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HomeMy WebLinkAboutCT 05-05; LA COSTA GREENS NGBHD 1.16; UPDATE GEOTECHNICAL REPORT; 2008-06-10RECORD COpy Rs-:r-7 .. u-og , Initial Date UPDATE GEOTECHNICAL RE'PORT VILLAGES OF LA COSTA- THE GREENS, 'PHASE 2 NEIGHBORHOOD 1.16 LOTS 1 THROUGH 26 CARLSBAD, CALIFORNIA PREPARED FOR K B HOME COASTAL INCORPORATED WILDOMAR, CALIFORNIA JUNE 10, 2008 PROJECT NO. 06403-52-27 I , ~~t I~ ::) 1----:, ',' j -:ff i ,. ~~I~! I~ ~;::J 1::;--', " :l ~'7 i f .... .•..... ::;:;;. ',' I::: :;::~:; I~ ~"4' ....•.. I:;" GEOCON INCORPORATED , . GEOTECHNICAL CONSULTANTS Project No. 06403-52-27 June 10, 2008 KB Home Coastal Incorporated 36310 Inland Valley Drive Wildomar, California 92595 Attention: Ms. Jessica Moore Subject: VILLAGES OF LA COSTA -THE GREENS, PHASE 2 NEIGHBORHOOD 1.16, LOTS 1 THROUGH 26 CARLSBAD, CALIFORNIA UPDATE GEOTECHNICAL REPORT Dear Ms. Moore: In accordance with your authorization of our Proposal No. LG-08193 dated June 5, 2008, we have prepared this update geotechnical report for the subject project. The accompanying report presents the results of our study and conclusions and recommendations pertaining to th~ geotechnical aspects of proposed development of the site. The site was sheet graded as part of the mass grading for the Villages of La Costa -The Greens, Phase 2 development and is located within the southwest central portion of the Greens development in Carlsbad, California. The grading operations for Neighborhood 1.16 was completed in November of 2005. Dense formational deposits of the Santiago Formation and compacted fill und~r1ie the site. Provided the recommendations contained in this update report are followed, the site is considered suitable for construction and support of the proposed development. Should you have any questions regarding this report, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON INCORPORATED AS:SW:dmc (3/del) Addressee (2/del) 'Hunsaker and Associates Attention: Mr. David Blalock ) Shawn Weedon GE2714 6960 Flanders Drive III San Diego, California 92121-2974 III Telephone (858) 558-6900 III fax (858) 558-6159 I::' ":.:::.-,::, , • .t.' I::::;:~ :.'. TABLE OF CONTENTS 1. PlJRPOSE AND SCOPE ................................................................................................................. 1 2. PREVIOUS SITE DEVELOPMENT .............................................................................................. 1 3. SITE AND PROJECT DESCRIPTION ........................................................................................... 1 4. SOIL AND GEOLOGIC CONDITIONS ........................................................................................ 2 4.1 Compacted Fill (Qcf) ............................................................................................................. 2 4.2 Santiago Formation (Ts) ................................................................... : ................................. , .. 2 5. GROUNDWATER .......................................................................................................................... 2 6. GEOLOGIC HAZARDS ................................................................................................................. 3 6.1 Faulting and Seismicity ......................................................................................................... 3 6.2 Liquefaction ........................................................................................................................... 4 6.3 Landslides .............................................................................................................................. 4 7. conclusions and recommendations ................................................................................................... 5 7.1 General ................................................................................................................................... 5 7.2 Excavation and Soil Characteristics ...................................................................................... 5 7.3 Seismic Design Criteria .... , ................................................................................. ; .................. 6 7.4 Grading .................................................................................................................................. 7 7.5 Slopes ................................................................................................................... , ................. 8 7.6 Foundation and Concrete Slabs-On-Grade Recommendations ............................................. 9 7.7 Retaining Walls and Lateral Loads ...................................................................................... 13 7.8 Preliminary Flexible Pavement Recommendations ................................................. , ........... 14 7.9 Slope Maintenance ...................................... ~ ....................................................................... 15 7.10 Site Drainage and Moisture Protection .......................... ' ...................................................... 16 7.11 Grading and Foundation Plan Review ............................................. , ............... : ................... 16 LIMITATIONS AND UNIFORMITY OF CONDITIONS FIGURES Figure 1, Vicinity Map Figure 2, Wall/Column Footing Dimension Detail Figure 3, Retaining Wall Drain Detail TABLES Table I, Summary of As-Graded Building Pad Conditions and Foundation Category Table II, Summary of Finish Grade Expansion Index Test Results Table ill, Summary of Laboratory Water-Soluble Sulfate Test Results APPENDIX A RECOMMENDED GRADING SPECIFICATIONS I' ~~" I~~:.:, :-" ;:J- I UPDATE GEOTECHNICAL REPORT 1. PURPOSE AND SCOPE This report presents the results of the update geotechnical study for the proposed residential development of Neighborhood 1.16, Lots 1 through 26 and associated improvements located in Phase 2 of the Villages of La Costa -The Greens development: The site is situated north of Dove Lane and west of the existing La Costa Resort and Spa golf course (see Vicinity Map, Figure 1). The purpose of this update report is to provide foundation, grading, and retaining wall design recommendations. The scope of the study included a review of the following: 1. Update Soil and Geological Investigation, Volume I and II, Villages of La Costa -The Greens, Carlsbad, California, prepared by Geocon mcorporated, dated June 25, 2001 (Project" No. 06403-12-03). 2. Final Report of Testing and Observation Services Performed During Site Grading, Villages of La Costa -The Greens, Neighborhoods 1.16 Lots 1 through 25, Carlsbad, California, prepared by Geocon mcorporated, dated December 15,2005 (Project No. 06403-52-19A). 3. Grading and Erosion Control Plans for: La Costa Greens Neighborhood 1.16 & 1.17, prepared by Hunsaker and Associates, City of Carlsbad approval dated May 10,2005. 2. PREVIOUS SITE DEVELOPMENT Neighborhood 1.16, Lots 1 through 26, was graded to. fmish-pad configuration during mass grading . . operations' for Phase 2 of The Greens development. Grading was performe~ in conjupction with the observation and testing services of Geocon mcorporated. A summary of the observations, compaction test results, and professional opinions pertaining to the grading are presented in the referenced report of grading dated December 15,2005. Mass grading for the subject area has been completed and consisted of developing 26 multi-family residential lots and associated streets. Fill and cut slopes were created with design inclinations of 2: 1 (horizontal:vertical) or flatter, with 11 maximum height of approximately 40 feet. The maximum thickness of the compacted fill is approximately 46 feet. 3. SITE AND PROJECT DESCRIPTION The development of The Greens -Neighborhood 1.16 consists of 26 multi-family residential pads and associated improvements. Compacted fill is exposed at grade and is underlain by the Santiago Formation. The Santiago Formation is also exposed at grade on cut slopes, cut pads and within some roadways. The "As-Graded" Geologic Map for the project is included in the referenced final report of grading. A summary of the as-graded pad conditions for the lots is provided on Table 1. m general, the on-site fill materials generally consist of silty, fine sand and sandy to silty clay. Project No. 06403-52-27 -1-June 10, 2008 I' r ::.:/ .. : I i g~~~ t , , :'::::. I~~: :-.i I~: '.' ~:~:~~ ._--.' 1==· '~ g.~!, I~: ::'4 do I~~ ,":i :'::=':.' .. i: :-:.-:,. -:.:.:; ~. I"::, ..... I~' The locations and descriptions of the site and proposed improvements are based on a site reconnaissance, a review of the referenced grading plans, and our understanding of project development. If project details vary significantly from those described above, Geocon Incorporated should be contacted to determine the necessity for review and revision ofthis report. 4. SOIL AND GEOLOGIC CONDITIONS The Santiago Formation and compacted fill underlie the site. The predominant materials within 3 feet, of grade consist of clayey to silty sand and possess a "very low" to "low" expansion potential. The soil type and geologic unit are discussed below. 4.1 Compacted Fill (Qct) In general, the fill materials consist of light yellowish brown, sandy to silty clay and silty sand. The maximum fill thickness is approximately 46 feet. Fill soil was placed in conjunction with the observation and testing services of Geocon Incorporated, which are summarized in the referenced final report of grading [2]. The compacted fill is considered suitable to provide adequate support for the proposed development. 4.2 Santiago Formation (Ts) The Eocene-age Santiago Formation, consisting of dense, massive, white to light green, silty, fine to coarse sandstones and hard, greenish-gray to brown claystones and siltstones, underlies the compacted fill at the site. The formational materials are considered suitable for the support of the proposed development. 5. GROUNDWATER We encountered groundwater during grading operations in the alluvial soil; however, we do not expect groundwater to adversely impact the development of the property. Due to the nature of the Santiago Formation, which consists of interbedded sandstone and claystone/siltstone, we encountered seepage in several cut slopes. The grading contractor installed stability fill slopes with drains to mitigate the seepage conditions. It is not uncommon for groundwater or seepage conditions to develop where none previously existed. Groundwater elevations are dependent on seasonal precipitation, irrigation, and land use, among other factors, and vary as a result. Proper surface drainage will be important to future performance of the project. Project No. 06403-52-27 -2-June 10,2008 6. GEOLOGIC HAZARDS 6.1 Faulting and Seismicity It is our opinion, based on the previous site grading operations and a review of published geologic maps and reports that the site is not located on any known active, potentially active, or inactive fault traces. The nearest known active fault is the Rose Canyon Fault Zone located approximately 7 miles west of the site. Earthquakes that might occur on the Rose Canyon Fault Zone or other faults within the southern California and northern Baja California area are potential generators of significant ground motion at the site. We used the computer program EQF A ULT to calculate the distance of known faults to the site. Earthquakes on the Rose Canyon Fault Zone having a maximum magnitude of 7.2 are considered representative of the potential for seismic ground shaking within the prope~ty. The maximum magnitude is defined as the maximum earthquake that appears capable of occurring under the presently known tectonic framework (California Geological Survey, Number 43). We calculated the estimated maximum ground acceleration expected at the site to be approximately O.33g using the Sadigh, et at. (1997), acceleration-attenuation relationship. Table 6.1 presents the earthquake events and site accelerations for the most significant faults considered most likely to subject the site to ground. shaking. TABLE 6.1 DETERMINISTIC SITE PARAMETERS FOR SELECTED FAULTS Fault Name Distance from Maximum Maximum Site Site (miles) Earthquake Acceleration (g) Rose Canyon 7 7.2 0.33 Newport-Inglewood (Offshore) 10 1.1 0.26 Coronado Banks Fault Zone 22 7.6 0.17 Elsinore-Julian 23 7.1 0.12 Elsinore-Temecula 23 6.8 0.10 Elsinore-Glen Ivy 37 6.8 0.06 Earthquake Valley 40 6.5 0.04 Palos Verdes 41 7.2 0.06 San J acinto-Anza 46 7.2 0.06 In the event of a major earthquake on any of the referenced faults in Table 6.1 or other significant faults in the southern California/northern Baja California area, the site could be subjected to moderate to severe ground shaking. With respect to this hazard, the site is considered comparable to others in the general vicinity. While listing peak accelerations is useful for comparison of potential effects of fault activity in a region, other considerations are important in seismic design, including the frequency and Project No. 06403-52-27 -3-June 10; 2008 I I. I I I' I , I .: ' ( I .; > I :~ I " " " " , .. l' , i: I I.' I I~ duration of motion and the soil conditions underlying the site. The structures should be built in accordance with the seismic design criteria presented in the California Building:Cbde (CBC). &.2 Liquefaction Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are cohesionless, groundwater is encountered within 50 feet of the surface, and soil relative densities are less than about 70 percent. If the four previous criteria are met, a seismic event could result in a rapid pore water pressure increase from the earthquake-generated ground accelerations. Due to the dense np.ture of the compacted fill and formational materials and the lack of a permanent groundwater table, the potential for liquefaction occurring at the site is considered to be very low. 6.3 Landslides Examination of aerial photographs in our files, review of available geologic maps and geotechnical reports for the site vicinity, and the results our field investigation indicate that landslides are not present at the property or at a location that could impact the site . Project No, 06403-52-27 -4-June 10, 2008 7.1 7.1.1 7.1.2 7.1.3 7.1.4 7. CONCLUSIONS AND RECOMMENDATIONS General No-soil or geologic conditions were encountered during previous geotechnical investigations or grading operations that, in our opinion, would preclude the continued development of the property as presently planned, provided that the recommendations of this report are . followed. The site is underlain by compacted fill composed of silty, fine sand and sandy to silty clay and materials of the Santiago Formation consisting of interbeds of dense sandstone, siltstone, . and claystone. The formational materials and the fill are considered suitable for support of additional structural fill and/or loads from the proposed development; however, processing, moisture conditioning as necessary, and compaction of the near-surface soil will be required. The site is considered suitable for the use of conventional foundations and slab-on-grade and/or a post-tensioned foundation system. The building pads should be graded such that at least the upper 3 feet of materials below proposed pad grade are composed of compacted fill. The undercuts should be sloped to drain away from the building pads and toward adjacent streets or toward the deeper fill. 7.2 Excavation and Soil Characteristics 7.2.1 Soil encountered during mass grading is considered to be "expansive" (expansion index [EI] greater than 20) as defined by 2007 California Building C9de (CBC) Section 1802.3.2. Table 7.2.1 presents soil classifications based on the expansion index. The soil possesses a "very low" to "low" expansion potential (Expansion fudex of 50 or less). TABLE 7.2.1 SOIL CLASSIFICATION BASED ON EXPANSION INDEX Expansion Index (EI) Soil Classification 0-20 Very Low - 21-50 Low 51-90 Medium 91-130 High Greater Than 130 Very High Project No. 06403-52-27 -5-June 10, 2008 I :.. ..... I:~ ~:::;: I i :-..: .... , ~.".'. IrJ~ . .;~ ~~~~:~; I:' ;~.;~~ . ...... 1":,:: .. ):, 7.2.2 7.2.3 7.3 7.3.1 We tested samples of the site materials during mass grading operations to evaluate the percentage of water-soluble sulfate content. Results from the laboratory water-soluble sulfate content tests are presented in Table III and indicate that the on-site materials at the locations tested possesses "negligible" to "severe" sulfate exposure to concrete structures as defined by 2007 CBC Section 1904.3 and ACI 318. Table 7.2.2 presents a summary of concrete requirements set forth by 2007 CBC Section 1904.3 and ACI 318. The presence of water- soluble sulfates is not a visually discernible characteristic; therefore, other soil samples from the site could yield different concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers and other soil nutrients) may affect the concentration. Sulfate Exposure Negligible Moderate Severe Very Severe TABLE 7.2.2 REQUIREMENTS FOR CONCRETE EXPOSED TO SULFATE-CONTAINING SOLUTIONS Water-Soluble Cement Maximum Water Sulfate Percent Type to Cement Ratio by Weight by Weight 0.00-0.10 ---- 0.10-0.20 II 0.50 0.20-2.00 V 0.45 >2.00 V 0.45 Minimum Compressive Strength (psi) -- 4000 4500 4500 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if improvements that could be susceptible to corrosion are planned, further evaluation by a corrosion engineer should be performed. Seismic DeSign Criteria We used the computer program Seismic Hazard Curves and Uniform Hazard Response Spectra, provided by the USGS to calculate the seismic design criteria. Table 7.3 summarizes site-specific design criteria obtained from the 2007 CBC, Chapter 16 Structural Design, Section 1613 Earthquake Loads. The short spectral response has a period of 0.2 second. Project No. 06403-52-27 -6-June 10, 2008 i I ~ •• __ 'J :.:-:;.' I :> i 1'::·\ ,. .... .. :_/;.: '=0°_ .. I :::q· ::. ,".' 7.3.2 7.4 7.4.1 7.4.2 7.4.3 TABLE 7.3 2007 CBC SEISMIC DESIGN PARAMETERS Parameter Value IBC-06 Reference Fill Thickness, T (feet) T<20 T~20 -- Site Class C D Table 1613.5.2 Spectral Response -Class B (short), Ss 1.147g 1.147g Figure 1613.5(3) Spectral Response -Class B (1 sec), Sl O.434g O.434g . Figure 1613.5(4) Site Coefficient, Fa 1.000 1.041 Table 1613.5.3(1) Site Coefficient, Fv 1.366 1.566 Table 1613.5.3(2) Maximum Considered Earthquake 1.147g 1.194g Section 1613.5.3 (Eqn 16-37) Spectral Response Acceleration (short), SMS Maximum Considered Earthquake 0.592g 0.679g Section 1613.5.3 (Eqn 16-38) Spectral Response Acceleration -(1 sec), SMI 5 % Damped Design 0.765g 0.796g Section 1613.5.4 (EqIi 16-39) Spectral Response Acceleration (short), SDS 5% Damped Design O.395g O.453g Section 1613.5.4 (Eqn 16-40) Spectral Response Acceleration (1 sec), SDI Conformance to the criteria for seismic design in Table 7.3 does.not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur if a maximum level earthquake occurs. The primary goal of seismic design is to protect life and not to avoid damage, since such design may be economically prohibitive. Grading Grading should be performed in accordance with the Recommended Grading Specifications contained in Appendix A. Where the recommendations of this section conflict with those of Appendix A, the recommendations of this section take precedence. Earthwork should be observed and fill tested by Geocon Incorporated. Prior to commencing grading operations, a preconstruction meeting should be held at the site with the owner or developer, grading contractor, civil engineer, and geotechnical engineer in attendance. Special soil handling andlor the grading plans can be discussed at that time. Site preparation should begin with the removal of deleterious matter and vegetation. The depth of removal should be such that materials to be used in fills are generally free of organic matter. Material generated during stripping operations andlor site demolition should be exported from the site. Project No. 06403-52-27 -7-June 10, 2008 I@~: ~::'. ,. ::::=::j -,:~:-;/ ,,' I ':', .:.;-; .. 0-'-"·:" j:" 7.4.4 7.4.5 7.4.6 7.4.7 7.5 7.5.1 7.5.2 In general, the upper 1 to 2 feet of existing fill should be processed, moisture conditioned as necessary, and compacted prior to placing additional fill or improvements. Deeper removals and/or moisture conditioning should be expected within the eroded and silted areas. In addition, building pads with formational cut-fill transitions should be undercut a minimum of 3 feet and replaced with properly compacted fill. Undercuts should be sloped a minimum of 1 percent and drain toward the adjacent on-site streets or driveways. After preparation of the ground surface, the site should be brought to design elevations with fill compacted in layers. The site material is considered suitable for use as fill provided it is generally free from vegetation, debris and other deleterious matter. Layers of fill should not be thicker than will allow for adequate bonding and compaction. Fill, including wall and trench backfill and scarified ground surfaces, should be compacted to a dry density of at least 90 percent of laboratory maximum dry density near to slightly above optimum moisture content as determined by ASTM Test Procedure D 1557-02. Import fill (if necessary) should consist of granular materials with a "very low" to "low" expansion potential (EI of 50 or less), free of deleterious material or rocks larger than 3 inches, and should be compacted as recommended herein. Geocon Incorporated should be notified of the import soil source and should perform laboratory testing of import soil prior to its arrival at the site to determine its suitability as fill material. Oversize material (fragments greater than 6 inches in maximum dimension), if generated, should not be placed within 3 feet of finish grade in pad areas and 12 inches of subgrade in driveways. Material greater than 6 inches in maximum dimension, if generated, should be placed in deeper fill areas. Due to the absence of large areas of available fill volume,it is unlikely that all of the oversize material could be placed as compacted fill during the grading operation; hence, the oversize material may require exportation. Slopes Based on the referenced geotechnical reports for Villages of La Costa -The Greens development, existing fill slopes at the site (constructed at 2: 1 inclinations) possess a factor of safety greater than 1.5 against deep-seated and surficial failure. Slopes should be landscaped with drought-tolerant vegetation, having variable root depths and requiring minimal landscape irrigation. In addition, slopes should be drained and properly maintained to reduce erosion. Project No, 06403-52-27 -8-June 10, 2008 :0:-:. i ~-.. I :;:;::. I: i f.~~: I~?~ -::. :.:.::._1 :~;;~:; I::' . ::~:-;. 1':::::::- .. ::.' ........ I::'::~;:: " 7.6 7.6.1 7.6.2 7.6.3 Foundation and Concrete Siabs-On-Grade Recommendations The foundation recommendations herein are for proposed one-to' two-story residential structures. The foundation recommendations have been separated into three categories based on either the maximum and differential fill thickness or Expansion Index. The foundation category criteria are presented in Table 7.6.1. Foundation Category I II III TABLE 7.6.1 FOUNDATION CATEGORY CRITERIA Maximum Fill Differential Fill Thickness, T (feet) Thickness, D (feet) T<20 -- 20<T<SO 10<D<20 T>SO D>20 Expansion Index (EI) El<SO SO<EI<90 90<Ek130 Final foundation categories for each building or lot will be provided after finish pad grades have been achieved and laboratory testing of the sub grade soil has been completed. Table 7.6.2 presents minimum foundation and interior concrete slab design criteria for conventional foundation systems. TABLE 7.6.2 CONVENTIONAL FOUNDATION RECOMMENDATIONS BY CATEGORY .. Foundation Minimum Footing Continuous Footing Interior Slab Embedment Depth Category (inches) Reinforcement Reinforcement I 12 Two No.4 bars, 6 x 6 -10/10 welded wire one top and one bottom mesh at slab mid-point II 18 Four No.4 bars, No.3 bars at 24 inches two top and two bottom on center, both.directions III 24 Four No. S bars, No.3 bars at 18 inches two top and two bottom . on center, both directions 7.6.4 The embedment depths presented in Table 7.6.2 should be measured from the lowest adjacent pad grade for both interior and exterior footings. The converiti~nal foundations should have a minimum width of 12 inches and 24 inches for continuous and isolated footings, respectively. A typical wall/column footing dimension detail is presented in Figure 2 . Project No. 06403-52-27 -9-Julie 10, 2008 I- I: ::::;:" I , ~~~~? I :;:, .. .. -:", ::::;:; .... : .. , I······ .... . ' .:.:.::.- I·::::~::· .' .' ........ .::. 7.6.5 7.6.6 . 7.6.7 The concrete slab-on-grade should be a minimum of 4 inches thick for Foundation Categories I and II and 5 inches thick for Foundation Category III. Concrete slabs on grade should be underlain by 2 inches of .clean sand to reduce the potential for differential curing, slab curl, and cracking. Slabs that may receive moistute.;.sensitiye floor coverings or may be used to store moisture-sensitive materials should be underlain by a vapor inhibitor covered with at least 2 inches of clean sand or crushed rock. The vapor inhibitor should meet or exceed the requirements of ASTM E 1745-97 (Class A), and exhibit permeance n9t greater than 0.012 perm (measured in accordance with ASTM E 96-95. This vapor inhibitor may be placed directly on finish pad grade. The vapor inhibitor should be installed in general conformance with ASTM E 1643-98 and the manufacturer's recommendations. Floor coverings should be installed in accordance with the man~facturer' s recommendations. As an alternative to the conventional foundation recommendations, consideration should be given to the use of post-tensioned concrete slab and foundation systems for the support of the proposed structures. The post-tensioned systems should be designed by a structural engineer experienced in post-tensioned slab design and design. criteria of the Post-Tensioning Institute (PTI) , Third Edition, as required by the 2007 California Building Code (CBC Section 1805.8). Although this procedure was developed for expansive soil conditions, we understand it can also be used to reduce the potential for foundation distress due to differential fill settlement. The post-tensioned design should incorporate the geotechnical .. parameters presented on Table 7.6.3 for the particular Foundation Category designated. The parameters presented in Table 7.6.3 are based on the guidelines presented in the PT!, Third Edition design manual. TABLE 7.6.3 POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS Post-Tensioning Institute (PTI), Foundation Category Third Edition Design Parameters I II IiI Thornthwaite Index -20 -20 -20 Equilibrium Suction 3.9 3.9 3.9 Edge Lift Moisture Variation Distance, eM (feet) 5.3 5.1 4;9 Edge Lift, YM (inches) 0.61 1.10 1.58 Center Lift Moisture Variation Distance, eM (feet) 9.0 9.0 9.0 Center Lift, YM (Inches) 0.30 0.47 0.66 Project No. 06403-52-27 -10-. June 10, 2008 I :, :.1 . ;i.: I ::, -;, .. :::: , I~:: .' .' . . ' I:' :', I~·· ',' .7.6.8 7.6.9 The foundations for the post -tensioned slabs should be embedded in accordance with the recommendations of the structural engineer. If a post-tensioned mat foundation system is planned, the slab should possess a thickened edge with a minimum width of 12 inches and extend below the clean sand or crushed rock layer. If the structural engineer proposes .a post-tensioned foundation design m~thod other than PT!, Third Edition: • The deflection criteria presented in Table 7.6.3 are still applicable. • Interior stiffener beams should be used for Foundation Categories II and III. • The width of the perimeter foundations should be at least 12 inches. • The perimeter footing embedment depths should be at least 12 inches, 18 inches and 24 inches for foundation categories I, II, and ill, respectively. The embedment depths should be measured from the lowest adjacent pad grade. 7.6.10 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift, regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the perimeter footings and the interior stiffener beams may mitigate this potential. :Cl,lITent PTI design procedures primarily address the potential center lift of slabs but, because of the placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after tensioning reduces the ability of the system to mitigate edge lift. The structural engineer should design the foundation system to reduce the potential of edge lift occurring for the proposed structures. 7.6.11 During the construction of the post-tension foundation system, the concrete should be placed monolithically. Under no circumstances should cold joints form between the footings/grade beams and the slab during the construction of the post-tension foundation system. 7.6.12 Category I, II, or III foundations may be designed for an allowable soil bearing pressure of 2,000 pounds per square foot (psf) (dead plus live load). This bearing pressure may be increased by one-third for transient loads due to wind or seismic forces. The estimated maximum total and differential settlement for the planned structures due to foundation loads is 1 inch and Yz inch, respectively. 7.6.13 Isolated footings, if present, should have the minimum embedment depth and width recommended for conventional foundations for a particular foundation category. The use of isolated footings, which are located beyond the perimeter of the building and support structural elements connected to the building, are not recommended for Category III. Where this condition cannot be avoided, the isolated footings should be connected to the building foundation system with grade beams. Project No, 06403-52-27 -11-June 10, 2008 :::::- I{::!' .::. ~~~i~ I ', .~ " '-•••• J :::-::. I::::~: " : -:.::", I::~~~ ~, Ii I 7.6.14 7.6.15 7.6.16 For Foundation Category III, consideration should be given to using interior stiffening beams and connecting isolated footings and/or increasing the slab thickness. ill addition, consideration should be given to connecting patio slabs, which exceed 5 feet in width, to the building foundation to reduce the potential for future separation to occur. Special subgrade presaturation is not deemed necessary prior to placing concrete; however, the exposed foundation and slab subgrade soil should be moisture conditioned, as nece~saJ':y, to maintain a moist condition as would be expected in any such concrete placement. Where buildings or other improvements are planned near the top of a slope steeper than 3: 1 (horizontal:vertical), special foundations and/or design considerations are recommended due to the tendency for lateral soil movement to occur. • For fill slopes less than 20 feet high or cut slopes regardless of height, building footings should be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally from the face of the slope. • When located next to a descending 3: 1 (horizontal:vertical) fill slope or steeper, the foundations should be extended to a depth where the minimum horizontal distance is equal to H/3 (where H equals the vertical distance from the top of the fill slope to the base of the fill soil) with a minimum of 7 feet but need not exceed 40 feet. The horizontal distance is measured from the outer, deepest edge of the footing to the face of the slope. An acceptable alternative to deepening the footings would be the use of a post-tensioned slab and foundation system or increased footing and slab reinforcement. Specific design parameters or recommendations for either of these alternatives can be provided once the building location and fill slope geometry have been determined. . • If swimming pools are planned, Geocon illcorporated should be contacted for a review of specific site conditions. • Swimming pools located within 7 feet of the top of cut or fill slopes are not recommended. Where such a condition cannot be avoided, the portion of the swimming pool wall within 7 feet of the slope face be designed assuming that the adjacent soil provides no lateral support. This recommendation applies t9 fill slopes up to 30 feet in height, and cut slopes regardless of height. For swimming pools located near the top of fill slopes greater than 30 feet in height, additional recommendations may be required and Geocon illcorporated should be contacted for a review of specific site conditions. • Although other improvements, which are relatively rigid or brittle, such as concrete flatwork or masonry walls, may experience some distress if located near the top of a slope, it is generally not economical to mitigate this potential. It may be possible, however, to incorporate design measures which would perniit some lateral soil movement without causing extensive distress. Geocon illcorporated should be consulted for specific recommendations. Project No, 06403-52-27 -12-June 10, 2008 7.6.17 The recommendations of this report are intended to reduce the potential for cracking of slabs due to expansive soil (if present), differential settlement of existing soil or soil with varying thicknesses. However, even with the incorporation ofthe recommendations presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of concrete shrinkage cracks is independent of the supporting soil characteristics. Their occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper concrete placement and curing, and by the placement of crack control joints at periodic intervals, in particular, where re-entrant slab comers occur. 7.6.18 Geocon Incorporated should be consulted to provide additional design parameters as required by the structural engineer. 7.7 .Retaining Walls and Lateral Loads 7.7.1 Retaining walls not restrained at the top and having a level backfill surface should be designed for an active soil pressure equivalent to the pressure exerted by-a fluid density of 35 pounds per cubic foot (pet). Where the backfill will be inclined at no steeper than 2 to 1, backfill materials within an area bounded by the wall and a 1: 1 plane extending upward from the base of the wall possess an Expansion' fudex of 50 or less. Where backfill materials do not conform to the criteria herein, Geocon fucorporated should be consulted for additional recommendations. 7.7.2 Unrestrained walls are those ~hat are allowed to rotate more than O.OOlH (where H equals the height of th~ retaining wall portion of the wall in feet) at the top of the wall. Where walls are restrained from movement at the top, an additional uniform pressure of 7H psf should be added to the above active soil pressure. For retaining walls subjected to vemcular loads within a horizontal distance equal to two-thirds of the wall height, a surcharge equivalent to 2 feet soil should be added. 7.7.3 Retaining walls should be provided with a drainage system adequate to prevent the buildup of hydrostatic force~ and should be waterproofed as required by the project architect. The use of drainage openings through the base of the wall (weep holes, etc.) is not recoIIl111ended where the seepage could be a nuisance or otherwise adversely impact the property adjacent to the base of the wall. A typical retaining wall drainage system is presented as Figure 3. The recommendations herein assume a properly compacted granular (Expansion fudex of 50 or less) backfill material with no hydrostatic forces or imposed surcharge load. If conditions different than those described are expected, or if specific drainage details are desired, Geocon Incorporated should be contacted for additional recommendations. Project No. 06403-52-27 -13-June 10, 2008 j '" ~~. I~ .' :::::~ I':::~ ., , 11 ~~::1 1:7~: :-;. -;:::.1 i I @%=.j I:' ~:~~~~ C i (' I;;' ",-.- I: I;: 7.7.4 7.7.5 7.7.6 In general, wall foundations having a minimum depth and width of one foot may be designed for an allowable soil bearing pressure of 2,000 psf, provided the soil within 3 feet below the base of the wall has an Expansion Index of 90 or less. The proximity of the foundation to the top of a slope steeper than 3: 1 could impact the allowable soil bearing pressure. Therefore, Geocon Incorporated should be consulted where such a condition is expected. For resistance to lateral loads, an allowable passive earth pressure equivalent to a fl1Jid density of 300 pcf is recommended for footings or shear keys poured neat again~t properly compacted granular fill soil or undisturbed natural soil. The allowable passive pressure assumes a horizontal surface extending at least 5 feet or three times the surface generating the passive pressure, whichever is greater. The upper 12 inches of material not protected by floor slabs or pavement should not be included in the design for lateral resistance. An allowable friction coefficient of 0.4 may be used for resistance to sliding between soil and concrete. This friction coefficient may be combined with the allowable passive earth pressure when determining resistance to lateral loads. The structural engineer should determine the seismic design category for the project. If the project possesses a seismic design category of D, E, or F, the proposed retaining walls should be designed with seismic lateral pressure. The seismic load exerted on the wall should be a triangular distribution with a pressure of 23H (where H is the height of the wall, in feet, resulting in pounds per square foot [psf]) exerted at the top of the wall and zero at the base of the wall. 7.7.7 Although we evaluated this seismic loading on the wall for an active pressure case and the walls will be in an at-rest condition, some researchers have reported that this analysis produces reasonable design earth pressures. Because seismic loads will be analyzed using lower factors of safety than static earth pressures, we expect the design can be controlled by static loads. 7.7.8 The recommendations presented herein are generally applicable to the desigo. of rigid concrete or masonry retaining walls having a maximum height of 8 feet. In the event that walls higher than 8 feet or other types of walls (such as crib-type walls) are planned, Geocon Incorporated should be consulted for additional recommendations. 7.8 Preliminary Flexible Pavement Recommendations 7.8.1 Preliminary pavement recommendations provided are based on our experience with similar soil conditions. For driveways and parking areas, design and construction criteria should conform to City of Carlsbad standards. We assume the pavement surface will have automobile and light-duty truck traffic. We have also assumed an R-value of 15 for the Project No. 06403-52-27 -14-June 10, 2008 7.8.2 7.8.3 proposed subgrade soil. Table 7.8 presents preliminary pavement recommendation is for planning and estimating purposes only, and not for construction. Location Driveways TABLE 7.8 PRELIMINARY PAVEMENT SECTION Assumed Assumed Asphalt Concrete Traffic Index R-Value (inches) 5.0 15 4 Aggregate Base Material (inches) 6 The upper 12 inches of the subgrade supporting the structural section should be scarified, moisture conditioned as necessary, and compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly over optimum moisture as determined by ASTM Test Method D 1557-02. Aggregate base materials should be compacted to a dry density at least 95 percent of the laboratory maximum dry density at near to slightly above optimum moisture content. 7.8.4 Asphalt concrete should be compacted to a density of at least 95 percent of the Hveem density as determined by ASTM D 2726-05A. 7.8.5 Asphalt concrete should conform to Section 203-6 of the Standard Specifications for Public Works Construction (Greenbook). Aggregate base (Class II) materials should conform to Section 26-1.02A of the Standard Specifications of the State of California, Department of Transportation (Caltrans) or approved equivalent. Additionally, all materials should conform to City of Carlsbad specifications. 7.9 Slope Maintenance 7.9.1 Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions that are both difficult to prevent and predict, be susceptible to near-surface (surficial) slope instability. The instability is typically limited to the outer 3 feet of a portion of the slope and usually does not directly impact the improvements on the pad areas abov(} or below the slope. The occurrence of surficial instability is more prevalent on fill slopes and is generally preceded by a period of heavy rainfall, excessive irrigation, or the migration of subsmface seepage. The disturbance and/or loosening of the surficial soil, as might result from root growth, soil expansion, or excavation for irrigation lines and slope planting, may also be a significant contributing factor to surficial instability. It is therefore recommended that, to the maximum extent practical: (a) disturbed/loosened surficial soil be either removed or properly recompacted; (b) irrigation systems be periodically inspected and maintained to eliminate Project No. 06403-52-27 -15-June 10; 2008 , I~;:::: .J :{.:; .w ..... " I····, .::.~:.' leaks and excessive irrigation; and (c) surface drains on and adjacent to slopes be periodically maintained to preclude ponding or erosion. It should be noted that although the incorporation of the above recommendations should reduce the potential for surficial slope instability, it will not eliminate the possibility, and, therefore, it may be necessary to rebuild or repair a portion of the project's slopes in the future. 7.10 Site Drainage and Moisture Protection 7.10.1 Adequate site drainage is critical to reduce the potential for differential soil movement, erosion and subsurface seepage. Under no circumstances should water be allowed to pond adjacent to footings. The site should be graded and maintained such that surfa,ce drainage is directed away from structures in accordance with 2007 CBC 1803.3 or other applicable standards. In addition, surface drainage should be directed away from the top of slopes into swales or other controlled drainage devices. Roof and pavement drainage should be directed into conduits that carry runoff away from the proposed structure. 7.10.2 If detention basins, bioswales, or retention basins are planned, distress may be caused to planned improvements and properties located hydrologically downstream. The distress depends on the amount of water to be detained, its residence time, soil permeability, and other factors. We have not performed a hydrogeology study at the site. Downstream properties may be subjected to seeps, springs, slope instability, raised groundwater, movement of foundations and slabs, or other impacts as a result of water infiltration through the detention basins, bios wales, or retention basins. . . . 7.11 Grading and FOUl1datiori Plan Review 7.11.1 Grading and foundation plans should be reviewed by Geocon Incorporated to check that-the plans have been prepared in substantial conformance with the recommendations of this report. Project No. 06403-52-27 -16-JJine 10, 2008 I I '~~~~l I:;' :;::,:- I:: I:; 1. 2. 3. 4. LIMITATIONS AND UNIFORMITY OF CONDITIONS Recommendations of this report pertain only to the site investigated and are based upon the assumption that the soil conditions do not deviate from those disclosed in the investigation. If any variations or undesirable conditions are encountered during construction, or if tbe proposed c0nstruction will differ from that anticipated herein, Geocon illcorporated should be notified so that supplemental recommendations can be given. The evaluation or identification of the P9tential presence of hazardous or corrosive materials was not part of the scope of services provided by Geocon illcorporated. This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project and incorporated into the plan~, and that the necessary steps are taken to see that the contractor and subcontractor~ carry out such recommendations in the field. The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time, whether they are due to natural processes or the works of man on this or adjacent properties. ill addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. The firm that performed the geotechnical investigation for the project should be retained to prov"ide testing and observation services during construction to provide continuity of geotechnical interpretation and to check that the recommendations presented for geotechnical aspects of site development are incorporated during site grading, construction of improvements, and excavation of foundations. If another geotechnical firm is selected to perform the testing and observation services during construction operations, that firm should prepare a letter indicating their inte:p.t to assume the responsibilities of project geotechnical engineer of record. A copy of the letter should be provided to the regulatory agency for their records. ill addition, that firm should provide revised recommendations concerning the geotechnical aspects of the proposed development, or a written acknowledgement of their concurrence with the recommendations presented in our rel?0rt. They should also perform additional analyses deemed necessary to assUme the role of Geotechnical Engineer of Re:cord. Project No. 06403-52-27 June 10,2008 I I·· I I • J I; ,; I~ : '~ , , I) .. I; I:, , , , , I~ I I I SOURCE: 2007 THOMAS BROTHERS MAP SAN DIEGO COUNTY, CALIFORNIA "MAP © RAND McNALLY, R.L.07-S-S2, REPRODUCED WITH PERMISSION. IT IS UNLAWFUL TO COPY OR REPRODUCE ALL OR ANY PART THEREOF, WHETHER FOR PERSONAL USE OR RESALE, WITHOUT PERMISSION" GEDeON INCORPORATED GEOTECHNICAL CONSULTANTS --------.. -L~~ \ \ \ 6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858558-6900'-FAX 858558-6159 8 .. RANC~08Rii)A 9 . ~ASEO sALlNERO t N NO SCALE VICINITY MAP VILLAGES OF LA COSTA -THE GREENS NEIGHBORHOOD 1 .16 CARLSBAD I CALIFORNIA AS/RA I I DSKlGTYPD DATE 06 -10 -2008 I PROJECT NO. 06403 -52 -27 I FIG. 1 VicinIty Mop i "'" I :, ;;.' .... ;::~: .. I··::·· .. ...... ;. I,: WALL FOOTING MOISTURE INHIBITOR (WHERE REQUIRED) COLUMN FOOTING MOISTURE INHIBITOR· (WHERE REQUIRED) CONCRETE SLAB CONCRETE SLAB '", .•..... :~, . : ~. QCt4,'.' .' PAD GRADE \-------FOOTING WIDTW ------{ * .... SEE REPORT FOR FOUNDATION WITDH AND DEPTH RECOMMENDATION WALL / COLUMN FOOTING DIMENSION DETAIL GEDeON • VILLAGES OF LA COSTA -THE GREENS INCORPORATED NEIGHBORHOOD 1.16 GEOTECHNICAL CONSULTANTS CARLSBAD, CALIFORNIA 6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858558-6900 -FAX 858 558-6159 AStRA I I DSKlGTYPD DATE 06 -10 -2008 I PROJECT NO. 06403 ~ 52 -27 I ~IG. 2 . Y:/R1AT<MP/tAUTOCAD PtA TE T<MPtATEIl.DETAlUCOlUMN FOOTING/COlFOOT2.DWG ::.:.:. I:;~ '." , .~.::>-;~:::} I-~ :~ .'. :;;i) I·:~~~; .5, i ~~~ t J t~ 1_.::, -;: n 8~: i .. :.: .... I:t~:.i .... I:}: ·1···· ~ .. , -0::'-:' 1':-:::·, . '.' •• 0' PROPOSED RETAINING WALL 2/3 H <! • • • GROUND SURFACE . . . . TEMPORARY'BACKCUT PER OSHA MlRAFI140N FILTER FABRIC (OR EQUIVALENT) OPEN GRADED 1" MAX. AGGREGATE GROUND SURFACE \ Ik~~i ,:r 4" DIA. PERPORATED PVC PIPE MIN. 1/2% FALL TO APPROVED OUTLET NO SCALE RETAINING WAll DRAIN DETAil GEDeON INCORPORATED o GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858 558-6900 -FAX 858 558-6159 AS/RA DSKlGTYPD Y:/RlATEMP/l_AUTOCAD PLATE TEMPLA TEIl.DETAIl/RETAINING WALL DRAINAGEIRETW ALLtDWG VILLAGES OF LA COSTA -THE GREENS NEIGHBORHQOD 1.16 CARLSBAD, CAEIFORNIA DATE 06 -10 -2008 PROJECT NO. 06403 -52 -27 FIG. 3 I ::: Ii f:§~~ I: -;::';;'~~ i II! -;I ~i~~ I·:~' ,7 '.' ..... :~::j :..z.? Il~l .- £:4 .-:r::l :::::;:) I;::~~ =;:: " ~~~~:~;~ I ,·, .~'/ .' --.-~-.. " I"::;:' ..... ' .... , , TABLE I SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND FOUNDATION CATEGORY FOR NEIGHBORHOOD 1.16, LOT NOS. 1 THROUGH 26 Approximate Approximate Expansion Foundation Lot No. Pad Condition Maximum Depth Maximum Depth of Index Category of Fill (feet) Differential Fill (feet) 1 Cut N/A N/A 1 I 2 Cut N/A N/A 1 I 3 Cut N/A N/A 1 I 4 Cut N/A N/A 35 I 5 Cut N/A N/A 35 I 6 Cut N/A N/A 35 I 7 Cut N/A N/A 35 I 8 Cut N/A N/A 14 I 9 Cut N/A N/A 14 I 10 Cut N/A N/A 43 I 11 Cut N/A N/A 43 I 12 Cut N/A N/A" 43 I 13 Undercut due to 4 1 43 I concretions 14 Undercut due to 4 1 38 I concretions 15 Undercut due to 4 1 38 I concretions 16 Undercut due to 4 ,. 1 38 I concretions 17 Undercut due to 29 26 22 III cut fill transition 18 Undercut due to 24 21 22 III cut fill transition 19 Undercut due to 24 21 22 III cut fill transition 20 Undercut due to 23 20 3 ill cut fill transition 21 Undercut due to 36 26 3 IIi cut fill transition - 22 Fill 31 26 3 III 23 Fill 37 34 29 III 24 Fill 46 43 29 III 25 Fill 31 28 29 III 26 Undercut due to 25 21 29 III cut fill transition Project No, 06403-52-27 June 10, 2008" I "'· ,.~ .,- .;~~~~ I:·::::, .' .' . .. ~;:" .;-:;:;:!. I~:·;:;:: ~:~ TABLE II SUMMARY OF FINISH GRADE EXPANSION INDEX TEST RESULTS VILLAGES OF LA COSTA; THE GREENS NEIGHBORHOOD 1.16, LOTS 1 THROUGH 25 Lot Numbers Sample at Finish Grade Expansion Index UBC Classification 1 through 3 EI-A 1 Very Low . 4 through 7 EI-B 35 Low 8 and 9 EI-C 14 VeryLbw lO through 13 EI-D 43 Low 14 through 16 EI-E 38 Low 17 through 19 EI-F 22 Low 20 through 22 EI-G 3 Very Low 23 through 26 EI-H 29 Low TABLE III SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST 417 .. Sample No. Water-Soluble Sulfate (%) Sulfate Exposure EI-A 0.030 Negligible. EI-B 0.032 Negligible EI-C 0.490 Severe EI-D 0.350 Severe EI-E 0.030 Negligible EI-F 0.050 Negligible .. EI-G 0.021 Negligible EI-H 0.150 Moderate Project No. 06403-52-27 June 10, 2008 I I I I I I I I I I I I I. I I. I I I I APPENOIX·A RECOMMENDED GRADING SPECIFICATIONS FOR VILLAGES OF LA COSTA -THE GREENS, PHASE 2 NEIGHBORHOOD 1.16; LOTS 1 THROUGH 26 CARLSBAD, CALIFORNIA. ' PROJECT NO. 06403-52-27 I I I I I I I I I I I I I I I I I I I 1.1 1.2 1.3 2.1 2.2 2.3 RECOMMENDED GRADING SPECIFICATIONS 1. GENERAL These Recommended Grading Specifications shall be used in conjunction with the Geotechnical Report for the project prepared by Geocon Incorporated. The recommendations contained in the text of the Geotechnical Report are a part of the earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case of conflict. Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be employed for the purpose of observing earthwork procedures and testing the fills for substantial conformance with the recommendations of the Geotechnical Report and these specifications. The Consultant should provide adequate testing and observation services so that they may assess whether, in their opinion, the work was performed in substantial conformance with these specifications. It shall be the responsibility of the Contractor to assist the Consultant and keep them apprised of work schedules and changes so that personnel may be scheduled accordingly. It shall be the sole responsibility of the Contractor to provide adequate equipment and methods to accomplish the work in accordance with applicable grading codes or agency ordinances, these specifications and the approved grading plans. If, in the opinion of the Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture condition, inadequate compaction, adverse weather, result in a quality of work not in conformance with these specifications, the Consultant will be empowered to reject the work and recommend to the Owner that grading be stopped until the unacceptable conditions are corrected. 2. DEFINITIONS Owner shall refer to the owner of the property or the entity on whose behalf the grading work is being performed and who has contracted with the Contractor to have grading performed. Contractor shall refer to the Contractor performing the site grading .work.. Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer or consulting firm responsible for preparation of the grading plans, surveying and verifying as-graded topography. GI rev. 10/06 I I I I I I I I I I I I I I I I I I I 2.4 2.5 2.6 2.7 3.1 Consultant shall refer to the soil engineering and engineering geolo~y consulting firm retained to provide geotechnical services for the project. Soil Engineer shall refer to a California licensed Civil Engineer retaineo. by th~ Owner, who is experienced in the practice of geotechnical engineering. The·Soil Engineer shall be responsible for haying qualified representatives on-site to observe and test the Contractor's work for conformance with these specifications. Engineering Geologist shall refer to a California licensed Engineering Geologist retained by the Owner to provide geologic observations and recommendations during the site grading. Geotechnical Report shall refer to a soil report (including all addenda) which may include a geologic reconnaissance or geologic investigation that was prepared specifically for the development of the project for which these Recommended Grading Specifications are intended to apply. 3. MATERIALS Materials for compacted fill shall consist of any soil excavated from the cut areas or imported to the site that, in the opinion of the Consultant, is suitable for use in construction of fIlls. In general, fill materials can be classified as soil fills, soil-rock fills orro.ck fills, as defined below. 3.1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than 12 inches in maximum dimension and containing at least 40 percent by weight of material smaller than % inch in size; 3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than 4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow for proper compaction of soil fill around the rock fragments or hard lumps as specified in Paragraph 6.2. Oversize rock is defined as material greater than 12 inches. 3.1. 3 Rock iIlls are defined as fills containing no rocks or hard lumps larger than 3 feet in maximum dimension and containing . little or no fines. Fin~s are defined as material smaller than % inch in maximum dimension. The quantity of fines shall be less than approximately 20 percent of the rock fill quantity. GJrev.. 10/06 I I I I I I I I I I I I I I -I I I I I 3.2 3.3 3.4 3.5 3.6 4.1 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the Consultant shall not be used in fills. Materials used for fill, either imported or on-site, shall not contain hazardous materials as defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9 and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall not be responsible for the identification or analysis of the potential presence of hazardous materials. However, if observations, odors or soil discoloration cause Consultant to suspect the presence of hazardous materials, the Consultant may request from the Owner the termination of grading operations within the affected area. Prior to resurrring grading operations, the Owner shall provide a written report to the Consultant indicating that the suspected materials are not hazardous as defined by applicable laws and regulations. The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of properly compacted soil fill materials approved by the Consultant. Rock fill may extend to the slope face, provided that the slope is not steeper than 2: 1 (horizontal:vertical) and a soil layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This procedure may be utilized provided it is acceptable to the governing agency, Owner and Consultant. Samples of soil materials to be used for fill should be tested in the laboratory by the - Consultant to determine the maximum density, optimum moisture content, and, where appropriate, shear strength, expansion, and gradation characteristics of the soil. During grading, soil or groundwater conditions other than those identified in the Geotechnical Report may be encountered by the Contractor. The Consultant shall be notified immediately to evaluate the significance of the unanticipated condition 4. CLEARING AND PREPARING AREAS TO BE FILLED Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of complete removal above the ground surface of trees, stumps, brush, vegetation, man-lTIade structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried logs and other unsuitable material and shall be performed in areas to be graded. Roots and other projections exceeding 1 Y2 inches in diameter shall be removed to a depth of 3 feet below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to provide-suitable fill materials. GI rev. 10/06 I I I I I I I I I I I I I I I I I I I 4.2 4.3 4.4 Any asphalt pavement material removed during clearing operations should be properly disposed at an approved off-site facility. Concrete fragments that are free of reinforcing steel may be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this document. After clearing and grubbing of organic matter and other unsuitable material, loose or porous soils shall be removed to the depth recommended in the Geotechnical Report. The depth of removal and compaction should be observed and approved by a representative of the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth of 6 inches and until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment to be used. Where the slope ratio of the original ground is steeper than 5: 1 (horizontal:vertica1), Or where recommended by the Consultant, the original ground should be benched in accordance with the following illustration. TYPICAL BENCHING DETAIL Finish Grade Remove All Unsuitable Material As Recommended 8y Consultant Slope To 8e Such That Sloughing Or Sliding Does Not Occur Original Ground / Finish Slope Surface 1----1.1 '--_--J~c:;;;:::--==-O__. I "8" ·See Note 1 No Scale DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit complete coverage with the compaction equipment used. The base of the key should be graded horizontal, or inclined slightly into the natural slope. (2) The outside of the key should be below the topsoil or unsuitable surficial material and at least 2 feet into dense formational material. Where hard rock is exposed in the bottom of the key, the depth and configuration of the key may be modified as approved by the Consultant. GI rev. 10106 I I I I I I I I I I I I I I I I I I I 4.5 5.1 5.2 6.1 After areas to receive fill have been cleared and scarified, the surface should be moisture conditioned to achieve the proper moisture content, and compacted as recommended in Section 6 of these specifications. 5. COMPACTION EQUIPMENT Compaction of soil or soil-rock fill shall be accomplished by sheepsfbot or segmented-steel wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of acceptable compaction equipment. Equipment shall be of such a design that it will be capable of compacting the soil or soil-rock fill to the specified relative compaction at the specified moisture content. Compaction of rock fills shall be performed in accordance with Section 6.3. 6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with the following recommendations: 6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, shOuld generally not exceed 8 inches. Each layer shall be spread evenly and shall be thoroughly mixed during spreading to obtain uniformity of material and moisture in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock materials greater thall' 12 inches in maximum dimension shall be placed in accordance with Section 6.2 or 6.3 of these specifications. 6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the optimum moisture content as determined by ASTM D 1557-02. 6.1.3 When the moisture content of soil fill is below that specified by the Consultant, water shall be added by the Contractor until the moisture content is in the range specified. 6.1.4 When the moisture content of the soil fill is above the range specified by the Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by the Contractor by blading/mixing, or other satisfactory methods until the moisture content is within the range specified. cn rev. 10/06 I I I I I I I I I I I I I I I I I I I 6.2 6.1.5 After each layer has been placed, mixed, and spread evenly, it shall J::je thoroughly compacted by the Contractor to a relative compaction of at least 90 percent. Relative compaction is defined as the ratio (expressed in percent) of the in-place dry density of the compacted fill to the maximum hiborat0fY dry density as . determined in accordance with ASTM D 1557-02. Compaction shall be continuous over the entire area, and compaction equipment shall make sufficient passes so that the specified minimum relative compaction has been achieved throughout the entire fill. 6.1.6 Where practical, soils having an Expansion Jndex greater than 50 should be placed at least 3 feet below finish pad grade and should be compacted at a moisture content generally 2 to 4 percent greater than the optimum moisture content for the material. 6.1.7 Properly compacted soil fill shall extend to the design surfa:ce of fill slopes. To achieve proper compaction, it is recommended that fill slopes be <?ver-built by at least 3 feet and then cut to the design grade. This procedure is considered preferable to track-walking of slopes, as described in the following paragraph. 6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height intervals. Upon completion, slopes should then be track-walked with a D-8 dozer or similar equipment, such that a dozer track covers all slope surfaces at least twice. Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance with the following recommendations: 6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be incorporated into the compacted soil fill, but shall be limited to the area measured 15 feet minimum horizontally from the slope face and 5 feet below finish grade or 3 feet below the deepest utility, whichever is deeper. 6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be individually placed or placed in windrows. Under certain conditions, rocks or rock fragments up to 10 feet in maximum dimension may be placed using similar methods. The acceptability of placing rock materials greater than 4 feet in maximum dimension shall be evaluated during grading as specific cases arise and shall be approved by the Consultant prior to placement. Olrev. 10/06 I I I I I I I I I I I I I I I I I I I 6.3 6.2.3 For individual placement, sufficient space shall be provided between rocks to allow for passage of compaction equipment. 6.2.4 For windrow placement, the rocks should be placed in trenches excavated in properly compacted soil fill. Trenches should be approximately 5 feet wide and 4 feet deep in maximum dimension. The voids around and beneath rocks should be filled with approved granular soil having a Sand Equivalent of 30 or greater and should be compacted by flooding. Windrows may also be placed utilizing an "open-face" method in lieu of the trench procedure, however, this method should first be approved by the Consult~nt. 6.2.5 Windrows' should generally be parallel to each other and may be placed either parallel to or perpendicular to the face of the slope depending on the site geometry, The minimum horizontal spacing for windrows shall be 12 feet center-to-center with a 5-foot stagger or offset from lower courses to next overlying course. The minimum vertical spacing between windrow courses shall be 2 feet from the top of a lower windrow to the bottom of the next higher windrow. 6.2.6 Rock placement, fill placement and flooding of approved granular soil in the windrows should be continuously observed by the Consultant. Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with the following recommendations: 6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2 percent). The surface shall slope toward suitable sUbdrainage outlet-facilities. The rock fills shall be provided with subdrains during construction so that a hydrostatic pressure buildup does not develop. The subdrains shall be permanently connected to controlled drainage' facilities to control post-construction infiltration of water. 6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement s'halI be by rock trucks traversing previously placed lifts and dumping at the edge of the currently placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the rock. The rock fill shall be watered heavily during placement. Watering shall consist of water trucks traversing in front of the current rock lift face and spraying water continuously during rock placement. Compaction equipment with compactive energy comparable to or greater than that of a 20-ton steel vibratory roller or other compaction equipment providing suitable energy to achieve the ,oi rev. 10/06 I I I I I I I I I I I I I I I I I I I required compaction or deflection as recommended in Paragraph 6.3.3 shan be utilized. The number of passes to be made should be determined as described in Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional /' rock fill lifts will be permitted over the soil fill. 6.3.3 Plate bearing tests, in accordance with ASTM D 1196-93, may be performed in both the compacted soil fill and in the rock fill to aid in determining the required minimum number of passes of the compaction equipment. If performed, a minimum of three plate bearing tests should be performed in the properly compacted soil fill (minimum relative compaction of 90 percent). Plate bearing tests shall then be performed on areas of rock fill having two passes, four passes and six passes of the compaction equipment, respectively. The number of passes required for the rock fill shall be determined by comparing the results of the plate bearing tests for the soil fill and the rock fill and by evaluating the deflection variation with number of passes. The required number of pass~s ,of the compaction equipment will be performed as necessary until the plate bearing deflections are equal to or less than that determined for the properly compacted soil· fill. In no case will the required number of passes be less than two. 6.3.4 6.3.5 A representative of the Consultant should be present during ,rock fill operations to observe that the minimum number of "passes" have been obtained, that water is being properly applied and that specified procedures are being followed. The actual number of plate bearing tests will be determined by the.Consultant during grading. Test pits shall be excavated by the Contractor so that the Consultant can state that, in their opinion, sufficient water is present and that voids between large rocks are properly filled with smaller rock material. ill-place density testing will not be required in the rock fills. 6.3.6 To reduce the potential for "piping" of fines into the rock fill from overlying soil fill material, a 2-foot layer of graded filter material shall be placed above th~. uppermost lift of rock fill. The need to place graded filter material below the rock should be determined by the Consultant prior to cOinmencing wading. The gradation of the graded filter material will be determined, at the time the rock fill is . . being excavated. Materials typical of the rock fill should be submitted to the Consultant in a timely manner, to allow design of the graded filter prior to the commencement of rpck fill placement. 6.3.7 Rock fill placement should be continuously observed during placement by the Consultant. GI rev. 10/06' I I I I I I I I I I I I I I I I I I I 7.1 7.2 7.3 7.4 7.5 7.6 7. OBSERVATION AND TESTING The Consultant shall be the Owner's representative to observe and )?erfonn tests during clearing, grubbing, filling, and compaction operations. In geperal, no more than 2 feet in vertical elevation of soil or soil-rock fill should be placed without at least one field density, test being perfonned within that intervaL In addition, a minimum of one field density test should be performed for every 2,000 cubic yards of soil or soil-rock fill 'placed and compacted. The Consultant should perfonn a sufficient distribution of field density tests of the compacted soil ~r soil-rock fill to provide a basis for'expressing an opinion whether the fill material is compacted as specified. Density tests shall be perfonned in the compacted materials below any disturbed surface. When these tests indicate that the density of any layer of fill or portion thereof is below that specified, the particular layer or areas represented by the test shall be reworked until the specified density has been achieved. During placement of rock fill, the Consultant should observe that the minimum number of passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant should request the excavation of observation pits and may perfonn plate bearing tests on the placed rock fills. The observation pits will be excavated to provide a basis for expressing an opinion as to whether the rock fill is properly seated and sufficient moisture has been applied to the material. When observations indicate that a layer of rock fill or any portion thereof is below that specified, the affected layer or area shall be reworked until the rock fill has been adequately seated and sufficient moisture applied. A settlement monitoring program designed by the Consultant may be conducted in areas of rock fill placement. The specific design of the monitoring program shall be as recommended in the Conclusions and Recommendations section of the project Geotechnical Report or in the final report of testing and observation services perfonned during grading. The Consultant should observe the placement of subdrains, to verify that the drainage devices have been placed and constructed in substantial confonnan<;e with project specifications. Testing procedures shall confonn to the following Standards as appropriate: Gl rev. 10/06 I I I I I I I I I I I I I I I I I I I 8.1 8.2 7.6.1 Soil and Soil-Rock Fills: 7.6.1.1 Field Density Test, ASTM D 1556-02, Density of Soil In-Place By the Sand-Cone Method. 7.6.1.2 Field Density Test, Nuclear Method, ASTM D 2922-01, Density of Soil and Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth). 7.6.1.3 Laboratory Compaction Test, ASTM D 1557-02, Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using lO-Pound Hammer and I8-Inch Drop. 7.6.1.4. Expansion Index Test, ASTM D 4829-03, Expansion Index Test. 7.6.2 Rock Fills 7.6.2.1 Field Plate Bearing Test, ASTM D 1196-93 (Reapproved 1997) Standard Methodfor Nonreparative Static Plate Load Tests of Soils and Flexible Pavement Components, For Use in Evaluation and Design of Airport and Highway Pavements. 8. PROTECTION OF WORK During construction, the Contractor shall properly grade all excavated surfaces to provide positive drainage and prevent ponding of water. Drainage of surface water shall be controlled to avoid damage to adjoining properties or to finished work on the site. The Contractor shall take remedial measures to prevent erosion of freshly graded areas until such time as permanent drainage and erosion control features have been installed: Areas subjected to erosion or sedimentation shall be properly prepared in accordance with the Specifications prior to placing additional fill or structures. After completion of grading as observed and tested. by the Consultant, ncr further excavation or filling shall be conducted except in conjunction with the services of the Consultant. GI rev. 10/06 I I I I I I I, I I I I I I' I I I I I I 9.1 9.2 9. CERTIFICATIONS AND FINAL REPORTS Upon completion of the work, Contractor shall furnish Owner a certification by the Civil Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot horizontally of the positions shown on the grading plans. Aft,er installation of a section of subdrain, the project Civil Engineer should survey its location and prepare an as-built plan of the subdrain location. The project Civil Engineer should verify the proper outlet for the subdrains and the Contractor should ensure that the drain system is free of obstructions. The Owner is responsible for furnishing a final as-graded soil and geologic report satisfactory to the appropriate governing or accepting agencies. The as-graded report should be prepared and signed by a California licensed Civil Engineer experienced in. geotechnical engineering and by a California Certified Engineering Geologist, indicating that the geotechnical aspects of the grading were performed in substantial conformance with the Specifications or approved changes to the Spec~fications. GI rev. 10/06