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Home My WebLink AboutCT 05-16; VILLAGES OF LA COSTA OAKS NORTH; UPDATE GEOTECHNICAL REPORT; 2010-01-05&r o 4 ç0 UPDATE GEOTECHNICAL REPORT VILLAGES OF LA COSTA - THE OAKS NORTH NEIGHBORHOODS 3.4 AND 3.5 LOTS I THROUGH 83 CARLSBAD, CALIFORNIA PREPARED FOR PULTE HOMES MISSION VIEJO, CALIFORNIA L co (1) cc JANUARY 5, 2010 PROJECT NO. 06105-52-27 GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS Project No. 06105-52-27 January 5, 2010 Pulte Homes 27101 Puerta Real, Suite 300 Mission Viejo, California 92619 Attention: Mr. David Hutchins Subject: VILLAGES OF LA COSTA - THE OAKS NORTH NEIGHBORHOODS 3.4 AND 3.5 LOTS 1 THROUGH 83 CARLSBAD, CALIFORNIA UPDATE GEOTECHNICAL REPORT Dear Mr. Hutchins: In accordance with your request and our proposal (LG-09313) dated December 4, 2009, 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 the geotechnical aspects of proposed development of the site. The site was graded as part of the Villages of La Costa - Oaks North development. The grading for Lots 1 through 83 was completed in September 2007. Compacted fill and formational materials of Santiago Peak Volcanics and Escondido Creek Granodiorite underlie the site. Provided the recommendations contained in this update report are followed, the site is considered suitable for construction and support of the proposed residential structures. Should you have questions regarding this report, or if we may be of further service, please contact the undersigned at your convenience. GEOCON INCORPORATED 4 Ali Sa CEG 1778 tAAL AU SADR No 1778 CERTIFIED * ENGINEERING GEOLOGIST . Shawn Weedon GE 2714 (OFESS &r' No. 2714 z\2 EXP.06/30/11 ,On (4/del) Addressee 6960 Flanders Drive 0 Son Diego, California 92121-2974 I Telephone (858) 558-6900 I FcLx (858) 558-6159 TABLE OF CONTENTS PURPOSE AND SCOPE......................................................................................................................1 SITE AND PROJECT DESCRIPTION................................................................................................1 PREVIOUS SITE DEVELOPMENT ...................................................................................................2 SOIL AND GEOLOGIC CONDITIONS .............................................................................................2 4.1 Compacted Fill (Qcf& Quc)......................................................................................................2 4.2 Santiago Peak Volcanics (Jsp)....................................................................................................3 4.3 Escondido Creek Granodiorite (Ke) ...........................................................................................3 GROUNDWATER ...............................................................................................................................3 GEOLOGIC HAZARDS ......................................................................................................................3 6.1 Faulting and Seismicity ..............................................................................................................3 6.2 Liquefaction................................................................................................................................6 CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 7 7.1 General........................................................................................................................................7 7.2 Finish Grade Soil Conditions......................................................................................................7 7.3 Seismic Design Criteria..............................................................................................................8 7.4 Future Grading............................................................................................................................9 7.5 Foundation and Concrete Slabs-On-Grade Recommendations ..................................................9 7.6 Retaining Walls and Lateral Loads...........................................................................................14 7.7 Slope Maintenance....................................................................................................................15 7.8 Site Drainage ............................................................................................................................16 7.9 Foundation Plan Review ............................................................................................................ 17 LIMITATIONS AND UNIFORMITY OF CONDITIONS FIGURES Vicinity Map Wall/Column Footing Dimension Detail Typical Retaining Wall Drain Detail TABLES Summary of As-Graded Building Pad Conditions and Recommended Foundation Categories Summary of Laboratory Expansion Index Test Results Summary of Finish Grade Expansion Index Test Results Summary of Laboratory Water-Soluble Sulfate Test Results Summary of Soil 2007 CBC Site Class UPDATE GEOTECHNICAL REPORT 1. PURPOSE AND SCOPE This report presents the results of the update geotechnical study for Lots 1 through 83 located at the Villages of La Costa - The Oaks North, Neighborhoods 3.4 and 3.5. The purpose of this update report is to provide information regarding the geologic conditions underlying the site and to provide foundation and retaining wall design recommendations. The scope of the study included a review of: Update Geotechnical Investigation, Villages of La Costa—The Oaks, Carlsbad, California, prepared by Geocon Incorporated, dated August 3, 2001 (Project No. 06105-12-04). Final Report of Testing and Observation Services Performed During Site Grading, Villages of La Costa - The Oaks North, Neighborhood 3.4, Lots 40 through 83, prepared by Geocon Incorporated, September 10, 2007 (Project No. 06403-52-20). Final Report of Testing and Observation Services Performed During Site Grading, Villages of La Costa - The Oaks North, Neighborhood 3.5, Lots 1 through 39, prepared by Geocon Incorporated, October 30, 2007 (Project No. 06403-52-20). Rough Grading and Erosion Control Plans for La Costa Oaks North Neighborhood 3.4 & I 3.5, Drawing No. 446-6A, City of Carlsbad approval date July 12, 2007 I 2. SITE AND PROJECT DESCRIPTION - The subject lots are within the Villages of La Costa - The Oaks North, Neighborhoods 3.4 and 3.5 development located no rth and south of the intersection of Rancho Santa Fe Road and Avenida Soledad in the City of Carlsbad, California (see Vicinity Map, Figure 1). Proposed development includes the construction of 83 single-family residential homes and associated improvements. Compacted fill is exposed at grade and is underlain by volcanic rock consisting of Santiago Peak I Volcanics and granitic rock consisting of Escondido Creek Granodiorite. A summary of the as-graded pad conditions for each lot is provided on Table I. In general, the on-site fill materials vary between I angular gravels and boulders produced by on-site blasting of hard rock to silty, fine to coarse sand and sandy clay derived from the surficial soil and weathered formational materials. I The locations and descriptions of the site and proposed improvements are based on a site reconnaissance, observations during site grading, a review of the referenced reports and grading I plans, and our understanding of project development. If project details vary significantly from those described herein, Geocon Incorporated should be contacted to review and revise this report. I Project No. 06105-52-27 -1- January 5, 2010 3. PREVIOUS SITE DEVELOPMENT The subject lots were graded to the current configuration during mass grading operations for the Villages of La Costa - The Oaks North. We performed observation and testing services during the grading operations. A summary of the observations, compaction test results, and professional opinions pertaining to the grading operations is presented in the referenced reports dated September 10, 2007 and October 30, 2007. The majority of the grading operations consisted of removal and recompaction of surficial soil, placing compacted fill, and performing cuts within formational material to the design elevations. Due to the difficult excavation characteristics of the volcanic and granitic rock, cut lots were undercut approximately three to four feet and replaced with compacted fill to the design elevations. In addition, lots that possessed a cut-fill transition were undercut approximately three to four feet and replaced with compacted fill. A summary of the as-graded pad conditions for the lots are presented in Table I. 4. SOIL AND GEOLOGIC CONDITIONS The site is underlain by compacted fill and geologic formations of the Jurassic-aged Santiago Peak Volcanics and Cretaceous-aged Escondido Creek Granodiorite. The predominant materials within three to four feet of grade consist of silty sand and gravel and possess a "very low" to "low" expansion potential (expansion index of 50 or less). The soil type and geologic units are discussed herein. 4.1 Compacted Fill (Qcf & Quc) In general, structural fill placed and compacted at the site consisted of material that can be classified into three zones: Zone A Material placed within 3 feet from pad grade, 6 feet from parkway grade, and within roadways to at least 1 foot below the deepest utility consisted of "soil" fill with an approximate maximum particle dimension of 6 inches. Zone B Material placed within 10 feet from pad grade and below Zone A, outer 6 feet of fill slopes and 2 feet below Zone A for fills in roadways and parkways, consisted of "soil rock" fill with a maximum particle dimension of 12 inches. Zone C Material placed below Zone B consisted of "soil rock" fill with a maximum particle dimension of 48 inches. Larger rocks with a maximum dimension of approximately 8 feet were buried individually during "rock" fill grading operations. The maximum fill thickness is approximately 54 feet. The compacted fill is considered suitable to provide support for the proposed development. I Project No. 06105-52-27 -2- January 5,201 4.2 Santiago Peak Volcanics (Jsp) The Jurassic-aged Santiago Peak Volcanics comprises a portion of the underlying bedrock. These I rocks were deposited as an alternating succession of volcanic flows, tuffs, and breccias and typically have an andesite or dacite composition. Subsequently, this sequence of rocks was folded, faulted, and I weakly metamorphosed. As encountered during grading, this unit is highly fractured. Closely spaced parallel fractures and joints form "sheeted" zones containing colorful alterations and/or oxidation minerals such as limonite and hematite. Even though the majority of the Santiago Peak Volcanics I appears to be highly fractured and altered, the "sheeted" zones typically have steeply dipping, clay- filled fractures. 4.3 Escondido Creek Granodiorite (Ke) The Cretaceous-aged Escondido Creek Granodiorite intruded the surrounding Jurassic-aged Santiago Peak Volcanics and comprises a portion of the underlying bedrock. In published literature, this unit is described as a "leucogranodiorite" because of the overall light color, but averages of composition are typically granodiorite. During grading operations, the exposed bedrock consisted of light brown to olive, very siliceous, blocky and very strong granitic rock, with little or no weathering. The granitic rock is considered suitable for the support of the planned development. 5. GROUNDWATER We did not encounter groundwater during grading operations. Groundwater is not expected to adversely impact the development of the property. Due to the fractured nature of the formational materials, we encountered some areas of seepage. Subdrains were installed during remedial grading. 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 drainage will be important to future performance of the project. 6. GEOLOGIC HAZARDS 6.1 Faulting and Seismicity A review of the referenced geologic materials and our knowledge of the general area indicate that the site is not underlain by active, potentially active, or inactive faults. The site is not located within a State of California Earthquake Fault Zone established for known active faults. An active fault is defined by the California Geological Survey (CGS) as a fault showing evidence for activity within the last 11,000 years. According to the computer program EZ-FRISK (Version 7.35), nine known active faults are located within a search radius of 50 miles from the property. The nearest known active fault is the Rose Project No. 06105-52-27 - 3 - January 5, 2010 I Canyon Fault, located approximately 8 miles west of the site and is the dominant source of potential ground motion. Earthquakes that might occur on the Rose Canyon Fault Zone or other faults within I the southern California and northern Baja California area are potential generators of significant ground motion at the site. The estimated maximum earthquake magnitude and peak ground acceleration from a deterministic analysis for the Rose Canyon Fault are 7.2 and 0.29g, respectively. I Table 6.1 .1 lists the estimated maximum earthquake magnitude and peak ground acceleration for the faults within 50 miles of the site location. We calculated peak ground acceleration (PGA) using I Boore-Atkinson (2008) NGA USGS2008, Campbell-Bozorgnia (2008) NGA USGS 2008, and Chiou- Youngs (2008) NGA acceleration-attenuation relationships. TABLE 6.1.1 DETERMINISTIC SITE PARAMETERS Fault Name Distance from Site (miles) Maximum Earthquake Magnitude (Mw) Peak Ground Acceleration Boore- Atkinson 2008 (g) Campbell- Bozorgnia 2008 (g) Chiou- Youngs 2008 (g) Rose Canyon 8 7.2 0.29 0.17 0.22 Newport-Inglewood 12 7.1 0.26 0.15 0.18 Elsinore (Julian) 23 7.1 0.26 0.11 0.13 Elsinore (Temecula) 23 6.8 0.22 0.10 0.12 Coronado Bank 23 7.6 0.24 0.12 0.16 Earthquake Valley 38 6.5 0.14 0.07 0.06 Elsinore (Glen Ivey) 38 6.8 0.17 0.07 0.08 aquin Hills Thrust EtpalosVerdes 43 7.4 0.14 0.08 0.07 43 7.3 0.18 0.08 0.09 We also used the computer program EZ-FRISK to perform a probabilistic seismic hazard analysis. The computer program EZ-FRISK operates under the assumption that the occurrence rate of earthquakes on each mappable Quaternary fault is proportional to the faults slip rate. The program accounts for fault rupture length as a function of earthquake magnitude, and site acceleration estimates are made using the earthquake magnitude and distance from the site to the rupture zone. The program also accounts for uncertainty in: (1) earthquake magnitude, (2) rupture length for a given magnitude, (3) location of the rupture zone, (4) maximum possible magnitude of a given earthquake, and (5) acceleration at the site from a given earthquake along each fault. By calculating the expected accelerations from considered earthquake sources, the program calculates the total average annual expected number of occurrences of site acceleration greater than a specified value. We utilized acceleration-attenuation relationships suggested by Boore-Atkinson (2008) NGA USGS2008, Campbell-Bozorgnia (2008) NGA USGS 2008, and Chiou-Youngs (2008) in the Project No. 06105-52-27 -4- January 5, 20 10 analysis. Table 6.1.2 presents the site-specific probabilistic seismic hazard parameters including acceleration for each attenuation relationships and the probability of exceedence. TABLE 6.1.2 PROBABILISTIC SEISMIC HAZARD PARAMETERS Probability of Exceedence Peak Ground Acceleration Boore-Atkinson, 2007 (g) Campbell-Bozorgnia, 2008 (g) Chiou-Youngs, 2008 (g) 2% in a 50 Year Period 0.75 0.33 0.39 5% in a 50 Year Period 0.61 0.27 1 0.32 10% in a 50 Year Period 0.51 0.23 1 0.27 The California Geologic Survey (CGS) has a program that calculates the ground motion for a 10 percent of probability of exceedence in 50 years based on an average of several attenuation relationships. Table 6.1.3 presents the calculated results from the Probabilistic Seismic Hazards Mapping Ground Motion Page from the CGS website. TABLE 6.1.3 PROBABILISTIC SITE PARAMETERS FOR SELECTED FAULTS CALIFORNIA GEOLOGIC SURVEY Calculated Acceleration (g) Firm Rock Calculated Acceleration (g) Soft Rock Calculated Acceleration (g) Alluvium 0.25 0.27 0.31 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 duration of motion and the soil conditions underlying the site. Seismic design of the structures should be evaluated in accordance with the California Building Code (CBC) guidelines currently adopted by the County of San Diego. In the event of a major earthquake along the referenced faults or other faults in the Southern California region, the site could be subjected to moderate to severe ground shaking. With respect to I seismic shaking, 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 the region, other considerations are important in seismic design including the frequency and duration of motion and I the soil conditions underlying the site. Seismic design of structures should be performed in accordance with the 2007 California Building Code (CBC) currently adopted by the City of Carlsbad. 1 Project No. 06105-52-27 -5- January 5, 20 10 I 6.2 Liquefaction Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are cohesionless or silt/clay with low plasticity, 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 nature of the compacted fill and the formational materials and absence of a permanent groundwater table, the potential for liquefaction occurring at the site is considered to be very low. Project No. 06105-52-27 -6- January 5,201 7. CONCLUSIONS AND RECOMMENDATIONS 7.1 General 7.1.1 No soil or geologic conditions were encountered during previous geotechnical investigations or grading operations, which in our opinion would preclude the continued development of the property as presently planned, provided that the recommendations of this report are followed. 7.1.2 The site is underlain by compacted fill and formational materials of the Santiago Peak Volcanics and Escondido Creek Granodiorite. We observed the placement of compacted fill during mass grading operations and performed in-place density tests to evaluate the dry density and moisture content of the fill material. In general, the in-place density test results indicate that the fill soil has a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content at the locations tested. 7.1.3 The site is considered suitable for the use of conventional foundations and slab-on-grade and/or a post-tensioned foundation system. We understand that a post-tensioned foundation system is being considered and recommendations are included herein. 7.1.4 Excavations within the fill materials should generally be possible with moderate to heavy effort using conventional heavy-duty equipment. Excavations below the fill and into the Santiago Peak Volcanic or Escondido Creek Granodiorite may require localized blasting and may generate oversize rocks. 7.2 Finish Grade Soil Conditions 7.2.1 Observations and laboratory test results obtained during mass grading operations indicate that the prevailing soil conditions within the upper approximately three to four feet of finish grade pads have is considered to be "non-expansive" and "expansive" (expansion index [El] of 20 or less and greater than 20) as defined by 2007 California Building Code (CBC) Section 1802.3.2. Table 7.2 presents soil classifications based on the expansion index. The prevailing soil conditions possess a "very low" to "low" expansion potential (expansion index of 50 or less). Tables II and III present the laboratory expansion index testing for the project. 7 Project No. 06105-52-27 - 7 - January 5, 20 10 TABLE 7.2 SOIL CLASSIFICATION BASED ON EXPANSION INDEX Expansion Index (El) Soil Classification 0-20 Very Low 21-50 Low 51-90 Medium 91-130 High Greater Than 130 Very High 7.2.2 We performed laboratory tests on samples of the site materials to evaluate the percentage of water-soluble sulfate content. Results from the laboratory water-soluble sulfate content tests are presented in Table IV and indicate that the on-site materials at the locations tested possess "negligible" sulfate exposure to concrete structures as defined 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. Table IV presents the laboratory water-soluble sulfate testing. 7.2.3 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. I 7.3 Seismic Design Criteria 7.3.1 We used the computer program Seismic Hazard Curves and Uniform Hazard Response I 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 I Structural Design, Section 1613 Earthquake Loads. The short spectral response has a period of 0.2 second. I I I Project No. 06105-52-27 - 8 - January 5, 2010 I TABLE 7.3 2007 CBC SEISMIC DESIGN PARAMETERS E I Parameter Value IBC-06 Reference Site Class C D Table 1613.5.2 Fill Thickness, 1 (Feet) 1<20 1>20 -- Spectral Response - Class B (short), Ss 1.082g 1.082g Figure 1613.5(3) Spectral Response - Class B (1 sec), S1 0.408g 0.408g Figure 16 13.5(4) Site Coefficient, Fa 1.000 1.067 Table 1613.5.3(1) Site Coefficient, F 1.392 1.592 Table 1613.5.3(2) Maximum Considered Earthquake Spectral Response Acceleration (short), SMS 1.082g 1.155g Section 1613.5.3 (Eqn 16-37) Maximum Considered Earthquake Spectral Response Acceleration —(1 sec), SMI 0.568g 0.649g Section 16 13.5.3 (Eqn 16-38) 5% Damped Design Spectral Response Acceleration (short), SDS 0.722g 0.770g Section 16 13.5.4 (Eqn 16-39) 5% Damped Design Spectral Response Acceleration (1 sec), SD, 0.379g 0.433g Section 1613.5.4 (Eqn 16-40) Based on a review of the as-graded conditions presented in the referenced as-graded report, the lots are assigned the seismic design parameters as indicated in Table V. I I I I I I 7.3.2 I 7.3.3 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. 7.4 Future Grading 7.4.1 Additional grading performed at the site should be accomplished in conjunction with our observation and compaction testing services. Grading plans for future grading should be reviewed by Geocon Incorporated prior to finalizing. Trench and wall backfill should be compacted to a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content. This office should be notified at least 48 hours prior to commencing additional grading or backfill operations. 7.5 Foundation and Concrete Slabs-On-Grade Recommendations 7.5.1 The foundation recommendations herein are for proposed one- to two-story residential structures. The foundation recommendations have been separated into three categories Project No. 06105-52-27 -9 - January 5, 2010 based on either the maximum and differential fill thickness or Expansion Index. The foundation category criteria are presented in Table 7.5.1. TABLE 7.5.1 FOUNDATION CATEGORY CRITERIA Foundation Category Maximum Fill Thickness, T (Feet) Differential Fill Thickness, D (Feet) Expansion Index (El) I 1<20 -- EI<50 II 20<1<50 10<D<20 50<EI<90 III 1>50 D>20 90<EI<130 7.5.2 Table 7.5.2 presents minimum foundation and interior concrete slab design criteria for conventional foundation systems. A typical wall/column dimension detail is presented in Figure 2. TABLE 7.5.2 CONVENTIONAL FOUNDATION RECOMMENDATIONS BY CATEGORY Foundation Minimum Footing Continuous Footing Interior Slab Category Embedment Depth (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 to top and two bottom on center, both directions III 24 Four No. 5 bars No. 3 bars at 18 inches two top and two bottom I on center, both directions 7.5.3 The embedment depths presented in Table 7.5.2 should be measured from the lowest adjacent pad grade for both interior and exterior footings. The conventional foundations should have a minimum width of 12 inches and 24 inches for continuous and isolated footings, respectively. 7.5.4 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 HI. 7.5.5 Concrete slabs on grade should be underlain by 4 inches of clean sand (3 inches for a 5- inch-thick slab) to reduce the potential for differential curing, slab curl, and cracking. Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture- sensitive materials should be underlain by a vapor retarder placed near the middle of the sand Project No. 06105-52-27 _10- January 5, 2010 I bedding. The vapor retarder used should be specified by the project architect or developer based on the type of floor covering that will be installed. The vapor retarder design should be I consistent with the guidelines presented in Section 9.3 of the American Concrete Institute's (AC!) Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials I (AC1302.2R-06). 7.5.6 As an alternative to the conventional foundation recommendations, consideration should be I 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 I 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 7.5.3 for the particular Foundation Category I designated. The parameters presented in Table 7.5.3 are based on the guidelines presented in the PTI, Third Edition design manual. Conventional foundations located outside of the I post-tensioned slab area should be embedded in accordance with the conventional shallow foundation recommendations. TABLE 7.5.3 POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS Post-Tensioning Institute (PT!) Third Edition Design Parameters Foundation Category II in 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 I 7.5.7 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. I Project No. 06105-52-27 - 11 - -- January 5, 20 10 I 7.5.8 If the structural engineer proposes a post-tensioned foundation design method other than PTI, Third Edition: The deflection criteria presented in Table 7.5.3 are still applicable. Interior stiffener beams should be used for Foundation Categories II and Ill. 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. 7.5.9 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. Current 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. 7.5.10 During the construction of the post-tension foundation system, the concrete should be I 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 i system. 7.5.11 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 I maximum total and differential settlement for the planned structures due to foundation loads is 1 inch and Y2 inch, respectively. I 7.5.12 Isolated footings, if present, should have the minimum embedment depth and width recommended for conventional foundations for a particular foundation category. The use of I 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 I building foundation system with grade beams. I 7.5.13 For Foundation Category III, consideration should be given to using interior stiffening beams and connecting isolated footings and/or increasing the slab thickness. In addition, I LII Project No. 06105-52-27 -12- January 5, 2010 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. 7.5.14 Special subgrade presaturation is not deemed necessary prior to placing concrete; however, the exposed foundation and slab subgrade soil should be moisture conditioned, as necessary, to maintain a moist condition as would be expected in any such concrete placement. 7.5.15 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 Incorporated 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 to 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 Incorporated 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 that would permit some lateral soil movement without causing extensive distress. Geocon Incorporated should be consulted for specific recommendations. I Project No. 06105-52-27 - 13 - January 5, 2010 I 7.5.16 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 I varying thicknesses. However, seven with the incorporation of the 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 I 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 I concrete placement and curing, and by the placement of crack control joints at periodic intervals, in particular, where re-entrant slab corners occur. I 7.5.17 Geocon Incorporated should be consulted to provide additional design parameters as required by the structural engineer. 7.6 Retaining Walls and Lateral Loads I 7.6.1 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 (pcf). Where the backfill will be inclined at no steeper than 2:1 I (horizontal: vertical), an active soil pressure of 50 pcf is recommended. These soil pressures assume that the backfill materials within an area bounded by the wall and a 1:1 plane I extending upward from the base of the wall possess an expansion index of 50 or less. For those lots with finish-grade soils having an expansion index greater than 50 and/or where I backfill materials do not conform to the criteria herein, Geocon Incorporated should be consulted for additional recommendations. 1 7.6.2 Unrestrained walls are those that are allowed to rotate more than 0.00111 (where H equals the height of the retaining portion of the wall) 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 active soil pressure. For retaining walls subject to vehicular loads within a horizontal distance equal to two-thirds the wall height, a surcharge equivalent to 2 feet of I fill soil should be added. I 7.6.3 Retaining walls should be provided with a drainage system adequate to prevent the buildup of hydrostatic forces and waterproofed as required by the project architect. The use of drainage openings through the base of the wall (weep holes) is not recommended where the I seepage could be a nuisance or otherwise adversely affect the property adjacent to the base of the wall. The above recommendations assume a properly compacted free-draining I backfill material (El of 50 or less) with no hydrostatic forces or imposed surcharge load. Figure 3 presents a typical retaining wall drainage detail. If conditions different than those I Project No. 06105-52-27 -14 - January 5, 2010 I described are expected, or if specific drainage details are desired, Geocon Incorporated should be contacted for additional recommendations. 7.6.4 In general, wall foundations founded in properly compacted fill or formational materials should possess a minimum depth and width of one foot and 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 conditiQn is expected. 7.6.5 For resistance to lateral loads, an allowable passive earth pressure equivalent to a fluid density of 300 pcf is recommended for footings or shear keys poured neat against properly compacted fill 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. A friction coefficient of 0.35 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. 1 7.6.6 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 I should be designed with seismic lateral pressure. The seismic load exerted on the wall should be a triangular distribution with a pressure of 22H (where H is the height of the I wall, in feet, resulting in pounds per square foot [psfj) exerted at the base of the wall and zero at the top of the wall. 1 7.6.7 Unrestrained walls will move laterally when backfilled and loading is applied. The amount of lateral deflection is dependant on the wall height, the type of soil used for backfill, and I loads acting on the wall. The retaining walls and improvements above the retaining walls should be designed to incorporate an appropriate amount of lateral deflection as determined I by the structural engineer. 7.7 Slope Maintenance 1 7.7.1 Slopes that are steeper than 3:1 (horizontal: vertical) may, under conditions which are both difficult to prevent and predict, be susceptible to near surface (surficial) slope instability. I The instability is typically limited to the outer three feet of a portion of the slope and usually does not directly impact the improvements on the pad areas above or below the slope. The occurrence of surficial instability is more prevalent on fill slopes and is Project No. 06105-52-27 - 15 - - January 5, 2010 I generally preceded by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage. The disturbance and/or loosening of the surficial soils, as might result I 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, recom- mended that, to the maximum extent practical: (a) disturbed/loosened surficial soils be I either removed or properly recompacted, (b) irrigation systems be periodically inspected and maintained to eliminate 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 I may be necessary to rebuild or repair a portion of the project's slopes in the future. 7.8 Site Drainage 7.8.1 Adequate 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 or behind retaining walls. The site should be graded and maintained such that surface drainage is directed away from structures and 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. 1 7.8.2 Underground utilities should be leak free. Utility and irrigation lines should be checked periodically for leaks for early detection of water infiltration and detected leaks should be repaired promptly. Detrimental soil movement could occur if water is allowed to infiltrate the soil for a prolonged period of time. 7.8.3 Landscaping planters adjacent to paved areas are not recommended due to the potential for surface or irrigation water to infiltrate the pavement's subgrade and base course. We recommend that drains to collect excess irrigation water and transmit it to drainage structures, or impervious above-grade planter boxes be used. In addition, where landscaping is planned adjacent to the pavement, we recommended construction of a cutoff wall along the edge of the pavement that extends at least 6 inches below the bottom of the base material. 7.8.4 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 surface drainage is I 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 I Project No. 06105-52-27 -16- January 5, 2010 swales or other controlled drainage devices. Roof and pavement drainage should be directed into conduits that carry runoff away from the proposed structure. 7.8.5 If detention basins, bioswales, retention basins, or water infiltration devices are being considered, Geocon Incorporated should be retained to provide recommendations pertaining to the geotechnical aspects of possible impacts and design. 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. 7.9 Foundation Plan Review 7.9.1 Geocon Incorporated should review the foundation plans for the project prior to final design submittal to evaluate if additional analyses and/or recommendations are required. Project No. 06105-52-27 - 17- January 5, 2010 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 the proposed construction will differ from that anticipated herein, Geocon Incorporated should be notified so that supplemental recommendations can be given. The evaluation or identification of the potential presence of hazardous or corrosive materials was not part of the scope of services provided by Geocon Incorporated. This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project and incorporated into the plans, and the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. 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. In 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. I 4. The firm that performed the geotechnical investigation for the project should be retained to provide testing and observation services during construction to provide continuity of geotechnical interpretation and to check that the recommendations presented for geotechnical I aspects of site development are incorporated during site grading, construction of improvements, and excavation of foundations. If another geotechnical firm is selected to I . perform the testing and observation services during construction operations, that firm should - . prepare a letter indicating their intent to assume the responsibilities of project geotechnical engineer of record. A copy of the letter should be provided to the regulatory agency for their I records. In addition, that firm should provide revised recommendations concerning the geotechnical aspects of the proposed development, or a written acknowledgement of their I concurrence with the recommendations presented in our report. They should also perform additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record. Li I I, Project No. 06105-52-27 January 5, 2010 - \ - r~k A DR:I-.. - - 111 RD _ 7 -- - t) F 11 ! / tLk IN I F I \---r- - 1.1 - c-.— r . r 4 THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY G000LE EARTH, 1 .1 SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; if IS NOT INTENDED FOR CLIENTS USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT NO SCALE SHALL INDEMNIFY, DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT OF SUCH USE OR RELIANCE BY CLIENT. GEOCON (low) INCORPORATED GEOTEa-INICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858 558-6900 — FAX 858 558-6159 AS! RA IJSK/GIYPD VICINITY MAP VILLAGES OF LA COSTA - THE OAKS NORTH NEIGHBORHOOD 3.4 AND 3.5 LOTS 1-83 CARLSBAD, CALIFORNIA DATE 01-05-2010 PROJECTNO. 06105-52-27 FIG. 1 yMcp YIEI4TENPILGEOTECHII_GEOTECH_RUBENIGEOCON 2010106105-52-21 VILLAGES OF LA COSTA-THE OAKS NORTH (NEIGH.3A-3. Wi6y4wg WALL FOOTING CONCRETE SLAB SAND - - PAD GRADE I VISQUEEN 0 8 o m U- U- L WIDTH COLUMN FOOTING SAND VISQUEEN : FOOTING WIDTH* NO SCALE *SEE REPORT FOR FOUNDATION WITDH AND DEPTH RECOMMENDATION I WALL/ COLUMN FOOTING DIMENSION DETAIL I GEOCON INCORPORATED Q) GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974 PHONE 858 558-6900 - FAX 858 558-6159 AS /RA j------------------------------DSKIE0000 VILLAGES OF LA COSTA - THE OAKS NORTH NEIGHBORHOOD 3.4 AND 3.5 LOTS 1 - 83 CARLSBAD, CALIFORNIA I DATE 01-05-2010 I PROJECT NO. 06b0552-27 1 FiG.2 Y.R14TEMFI_GEOTECILGEOTECH_RUBEMGEOCON 201(5061054247 VILLAGES OF LA COSTA-THE OAKS NORTH (NEGH4-3. COLFOOT24, GROUND SURFACE CONCRETE BROWDITCH PROPOSED RETAINING WALL - - ..•• . •• 2/3M -.:,••• GROUND SURFACE FOOTING TEMPORARY BACKCUT PER OSHA MIRAFI 140N FILTER FABRIC (OR EQUIVALENT) - OPEN GRADED 3/4 MAX. AGGREGATE 4 DIP.. PERFORATED SCHEDULE 40 PVC PIPE EXTENDED TO APPROVED OUTLET 12 CONCRETE BROWDITCH RETAINING - WALL . 2/3 H WATER PROOFING PER ARCHITECT DRAINAGE PANEL (MIRADRAIN 6000 OR EQUIVALENT) -111 3/4 CRUSHED ROCK IF7-77 1V/1 CU.FTJFT.) PROPOSED ____ffi f . FILTER FABRIC ENVELOPE GRADE\ 1 '}-MIRAF1 140N OR EQUIVALENT 4 DIP.. SCHEDULE 40 PERFORATED I PVC PIPE OR TOTAL DRAIN EXTENDED FOOTING TO APPROVED OUTLET NOTE: DRAIN SHOULD BE UNIFORMLY SLOPED TO GRAVITY OUTLET OR TOP. SUMP WHERE WATER CAN BE REMOVED BY PUMPING NO SCALE I TYPICAL RETAINING WALL DRAIN DETAIL I GE 0 CON VILLAGES OF LA COSTA - THE OAKS NORTH INCORPORATED NEIGHBORHOOD 3.4 AND 3.5 LOTS 1 -83 GEOTEO-INICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974 CARLSBAD, CALIFORNIA PHONE 858 558-6900 - FAX 858 558-6159 ASS FA DSK/GTYPD DATE 01 - 05 - 2010 PROJECT NO. 06105 -52- 27 FIG. 3 YTH14TSMI1OEOTEE0TE1_RJEMOEOCON 2U1CJW105-52-Z7 VILLAGES OF LA COSTA-THE OAKS NORTH (HEH4-3 RW.dWg TABLE I SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND RECOMMENDED FOUNDATION CATEGORIES FOR VILLAGES OF LA COSTA - THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5 LOTS I THROUGH 83 Approximate Approximate Maximum Maximum Expansion • Recommended Lot No. Pad Condition Depth of Fill Depth of Fill Index Foundation (feet) Differential Category (feet) Undercut due to cut-fill transition 5 1 I_ 0 2 Undercut due to 8 3 0 I cut-fill transition 3 Fill 22 15 0 II 4 Undercut due to 29 26 0 III cut-fill transition 5 Undercut due to 29 26 0 III cut-fill transition 6 Undercut due to 27 24 0 III cut-fill transition 7 Fill 24 18 0 II 8 Fill 25 17 0 11 9 Fill 35 24 0 111 10 Undercut due to 20 15 0 II cut-fill transition 11 Undercut due to 15 II 0 II cut-fill transition 12 Undercut due to 5 2 0 1 cut-fill transition 13 Undercut due to hard rock 5 1 0 I 14 Undercut due to hard rock 4 1 0 1 15 Undercut due to hard rock 3 0 0 I 16 Undercut due to 6 2 0 I cut-fill transition 17 Fill 9 4 2 I 18 Fill 11 2 2 I 19 Fill 13 3 2 I 20 Fill 13 4 2 I 21 Fill 12 5 2 1 22 Fill 12 4 2 1 23 Fill 16 10 2 it 24 Fill 19 11 2 II 25 Fill 18 11 0 11 26 Fill 24 15 0 II 27 Fill 26 16 1 0 II Project No. 06105-52-27 - January 5, 20 10 TABLE I (Continued) SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND RECOMMENDED FOUNDATION CATEGORIES FOR VILLAGES OF LA COSTA - THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5 LOTS I THROUGH 83 Approximate Approximate Maximum Maximum Expansion Recommended Lot No. Pad Condition Depth of Fill Depth of Fill Index Foundation (feet) Differential Category (feet) 28 Fill 26 14 0 II 29 Fill 26 14 0 11 30 Fill 26 15 0 II 31 Fill 28 16 0 II 32 Fill 30 15 0 II 33 Fill 32 17 0 11 34 Fill 33 4 0 II 35 Fill 41 14 0 11 36 Undercut due to hard rock 4 1 18 1 37 Undercut .due to hard rock 4 1 18 1 38 Undercut due to hard rock 4 1 0 1 39 Undercut due to hard rock 4 1 0 1 40 Undercut due to hard rock 4 1 0 I 41 Undercut due to 9 5 0 1 cut-fill transition 42 Undercut due to 10 6 0 1 cut-fill transition 43 Undercut due to 7 3 0 I cut-fill transition 44 Undercut due to 14 10 0 11 cut-fill transition 45 Undercut due to 18 10 0 II cut-fill transition 46 Fill 20 9 0 II 47 Fill 20 9 0 II 48 Fill 30 15 0 II 49 Fill 23 6 0 II 50 Fill 20 9 0 II 51 Undercut due to 14 10 0 II cut-fill transition 52 Undercut due to hard rock 6 3 0 53 Undercut due to hard rock 6 1 0 54 Undercut due to hard rock 4 1 0 I 55 Undercut due to hard rock 8 6 0 1 56 Fill 21 13 0 II I Project No. 06105-52-25 January 5, 2010 TABLE I (Continued) SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND RECOMMENDED FOUNDATION CATEGORIES FOR VILLAGES OF LA COSTA - THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5 LOTS I THROUGH 83 Lot No. Pad Condition Approximate Maximum Depth of Fill (feet) Approximate Maximum Depth of Fill Differential (feet) Expansion Index Recommended Foundation Category 57 Undercut due to 18 cut-fill transition 15 0 II 58 Undercut due to 15 cut-fill transition 11 0 II 59 Fill 17 10 0 II 60 Fill 24 10 0 II 61 Fill 35 14 0 II 62 Fill 40 9 0 II 63 Fill 40 6 0 II 64 Fill 38 10 0 11 65 Fill 35 7 0 II 66 Fill 38 18 0 11 67 Fill 43 15 0 II 68 Fill 50 20 0 III 69 Fill 50 18 0 III 70 Fill 54 21 0 III 71 Fill 46 23 0 III 72 Fill 44 11 22 11 73 Fill 42 6 22 II 74 Fill 39 5 22 II 75 Fill 23 15 0 II 76 Fill 24 11 0 II 77 Fill 27 17 0 II 78 Fill 29 20 0 III 79 Fill 28 14 1 11 80 Fill 25 11 1 II 81 Fill 21 9 1 II 82 Fill 13 4 1 1 83 Fill 14 1 11 1 II I Project No. 06105-52-25 -- January 5, 2010 I TABLE II SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS ASTM D 4829-03 Sample No. Moisture Content (%) Dry Density (pcf) Expansion index Expansion Classification Before Test After Test El-A 7.4 13.4 118.7 0 Very Low El-B 7.6 14.6 118.9 0 Very Low El-AL 7.7 13.1 118.4 0 Very Low El-AM 7.6 13.1 118.4 0 Very Low El-AN 7.7 13.3 118.4 0 Very Low El-AO 7.4 13.0 118.8 0 Very Low El-AP 7.5 13.8 118.8 0 Very Low El-AR 8.3 12.0 117.9 0 Very Low El-AS 8.5 14.1 117.7 0 Very Low El-BC 7.7 12.9 118.5 1 Very Low El-BN 10.4 18.7 109.3 18 Very Low El-BY 10.1 19.3 109.6 22 Low El-BZ 9.1 15.7 113.1 0 Very Low El-CD 7.0 13.1 120.5 0 Very Low El-CE 7.0 12.6 120.6 0 Very Low El-CF 7.7 13.3 118.5 0 Very Low EI-CG 7.6 13.7 118.3 0 1 Very Low El-CH 7.8 14.4 118.5 2 Very Low El-Cl 7.5 14.2 118.6 2 Very Low Project No. 06105-52-27 January 5, 2010 TABLE III SUMMARY OF FINISH GRADE EXPANSION INDEX TEST RESULTS VILLAGES OF LA COSTA—THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5 LOTS I THROUGH 83 Lot No Sample at Finish Grade Expansion Index Expansion Classification 1 through 3 El-CE 0 Very Low 4 through 8 El-CD 0 Very Low 9 through 12 El-CF 0 Very Low 13 through 16 El-CG 0 Very Low 17 through 20 El-CH 2 Very Low 21 through 24 El-Cl 2 Very Low 25 through 29 El-AR 0 Very Low 30 through 35 El-AS 0 Very Low 36 and 37 El-BN 18 Very Low 38 and 39 El-CE 0 Very Low 40 through 45 El-AP 0 Very Low 46 through 50 El-AO 0 Very Lo w 51 through 55 El-AM 0 Very Low 56 through 60 El-AL 0 Very Low 61 through 65 El-AN 0 Very Low 66 through 68 El-B 0 Very Low 69 through 71 El-A 0 Very Low 72 through 74 El-BY 22 Low 75 through 78 El-BZ 0 Very Low 79 through 83 El BC 1 Very Low I Project No. 06105-52-27 January 5, 20 10 I I TABLE IV SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST 417 Sample No. Water-Soluble Sulfate (%) Sulfate Exposure El-A 0.006 Negligible El-B 0.003 Negligible El-AL 0.004 Negligible El-AN 0.004 Negligible El-AR 0.005 Negligible El-AS 0.006 Negligible El-BC 0.012 Negligible El-BN 0.030 Negligible EI-BZ 0.060 Negligible El-CD 0.019 Negligible El-CE 0.017 Negligible El-CF 0.016 Negligible El-CO - 0.038 Negligible EI-CH 0.041 Negligible El-Cl 0.038 Negligible ... -t TABLE - SUMMARY-OF SOIL 2007 CBC SITE CLASS Lot Nos. 2007 CBC Classification l and 2 C 3 through lo D 11 through 25 C 26 through 35 D 36 through 45 C 46 through 50 D 51 through 55 C 56 D 57 through 59 C 60 through 81 D 82 and 83 C Project No. 06105-52-27 January 5, 2010