west by a descending slope to existing commercial property, on the south by Gateway Road, and on the east by Innovation Way with Slater Place cul-de-sac projecting approximately 300 feet I into the site in a western direction perpendicular from Innovation Way. The total area of the proposed project is approximately 8.27 acres (360,000 ft2) and I . recently abated vegetation consisting of native grasses and weeds. A total of four desilting basins exist throughout site that are approximately 6 feet below the adjacent grades. As background, the mass grading operations for the overall area, Planning Area PA-1 to PA-5 and the associated streets was performed between September I 2003 and May 2004 (Leighton, 2004a). The rough grading resulted in a generally southwest sloping sheet-graded pad. The mass graded pad elevation ranges 1 .from approximately 365 feet mean sea level (msl) in the southwest portion of the site to 375 feet msl in the northeast portion. The grading operations were performed by Nelson and Belding, while Leighton and Associates performed the I .geotechnical observation and testing services. Grading of the site included: 1) the removal of potentially compressible desiccated older fill soils, undocumented fill soils, topsoil, colluvium, alluvium, and weathered formational material; 2) the. I . excavation of fill slope keys; 3) preparation of areas to receive fill; 4) the placement of a subdrain in the canyon bottom; 5) excavation of formational material; and 6) the placement of compacted fill soils. Site Latitude and Longitude I 33.12860 N . . . -117.2606°W I 1.3 Proposed Development . I . the proposed development is anticipated to consist of two 54,000 ft2 commercial/industrial buildings, truck loading docks, patio areas, driveways, parking areas, minor slopes, and associated landscaped areas (Shea, 2013). We I ,. ... . I . Leighton Geotechnical Update Report, Bressi Ranch Carlsbad. California - - 10570.001 anticipate that the proposed buildings will be concrete ..tilt-up. structures with concrete slab-on-grade floor and conventional foundations. Currently, precise grading plans were not available; however, we anticipate. that the proposed site grades will remain close to existing grades (i.e., relatively minor cuts and fills to achieve site grade(s) and a balanced site). ... . LI Leighton -3- Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING - On January 7 and January 8, 2014 our subsurface investigation of Lots 19 to 22 included the excavation of eight (8) exploratory test pits to depths ranging from approximately 5.5 to 9.5 feet below the existing ground surface (bgs) and two (2) field percolation tests advanced to approximately 4 feet bgs. The test pits were excavated with a 430 Caterpillar backhoe with a 24-inch wide bucket. The field percolation test holes were advanced with a 3.25-inch diameter hand auger. The purpose of these excavations was to evaluate the engineering characteristics of the onsite soils with regard to the proposed development. Our subsurface investigation allowed evaluation of the onsite soils, including those likely to be encountered at the proposed 'foundation elevations and provided representative samples for laboratory testing. A log of the test pits (T-1 through T-8) and data from the 'field percolation tests (P-i and P-2) are presented in Appendix B. The exploratory excavations were logged by a geologist from our firm. Representative bulk samples were obtained at selected intervals for laboratory testing. The approximate locations of the test pits and field percolation tests are shown on the Geotechnical Map (Plate 1). Subsequent to logging and sampling, the test pits were backfilled with native soils, and a compactive effort was applied to the backfill utilizing a compaction wheel. The compactive effort was observed and probed by a representative from our firm; however, compaction testing was not performed. Laboratory testing for was performed on representative samples to evaluate the I ' expansion potential, maximum density, shear strength parameters, and geochemical tests consisting of soluble sulfate and chloride contents, and minimum resistivity and pH ' tests, A discussion of the laboratory tests performed and a summary of the laboratory test results are presented in Appendix C. 1 I I NO j -4- . Leighton Geotechnical Update Report, Bressi Ranch, Carlsbad. California - - 10570.001 3.0 SUMMARY OF GEOTECHNICAL CONDITIONS 3.1 Geologic Setting . The subject site is located, in the coastal section of .the Peninsular Range Province, a geomorphic province with a long and active geologic history throughout Southern California. Throughout the last 54 million years, the area known as the "San Diego Embayment" has undergone several episodes of marine inundation and subsequent marine regression, resulting in the deposition of a thick sequence of marine and nonmarine sedimentary rooks on the basement rock of the Southern California batholith. Gradual emergence of the region from the sea occurred in Pleistocene time, and numerous wave-cut platforms, most of which were covered by relatively thin marine and nonmarine terrace deposits, formed as the sea receded from the land. Accelerated fluvial erosion during periods of heavy rainfall, coupled with the lowering of the base sea level during Quaternary time, resulted in the rolling hills, mesas, and deeply incised canyons which characterize the landforms we see in the general site area today. 3.2 As-graded Geologic Conditions The geologic or geotechnical conditions encountered during our current update study of the site were essentially as anticipated. A comprehensive summary of the geologic conditions (including geologic units, geologic structure, and faulting) are presented below. 3.3 Site-Specific Geology The geologic units encountered during our investigation and site grading consisted of artificial documented fill soils and the Santiago Formation. The approximate limits of the geologic units encountered are presented on the Geotechnical Map (Plate 1) and discussed (youngest to oldest) below. 3.3.1 Artificial Documented Fill (Map Symbol-Al) Documented fill soils placed during the prior grading operations that were observed and tested by Leighton and Associates are generally located -5- Leighton I I , 1 1 I 1. I I Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 along the western perimeter, a central section and in the southeast corner of the site (as indicated on Plate 1). In addition to the fill limits, the elevations of the bottom of the fill are provided on the geotechnical map so that potential fill differentials across the site can be identified. The field density test results presented in the as-graded geotechnical report for the project (Leighton, 2004c) indicated the fill soils were placed and compacted to at least a 90 percent relative compaction with moisture contents at or near the optimum moisture content. During our update study, the upper portion of the fill soils was found to be desiccated and. removals and/or scarification and recompaction will be necessary prior to the placement of additional fill or structural improvements. The fill soils typically consisted of silty sands, clayey sands, and to a lesser extent sandy to silty clays. Based on our review of the as graded geotechnical report (Leighton, 2004c), the thickness of fill on the site ranges from zero to approximately 53 feet below existing grades. 3.3.2 Santiago Formation (Map Symbol-Tsa) The Tertiary-aged Santiago Formation, as encountered during our update study, consisted primarily of massively bedded siltstones and claystones, and to a lesser extent sandstone. The sandstone generally consisted of orange-brown (iron oxide staining) to light brown, damp to moist, dense to very dense, silty very fine to medium grained sandstone. The siltstones and claystones were generally olive-green, dry to moist, stiff to hard, moderately weathered in the upper 5 feet, and occasionally fractured and moderately sheared. . Several well-cemented fossiliferous sandstone beds and clay seams were encountered during the mass grading (Leighton, 2004c). High to very high expansive formational claystones and siltstones are present at the existing finish grade elevation of the sheet-graded pad in the northeastern portions of the site: Well-cemented fossiliferous sandstone beds may' be present in the Santiago Formation near the surface or at depth. Deep excavations should anticipate the well-cemented beds and be prepared to utilized -6- 1 Leighton I Geotechnical Update Report, Bressi Ranch, Carlsbad, California - - 10570.001 larger excavations, breakers, and single-shank ripper to excavate I trenches. - ' 3.4 Surface and Ground Water No indication of surface water or evidence of surface ponding was observed site I visit. However, surface water may drain as sheet flow across the site during rainy periods and accumulate in lower elevations and in the on-site desilting basins. Ground water was not observed in the test pits during our investigation; however, I perched ground water levels may develop and fluctuate during periods of precipitation and after initial landscaping and irrigation has been installed. 3.4.1 Infiltration We performed two field percolation tests to evaluate the soil for potential infiltration of storm water. Field percolation test, P-i, is located within weathered Santiago Formational material; and field percolation test, P-2, and is located within documented artificial fill. The results of the field percolation tests indicated that the existing onsite soils generally have a percolation rates at 62 minutes per inch and 83 minutes per inch in P-i and P-2, respectively. It should be noted that generally, a percolation rate less than 120 minutes per inch is considered necessary to consider a site suitable for onsite surface infiltration of storm water. However, the site artificial fill consists of mixture of soils ranging from silty sands to clays with permeable and impermeable layers, which can transmit and perched ground water in unpredictable ways. Therefore, Low Impact Development (LID) measures may impact down gradient improvements and the use of some LID measures may not be appropriate for this project. Infiltration and Bio-retention Stormwater Systems design should be reviewed by geotechnical consultant. 'I -7- Li.ghtn Geotechnical Update Report, Bressi Ranch, Carlsbad. California - - - 10570.001 - 3.5 Graded Slopes Graded and natural slopes within the developed portion of the tract are considered grossly and surficially stable from a geotechnical standpoint. Manufactured cut and fill slopes within the tract were surveyed by the civil engineer are understood to have been constructed with slope inclinations of 2:1 (horizontal to vertical) or flatter. 3.6 Soil Corrosivity A preliminary corrosive soil screening for the on-site materials was completed to evaluate their potential effect on concrete and ferrous metals. The corrosion potential was evaluated using the results of laboratory testing on one representative soil sample obtained during our subsurface evaluation. Laboratory testing was performed on two representative samples to evaluate pH, minimum electrical resistivity, and chloride and soluble sulfate content. The samples tested had a measured pH ranging from 7.7 to 8.0, and. a measured minimum electrical resistivity ranging from 618 to 697 ohm-cm. Test results also indicated that the samples had a chloride content ranging from 109 to 214 ppm, and a soluble sulfate content of less than 450. ppm. Geotechnical Update Report, Bressi Ranch Carlsbad California 10570 001.. 4.0 FAULTING AND SEISMICITY I Our discussion of faults on the site is prefaced with a discussion of California legislation 1 - and state policies concerning the classification and land-use criteria associated with faults. By definition of the California Mining and Geology Board, anactive fault is a fault that has I had surface displacement within Holocene time (about the last 11,000 years). The State Geologist has defined a potentially active fault as any fault considered to have been active during Quaternary time (last 1,600,000 years) but that has not been proven to be active or, I inactive. This definition is used in delineating Fault-Rupture Hazard Zones as mandated - by the Alquist-Priolo Earthquake Fault Zoning Act of 1972 and as most recently revised in I .2007. The intent of this act is to assure that unwise urban development does not occur• - across the traces of active faults. Based on our review of the Fault-Rupture Hazard Zones, the site is not located within any Fault-Rupture Hazard Zone as created by the I Alquist-Priolo Act (Bryant and Hart, 2007) San Diego, like the rest of southern California, is seismically active as a result of being . 1 •' located near the-active margin between the North American and Pacific tectonic plates. The principal source' of seismic activity is movement along the northwst-trending i : regional fault zones such as the San Andras, San Jacinto and Elsinore Faults Zones, - as well as along less active faults such as the Rose Canyon Fault Zone. As indicated in the Supplemental Geotechnical Report for the Bressi Ranch project (Leighton, 2001), I there are no known major or active faults on or in the immediate vicinity of the site The nearest known active fault is the Rose Canyon Fault Zone, which is located approximately 7.0 miles (.11 .2 kilometers) west of the site ..- . • S I - • . . - S • - •.. 5- 5 As discussed above, evidence of active faulting was not encountered within the site during 1 .. the mass grading operations in 2003-2004 (Leighton, 2004b) However, several minor, inactive faults were encountered within the limits of the Bressi Ranch development that are not considered a constraint to development of Planning Area 2 Geologic mapping of I the onsite minor faults, where topsoil was encountered over the faults, indicated that the faults did not extend into or offset the topsoil, suggesting that the faults are not active Because of the lack of known active faults on the site, the potential for surface rupture at the site is considered low. Shallow ground rupture due to shaking from distant seismic I events is not considered a significant hazard, although it is a possibility at any site 'However, due to the presence of slopes on-site, lurching and associated ground cracking near the tops of slopes is possible OW I se-s A. . •1 a i Leighton - - - .5 • 'i Geotechnithl Update Report, Bressi Ranch, Carlsbad. California •. - 10570.001 e . - I Liquefaction and dynamic settlement of soils can be caused by, strong vibratory motion due to earthquakes. Both research and historical data indicate that loose, saturated,' granular soils are susceptible to liquefaction and dynamic settlement. Liquefaction is, typified by a loss of shear strength in the affected soil layer,, thereby causing the soil to act as a viscous liquid. This effect may be manifested by'excessive settlements and sand boils at the ground surface. The fill and formational materials underlying the site are not considered liquefiable due to their fine-grained nature, dense physical. and unsaturated condition I characteristics, The effect of seismic shaking may be mitigated by adhering to the California Building I Code I and state-of-the-art seismic design practices of the, Structural Engineers Association of California. Provided below in Table 1 are the' . risk-targeted spectral acceleration parameters for the project determihed in accordance with the 2013 .I California Building Code (CBSC, 2013) and the USGS WorldwideSeismic Design Values tool (Version 3.1.0): —. •":•' - . I I I Table CBC Mapped Spectral Acceleration Parameters Site Class ' Fa 1.081 . Site Coefficients F .. 1.594 Mapped MCER Spectral Accelerations . - - 1047g S1 - = 0.406g' Site Modified MCER Spectral Accelerations SMS ,' 1.1 32g' - •.'. SM1 -' 0.647g Design.Spectral Accelerations S,DS : 0.755g 5D1 0:4319: Utilizing ASCE Standard 7-10, in accordance with Section 11.8.3, the' following additional parameters for the peak horizontal ground acceleration are associated with the Geometric Mean Maximum Considered Earthquake (MCEG).-The mapped -MCEG' - peak ground acceleration (PGA) is 0.401g for the site. For a Site Class D, the FPGA is I ,1 099 and the mapped peak ground acceleration adjusted for Site Class effects (PGAM) is 0.441 g for the site I4 10 - Lelghtn -- - -- I S 'Geotechnicat Update Report. Bressi Ranch, Carlsbad, California 10570.001 5.0 CONCLUSIONS I Based on the results of our update geotechnical study of the site, it is our professional I . opinion that the proposed commercial development is feasible from a geotechnical standpoint, provided the following conclusions and recommendations are incorporated I' into the project plans and specifications. The following is a summary of the geotechnical factors that may affect development of the site. Based on our subsurface exploration, the near-surface fill soils are locally disturbed (i.e., the upper 2 feet). These soils are not considered suitable for support of additional fill soils, structural loads or surface improvements in their present condition. Remedial grading' measures such as' scarification, removals and recompaction will be necessary to mitigate this condition if the disturbed soils are not removed by the proposed excavation. High to very high expansive formational claystones and siltstones are present at the existing finish grade elevation of the sheet-graded pad in the northeastern portions - of the site. Remedial grading of this area will be required' for proposed improvements. A cut/fill transition condition is anticipated beneath proposed northern building, and I will need to be mitigated by the over excavation of the cut portion of the building pad. Note that once final civil and building structural plans are completed, a geotechnical review will required to evaluate cut/fill transitions conditions and determine the I recommended over excavation depths for mitigation. 'I ' • Laboratory test results indicate the fill soils present on the site have a moderate potential for sulfate attack on normal concrete, and are moderately to severely corrosive on buried metal pipes and conduits. The existing onsite soils, with exception of the highly expansive soil in the northeastern po rtion of the site, appear to be suitable material for reuse as fill provided they are relatively free of organic material, debris, and rock fragments larger than 8 inches in maximum dimension. .5.-, I 4 Leighton Geotechnical UDdate Reoort. Bressi Ranch. Carlsbad. California—" ' - 10570.001 Near surface ground water or seepage was not' encountered during, our investigation; however, perched ground -water and seepage may develop during penods of precipitation and after site irrigation. Although foundation plans have not been developed nor building loads determined, we anticipate that conventional foundation system, consisting of continuous and spread footings with slab-on-grade flooring supported by competent fill or formational materials, will be used. -12- . . ' Leighton I Geotechnical Update Report, BressiRanch. Carlsbad, California -' . - -' .- - 10570.001 6.0 RECOMMENDATIONS 6.1 Earthwork We anticipate that earthwork at the site will consist of site preparation, remedial and fine grading, utility trench excavation and backfill, and driveway and parking area pavement section preparation and compaction. We recommend that the earthwork on site be performed in accordance with the following recommendations, the General Earthwork and Grading Specifications for Rough Grading included in Appendix D, and the City of Carlsbad grading requirements. In case of conflict, the following recommendations shall supersede those in Appendix D. The contract between the developer and earthwork contractor should be worded such that it is the responsibility of the contractor to place the fill I' properly and in accordance with the recommendations of this report and the specifications in Appendix D, notwithstanding the testing and observation of the geotechnical consultant. 6.1.1 Site Preparation During grading, the areas to receive structural fill or engineered structures should be cleared of surface obstructions, potentially compressible material (such 'as desiccated fill soils or weathered formational material), and stripped of vegetation. Vegetation and debris should be removed and properly disposed of offsite. Holes resulting from removal of buried obstructions that extend below finish site grades should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be reprocessed to a minimum depth of 24 inches, brought to 2 percent above optimum moisture condition, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). If the length of time between the completion of grading and the construction is longer than six months, we recommend that the building pads be evaluated by the geotechnical consultant and, if needed, the finish grade soils on the building pads should be scarified a minimum of 12 inches, moisture-conditioned to 2 percent above optimum moisture-content and recompacted to a minimum 90 percent relative compaction (based on ASTM Test Method D1557). Aps -13- 0 , Leighton. Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 6.1.2 Mitigation of Cut/Fill Transition Conditions In order to reduce the potential for differential settlement of the proposed buildings in areas of cut/fill transitions, we recommend the entire cut portion of the building pad be overexcavated and replaced with properly compacted fill. Currently, we recommend that the overexcavation of the cut portion of the building pad should be made a minimum of 5 feet below the lowest planned footing elevation or load dock bottom, and it should extend laterally at least 10 feet beyond the building perimeter or footprint. Note that once final civil and building structural plans are completed, a geotechnical review will required to evaluate cut/fill transitions conditions and determine the recommended over excavation depths for mitigation 6.1.3 Mitigation of High to Very High Expansive Soils at Finish Grade High to very high expansive soils were encountered in the northeastern portion of the site during the original site grading (Leighton, 2014c). Therefore, we recommend that these soils be removed and replaced with low to medium expansive soils below the planned finish grade of the proposed buildings and other movement sensitive improvements. The removal depth should be a minimum of 3 feet below the lowest planned footing elevation or until lower expansive sandy soils are encountered. We also recommend that the overexcavation bottom be tilted a minimum of 2- percent toward the fill side of the building pad or toward the street/driveway in order to minimize perched ground water conditions. The resulting excavation should be replaced with properly compacted fill possessing a lower expansion potential. The actual location of the claystones and siltstones at or near finish grade at the site should be evaluated during the future fine grading operations. It should also be noted that the reuse of the highly expansive soils is questionable and/or limited, and offsite disposal may be required. 6.1.4 Excavations Excavations of the on-site materials may generally be accomplished with conventional heavy-duty earthwork equipment. It is not anticipated that blasting will be required or that significant quantities of oversized rock (i.e. rock with maximum dimensions greater than 8 inches) will be generated during future grading. However, localized cemented zones within the out I -14- EM I,. Geotechnical Update Report, Bressi Ranch, Car'sbad. California . 10570.001 areas and oversized rock placed within the compacted fill may be I encountered on-the site that may require heavy ripping and/or removal. If oversized rock is encountered, it should be placed in accordance with the I . recommendations presented in Appendix D, hauled offsite, or placed in non- structural or landscape areas. Deep excavations should anticipate well- cemented sandstone beds across the site. Larger excavations, breakers, I and single-shank ripping may be required in deep utility and in-grading excavations. I Due to the relatively dense characteristics of the on-site soils, temporary excavations such as utility trenches in the on-site soils should remain stable I . for the period required to construct the utility, provided they are constructed and monitored in accordance with OSHA requirements. 6.1.5 Fill Placement and Compaction The on-site soils are generally suitable for use as compacted fill provided they are free or organic material, debris, and rock fragments larger than 8 inches in maximum dimension. We do not recommend that high or very high expansive soils be utilized as fill for the building pads or, as retaining wall backfill. All fill soils should be brought to 2-percent over the optimum moisture content and compacted in uniform lifts to at least 90 percent relative compaction based on the laboratory maximum dry density (ASTM Test Method D1557). The optimum lift thickness required to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in lifts not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in general accordance with Appendix D, the current City of Carlsbad grading ordinances, sound construction practices, and the geotechnical recommendations presented herein. 6.2 Foundation and Slab Design Considerations The foundations and slabs for the proposed buildings should be designed in accordance with structural considerations and the following preliminary recommendations. These preliminary recommendations assume that the soils I am -15- . Leighton. HI 11, Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 encountered within 5 feet of finish pad grade will have a very low to medium potential for expansion. If highly expansive soils are encountered within 5 feet of the proposed finish grade elevations during site grading, these expansive soils should be removed and replaced with lower expansive soils. If replacement of the expansive soils is not feasible, additional foundation design will be necessary. The proposed buildings may be supported by conventional, continuous or isolated spread footings. Footings should extend a minimum of 24 inches beneath the lowest adjacent soil grade. At these depths, footings may be designed for a maximum allowable bearing pressure of 2,500 pounds per square foot (psf) if founded in properly compacted fill soils or formational material. An allowable capacity increase of 500 psf for every 6 inches of additional embedment may be used to a maximum of 3,500 psf. The allowable pressures may be increased by one-third when considering loads of short duration such as wind or seismic forces. The minimum recommended width of footings is 18 inches for continuous footings and 24 inches for square or round footings. Footings should be designed in accordance with the structural engineer's requirements and have a minimum reinforcement of four No. 5 reinforcing bars (two top and two bottom). . I I The slab-on-grade finish floors should be at least 5 inches thick and be reinforced with No. 4 rebars 18 inches on center or No. 5 rebars at 24 inches on center, each way. All reinforcing should be placed at mid-height in the slab. Slabs should be underlain by a 2-inch layer of clean sand (sand equivalent greater than 30), which is in-turn underlain by a minimum 10-mil plastic sheeting (moisture barrier) and an additional 2 inches of clean sand. We recommend that control joints be provided across the slab at appropriate intervals as designed by the project architect. Some moisture sensitive flooring may require additional measures to mitigate moisture migration through the slab as designed by the project architect. For heavy equipment loading, greater slab-on-grade thicknesses and increased reinforcing may be required, as determined by the structural engineer. Based on the anticipated subgrade soil, we recommend using a modulus of subgrade reaction of 100 psi per inch for the design of the interior slab-on-grade floor subject to equipment loading. I -16- Leighton. U U U I U I Geotechnical Update Report, Bressi Ranch, Carlsbad, California - '--' . - - 10570.001 The potential for slab cracking may be reduced by careful control of I water/cement ratios. The contractor should take appropriate curing precautions during the pouring of concrete 'in hot weather to minimize cracking of slabs. We recommend that a slipsheet (or equivalent) be utilized if grouted tile, marble tile, or other crack-sensitive floor covering is planned directly on concrete slabs. All I slabs should be designed in accordance with structural considerations. 6.2.1 Moisture Conditioning I I I' I I I I I I . I I I I I' The slab subgrade soils underlying the , foundation systems ,of the proposed structures should be presoaked in accordance with the recommendations presented in Table 2 prior to placement of the moisture barrier and slab concrete. The subgrade soil moisture content should be checked by a representative of Leighton and Associates prior to slab construction. . Table 2 Presaturation Recommendations Based on Finish Grade Soil Expansion Potential Expansion Potential Very Low Low Medium Presaturation Criteria (0-20) (21-50) (51-90) Minimum Presoaking Depth 6 12 , 18 (in- inches) Minimum 2% above 1.3 times 1.4 times optimum Recommended optimum ' optimum moisture Moisture Content moisture moisture Presoaking or moisture conditioning may be achieved in a number of ways, bLlt based on our professional experience, we have found that minimizing the moisture loss of pads that have been completed (by periodic wetting to keep the upper portion of the pad from drying out) and/or berming the lot and flooding if for a short period of time (days to a few weeks) are some of the more efficient ways to meet the presoaking -17- Table 3 Minimum Foundation Setback from Descending Slope Faces Slope Height ' Minimum Recommended Foundation Setback Less than 5 feet 5 feet 5 to 15 feet 7 feet I I I I Geotechnical Update Report, Bressi Ranch, Carlsbad. California -' 10570.001 . requirements. If flooding is performed, a couple of days to let the upper I portion of the pad dry out and form a crust so equipment can be utilized should be anticipated. ' 6.2.2 Foundation Setback I We recommend a minimum horizontal setback distance from the face of slopes or adjacent retaining walls for all structural foundations, footings, and other settlement-sensitive structures as indicated on Table 3. This distance ' . is measured from the outside bottom edge of the footing, horizontally to the slope face and is based on the slope height and type of soil.. However, the foundation setback distance may be revised by the geotechnical consultant on a case-by-case basis if the geotechnical conditions are different than anticipated. I Please note that the soils within the structural setback area possess poor lateral stability, and improvements (such as. retaining walls, sidewalks, fences, pavements, etc.) constructed within this setback area may be subject to lateral movement and/or differential settlement. Potential distress to such improvements may be mitigated by providing a deepened footing or a pier and grade beam foundation system to. support the improvement. The deepened footing should meet the setback as described above., 6.2.3 Anticipated Settlement Settlement is 'anticipated to occur at varying times over the life of the project. Short-term settlement typically occurs upon application of the -18- Leighton I I I Geotechnical Update ReDort, Bressi Ranch, Carlsbad, Cahfomia 10570.001 foundation loads and is essentially completed within the construction period. Long-term (hydroconsolidation) settlement typically occurs in deep fills upon additional water infiltration into the fill soils (even in properly I compacted fill soils and even with subdrains provided). This settlement typically occurs over many years. Long-term settlement values and the effects on the foundations should be evaluated after the site is graded and I . the actual fill thicknesses beneath the proposed foundations known. However, for preliminary planning purposes, total future settlement is expected to be order of 1 inch and differential- settlement-is- estimated-to I . be on the order of 1/2 inch in 50 feet. 6.3 Lateral Earth Pressures The recommended lateral pressures for the onsite very low to low expansive soil I - (expansion index less than 50) and level or sloping backfill are presented on Table 4. High to very high expansive soils (having an expansion potential greater than 91) should not be used as backfill soils on the site. Embedded structural walls should be designed for lateral earth pressures exerted on them. The magnitude of these pressures depends on the amount of deformation that the wall can yield under load. If the wall can yield enough to mobilize the full shear strength of the soil, it can be designed for "active" pressure. If the wall cannot yield under the applied load, the shear strength of the soil cannot be mobilized and the earth pressure will be higher. Such walls should be designed for "at rest" I conditions: If a structure moves toward the soils, the resulting resistance developed by the soil is the "passive" resistance. The above noted passive resistance assumes an appropriate setback per Section6.2.2. I I I I - -19- -. - Le9hton Geotechnical Update Report, Bressi Ranch. Carlsbad, California 10570.001 Table 4 Lateral Earth Pressures Conditions Equivalent Fluid Weight (pcf) Very Low to Low Expansive Soils Expansion Index less than 50' Level 2:1 Slope Active 35 55 At-Rest 55 65 Passive 350 150 I For design purposes, the recommended equivalent fluid pressure for each case for walls founded above the static ground water and backfilled with soils of very low to low expansion potential or medium expansion potential is provided on Table 4. The I . 'equivalent fluid pressure values assume free-draining conditions. If conditions other than those assumed above are anticipated, the equivalent fluid pressures values should be provided on an individual-case basis by the geotechnical engineer. The I ' geotechnical and structural engineer should evaluate surcharge-loading effects from the adjacent structures. All retaining wall structures should be provided with I . appropriate drainage and appropriately waterproofed. The outlet pipe should be sloped to drain to a suitable outlet. Typical wall drainage design is illustrated in I .Appendix D. . For sliding resistance, the friction coefficient of 0.35 may be used at-the concrete and soil interface. In combining the total lateral resistance, the passive pressure or I the frictional resistance should be reduced by 50 percent. Wall footings should be designed in accordance with structural considerations. The passive resistance I .value may be increased by one-third when considering loads of short duration including wind or seismic loads. The horizontal distance between foundation elements providing passive resistance should be minimum of three times the depth I. 20- . eighton 1 Geotechnical Update ReDort, Bressi Ranch, Carlsbad, California - . 10570.001 of the elements to allow full development of these passive pressures. The total I depth of retained earth, for the design of cantilever walls should be the vertical distance below the ground surface measured at the wall face for stem design or I measured at the heel of the footing for overturning and sliding. All wall backcuts should be made in accordance with the current OSHA requirements. I The granular and native backfill soils should be compacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). The granular fill should extend horizontally to a minimum distance equal to one-half the wall height behind I the walls. The walls should be constructed and backfilled as soon as possible after backcut excavations. Prolonged exposure of backcut slopes may result in some I localized slope instability. Foundations for retaining walls in competent formational soils or properly I compacted fill should be, embedded at least 24 inches below lowest adjacent grade. At this depth, an allowable bearing capacity of 2,000 psf may be assumed. I 6.4 Fences and Freestanding Walls I Footings for freestanding walls should be founded a minimum of 24 inches below lowest adjacent grade. To reduce the potential for unsightly cracks in freestanding walls, we recommend inclusion of construction joints at a maximum of 15-foot I .intervals. This spacing may be altered in accordance with the recommendations of the structural engineer, based on wall reinforcement details. I Our experience on similar sites in older developments indicates that many walls on shallow foundations near the top-of-slopes tend to tilt excessively over time as I a result of slope creep. If the effects of slope creep on top-of-slope walls are not deemed acceptable, one or a combination of the options provided in the following paragraphs should be utilized in the design of such structures, based on the I desired level of mitigation of creep-related effects on them. A relatively inexpensive option to address creep related problems in top-of-slope I walls and fences is to allow some degree of creep damage and design the structures so that tilting or cracking will be less visually obvious, or such that they I may be economically repaired or replaced. If, however, a better degree of creep mitigation is desired, the walls and fences may be provided with the deepened I Geotechnical Update Report, Bressi Ranch Carlsbad, California-- 10570.001 foOtings to meet the foundation setback criteria, or these structures may be 1 constructed to accommodate potential movement. I Under certain circumstances, an effective solution to minimize the effects of creep on top-of-slope walls and fences is to support these structures on a pier-and-- grade-beam system. The piers normally consist of minimum 1 2-inch diameter cast- in-place caissons spaced at a maximum of 8 feet on center, and connected - together by a minimum 12-inch-thick grade beam at a shallow depth. The piers are - typically at least 10 feet deep for medium or high-expansive--soil. The steel I reinforcement for the system should be designed *ith consideration of Wall/fence type and loading. Walls or fences aligned essentially perpendicular to the top of the I slope are normally supported on the pier-and-grade-beam system for at least that part of the wall that is within 15 feet from the top-of-slope. Caisson support is recommended for all top-of-slope walls where slopes are greater than 10 feet in I height and/or the soil on and adjacent to the slope consists of high to very high expansive soils. I - 6.5 Concrete Flatwork Some of the on-site soils possess a high expansion potential. If possible, selected grading should be performed to reduce the amount of expansive soil placed at ubgrade elevations in the areas of concrete flatwork. Based on the anticipated conditions and experience the adjacent commercial development, we recommend that the upper 24 inches of subgrade soils be pre-saturated to at - least 5 percent above optimum moisture content prior to placement of concrete flatwork. For areas previously graded that require reprocessing, we recommend that the upper 18 inches of subgrade soils be scarified and moisture conditioned and lightly re-compacted prior to placement of the concrete . flatwork. The reprocessed subgrade soils should be moisture-conditioned to at least 5 percent above optimum moisture content and compacted to around 90 percent relative compaction based on. American Standard of Testing and Materials (ASTM) Test Method D1557. Note that these recommendations are for sidewalks and other concrete flatwork only and are not applicable to concrete pavement areas subject to traffic loading. We also recommend that the sidewalk and/or concrete flatwork be at least 4, inches thick and be reinforced with No. 3 rebars at a minimum spacing of at least 18 inches, each way. In addition, the sidewalk sections should be doweled into -22- Leighton I Geotechnical Update Report, Bressi Ranch, Carlsbad, California - 10570.001 the adjacent curbs at a spacing of 36 inches on center and doweled into adjacent I existing sidewalk sections and slabs (at doorways) at a minimum spacing of 18 inches on center. Note that our representative should also observe and test the I, compaction of the reprocess subgrade soil prior to placement of the reinforcement for new sidewalk sections. •. . - 6.6 Geochemical Considerations Geochemical screening of-the representative onsite soils was performed as part I of our original study and the results presented in Appendix C. As indicated in Appendix C, the results of our limited testing and our professional knowledge of I similar soils in other portions of the Bressi Ranch project, indicates that concrete in contact with the on-site soils should be designed in accordance with the "severe" category. In addition, the onsite soils are anticipated to have a corrosive I .environment for buried metal pipes or uncoated metal conduits. Laboratory testing should be performed on the soils placed at or near finish grade after I . completion of site grading to ascertain the actual corrosivity characteristics. 6.7 Preliminary Pavement Design I Based on our past experience on adjacent development to the northeast and east a preliminary R-Value of 5 is factored into our pavement analysis. The appropriate I . pavement sections will depend on the type of subgrade soil, shear strength, traffic load, and planned pavement life. Since an evaluation of the actual subgrade soils cannot be made at this time, we have assumed an R-value of 5 and Traffic Indexes I (TI) of 4.0, 5.0, and 6.0. The Asphalt Concrete (AC) and Class 2 aggregate base (AB) pavement sections presented on Table 4 should be used for preliminary planning purposes only. The pavement sections for the onsite truck and vehicle driveways should be based I . on an assumed TI of 6.0 and 5.0, respectively. The pavement sections for vehicle parking stalls should be based on a TI of 4.0. Final pavement designs should be completed in accordanóe with the City of Carlsbad design criteria after R-value I tests have been performed on the actual subgrade materials. I I . I -2- . Lighton Geotechnical Update Report, BressiRarch, Carlsbad, California - - 10570.001 Table 5 Preliminary Pavement Section Designs Traffic Assumed Preliminary Pavement Sections AC and Base Section Full Depth AC Section Index R-Value 4 inches AC over 5 inches 6.5 inches AC over native 4 0 5 • Class 2 Aggregate Base subgrade soils 4 inches AC over 8 inches 8.0 inches AC over native 5.0 5 Class 2 Aggregate Base subgrade soils 4. inches AC over 12 inches 10 inches AC over native 6.0 5 Class 2 Aggregate Base subgrade soils Asphalt Concrete (AC) and Class 2 aggregate base materials should conform to and be placed in accordance with the latest revision of California Department. of Transportation Standard Specifications. Prior to placing the pavement section, the subgrade soils should have a relative compaction of at least 95 percent to a minimum depth of 12 inches (based on ASTM Test Method D1557). Arëgate Base should be compacted to a minimum of 95 percent relative compaction (based on ASTM Test Method D1557) prior to placement of the AC. For pavement areas subject to heavy truck loading (i.e., delivery trucks, fork lifts etc.), we recommend a full depth of Portland Cement Concrete (PCC) section of 8 inches with steel reinforcement (number 4 bars at 18-inch centers, each way) and crack-control joints at a minimum spacing of 10 feet. We recommend that sections be as nearly square as possible. A 3,500-psi mix that produces a 600- psi modulus of rupture should be utilized. The actual pavement design should also be in accordance with City of Carlsbad and ACI design criteria. If pavement areas are adjacent to heavily watered landscaping areas, we recommend some measures of moisture control be taken to prevent the subgrade soils from becoming saturated. It is recommended that the concrete curbing, separating the landscaping area from the pavement, extend below the aggregate I •. •- .. - . . -24- . L:Ighton I Geotechnical Update Report, Bressi Ranch, Carlsbad. California . 10570.001 base to help seal the ends of the sections where heavy landscape watering may 1 have access to the aggregate lase. Concrete sWales should be designed if asphalt pavement is used for drainage of surface waters. 1 6.8 Control of Surface Water and Drainage Regarding Low Impact Development (LID) measures, we are of the opinion that infiltration basins, and other onsite storm water retention and infiltration systems can potentially create adverse perched ground water conditions. In addition, the existing onsite soils are anticipated to provide relatively low or minimal infiltration rates for the surface water. Therefore, given the site location and underlying I geologic conditions, infiltration type LID measures are not considered to be appropriate for this site and project. I Surface drainage should be carefully taken into consideration during precise grading, landscaping, and building construction. Positive drainage (e.g., roof gutters, downspouts, area drain, etc.) should be provided to direct surface water 1 away from structures and towards the street or suitable drainage devices. Ponding of water adjacent to structures should be avoided; roof gutters, downspouts, and I . area drains should be aligned so as to transport surface water to a minimum distance of 5 feet away from structures. The performance of structural foundations is dependent upon maintaining adequate surface drainage away from structures. Water should be transported off the site in approved drainage devices or unobstructed swales. We recommend that the minimum flow gradient for the drainage be 1-percent for area drains and paved drainage swales; and 2-percent for unpaved drainage swales. We recommend that where structures will be located within 5 feet of a proposed drainage swale, the surface drainage adjacent to the structures be accomplished with a gradient of at least 3-1/2 percent away from the structure for a minimum horizontal distance of-3,-feet. Drainage should be further maintained by a swale or drainage path at a gradient of at least 1- percent for area drains and paved drainage swales and 2-percent for unpaved drainage swales to a suitable collection device (i.e. area drain, street gutter, etc.). We also recommend that structural footings within 4 feet of the drainage swale flowline be deepened so that the bottom of the footing is at least 12 inches below the flow-line of the drainage swale. In places where the prospect of maintaining the minimum recommended gradient for the drainage swales and the construction -25- Leighton I. Geotechnical Update Report, Bressi Ranch, Carlsbad. California . 10570.001 of additional area drains is not feasible, provisions for specific recommendations I may be necessary, outlining the importance of maintaining positive drainage. ' The impact of heavy irrigation or inadequate runoff gradient can create perched water conditions, resulting in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and controlled I irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements (such as heaving and shrinkage due to the. change in moisture content -of-foundation-soils,---which-maycause distress to-a—.=-- structure or improvement), the moisture content of the soils surrounding the structure should be kept as relatively constant as possible. I All area drain inlets should be maintained and kept clear of debris in order to function properly. Rerouting of site drainage patterns and/or installation of area I drains should be performed, if necessary. A qualified civil engineer or a landscape architect should be consulted prior to rerouting of drainage. 1 6.9 Slope Maintenance Guidelines It is the responsibility of the owner to maintain the slopes, including adequate I . planting, proper irrigation and maintenance, and repair of faulty irrigation systems. To reduce the potential for erosion and slumping of graded slopes, all I slopes should be planted with ground cover, shrubs, and plants that develop dense, deep root structures and require minimal irrigation.. Slope planting should I . be carried out as soon as practical upon completion of grading. Surface-water runoff and standing ,water at the top-of-slopes should be avoided. Oversteepening of slopes should be avoided during construction activities and Maintenance of proper lot drainage, undertaking of property I landscaping. improvements in accordance with sound engineering practices, and proper maintenance of vegetation, including regular slope irrigation, should be 1 performed. Slope irrigation sprinklers should be adjusted to provide maximum uniform coverage with minimal of water usage and overlap. Overwatering and consequent runoff and ground saturation should be avoided. If automatic sprinklers systems are installed, their use must be adjusted to account for rainfall conditions. . . Trenches excavated on a slope face for any purpose should be properly backfilled and compacted in order to obtain a minimum of 90 percent relative , U9 -26- Leighton. I. Geotechnical Update Rerort, Bressi Ranch; Carlsbad, California 10570.001 compaction, in accordance with ASTM Test Method D1557. Observation/testing 1 and acceptance by the geotechnical consultant during trench backfill are recommended. A rodent-control program should be established and maintained. 1 . Prior to planting, recently graded slopes should be temporarily protected against erosion resulting from rainfall, by the implementing slope protection measures such as polymer covering, jute mesh, etc. U 6.10 Landscaping and Post-Construction I Landscaping and post-construction practices carried out by the owner(s) and their representative bodies exert significant influences on the integrity of structures founded on expansive soils. Improper landscaping and post-construction practices, which are beyond the control of the geotechnical engineer, are frequently the primary cause of distress to these structures. Recommendations for proper landscaping and post-construction practices are provided in the following. paragraphs within this section. Adhering to these recommendations will help in minimizing distress due to expansive soils, and in ensuring that such effects are I . limited to cosmetic damages, without compromising the overall integrity of structures. I Initial landscaping should be done on all sides adjacent to the foundation of a structure, and adequate measures should be taken to ensure drainage of water I away from the foundation. If larger, shade providing trees are desired, such trees should be planted away from structures (at a minimum distance equal to half the mature height of the tree) in order to prevent penetration of the tree roots beneath I the foundation of the structure. I Locating planters adjacent to buildings or structures should be avoided as much as possible. If planters are utilized in these locations, they should be properly designed so as to prevent fluctuations in the moisture content of subgrade soils. Planting areas at grade should be provided with appropriate positive drainage. Wherever possible, exposed soil areas should be above paved grades. Planters should not be depressed below adjacent paved grades unless provisions for I . drainage, such as catch basins and drains, are made. Adequate drainage gradients, devices, and curbing should be provided to prevent runoff from adjacent I pavement or walks into planting areas. Watering should be done in a uniform, systematic manner as equally as possible on all sides of the foundation, to keep the soil moist. Irrigation methods should 411, 27 •• Leighton Geotechnical Update Report. BressiRanch: Carlsbad: California - -- 10570.001 promote uniformity of moisture in planters and beneath adjacent concrete fiatwork. Overwatering and underwatering of landscape areas must be avoided. Areas of - soil that do not have ground cover may require more moisture, as they are more susceptible to evaporation. Ponding or trapping of water in localized areas adjacent to the foundations can cause differential moisture levels in subsurface soils and should, therefore, not be allowed. Trees located within a distance of 20 feet of foundations would require more water in periods of extreme drought, and in some cases, a root injection system may be required to maintain moisture equilibrium. During extreme hot and dry periods, close observations should be carried out around foundations to ensure that adequate watering is being undertaken to prevent soil from separating or pulling back from the foundations. - 6.11 Construction Observation and Testing Construction observation and. testing should be performed by the geotéchnical consultant during the remaining grading operations, future excavations and foundation or retaining wall construction on the graded portions of the site. Additionally, footing excavations should be observed and moisture determination tests of subgrade soils should be performed by the geotechnical consultant prior to the pouring of concrete. Foundation design plans should also be reviewed by the geotechnical consultant prior to excavations. -28- Geotechnical Update Reøort. Bressi Ranch. Carlsbad, California 10570.001 MIMI II 'AlIII V I[.liE The conclusions and recommendations presented in this report are based in part upon data that were obtained from a limited number of observations, site visits, excavations, samples, and tests. Such information is by necessity incomplete. The nature of many sites is such that differing geotechnical or geological conditions can occur within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. Therefore, the findings, conclusions, and -recommendations -• presented in this report can be relied upon only if Leighton has the opportunity to observe the subsurface conditions during grading and construction of the project, in order to confirm that our preliminary findings are representative forthe site. -29- • Leighton FIGURE Figure 1 Ii I.. I I I I i I, I .. I I I I I I I .. I i --.---' _::- -- / - .- •— .. --.-, -./ / .-- -. I - / - - / / - - - - - Addi .. I o1/QcocoI o - - — — — ----c - Tfsa \ —- I fi - - At , 761: 7 . Afo - - -'.--- - - -- Car / E At— / "All I \ ,- I \— — I iso b — — / Tsa tt I At IJ I Ii — n" — / r \ \ I I ZI A"Roxi-Tr. LOCATION—, OF RICH TO TRY iRA - CCLX 1 z Af / At \ N I /V /o'/ I / ' '! ".' '- I\ E ''•>' N - - - - / P I - - I Tso 1.4= - Al __ .H _j / - - — -' — "Aft -- ........... ' - . iso - JI ,I-' * I - - / - IT .11.IY•YY - / / I •-' ---'-- ..-,, 0' ..1 :.., -;;7 / R0A_ ,/ /,/• s - Af,= 44/=''......... ..... / .'k -_--- ,.0 - '- 2 -- -;'-' 1c.HH4, ,Tso At Trs / \ I,- / / aI/Y;;///; , . Af f I - LEGEND RI - P-2 RIO 01. ,0 ' N -, .0— am -- - I . - - PAIO5lV.mI El— ___________________________________________________________________ 0 ••' _ . APPENDIX A REFERENCES 'I Geotechnical Update Report, Bressi Ranch. Carlsbad. California 10570.001 APPENDIX A - REFERENCES I California Division of Mines and Geology (CDMG), 1995, Landslide Hazards in the I Northern Part of the San Diego Metropolitan Area, San Diego County, California, Open-File Report 95-04. 1996, Probabilistic Seismic Hazard Assessment for the State of California, Open-File Report, 96-08. 1998, Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada, dated February 1998. California Building Standards Commission (CBSC), 2013, California Building Code, Volume I and Volume II. California Geological Survey, 2003, The Revised California Probabilistic Seismic Hazard Assessment Maps, June 2003. Hannan, D., 1975, Faulting in the Oceanside, Carlsbad and Vista Areas, Northern San Diego County, California in Ross, A. and Dowlens, R.J., eds., Studies on the Geology of Camp Pendleton and Western San Diego County, California: San Diego Association of Geologists, pp. 56-59. Hart, E.W. and Bryant W.A., 2007, Fault-Rupture Hazard Zones in California, Aiquist- Priolo Special Studies Zones Act of 1972 with Index to Special Studies Zones Maps: Department of Conservation, Division of Mines and Geology, Special Publication 42. Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas, with Locations and Ages of Recent Volcanic Eruptions: California Division of Mines and Geology, California Geologic Data Map Series, Map No. 6, Scale 1:750,000. Kennedy, M.P. and Welday, E.E., 1980, Character and Recency of Faulting Offshore Metropolitan San Diego, California: -California Division of Mines and Geology Map Sheet 40.- A-1 I 1' 1 I I Geotechnical Update Renort, Bressi Ranch, Carlsbad, California 10570.001 APPENDIX A (continued) LI Leighton and Associates, Inc., 1997, Preliminary Geotechnical Investigation, Bressi Ranch, Carlsbad, California, Project No. 4971009-002, dated July 29, 1997. 2001, Supplemental Geotechnical Investigation for Mass Grading, Bressi Ranch, Carlsbad, California, Project No. 971009-0015, dated March 14, 2001. 2002, Geotechnical Conclusions Concerning the Mass Grading Recommendations Relative to Proposed Fine Grading and Review of the 40- Scale Tentative Maps, Bressi Ranch, Carlsbad, California, Project No. 971009- 007, dated September 12, 2002. - 2003a, Geotechnical Grading Plan Review of the Mass Grading Plans, Bressi Ranch, Carlsbad, California, Project No. 971009-007,' dated January 17, 2003. 2003b, Preliminary Residential and Commercial Foundation Design Recommendations, Bressi Ranch, Carlsbad, California, Project No. 971009-007, dated February 5, 2003. 2004a, Summary of the As-Graded Geotechnical Conditions and Partial Completion of Rough and Fine Grading, Planning Areas PA-1 Through PA-5, Bressi Ranch, Carlsbad, California, Project No. 91009-014, dated January 20, 2004. 2004b, Geotechnical Maps, Planning Areas PA-4 and PA-5, Bressi Ranch, Carlsbad, California, Project No. 971009-014, dated April 15, 2004. 2004c, As-Graded Report of Mass Grading, Planning Areas PA-11, PA-2, and PA-3, Metropolitan Street, and a Portion of Town Garden Road, Gateway Road, and Alicante Road, Carlsbad Tract No. 00-06, Bressi Ranch, Carlsbad, California, Project No. 971009-014, dated April 15, 2004. 1 A-2 Geotechnical Update Report, Bressi Ranch, Carlsbad, California 10570.001 APPENDIX A (continued) 2004d, Addendum to the As-Graded Reports of Mass Grading Concerning the Completion of Settlement Monitoring, Planning Areas PA-1 through PA-5, Bressi Ranch, Carlsbad, California, Project No. 971009-014, dated October 11, 2004. 2006, Geotechnical Update Investigation, Lots 24 through 28 of Planning Area PA-4, Bressi Ranch, Carlsbad, California, Project No. 971009-041, dated February 3, 2006 Leighton and Associates, Inc., 2007, As-Grade Report of Fine Grading, The Towers at Bressi Ranch, Lots 24 through 28 of Planning Area PA-4, Carlsbad Tract No. CT 02-15, Carlsbad, California, Project No. 971009-045, dated February 23, 2007. Leighton Consulting, Inc., 2012, Geotechnical Update Investigation, Proposed Bressi Ranch Hotels Lot 1 of Carlsbad Tract No. CT 06-20 (Planning Area PA-4,-Bressi Ranch), Carlsbad, California, Project No. 603446-001, dated May 15, 2012. Shea Properties Management Company, Inc., 2013, Conceptual Site Plan, Bressi Ranch Lots 19, 20, 21, & 22, Carlsbad, California, dated September 30, 2013, revised October 4, 2013. A-3 APPENDIX B TEST PIT LOGS I - - - - - - - - -' - - - - - - - - - - LOG OF TRENCH T-1 Project Name: She /Lots 19-22 Logged by: ChrisLivesey ENGINEERING PROPERTIES Project Number: 10570001 Elevation: 373' Equipment: Rrkhri'. Location/Grid: Spp rPntPrhnifnl Map USGS Sample No. Moisture (%) Density (pcf) GEOLOGIC DATE: January 7, 2014 DESCRIPTION: GEOLOGIC ATTITUDES UNIT Tertiary Santiago Formation (Tsa) Tsa @ 0'-1.7': SILTSTONE, light gray, dry, weathered, severely fractured, ' BB-1 manganeese oxidation, laminated folds of light reddish'brown fine silty sandstone, @0'- rootlets fragments. 1.5' @ 17-2.3% Fossiliferous silty SANDSTONE, orange brown, slightly moist, fine G.B. N50W, sand, abundant shell fragments and bivalve shells. , GB-1 6N @ 2.3'-2.6': CLAYSTONE, gray brown, moist, general bedding attitude @ 2.3'- @ 2.6-3.1': White, moist, calcium carbonate , 2.6' @ 3.1'-3.5': SILTSTONE, medium gray brown, ,moist, mottled with oxidized pea gravel fine sandstone. © 3.5'-4.2': SANDSTONE, light gray, slightly moist,fine sand. @ 4.2'-6':Silty SANDSTONE, orange brown, oist, fine sabd, calcium carbonate large gravel, gradational contact from above strata. © 6'-7': SILTSTONE, light gray, moist, oxidized. @ 7'-9': Sandy SILTSTONE, light gray, moist, fine sand. GRAPHICAL REPRESENTATION: East Wall SCALE: 1"=5' SURFACE SLOPE: Flat TREND: N5W Total Depth = 9 Feet No Ground Water Encountered J ' Backfiiled: January 7,2014 - - - M= - - - - - - - - - - - - - - LOG OF TRENCH: T-2 Project Name: ShealLots 19-22 Logged by: Chris_Livesey ENGINEERING PROPERTIES Project Number: ..10570_001 Elevation- 376' ... Equipment: R;1rikhnp Location/Grid: (PntAr.hnirI Map GEOLOGIC USCS Sample No. Moisture (%) Density (pcf) DATE: January 7, 2014 DESCRIPTION: . GEOLOGIC ATTITU D UNIT Tertiary Santiago Formation (Tsa) . . Tsa 1313-1 @ 0'-5.5': CLAYSTONE, medium gray, moist (upper 2' is dry), claystone bedding @ 0'- varies from laminated to thinly bedded, bedding is distinguished by interbeds of . 5.5' oxidized orange brown laminated silty sandstone and siltstone, very thin to thin beds of calcium carbonate, jointing and fractures well healed with calcium . . GB-11 carbonate. . . b:N20W,7S @2': General bedding attitude various b:N25E,10W @2.3': General bedding attitude location b:N5W,7W @2.5': General bedding attitude . GRAPHICAL REPRESENTATION: East Wall SCALE:1"5' . SURFACE SLOPE: Flat TREND: NS Total Depth 55 Feet - No Ground Water Encountered Backfihled: January 7 2014 — — — —. — — — — — —. — — — — — — — — LOG OF TRENCH: T-3. Project Name: Shea/Lots 19-22 Logged by:•_ Chris _Livesey ENGINEERING PROPERTIES Project Number: 10570 001 Elevation: 369' Equipment: Rakhôp Location/Grid: Se anthnirl Map7 77 Sample No. Moisture (%) Density (pcf) GEOLOGIC DATE: January 7, 2014 DESCRIPTION: GEOLOGIC UNIT ATTITUDES Artificial fill (Al) Af @ 0'-6': Silty SAND, light brown, slightly moist (upper foot is dry), fine sand, small SM BB-1 angular orange brown siltstone and light gray/black claystone, small I'-1.5' @ 0'4 diameter concretions GB-1 Tertiary Santiago Formation (Tsa) Tsa @ 4' 0 © 6'-8.5': Silty SANDSTONE light brown to light gray, moist, fine sand, laminated orange brown oxide bedding. GRAPHICAL REPRESENTATION: West Wall SCALE:I"=5' SURFACE SLOPE: Flat TREND: NS Ac' - ----.- -.-. Total Depth = 8.5 Feet No Ground Water Encountered Backfihled January 7 2014 LOG OF TRENCH T-4 Project Name: ShealLots 19-22 Logged by: Chris_Livesey ENGINEERING PROPERTIES Project Number: 10570_001_ Elevation: ._ Equipment . _Rackhce_. Location/Grid: Rpp_GnthniraI_Map USCS Sample No. Moisture i (%) Density (pci) GEOLOGIC DATE: 'January 7, 2014 DESCRIPTION:- . GEOLOGLC ATTITUDES UMT Artificial fill (Afl Al. GB-1 © 0'-7': Sandy SILT with various clay content, mottled light brown with light gray, ML @ 5' dry to moist with depth, small angular siltstone and claystone fragment, dessication cracks within the upper foot. Tertiary _Santiago Formation (Isa) Tsa @ 7'-9': Sandy SILTSTONE, light brown to light gray, slightly moist, fine sand, laminated, oxidized orange bedding differentiates thin bedding. GRAPHICAL REPRESENTATION: West Wall SCALE: 1'=5' SURFACE SLOPE: Flat TREND: NSE Total Depth = 9 Feet No Ground Water Encountered Backfilled January 7 2014 - - - . - —. - - - =.= - - - - - - - == LOG OF TRENCH: T-5 Project Name: Shea/Lots 19-22 Logged by: Chris.Liveséy ENGINEERING PROPERTIES Project Number: -.... 10570001_. _. _•. Elevation: 36Z'* Equipment: _._. R'khn _.. Location/Grid: See GeoterhDirnl Mp GEOLOGIC USCS Sample No. Moisture (%) Density (pcf) DATE: January 7, 2014 DESCRIPTION: GEOLOGIC DATTITU UNIT Artificial fill (Afi I Af GB-1 @ 0'-9.5': Sandy SILT with various clay content, light brown mottled with medium ML @ 4' gray and light brown, slightly moist (upper 2 feet is dry), small angular dark gray and ornage brown siltstone gravel, upper 2 feet exhibits dessication cracks. © 2'-3': Moist lense . GRAPHICAL REPRESENTATION: East Walt SCALE:1"5' . SURFACE SLOPE: Flat TREND: NIOE S. . S .. . S Total Depth 9.5 Feet \ J No Ground Water Encountered ( Backfihled: January 7, 2014 - - - - - - - - - - - - - - - - - - . LOG OF TRENCH: Project Name: Shea/Lots 19-22 Logged by: Chris_Livesey ENGINEERING PROPERTIES Project Number: 10570_001 Elevation- Equipment: Rckh- Location/Grid: pntprhnirl Map usás Sample No. Moisture, (%) Density (pcf) GEOLOGIC DATE: January 7, 2014 DESCRIPTION:—GEOLOGIC ATTITUDES UNIT Artificial fill (Afi Af BB-1 © 0'-7': Sandy SILT, light brown, dry to slightly moist, fine sand, small angular ML © 2'-3' gray siltstone and orange sandstone fragments, upper 1.5 feet is dry and exhibits dessicaUon cracks. GB-11 @4' GRAPHICAL REPRESENTATION: East Wall SCALE:1"=5' SURFACE SLOPE: Flat TREND: NS 7otal Depth 7 Feet No Ground - - - . - - - - - - - - - - - - - - - - LOG OFTRENCH: T-7 Project Name: Shea/Lots 19-22 Logged by: Chris.Uvesey ENGINEERING PROPERTIES Project Number: 1.0570_091 Elevation: _7V Equipment: Rkhr Location/Grid: See C ntithniaI Mp USCS Sample No. Moisture (%) Density (pcf) GEOLOGIC DATE: JanuarATTITUDESy 7, 2014 DESCRIPTION: . GEOLOGIC UNIT Artificial Fill (Afl . . Af © 0'-7.5': Sandy SILT, light brown mottled with light gray and orange brown, ML BB-1 slightly moist, fine sand, cobble size concretions, upper 2 feet is dry and exhibits © desication cracks GB-1 GB-2 @7' GRAPHICAL REPRESENTATION: East Wall SCALE:1"=5' SURFACE SLOPE: Flat TREND: NS . S S • \\ S __________ Total Depth 7.6 Feet No Ground Water Encountered S. Backfilled: January 7, 2014 LOG OF TRENCH. T-R Project Name: Shea/Lots 19-22 Logged by: Chris_Livesey ENGINEERING PROPERTIES • Project Number: 1570001__•.••, Elevation: _•372' • Equipment RnckhnA Location/Grid See Gotrhnicl M2p GEOLOGIC Sample No. Moisture (%) Density (pcf ATTITUDES •••••• • DATE: January 7, 2014 DESCRIPTION GEOLOGIC UNIT Artificial fill (Af) Af • @ V-15: CLAY .(CH), medium gray, dry grades to moist grades to very moist. CH 1.6-25: Silty SAND (SM), mottled tan brown and light gray, slightly moist, fine SM sand. @ 25-5': Sandy Clayey SILT (ML), mottled gray clay with light brown silt with ML orange brown fine sand, slightly moist. Tertiary Santiago Formation (Tsa) • Tsa © 6-65: SILTSTONE, medium gray, moist,.thinly bedded with orange brown sandy siltstone GRAPHICAL REPRESENTATION: East Wall SCALE: 1"=5' SURFACE SLOPE: Flat TREND: N5E • =ju=. • Total Depth 6.5 Feet • - No Ground Water Encountered Backfilled January 7 2014 - Leighton I,.. FIELD PERCOLATION TEST DATA SHEET Project Name: Shea/Lots 19 to 22 . Project No;: 10570.001 Proj. Address: Gateway & Innovation Way, Carlsbad, CA I SOIL TYPE'/ TEST LOCATION! BOREHOLE Soil Type: Af Location: See Geotechnicat Map Hole Dia:. 4" Depth 3.70' . . .Tested by: CDL Pre-Saturation Date: 1-7-2014 . Test Date: 1-8-2014 Notes: Measurements in lOOths of foot Time of Day Interval I Notes Water Level Time of Day . Interval I Notes Water Level 10:31 added water . 2.9 11:01 30" 2.94 11:31 . 30" 2.97 12:01 30" . 3.02 12:31 30' 3,05 12:33 30" 3.07 1:03 added water 2.85 1:33 30" 2.91 2:03 30" . 2.96 2:33 30" 3.03 3:03 30" 3.07 3:33 30" 3.1 I FOR OFFICE USE ONLY I DATE RECEIVED: By: . 1 Notes: 0.012 inch per minute or 83.3 minutes per inch I I 4. Leighton SHEET Project Name: Shea/Lots 19 to 22 . Project No.: 10570.001 PrOj. Address: Gateway & Innovation Way, Carlsbad, CA FL . SOIL TYPE/TEST LOCATION !BOREHOLE . .. I Soil Type: Tsa Location: See Geotechnical Map . Hole Dia: 4" Depth 3.60 Tested by: CDL Pre-Saturation Date: 1-7-2014 Test Date: 1-8-2014 Notes: Measurements in lOOths of foot Time of Day . Interval I Notes Water Level Time of Day Interval I Notes Water Level 10:12 . .. added water 2.9 10:42 . 30' 3.05 10:46 added water 2.77 11:16 30' 2.84 . ., 1146 30" 287 12:16 .., 30" .. 2,94 1218 added water 286 12:48 - 30" 2.96 12:49 added water 2.73 1:19 30" 2.75 1:49 30" . 2.8 2:19 30" 2.83 2:49 30" 2.87 3:19 30" 2.91 FOR OFFICE USE ONLY DATE RECEIVED By I Notes: 0.016 inch per minute or 62.5 minutes per inch I LI 11 APPENDIX C. LABORATORY TESTING PROCEDURES AND TEST RESULTS Geotechnical Update Renort, Bressi Ranch, Carlsbad, California 10570.001 APPENDIX C Laboratory Testincj Procedures and Test Results Expansion Index Tests: The, expansion potential of selected materials Was evaluated by the Expansion Index Test, ASTM Standard D4829. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with water until volumetric equilibrium is reached. The results of these tests are presented in the table below: Sample Location Sample Description . Expansion Index Expansion Potential T-1 @ 0 to 1 foot Light Brown CLAY 140 Very High T-6 @ 2 to 3 feet Brown lean sandy SILT 79 Medium E6* Olive-brown CLAY 163 Very High *Leighton 2004c Minimum Resistivity and pH Tests: Minimum, resistivity and pH tests were performed in general accordance with Caltrans Test Method C1643 for Steel or CT532 for concrete and standard geochemical methods. The results are presented in the table below: Sample Location Sample Description pH Minimum Resistivity (ohms-cm) T-3 Brown Silty SAND 7.7 . 6.18 T-7 . Brown Sandy SILT 8.0 ' 697 c-i Sulfate Content Potential Degree Sample Location (ppm) of Sulfate Attack T-3 450 - Moderate T-7 270 Moderate ) C-2 Geotechnical Update Report, Bressi Ranch, Carlsbad. California 10570001 APPENDIX C (Continued) I . Chloride Content: Chloride content was tested, in accordance with Caltrans Test Method CT422. The results are presented below: I I I' Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (Caltrans Test Method CT417). The test results are I presented in the table below: Chloride Attack Sample Location Chloride Content, ppm Potential T-3 214 Threshold T-7 109 Threshold APPENDIX D GENERAL EARTHWORK AND GRADING SPECIFICATIONS p I LEIGHTON AND ASSOCIATES, INC. I General Earthwork and Grading Specifications 1.0 General 1.1 Intent These General Earthwork and Grading Specifications are for the grading and earthwork shown on the approved grading plan(s) and/or indicated in' the geotechnical report(s). These Specifications are a part of 'the recommendations contained in the geotechnical report(s). In case of conflict, the specific recommendations in the geotechnical report shall supersede these more general Specifications. Observations of the earthwork by the project Geotechnical Consultant during the course of grading may result in new or revised recommendations that could supersede these specifications or the recommendations' in the geotechnical report(s). 1.2 The Geotechnical Consultant of Record Prior to commencement of work, the owner shall employ the Geotechnical Consultant of Record (Geotechnical Consultant). The Geotechnical Consultants shall be responsible for reviewing the approved geotechnical report(s) and accepting the adequacy of the preliminary geotechnical findings, conclusions, and recommendations prior to the commencement of the grading. Prior to commencement of grading, the Geotechnical Consultant shall review the "work plan" prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel to perform the appropriate level of observation, mapping, and compaction testing During the grading and earthwork operations, the Geotechnical Consultant shall observe, map, and document the subsurface exposures to verify the geotechnical design assumptions. If the observed conditions are found to be significantly different than the interpreted assumptions during the design phase, the Geotechnical Consultant shall inform the owner, recommend appropriate changes in design to accommodate the observed conditions, and notify the review agency where required. ,Subsurface areas to be geotechnically observed, mapped, elevations recorded, and/or tested include natural ground after it has been cleared for receiving fill but before fill is placed, bottoms of all "remedial removal" areas, all key bottoms, and benches made on sloping ground to receive fill. The Geotechnical Consultant shall observe the moisture-conditioning and processing of the subgrade and fill materials and perform relative compaction testing of fill to determine the attained level of compaction. The Geotechnical Consultant shall provide the test results to the owner and the Contractor on a routine and frequent basis. -1- I LEIGHTON AND ASSOCIATES, INC. I General Earthwork and Grading Specifications 1.3 The Earthwork Contractor The Earthwork Contractor (Contractor) shall be qualified, experienced, and knowledgeable in earthwork logistics, preparation and processing of ground to receive fill, moisture-conditioning and processing of fill, and compacting fill. The Contractor shall review and accept the plans, geotechnical report(s), and these Specifications prior to commencement of. grading. The Contractor shall be solely responsible for performing the grading in accordance with the plans and specifications. The Contractor shall prepare and submit to the owner and the Geotechnical Consultant .a work plan that indicates the sequence of earthwork grading, the number of "spreads" of work and the estimated quantities of daily earthwork contemplated for the site prior to commencement of grading. The Contractor shall inform the owner and the Geotechnical Consultant of changes in work schedules and updates to the work plan at least 24 hours in advance of such changes so that appropriate observations and tests can be planned and accomplished. The Contractor shall not assume that the Geotechnical Consultant is aware of all grading operations. The Contractor shall have the sole responsibility to provide adequate equipment and methods to accomplish the earthwork in accordance with the applicable grading codes and agency ordinances, these -. Specifications, and the recommendations in the approved geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory conditions, such as unsuitable soil, improper moisture condition, inadequate compaction, insufficient buttress key size, adverse weather, etc, are resulting in a quality of work less than required in these specifications, the Geotechnical Consultant shall reject the work and may recommend to the owner that construction be stopped until the conditions are rectified. . . 2.0 Preparation of Areas to be Filled 2.1 Clearing and Grubbing Vegetation, such as brush, grass, roots, and other deleterious material shall be sufficiently removed and properly disposed of in a method acceptable to the owner, governing agencies, and the Geotechnical Consultant. -2- LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications The Geotechnical Consultant shall evaluate the extent of these removals depending on specific site conditions. Earth fill material shall not contain more than 1 percent of organic materials (by volume). No fill lift shall contain more than 5 percent of organicmatter. Nesting of the. organic materials shall not be allowed. If potentially hazardous materials are encountered, the Contractor shall stop work in the affected area and a hazardous material specialist shall be informed immediately for proper evaluation and handling of these materials prior to continuing to work in that area. As presently defined by the State of California, most refined petroleum products (gasoline, diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered to be hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the ground may constitute a misdemeanor, punishable by fines and/or imprisonment, and shall not be allowed. I 2.2 Processing Existing ground that has been declared satisfactory for support of fill by the Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing ground that is not satisfactory shall be overexcav,ated as specified in the following section. Scarification shall continue until soils are broken down and free of large clay lumps or clods and the working I . surface is reasonably uniform, flat, and free of uneven features that would inhibit uniform compaction. 2.3Overexcavation . In addition to 'removals and bverexcavations recommended in the I ., . approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich, highly fractured or otherwise' unsuitable ground shall be overexcavated to competent ground as evaluated by the I . Geotechnical Consultant during grading. 2.4 Benching I . Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical units), the ground shall be stepped or benched. Please see the Standard Details for a graphic illustration. The lowest I . bench or key shall be a minimum of 15 feet wide and at least 2 feet deep, into competent material as evaluated by the Geotechnical Consultant. Other benches shall be excavated a minimum height of 4 feet into' I . . . . . competent material or as otherwise recommended by the Geotechnical -3- I I - LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications Consultant. Fill placed on ground sloping flatter than 5:1 shall also be benched or otherwise overexcavated to provide a flat subgrade for the fill. 2.5 Evaluation/Acceptance of Fill Areas All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide the survey control for determining elevations of processed areas, keys, and benches. 3.0 Fill Material 3.1 General Material to be used as fill shall be essentially free of organic matter and other deleterious substances evaluated and accepted by the Geotechnical Consultant prior to placement. Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill material. 3.2 Oversize Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 8 inches, shall not be buried or placed in fill unless location, materials, and placement methods are specifically accepted by the Geotechnical Consultant. Placement operations shall be such that nesting of oversized material does not occur and such that oversize material is. completely surrounded by compacted or densified fill. Oversize material shall not be placed within 10 vertical feet of finish grade or within 2 feet of future utilities or underground construction. 3.3 Import I If importing of fill material is required for grading, proposed import material shall meet the requirements of Section 3.1. The potential import source shall be given to the Geotechnical Consultant at least 48 hours (2 working I days) before importing begins so that its suitability can be determined and appropriate tests performed. -4- :1. LEIGHTON AND ASSOCIATES, INC. I General Earthwork and Grading Specifications 4.0 Fill Placement and Compaction I 4.1 Fill Layers I Approved fill material shall be placed in areas prepared to receive fill (per Section 3.0) in near-horizontal layers not exceeding 8 inches in loose thickness. The Geotechnical Consultant may accept thicker layers if I . testing indicates the grading procedures can adequately compact the thicker layers. Each layer shall be spread evenly and mixed thoroughly to I attain relative uniformity of material and moisture throughout. 4.2 Fill Moisture Conditioning . I Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a relatively uniform moisture content at or slightly over optimum. . Maximum density and optimum soil moisture content tests shall I . be performed in accordance with the American Society of Testing and Materials (ASTM Test Method D1557). 4.3 Compaction of Fill After each layer has been moisture-conditioned, mixed, and evenly I . spread, it shall be uniformly compacted to not less than 90 percent of maximum dry density (ASTM Test Method D1557). Compaction equipment shall be adequately sized and be either specifically designed I for soil compaction or of proven reliability to efficiently achieve the specified level of compaction with uniformity. 4.4 Compaction of Fill Slopes In addition to normal compaction procedures specified above, compaction I . of slopes shall be accomplished by backrolling of slopes with sheepsfoot rollers at increments of 3 to 4 feet in fill elevation, or by other methods produci,ng satisfactory results acceptable to the Geotechnical Consultant. I Upon completion of grading, relative compaction of the fill, out to the slope face, shall be at least 90 percent of maximum density per ASTM Test Method D1557. I 4.5 Compaction Testing . . I . Field-tests for moisture content and relative compaction of the fill soils shall be performed by the Geotechnical Consultant. Location and frequency of tests shall be at the Consultant's discretion based on field conditions encountered. Compaction test locations will not necessarily, be selected on a random basis. Test locations shall be selected to verify adequacy of compaction levels in areas that are judged to be prone to 5 • I I LEIGHTON AND ASSOCIATES, INC, I General Earthwork and Grading Specifications inadequate compaction (such as close to slope faces and at the fill/bedrock benches). 4.6 Frequency of Compaction Testing Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition, as a guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope face and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill construction is such that the testing schedule can be accomplished by the Geotechnical Consultant. The Contractor shall stop or slow down the earthwork construction if these minimum standards are not met. . 4.7 Compaction Test Locations The Geotechnical Consultant shall document the approximate elevation and horizontal coordinates of each test location. The Contractor shall coordinate with the project surveyor to assure that sufficient grade stakes are established so that the Geotechnical Consultant can determine the test locations with sufficient accuracy. At a minimum, two grade stakes within a horizontal distance of 100 feet and vertically less than 5 feet apart from potential test locations shall be provided. 5.0 Subdrain Installation Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line and grade after installation and prior to burial. Sufficient time should be allowed by the Contractor for these surveys. 6.0 Excavation I Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only. The actual extent of I .removal shall be determined by the Geotechnical Consultant based on the field evaluation of exposed conditions during grading. Where fill-over-cut slopes are 'to be graded, the cut portion of the slope shall be made, evaluated, and accepted I by the Geotechnical Consultant prior to placement of materials for construction of the fill portion of the slope, unless otherwise recommended by the Geotechnical Consultant. . . I i . -6- LEIGHTON AND ASSOCIATES, INC. General Earthwork and Grading Specifications 7.0 Trench Backfills 7.1 Safety The Contractor shall follow all OSHA and Cal/OSHA requirements for safety of trench excavations. - 7.2 Bedding and Backfill All bedding and backfill of utility trenches shall be performed in accordance with the applicable provisions of Standard Specifications of Public Works ConstrUction. Bedding material shall have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot over the top of the conduit and densified. Backfill shall be placed and densified to a minimum of 90 percent of relative compaction from 1 foot above the top of the conduit to the surface. The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one test should be made for every 300 feet of trench and 2 feet of fill. 7.3 Lift Thickness Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications of Public Works Construction unless the Contractor can demonstrate to the Geotechnical Consultant that the fill lift can be compacted to the minimum relative compaction by his alternative equipment and method. 7.4 Observation and Testing • The densification of the bedding around the conduits shall be observed by the Geotechnical Consultant. -7- - PROJECTED PLANE 1:1 - (HORIZONTAL: VERTICAL) MAXIMUM FROM TOE OF SLOPE TO APPROVED GROUND EXISTING GROUND SURFACE I [:1!5 FEE 2 FEET MIN.-3 LOV KEY DEPTH BENCH ALL-OVER-CUT SLOPE REMOVE 201 UNSUITABLE BENCH L MATERIAL BENCH HEIGHT (4 FEET TYPICAL) EXISTING GROUND SURFACE \ --=----------- - — — BENCH1 LBENCH HEIGHT (4 FEET TYPICAL) 1N 15 FEET MIN. — / LOWEST • REMOVE 2 FEET MIN. KEY BENCH (KEY) UNSUITABLE MATERIAL \ DEPTH CUT FACE SHALL BE CONSTRUCTED PRIOR TO / ...- FILL PLACEMENT TO ALLOW VIEW1NG/,- OF GEOLOGIC CONDITIONS - EXIS11NG—__,1 "CUT FACE SHALL BE elon"mn / ('(mJcTPIIr'Trr PRIOR CUT-OVER-FLL SLOPE SURFACE TO FILL PLACEMENT OVERBUILD A TRIM BACK PROJECTED PLANE DESIGN SLOPE 1 TO 1 MAXIMUM FROM TOE OF SLOPE TO APPROVED GROUND - 15 FEET MIN. 2 FEET MIN- LOWEST KEY DEPTH BENCH (KEY) -:-4- —REMOVE TJ 1 UNSUITABLE MATERIAL BENCH HEIGHT (4 FEET TYPICAL) BENCHING SHALL BE DONE WHEN SLOPE'S ANGLE IS EQUAL TO OR GREATER THAN 5:1. MINIMUM BENCH HEIGHT SHALL BE 4 FEET AND MINIMUM FILL WIDTH SHALL BE 9 FEET. GENERAL EARTHWORK AND KEYING AND BENCHING GRADING SPECIFICATIONS STANDARD DETAIL NISH GRADE SLOPE 7V7 WbL -------------------------- - ØMPCSED PiLL 1O MIN - 4 M -------------------- ----------------------- -------------- --- N~ OVERSIZE WINDROW * OVERSIZE ROCK IS LARGER THAN 8 INCHES IN LARGEST DIMENSION. EXCAVATE A TRENCH IN THE COMPACTED FILL DEEP ENOUGH TO BURY ALL THE - ROCK. * BACKFILL WITH GRANULAR SOIL JETTED OR FLOODED IN PLACE TO FILL ALL THE VOIDS. 00 NOT BURY ROCK WITHIN 10 FEET OF FINISH GRADE. WINDROW OF BURIED ROCK SHALL BE PARALLEL TO THE FINISHED SLOPE. GRANULAR MATERIAL TO BE DENSIFIED IN PLACE BY DETAIL FLOODING OR JETTING. .!jflfrifl GRANULAR MATERIAL TYPICAL PROFILE ALONG WINDROW OVERSIZE ROCK DISPOSAL GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL B / / "- ___-EXISTING / N GROUND SURFACE / ----------------------- ------------------- REMOVE BENCHING SUBDRAIN U MATERIAL NSUITABLE TRENCH SEE DETAIL BELOW FILTER FABRIC (MIRAFI 140N OR APPROVED OVERLAP.\ EQUIVALENT)' CALTRANS CLASS 2 PERMEABLE r 6 MIN. OR #2 ROCK (9F3/FT) WRAPPED COVER IN FILTER FABRIC /• :. '.:.•'i 4 L J 4 MIN. BEDDING COLLECTOR PIPE SHALL BE MINIMUM 6 DIAMETER SCHEDULE 40 PVC PERFORATED PIPE. SEE STANDARD DETAIL 0 FOR PIPE SPECIFICATIONS SUBDRAIN DETAIL DESIGN FINISH GRADE 0' MIN. FILTER FABRIC BACKFILL / (MIRAFI 140N OR APPROVED 7 EQUIVALENT) -------------------------------- 2% .-CALTRANS CLASS 2 PERMEABLE - OR #2 ROCK (9FT3/FT) WRAPPED MIN IN FILTER FABRIC NONPERFORATED DETAIL OF CANYON SUBDRAIN OUTLET CANYON SUBDRAINS GENERAL EARTHWORK AND At GRADING SPECIFICATIONS STANDARD DETAIL - 15' MIN. OUTLET PIPES 4 ØNOIVPERFORATED PIPE - /l"—._BACK CUT 100 WAX 0.C. HORIZONTALLY N. 1:1 OR FLATTER - 30' MAX O.C. VERTICALLY \--------------- SEE SUBDRAIN TRENCH --------------------------- --------------------------- ---- - - LOWEST SUBDRAIN SHOULD PILL POSSIBLE TO ALLOW SUITABLE OUTLET DETAIL --------------- -------------------------------- :-:-:-:-:-:•:-:-:-:-:-2% MIN.-:::-:-:-:-:-:-:-X:-: KEY WIDTH AS NOTED ON GRADING PLANS KEY 12" MIN. OVERLAP TH (15' MIN.) FROM THE TOP HOG (2' MIN.) RIND TIED EVERY FOR COLLECTOR 6 FEET T-CONNECTION PIPE TO OUTLET PIPE CALTRANS CLASS II PERMEABLE OR #2 1 6" WIN. ROCK (3 FT-3/FT) WRAPPED IN FILTER FABRIC COVER 4"0 4.'0 PERFORATED j_. PIPE OU - - TLET PIPE 57. MIN. 4" MIN. PROVIDE POSITIVE IFILTER FABRIC BEDDING SEAL AT THE ENVELOPE (MIRAFI JOINT 140 OR APPROVED EQUIVALENT) SUBDRAIN TRENCH DETAIL SUBDRAIN INSTALLATION - subdroin collector pipe sholl be instolled with perforation down or unless otherwise designated by the geotechnicol consultant. Outlet pipes shall be non-perforoted pipe. The subdroin pipe shall hove at least 8 perforations uniformly spaced per foot. Perforation shall be 1/4" to 1/2" if drill holes ore used. All subdroin pipes shall hove o grodieht of at least 2% towards the outlet. SUBDRAIN PIPE - Subdron pipe shall be ASTM D2751, SDR 23.5 or ASTM 01527. Schedule' 40, or ASTM D3034, SDR 23.5. Schedule 40 Polyvinyl Chloride Plostic (PVC) pipe, All outlet pipe shall be placed in a trench no wider than twice the subdroin pipe. BUTTRESS OR REPLACEMENT FILL SUB RA GENERAL EARTHWORK AND • GRADING SPECIFICATIONS STANDARD DETAIL D CUT-FILL TRANSITION LOT OVEREXCAVATION REMOVE UNSUITABLE - GROUND- - - - ' - - - - --------------- - \\/ OVEREXCAVATE - TYPICAL AND RECOMPACT BENCHING - - UNWEATHERED BEDROCK OR MATERIAL AP?ROVED BY THE GEOTECHNICAL CONSULTANT GENERAL EARTHWORK AND TRANSITION LOT FILLS GRADING SPECIFICATIONS STANDARD DETAIL E C SOIL BACKFILL. COMPACTED TO 90 PERCENT RELATIVE COMPACTION BASED ONASTMD1557 f RETAINING WALL-.,.. Ff 6" MIN. WALL WATERPROOFING ': OVERLAP I : FILTER URAFI F ABRIC ENVELOPE SPECIFICATIONS 0 o°I EQUIVALENT)*' PER ARCHITECT'S 1 0 140N OR APPROVED 1 MIN I..: 3/4 TO 1-1/2" CLEAN GRAVEL FINISH GRADE 4 (MIN.) DIAMETER PERFORATED / 0 PVC PIPE (SCHEDULE 40 OR J 00 -:-:-:- EQUIVALENT) WITH PERFORATIONS 0 0*:-:-:-:-: ORIENTED DOWN AS DEPICTED 0 MINIMUM 1 PERCENT GRADIENT CQMPACTED FILL 4 TO SUITABLE OUTLET :--:-:-:-:-:-:-: L. :3 MIN WALL FOOTING t COMPETENT BEDROCK OR MATERIAL AS EVALUATED BY THE GEOTECHNICAL CONSULTANT NOTE: UPON REVIEW BY THE GEOTECHNICAL CONSULTANT, COMPOSITE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR J-DRAIN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR CLASS 2 PERMEABLE, MATERIAL. INSTALLATION SHOULD BE PERFORMED IN ACCORDANCE WITH MANUFACTURERS SPECIFICATIONS. RETAINING WALL DRAINAGE GENERAL EARTHWORK AND GRADING SPECIFICATIONS STANDARD DETAIL ACTIVE ZONE FILTER FABRIC, ' REINFORCED RETAINED / P ZONE ZONE / 190 r f BACKDRAIN / T070%OF / WALL HEIGHT FILTER FABRIC / GRAVEL .•• :." DRAINAGE FILL WALL SUBDRAIN MIN 6" BELOW WALL . REAR SUBDRAIN: MIN 12' BEHIND UNITS 4" (MIN) DIAMETER PERFORATED PVC PIPE FOUNDATION SOILS I (SCHEDULE 40 OR EQUIVALENT) WITH PERFORATIONS DOWN. SURROUNDED BY I CU. FT/FT OF 3/4" GRAVEL WRAPPED IN FILTER FABRIC (MIRAFI 140N OR EQUIVALENT) OUTLET SUBDRAINS EVERY 100 FEET, OR CLOSER, NOTES: BY TIGHTLINE TO SUITABLE PROTECTED OUTLET 1) MATERIAL GRADATION AND PLASTICITY REINFORCED ZONE: GRAVEL DRAINAGE ALL: SIEVE SIZE % PASSING 1 INCH 100 SIEVE SIZE 1 INCH % PASSING 100 NO.4 20-100 3/4 INCH 75-100 NO. 40 0-60 NO.4 0-60 NO. 200 0-35 NO. 40 0-50 FOR WALL HEIGHT < 10 FEET, PLASTICITY INDEX <20 NO. 200 0-5 FOR WALL HEIGHT 10 TO 20 FEET, PLASTICITY INDEX < 10 FOR TIERED WALLS. USE COMBINED WALL HEIGHTS WALL DESIGNER TO REQUEST SITE-SPECIFIC CRITERIA FOR WALL HEIGHT >20 FEET CONTRACTOR TO USE SOILS WITHIN THE RETAINED AND REINFORCED ZONES THAT MEET THE STRENGTH REQUIREMENTS OF WALL DESIGN. GEOGRID REINFORCEMENT TO BE DESIGNED BY WALL DESIGNER CONSIDERING INTERNAL EXTERNAL, AND COMPOUND STABILITY. 3) GEOGRID TO BE PRETENSIONED DURING INSTALLATION. IMPROVEMENTS WITHIN THE ACTIVE ZONE ARE SUSCEPTIBLE TO POST-CONSTRUCTION SETTLEMENT. ANGLE a=45+0/2, WHERE CI IS THE FRICTION ANGLE OF THE MATERIAL IN THE RETAINED ZONE. BACKDRAIN SHOULD CONSIST OF J-DRAIN 302 (OR EQUIVALENT) OR 6-INCH THICK DRAINAGE FILL WRAPPED IN FILTER FABRIC. PERCENT COVERAGE OF BACKDRAIN TO BE PER GEOTECHNICAL REVIEW. SEGMENTAL .. I I RETAINING WALLS I GENERAL EARTHWORK AND GRADING SPECIFICATIONS. STANDARD DETAIL APPENDIX E ASFE L. Geotechnical Engineering Report II Geotechnical Services Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engi- neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique,each geotechnical engineering report is unique, preparpri solely for the client, No one except you should rely on your geotechnicai engineering report without first conferring with the geotechnical engineer who prepared it. And no one —not even you—should apply the report for any purpose or project except the one originally contemplated. Read the Full Report Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary. Do not read selected elements only. A Geotechnical Engineering Report Is Based on A Unique Set of Project-Specific Factors Geotechnical engineers consider a number of unique, project-specific fac- tors when establishing the scope of a study. Typical factors include: the clients goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground -utilities. Unless the geotechnical engineer who conducted the study specifically indicates otherwise, do not rely on a geotechnical engineering report that was: not prepared for you. not prepared for your project. not prepared for the specific site explored, or completed before important project changes were made. elevation, configuration, location, orientation, or weight of the proposed structure, composition of the design team, or project ownership. As a general rule, always inform your geotechnical engineer of project changes—even minor ones—and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed. Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineering report whose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctuations. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Are Professional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgment to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ—sometimes significantly— from those indicated in your report. Retaining the geotechnical engineer who developed your, report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. I I F I I Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: the function of the proposed structure, as when it's changed from a parking garage to an office building, or from a light industrial plant to a refrigerated warehouse, A Report's Recommendations Are Not Final Do not overrely on the construction recommendations included in your report. Those recommendations are not final, because geotechnical engi- neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual II' 1 I subsurface conditions revealed during construction. The geotechnical engineer who developed youc report cannot assume responsibility or liability for the report's recommendations if that engineer does not perform construction observation. A Ceotechnical Engineering Report Is Subject to Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems. Lower that risk by having your geo- technical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the design teams plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. Do Not Redraw the Engineer's togs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, but recognize that separating fogs from the report can elevate risk Give Contractors a Complete Report and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- tractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter,advise contractors lhat.the report was not prepared for purposes of bid development and that the reports accuracy is limited: encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contrac- tors have sufficient time to perform additional study. Only then might you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read Responsibility Provisions Closely Some clients, design professionals, and contractors do not recognize that geotechnical engineering is far less exact than other engineering disci- plines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce the risk of such outcomes, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled iimittions° many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions. Your geotechnical engineer should respond fully and frankly. Ceoenvironmental Concerns Are Not Covered The equipment, techniques, and personnel used to perform a .geoenviron- mental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenvironmental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated en vironmental problems have led to numerous project failures. If you have not yet obtained your own geoenvi- ronmental information, ask your geotechnical consultant for risk manage- ment guidance. Do not rely on an environmental report prepared for someone else. Obtain Professional Assistance To Deal with Mold Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. To be effective, all such strategies should be devised for the express purpose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mold prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed in this report, the geotechnical engineer in charge of this project is not a mold prevention consultant; none of the services per- formed in connection with the geotechnical engineer's slvdy were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this report will not of itself be sufficient to prevent mold from growing in or on the structure Involved. Rely on Your ASFE-Member Geoteclinical Engineer for Additional Assistance Membership in ASFE/The Geoprofessional Business Association exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit for everyone involved with a construction project. Confer with your ASFE-member geotechnical engineer for more information. ASFE THE GEOPROFESSIONAL BUSINESS ASSOCIATION 8811 Colesville Road/Suite 8106, Silver Spring, MD 20910 Telephone: 301/5652733 Facsimile: 301/589-2017 e-mail: info@asIe.org www.asfe.org Copyright 2004 byASFE Inc. Duplication, reproduction, or copying of this document, in whole or in part by any moans what oever Is strictly prohibited, except with ASFEk specific written permission. Exempting, quoting, or otherwise extracting wording from this document is permitted only with tire express writ/en permission of ASFE, and only for purposes of scholarly research or book review. Only members otASFE may use this document as a complement to or as an element of a geotechnical engineering report Any other f/tin, lndMdual, or other entity that so uses this document without being an ASFE member could be committing negligent or intentional (fraudulent) misrepresentation. IIGER0i115.0MRP