The URL can be used to link to this page

Home My WebLink AboutCT 04-15; LA COSTA GREENS NEIGHBORHOOD 1.06 & 1.07; UPDATE GEOTECHNICAL REPORT; 2006-01-13UPDATE GEOTECHNICAL REPORT VILLAGES OF LA COSTA THE GREENS - PHASE 2 NEIGHBORHOOD 1.07 LOTS I THROUGH 71 CARLSBAD, CALIFORNIA PREPARED FOR K. HOVNANIAN COMPANIES SOLANA BEACH, CALIFORNIA JANUARY 13, 2006 PROJECT NO. 06403-52-24 GE000N INCORPORATED - GEOTECHNICAL CONSULTANTS Project No 06403-52-24 January 13, 2006 K Hovnanian Companies 420 Stevens Avenue, Suite 170 Solana Beach, California 92075 Attention Mr. Jim Norum / Subject VILLAGES OF LA COSTA'- THE GREENS, PHASE 2 NEIGHBORHOOD 1.07, LOTS 1 THROUGH 71 CARLSBAD, CALIFORNIA • UPDATE GEOTECHNICAL REPORT Gentlemen In acàordance with your authorization of our Proposal No. LG-05552 dated December 30, 2005, we have prepared this update geotechnical report for the subject project. The accompanying report presents the results of our study and contains conclusions and recommendations pertaining to the geotechnical aspects of the proposed development of the site. Provided that the recommendations contained in this update report are followed, the site is considered suitable for construction and support of the proposed structures and improvements as presently planned. 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 - Michael C. Ertwine . i - Shane Rodacker Senior Staff Geologist CEG 1778 - RCE 63291 - FES K4L N. ROO 41 SRdmc (1/del) Gouvis Engineering Attention: Mr. Huan Nguyen QvIL Attention: Ms. Nehad K. Hindi ICA (2) Real Estate Collateral Management Company - Cf0 Morrow, Development Attention Mr. Tim O'Grady 6960 Flanders Drive 0 San Diego California 92121-2974 • Telephone (858) 558-6900 U Fax (858) 558-6159 0 • • TABLE OF CONTENTS • • PURPOSE AND SCOPE..................................................................................................................... PREVIOUS SITE DEVELOPMENT ...... ............................................. .1 • SITE AND PROJECT DESCRIPTION ..................................... . .......................................................... 1 • SOIL AND GEOLOGIC CONDITIONS ........................................................................................2 4.1 Compacted Fill (Qcf) .......... ...... . ............. .. ................................................................... . ............ 2 I 4.2 Alluvium (Qal) ............... .......................................................................................................... 2 2 • 4.3 Terrace Deposits (Qt)......................... ..................................................................................... 4.4 Santiago Formation (Ts) .................. . .............................. ......................................... ................ 3 1 S GROUNDWATER ......... ............................................................................................. .......................3 . GEOLOGIC HAZARDS ..................................................................................................................3 • 6.1 Faulting and Seismicity .......... . .................................................. ............................................. 3 6.2 Liquefaction ............................................................................... . .... .......................................... 4 • CONCLUSIONS AND RECOMMENDATIONS ..........................................................................5 7.1 General .....................................................................................................................................5 • 7.2 Seismic Design........................................................................................................................ . 7.3 Finish Grade Soil Conditions .................................................................................................6 • 7.4 Future Grading ........................................................................................................................7 7.5 Foundations ............................................................................................................................7 • 7.6 Retaining Walls ........................................... . ....................................................... . .................. 11 • 7.7 Lateral Loads ................ .......................................................................................................... 12 7.8 Slope Maintenance ..............................................................................................................12 • 7.9 Site Drainage ......... ................................. ..................................... ........................................ .13 LIMITATIONS AND UNIFORMITY OF CONDITIONS • Figures: • Vicinity Map • Typical Retaining Wall Drain Detail Tables: • I. Summary of As-Graded Building Pad Conditions and Foundation Category . 11. Summary of Finish Grade Expansion Index Test Results III. Summary of Laboratory Water-Soluble Sulfate Test Results • 'I S. .. • .. • . .. . .. . • ,.. . .,. UPDATE GEOTECHNICAL REPORT 1. PURPOSE AND SCOPE This report presents the results of the update geotechnical study for the proposed residential development of Neighborhood 1.07, Lots 1 through 71 and associated improvements located in Phase 2 of the Villages of La Costa -The Greens development. The site is situated north of the Poinsettia Lane, east of Alicante Road, and west of the adjacent Bressi Ranch development (see Vicinity Map, Figure 1) The purpose of this update report is to provide foundation 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 Incorporated, 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 1.06 and 1.07, Carlsbad, California, prepared by Geocon Incorporated, dated December 29, 2005. (Project No. 06403-52-19B). 3 Grading and Erosion Control Plans for La Costa Greens Neighborhood 1.06'& 1.07, prepared by Hunsaker and Associates, City of Carlsbad approval dated May 10, 2005 2 PREVIOUS SITE DEVELOPMENT Neighborhood 1.07, Lots 1 through 71, was graded to finish-pad configuration during mass grading operations for Phase 2 of The Greens development. Grading was performed in conjunction with the observation and testing services of Geocon Incorporated A summary of the observations, compaction test results, and professional opinions pertaining to the grading are presented in the above-referenced report of grading. Mass grading for the subject area has been completed and consisted of developing 71 single-family residential lots and associated streets. Fill and cut slopes were created with design inclinations of 2:1 (horizontal:vertical) or flatter, with a maximum height of approximately 40 feet. The maximum thickness of the compacted fill soils is approximately 71 feet. An "As-Graded" Geologic Map is provided in the above-referenced report and depicts the existing geologic conditions and topography. 3. SITE AND PROJECT DESCRIPTION The development of The Greens - Neighborhood 1.07 consists of 71 single-family residential homes and associated improvements. Compacted fill soils are exposed at grade and underlain by the Santiago Formation, Terrace Deposits, and alluvium. The Santiago Formation is also exposed at grade on cut slopes and within some roadways The "As-Graded" Geologic Map for the project is Project No. 06403-52-24 - I- January,] 3, 2006 • • included in the above-referenced final report of grading. A summary of the as-graded pad conditions for the lots is provided on Table I. In general, the on-site fill materials generally consist of fine sands and sandy to silty clay. 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 of this report. • 4. SOIL AND GEOLOGIC CONDITIONS I The Santiago Formation, Terrace Deposits, alluvium, and compacted fill soils underlie the site. The predominant materials within 4 feet of grade consist of clayey sand to silty sand and possess a low to • high expansion potential. The soil types and geologic unit are discussed below. • 'H • 4.1 Compacted Fill (Qcf) 0 In general, the fill materials consist of light yellowish brown, sandy clay and silty sand. The I maximum fill thickness is approximately 71 feet. Fill soils were placed in conjunction with the I observation and testing services of Geocon Incorporated, which are summarized in the above- referenced final report of grading. The compacted fill soils are considered suitable to provide adequate support for the proposed development. • • 4.2 Alluvium (Qal) : • A portion of the southwestern margin of Neighborhood 1.07 along Poinsettia Lane is underlain by I' alluvium (beneath the compacted fill materials); due to the presence of a shallow groundwater table • and the close proximity of the existing roadway embankment, complete removal of alluvium was not practical and some alluvium was left in place. Consequently, a surcharge and settlement monitoring • program was implemented. Settlement data presented in final report of grading represents measured - vertical movement in the field. Based on the survey measurements, it is our opinion that the primary settlement was essentially complete after 124 days and the area is suitable to provide support for the proposed development. 4.3 Terrace Deposits (Qt) Stream-deposited Terrace Deposits were exposed within cleanouts in localized portions of 10 Neighborhood 1.07. The Terrace Deposits generally consisted of medium dense to dense, silty to clayey sandstone and are considered suitable for the support of the proposed development. • • • Project No. 06403-52-24 -2-' January 13, 2006 • '. 4.4 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 and are considered suitable for the support of the proposed development. 5. GROUNDWATER Groundwater was encountered during grading operations in the alluvial soils but is not anticipated to adversely impact the development of the property. Due to the nature of the Santiago Formation, which consists of interbedded sandstone and claystone/siltstone, seepage was encountered in several cut slopes and mitigated by construction of drained stability fills. 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 of irrigation and rainwater will be important to future performance of the project 6 GEOLOGIC HAZARDS 6.1 Faulting and Seismicity Our review of pertinent geologic literature, the previously referenced geotechnical investigation report dated June 25, 2001, and our experience with the soil and geologic conditions in the general area indicate that no known active, potentially active, or inactive faults are located within the site The nearest known "active" faults are the Rose Canyon Fault and the Newport-Inglewood (offshore) located approximately 7 and 10 miles, respectively, to the west and the Coronado Banks Fault Zone, which lies approximately 22 miles to the southwest Portions of the Rose Canyon Fault have been included in a Special Study Earthquake Fault Zone. A Maximum Credible seismic event of Magnitude 7.2 is postulated for the Rose Canyon Fault with an estimated Maximum Credible peak site acceleration of 0.32 g based on the Sadigh, etal. (1997) acceleration-attenuation relationship. The seismicity of the site is influenced by both local and regional fault systems within the southern California and northern Baja 'California region. Table 6.1 lists the fault zones that present the greatest seismic impact to the site Project No. 06403-52-24 -3.- January 13, 2006 TABLE 6.1 FAULT SYSTEMS WITHIN THE SOUTHERN CALIFORNIA AND. NORTHERN BAJA CALIFORNIA REGION Fault Name 'Distance from Site (miles) Maximum Credible Earthquake Maximum Credible Site Acceleration (g) Rose Canyon 7 7.2 0.32 Newport—Inglewood (Offshore). 10 7.1 0.25 Coronado Banks Fault Zone 22 . 7.6 0.17 Elsinore—Julian.' 23, . 7i' 0.13 Elsinore—Temecula ' 23 6.8 0.10 Palos Verdes , 41. '... 7.3 0.08 Elsinore-Glen Ivy ' 37 ' 6.8 0.06 San Jacinto—Anza 49 7.2 0.06 In the event of a major earthquake along any, of the above-referenced faults or other faults in the southern California regiOn, the site could. be subjected to moderate to severe ground shaking. With respect to 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 the soil conditions underlying the site. We recommend that seismic design of structures be performed in accordance with the Uniform Building Code (UBC) currently adopted by the City of Carlsbad 6.2 . 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 all 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 formational materials, the fine-grained characteristic of the alluvium, and the additional consolidation from the loading induced by the compacted fill, the potential for liquefaction occurring at the site is considered to be very low. • ., O • '' • 7. CONCLUSIONS AND RECOMMENDATIONS • ., .,. • 7.1 General 7.1.1 No soil or, geologic • conditions were encountered during previous geotechnical 5 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. . 7.1.2 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 will be used throughout the project. Therefore, conventional footing . recommendations are not included in this report but can be provided upon request. Design criteria for post-tensioned slabs are provided in Section 7.5. • 7.2 SeismicDesign • 7.2.1 The site is located within Seismic Zone 4 according to UBC Figure 16-J. Compacted fill soils underline the proposed buildings. For seismic design, the site 'is characterized as soil - types. Sc and SD. Table 7.2.1 summarizes site design criteria. The values listed in . Table 7.2.1 are for the Rose Canyon Fault, which is identified as a Type B fault. The Rose S Canyon Fault is located approximately 7 miles west of the site. Table 7.2.2 presents a summary of soil profile type fdr, each building and the corresponding values from • . . Table 7:2.1 should be used for seismic design. . • . . . .- 5 TABLE 7.2.1 • . SITE SEISMIC DESIGN CRITERIA - Parameter . ' Soil Profile Type UBC Reference Sc 5D. Seismic Zone Factor 0.40' ' 0.40 Table 16-1 Soil Profile Sc SD " Table 16-J Seismic Coefficient, Ca ,. 0.40 . 0.44 Table I6Q Seismic Coefficient, C,, 0.56 0.64 Table 16-R Near-Source Factor, Na ' 1.0 ' ' 1.0 Table 16-S Near-Source Factor, N,, 1.0 .• ' 1.0 - Table 16-T Seismic Source . , . . B B Table 16-U ...p .. 7.2.2 Based on a review of the as-graded conditions preseiited in the as-graded report referened, below, as well as the seismic setting, the lots are assigned the seismic design parameters as S indicated in the following table • TABLE 7.2.2 SUMMARYOF SOIL PROFILE TYPE. Unit Lot Nos. . UBC Classification 1.07 1 through 4 SD 1.07 5 through 9 Sc 107 10 through 24 SD 1.07.25 through 27 Sc 107 28through35 SD 107 36 and 37 Sc 1.07 38 through 62 So 107 62 1.07 63 through 71 So 7.3 Finish Grade Soil Conditions 7.3. 1 Observations and laboratory test results indicate that the prevailing soil conditions within . the upper approximately 4 feet of finish grade have an expansion potential of "low" to . "high" (Expansion Index of 130 or less) as defined by Uniform Building Code (UBC) Table 18-I-B. Expansion Index test results for each lot are included on Table I. 5 7.3.2 It should be noted that although rocks larger than 6-inch-diameter were not intentionally S placed within the upper 4 feet of pad grades, some larger rocks may exist at random locations 7.3.3 Random samples obtained throughout the subject ñeighbdrhoods were subjected to waier-soluble sulfate testing to evaluate the amount of water-soluble sulfates within the • finish-grade soils These test results are used to determine the potential for sulfate attack on normal Portland Cement concrete The test results indicate sulfate contents that correspond • to "negligible" to "severe" sulfate, eposure ratings as defined by UBC Table 19-A-4. The results of the soluble-sulfate tests are summarized on Table III. Table 7.3 presents a summary of concrete requirements set forth by UBC Table 19-A-4 • • . 4 5 Project No 06403-52-24 6 January 13 2006 .' TABLE 7.3 REQUIREMENTS FOR CONCRETE EXPOSED TO ____________ SULFATE-CONTAINING SOLUTIONS • 7.3.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if improvements that could be susceptible to corrosion are planned, it is recommended that further evaluation by a corrosion engineer be performed. 'S • 7.4 Future Grading • 7.4.1 Any additional grading performed at the site should be accomplished in conjunction with our' observation and compaction testing 'services. Grading plans for any future grading • ' should be reviewed by Geocon Incorporated prior to finalizing. All trench and wall backfill ,should be compacted to a dry density of at least 90 percent of the laboratory maximum dry density at or slightly above optimum moisture content. This office should be notified at least 48 hours prior, to commencing additional grading or backfill'operations. ' 7.5 Foundations 7.5.1 The foundation recommendations that follow are for one7 or two-story residential structures and are separated into categories dependent on the thickness and geometry of the • underlying fill soils as well as the Expansion Index (El) of the prevailing subgrade soils of a particular building pad. Finish-grade Expansion Index test results are presented on / Table II, attached. The category criteria are summarized herein. • Category I: Maximum fill thickness is less than 20 feet and Expansion Index is less than or equal to 50. . . ' Category II: Maximum fill thickness is less than 50 feet and Expansion Index is less than or equal to 90, or variation in fill thickness is between 10 feet and 20 • . feet. , Category III: Fill thickness exceeds 50 feet, or variation in fill thickness exceeds 20 feet, or Expansion Index 90 but is exceeds 130 or less, or underlain by • ' alluvium. • , '' Project No. 06403-52-24 '. . ' - 7 - . January 13. 2006 Sulfate Water-Soluble Cement Maximum Water Minimum Exposure Sulfate Percent T Type yp to Cement Ratio Compressive by Weight by Weight Strength (psi) Negligible 0.00-0.10 -- -- -- Moderate 0.10-0.20 II' 0.50 4000 Severe 0.20-2.00 V 0.45 4500 Very Severe > 2.00 V 0.45 4500 .. . . .. O : ., Notes: • All footings should have a minimum width of 12 inches. - • Footing depth is measured from lowest adjacent subgrade. These depths apply to both exterior and interior footings. . . 0 All interior living area concrete slabs should be at least 5 inches thick. This applies to both building and garage slabs-on-grade. 0 - 4. All interior concrete slabs should be underlain by at least 4 inches of clean sand. . - 5. All slabs expected to receive moisture-sensitive floor coverings or used to store moisture-sensitive materials should be underlain by a vapor barrier placed at the midpoint of the clean sand recommended in No. 4-above. • .- ... 7.5.2 The post-tensioned systems should be designed by a structural engineer experienced in post-tensioned slab design and the design criteria of the Post-Tensioning Institute (UBC Section 1816). Although this procedure was developed for expansive soils, it is understood that 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 in the following table for the particular foundation category designated for each lot as presented on Table I. - - 0 TABLE 7.5 POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS Post-Tensioning Institute (P11) Design Parameters,- Foundation Category Thornthwaite Index -20 -20 -20 Clay Type - Montmorillonite Yes Yes Yes Clay Portion (Maximum) 30% 50% 70% Depth to Constant Soil Suction 7.0 ft. 7.0 ft. 7.0 ft. Soil Suction . 3.6 ft. 3.6 ft. 3.6 ft. Moisture Velocity 0.7 in/mo. 0.7 in./mo. 0.7 in./mo. Edge Lift MOisture Variation Distance 2.6 ft. 2.6 ft. 2.6 ft. Edge Lift 0.41-in. 0.78 in. 1.15 in. Center Lift Moisture Variation Distance 53 ft. 5.3 ft. 5.3 ft. Center Lift 2.12 in. 3.21 in. 4.74 in. .. . ... .. • • .. 7.5.3 UBC Chapter 18, Div. III, §1816 uses interior stiffener beams in its structural design S procedures. If the structural engineer proposes a post-tensioned foundation design method • other than UBC Chapter 18, Div. III, §1816, the following recommendations apply: • . The deflection riteria presented in Table 7.5 are still applicable.. . -. • : . 'Interior stiffener beams be used for Foundation. Categories II and III. • . The depth of the perimeter foundation should be at least 12 inches for Foundation S . Category I, 18 inches for Foundation Category II, and 24 inches for Foundation 'Category III. Geocon Incorporated should be consulted to provide additional design parameters as required by the structural .engineer.. ' . 7.5.4 During the construction of the "post-tension foundation system, the concrete should be S . '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. . . ..' 5 7.5.5 . Our experience indicates post-tensioned slabs are susceptible to excessive edge lift, 5 regardless of the underlying soil conditions, unless reinforcing steel is placed at the bottom . of the perimeter footings and the interior stiffener beams. Current PT! design procedures S . 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 I • . foundation system to reduce the potential of edge lift occurring for the proposed structures. 7.5.6 Foundations for Category I, II or III may be designed fOr au allowable sail 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 such as wind or seismic forces. S 7.5.7 The use of isolated footings that are located beyond the perimeter of the building and 5 . support structural elements connected to the building is not recommended for Category III. I . Where this condition cannot be avoided, the isolated footings should be connected to the 5 building foundation system with grade beams. . . . . • ' ., '• .. 7.5.8 No special subgrade presaturatioñ is deemed 'necessary prior to placing concrete; however, S the exposed foundation and slab subgrade soils should be moisture conditioned,' as necessary, th "maintain a moist condition as would be expected in any such concrete placement. • - . " . .' . • Project No. 06403-52-24 , . • . . -9 -" . ' January 13, 2006 • • " '5 7.5.9 Consideration should be given to connecting patio slabs that exceed feet in width to the S building foundation to reduce the potential for future separation to occur. 5 7.5'. 10 Where buildings or other improvements are planned near the top of a slope steeper than 3:1 S (horizontal:vertical), special foundations and/or design considerations are recommended 5 due to the tendency for lateral soil movement to occur. • • For cut and fill slopes, 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. . Where the height of the fill slope exceeds 20 feet, the minimum horizontal distance should be increased to H13 (where H equals the vertical distance from the top of . the slope to the toe) but need not exceed 40 feet. For composite (fill over cut) slopes, H equals the vertical distance from the top of the slope, to the bottom of the fill portion of the slope. An acceptable alternative to deepening the footings is 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. ., S • Swimming pools located, within 7 feet of the top of cut or fill slopes are not recommended. Where such a condition cannot be avoided, it. is recommended that . .. the portion of the swimming pool wall within 7 feet of the slope face be designed with the assumption 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 • , S ' S . Although other improvements that 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. . • . •5 7.5.11. Exterior slabs not subject to vehicle loads should be at least 4 inches thick and reinforced • with 6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh. The mesh should be placed within the • upper one-thirdof the slab. Proper mesh positioning is critical to future performance of the It has been our experience that the mesh must be physically pulled up into the slab S slabs. after concrete placement. The contractor should take extra measures to provide proper I conditioned mesh placement. Prior to construction of slabs, the subgrade should be moisture to at least optimum moisture content and compacted to at least 90 percent of S the laboratory maximum dry density. 5 ''.• '' . 0 •. .5 . '•5 'S Project No. 06403-52-24 JO- . 5 January 13, 2006 .5 ' 7.5.12 All concrete slabs should be provided with adequate construction joints and/or expansion joints to control unsightly shrinkage cracking. The design of joints should consider criteria' of the American Concrete Institute when establishing crack-control spacing patterns 7 5 13 Where exterior flatwork abuts the structure at entrant or extant points, the exterior slab should be dowelled into the structure's foundation stemwall. This recommendation is intended to reduce the potential for differential elevations that could result from differential settlement or minor heave of the flatwork. Dowelling details should be designed by the project structural engineer 7.5.14 , The recommendations of this report are intended to reduce the potential for cracking of slabs due to expansive soils (if present), differential settlement of deep fills, or fills of varying thicknesses. However, even 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 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 the placement of crack-control joints at periodic intervals, particularly where re-entrant slab corners occur. 7.6 Retaining Walls 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 to 1, an active soil pressure of 45 pcf is recommended These soil pressures assume that the 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 Index of less than 90 For those lots with finish-grade soils having an Expansion Index greater than 90 and/or where backfill materials do not conform to the above criteria, Geocon Incorporated should be consulted for additional recommendations 7.6.2 Unrestrained walls are those that are allowed to rotate more than 0.00.1 H (where ,H equals the height of the 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 vehicular loads within a horizontal distance equal to two-thirds of the wall height, a surcharge equivalent to 2 feet soil should be added Project No 06403-52- 24 1 I January 13 2006 • '. • "V.. 'V , 7.6.3 All retaining walls should be provided with a drainage system adequate to prevent the ' buildup of hydrostatic forces and should be waterproofed as required . by the project S . architect: The use of drainage openings through the base of the wall (weep holes, etc.) is S . not recommended 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 2. The above recommendations assume a properly compacted granular • . . ' (Expansion Index less than 90) backfill material with no hydrostatic forces or imposed • surcharge load. If conditions different than those described are anticipated, or if specific drainage details are desired, Geocon Incorporated should be contacted for additional recommendations . . 7.6.4 In general, wall foundations having .a minimum depth and width of one foot maybe . . . . 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 less than 90. The proximity of the foundation to the top of a slope steeper than 3:1 could impact the allowable soil bearing S pressure. Therefore, Geocon Incorporated should be consulted where such a condition is • . anticipated. The location of the wall footings, however, should comply with the recommendations presented in Section 7.5.10, . 7.7 Lateral Loads '. . . .. S 7.7.1 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 5 èompactéd granular fill Soils or undisturbed natural soils. The allowable passive pressure S . 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 coefflcientof0A may be used for resistance to sliding between soil and . . . concrete. This friction coefficient may be combined with the allowable passive earth V pressure when determining resistance.tó lateral loads. . .. 7.7.2 The recommendations presented, above are generally applicable to the design of rigid I . ' 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. ,.V VV . ." •.. • . 7.8 Slope Maintenance . . . . ., V V• • ". .:' . 7.8.1, Slopes that are steeper than 31 (horizontal:vertical) may, under conditions that are both • difficult to, prevent and predict, be susceptible to near-surface (surficial) slope instability. S Project No. 06403-52-24 ' ' .- i2- : . ' 'January 13, 2006 , • ''"V ' 'V. ", ,"'',' • .. O The instability is typically limited to the outer 3 feet of a portion of the slope and usually S does not directly impact the improvements on the pad areas above or below the slope. The S occurrence of surficial instability is more prevalent on fill slopes and is generally preceded 5 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 from root growth; soil expansion, or excavation for irrigation lines and slope planting, may also be a • . significant contributing factor to. surficiàl instability. It is therefore recommended that, to the maximum extent practical: (a) disturbed/loosened surficial soils be 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 I . 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 I rebuild instability, it will not eliminate the possibility, and, therefore, it may be necessary to or repair a portion of the project's slopes in the future. 5 7.9. Site Drainage ' . S . 7.9.1 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 S surface to footings or behind retaining walls. The site should be graded and maintained such that 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. . . • . "0 0 .., • . 7.9.2. . All underground utilities -should be leak free. Utility and irrigation lines should be checked 0 , 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 • 0 ' the soil for a prolonged period of time. • . 0 ,0, 0 0 0i'.' 7.9.3 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 I recommend that drains to collect excess irrigation water and transmit it to drainage I structures or impervious above-grade planter boxes be used. In addition, where landscaping is planned adjacent to the pavement, we recommend construction of a cutoff wall along the S edge of the pavement that extends, at least 6 inches below the bottom of the base material. • ':1 0 ,,0 • 0 •' :,.' 0 . • . .. 0 •'' 0 ' 'O 0.0 ,, , ':" O . :...... . 0. Project No. 06403-52-24 , ' -13- . January 13, 2006 • 0 0 , 0 • • S • LIMITATIONS AND UNIFORMITY OF CONDITIONS S 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 S any variations or undesirable conditions are encountered during construction, or if the S 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 S services provided by Geocon Incorporated. S. 5 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 5 brought to the attention of the architect and engineer for the project and incorporated into the plans, and that the necessary steps are taken to see that the contractor and subcontractors carryout 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 S 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 I 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. • S . • • • . 0 • S • • 0 • 0 • 0 • • 0 '0 0 0 • • 0 , 0 0 ., • 0, ' ,0 00, 'O 0" Project No. 06403-52-24 : 0 January 13, 2006 • 7ORjoN .01 0 rt 9TTA /" PARADM SYATE 16 FS, I, 2 I UJ WY jKSTO 00 1400 J 4 18 RACEWAY / 'PALO D 280- - 'L TIGER -- . HAWK CT - AIRPO. . N - (2800 ' -- -. a .RD J . - . EWAY EISVDP RD 8 i[c!•—< WAEMN -rx, ,GARDE i-- 7 I I CE H2 JM' / I FADED *1141W , , I P*SEO C.MES .- 4> !/ 15810 4. VIA SII1PATIA IS CONJ JDOR. ( N. EO - • - .- S \_.,CHO \ t B PATIOS VIA 1 S EL p#O 'ARR1 sco A 23 24 rp I ZIL9G ST SOURCE: 2006 THOMAS BROTHERS MAP SAN DIEGO COUNTY, CALIFORNIA REPRODUCED WITH PERMISSION GRANTED BY THOMAS BROTHERS MAPS. THIS MAP IS COPYRIGHT BY THOMAS BROS. MAPS. IT IS UNLAWFUL TO COPY OR REPRODUCE ALL OR ANY PART ThEREOF, WHETHER FOR PERSONAL USE OR NO SCALE RESALE. WITHOUT PERMISSION. GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121- 2974 PHONE 858 558-6900 - FAX 858 558-6159 I VICINITY MAP I VILLAGES OF LA COSTA - THE GREENS NEIGHBORHOOD 1.07 CARLSBAD, CALIFORNIA MCE / RA DSK/GTYPD II DATE 1-13-2006 I PROJECT NO. 06403-52-24 I-FIG. 1 VAAAyM,p GE000N VILLAGES OF LA COSTA - THE GREENS INCORPORATED NEIGHBORHOOD 1.07 GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121- 2974 CARLSBAD, CALIFORNIA PHONE 858 558-6900 - FAX 858 558-6159 MCE ' RA DSKIGTYPD DATE 1 13-2006 PROJECT NO. 06403-52 -24 FIG. 2 • I I P. I PKOI'KLY \'/4 11 II W LIJCIP.IL/KCIWILL&UWL'. • TABLE I SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND FOUNDATION CATEGORY FOR NEIGHBORHOOD 1.07 LOT NOS. I THROUGH 71 Lot No. Pad Condition Approximate Maximum Depth of Fill (feet) Approximate Maximum Depth of Differential Fill (feet) Expansion Index Foundation Category 1 Fill, 36 24 87 III 2 Fill 23 9 87 11 3 Fill 21 8 87 II 4 Fill 21 16 61 II 5 Undercut due to Cut/Fill Transition 1 85 II 6 Undercut due to Cut/Fill Transition 2 91 III 7 Undercut due to Cut/Fill Transition 2 63 11 8 Undercut due to Cut/Fill Transition 16 13 63 II 9 Undercut due to Cut/Fill Transition 6 2 63 II 10 Fill 35 32 105 111 11 Fill 41 22 105 III 12 Fill 41 11 105 III 13 Fill 44 14 105 III 14 Fill 44 16 64 II 15 Fill 41 18 64 II 16 Fill 31 26 64 III 17 Fill 57 34 75 III 18 Fill 69 25 75 III 19 Fill 71 16 75 III 20 Fill 66 11 48 III 21 Fill 59 2 48 III 22 Fill 46 6 48 II 23 Fill 39 12 48 II 24 Fill 25 12 60 II 25 Fill 13 6 60 II 26 Undercut due to Cut/Fill Transition 4 II Project No. 06403-52-24 .. January 13, 2006 TABLE I (Continued) SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND FOUNDATION CATEGORY FOR NEIGHBORHOOD 1.07 LOT NOS. I THROUGH 71 Lot No. Pad Condition Approximate Maximum Depth of Fill (feet) Approximate Maximum Depth of Differential Fill (feet) Expansion Index Foundation Category 27 Undercut due to Cut/Fill Transition 1 60 II 28 Fill 30 27 58 III 29 Undercut due to Cut/Fill Transition 24 21 58 III 30 Undercut due to 22 Cut/Fill Transition 19 58 II 31 Undercut due to Cut/Fill Transition 24 21 58 111 32 Undercut due Cut/Fill Transition 28 25 .58 III 33 Fill 28 12 63 II 34 Fill 29 16 63 II 35 Fill .29 18 63 II 36 Undercut due to Cut/Fill Transition 17 14 67 II 37 Undercut due to Cut/Fill Transition 6 67 II 38 Fill 27 24 59 111 39 Fill 26 4 59 II 40 Fill 36 15 59 II 41 Fill 33 20 III 42 Fill 36 27 67 III 43 Fill 34 27 67 III 44 Fill/Alluvium 31 3 67 III 45 Fill/Alluvium 27 . 3 67 III 46 Fill/Alluvium 26 2 67 111 47 Fill/Alluvium 25 2 50 111 48 Fill/Alluvium 22 1 50 III 49 Fill 23 3 50 II 50 Fill 36 7 . 62 II 51 Fill 46 5 62 II 52 Fill . 40 4 • 62 II 53 Fill 28 1 62 II Project No. 06403-52-24 January 13, 2006 TABLE I (Continued) SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS AND FOUNDATION CATEGORY FOR NEIGHBORHOOD 1.07 LOT NOS. I THROUGH 7I Approximate Approximate Lot Pad Condition Maximum Maximum Depth Expansion Foundation No. Depth of Fill of Differential Fill Index Category (feet) (feet) - 54 Fill 33 7 73 11 55 Fill 34 12 73 II 56 Fill 35 16 73 11 57 Fill 38 23 73 III 58 . Fill 35 20 . 69 III 59 Fill 33 20 69 II! 60 Fill 29 18 69 II 61 Undercut due to 20 17 69 II Cut/Fill Transition Undercut due to -. 62 Cut/Fill Transition 77 II Undercut due to 63 Cut/Fill Transition 24 20 77 III Undercut due to - 64 Cut/Fill Transition 39 36 77 III Undercut due to 65 Cut/Fill Transition 41 37 77 III Undercut due to 66 Cut/Fill Transition 25 22 77 III Undercut due to 67 Cut/Fill Transition 29 26 98 III Undercut due to 68 Cut/Fill Transition 29 - 26 98 III Undercut due to 69 Cut/Fill Transition 31 - 28 98 III Undercut due to 70 Cut/Fill Transition 30 27 32 III Undercut due to 71 Cut/Fill Transition 28 25 32 III Project No. 06403-52-24 January 13, 2006 TABLE 11 SUMMARY OF FINISH GRADE EXPANSION INDEX TEST RESULTS VILLAGES OF LA COSTA; THE GREENS, NEIGHBORHOOD 1.07, LOTS I THROUGH 71 Lot Numbers Sample at Finish Grade Expansion Index UBC Classification 1 through 3 El-E 87 Medium 4 El-Pa 61 Medium 5 El-Fb 85 Medium 6 EI-Fc 91 High 7 through 9 El-G , 63 Medium 10 through 13 EI-X 105 High 14 through 16 El-Y 64 Medium 17 through 19t El-P 75 Medium 20 through 23 EI-O 48 Low 24 through 27 El-N - * 60 Medium 28 through 32 EI-W 58 Medium 33 through 35 El-V 63 Medium 36 and 37 El-U 67 Medium 38 through 41 E1-T_ 59 Medium 42 and 43 El-U 67 Medium 44 through 46 El-S 62 Medium 47 through 49 El-R,' 50 Low 50 through 53 El-J 62 Medium 54 through 57 El-1 73 Medium 58 through 61 El-H 69 Medium 62 through 66 El-K 77 Medium 67 through 69 EI-L 98 High 70 and 71 EI-M 32 Low TABLE III SUMMARY OF WATER-SOLUBLE SULFATE LABORATORY TEST RESULTS CALIFORNIA TEST 417 Sample No. Water-Soluble Sulfate (%) Sulfate Exposure UBC Table 19-A-4 El-8 0 096 Negligible El-Fa 0.495 Severe Ei-Fb 0.120 Moderate El-Fe 0.255 Severe El-G 0.090 * Negligible. El-H 0.675 Severe El-I 0.540 Severe EI-J 0.735 Severe El-K 0.465 Severe EI-L 0.500 , Severe EI-M • 0.630 Severe El-N 0.210 Severe El-U 0.705 Severe El-P 0:645 Severe EI-R 0.360 Severe El-S 0.600 Severe EI-T 0.405 * Severe El-U 0.435 Severe El-V 0.255 - - Severe El-W . 0.280 Severe El-X 0.048 Negligible EI-Y . 0.405 Severe