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HomeMy WebLinkAboutParcel Map 34524 Parcel 1-2 Geotechnical Rough Grading.;. . ~ ~ INLAN.D, INC. Pm 3u ~2`-~ Geotechnical Consulting GEOTECHMCAL REPORT OF ROUGH GRADING FOR THE "HABIT.9 T FOR HUMANITY" DEVELOPMENT, TRACT 30990, SOUTHWEST CORNER OF PUJOL STREET AND FIRST STREET IN THE CITY OF TEMECULA, RIVERSIDE COUNTY, CALIFORNIA Praject No. I04629-30 Dated: Ju[y 28, 2006 Prepared for: Mrs. Tammy Marine HABITAT FOR HUMANITY 27475 Ynez Road, #390 Temecula, Califomia 92591 \ ww ~~. r._._ ca_'_` _ .' ' ' _ _ _ _ _ _ _ ~ INLAND, INC. ~ Geotechnical Consulting July 28, 2006 Mrs. Tammy Marine HABITAT FOR HUMANITY 27475 Ynez Road, #390 Temecula, California 92591 Project No. 104629-30 S~~bject: Geotechitical Report of Raugh Grading for the "Habitat for Humanity" Development, Tract 30990, Southwest Corner of Pujol Street and First Street in the Ciry of Temecula, Riverside County, California This report presents a summary of the observation and testing services provided by LGC Inland, Ina (LGC), during rough grading operations to develop the subject site in the City of Temecula, Riverside County, California. Conclusions and recommendations pertaining to the suitability of the grading for the proposed construction are provided herein, as well as foundation-design recommendations based on the as-graded soil conditions. The purpose ofgrading was to develop 5 lots for the "Habitat for Humanity" development. The proposed buildings will be one- and/or two-story structures with wood or steel-framed construction. Grading on the subject building pads began in April 2006 and was completed in July 2006. 1.0 REG(ILATORY COMPLIANCE Removal and recompaction of low-density surface soils, processing of the exposed bottom surfaces or placement of compacted fill under the purview of this report have been completed under the observation and with selective testing by LGC. Earthwork and grading operations were performed in general accordance with the recommendations presented in the referenced reports (see References) and the grading code of City of Temecula, California. The completed earthwork has bee~ reviewed and is considered adequate for the construction now planned. On the basis of our observations and field and laboratory testing, the recommendations presented in this report were prepared in conformance with generally accepted professional engineering practices and no further warranty is expressed or implied. ' 2.0 ENGINEERING GEOLOGY 2.1 General Geologic conditions exposed during the process of grading were frequently observed and mapped by LGC's geologic staff. v 41531 Date Street • Murrieta, CA 92562 •(951) 461-1919 • Fax (95~1 4R1-7677 ~ l.l Geolopic Units u Earth materials within the site included topsoil, Quaternary-age alluvium, and Pauba Formation bedrock. 2.3 Graundwater Z.4 During grading operations, groundwater was not encountered. Faultinp The subject site is located within the Riverside County Fault Zone, which was adopted in 2003 as part ofthe Riverside County Integrated Project (RCIP). Therefore, a representative from LGC was onsite to perform observation and geologic mapping of the removal areas. No faults were observed during grading operations on the site. 3. 0 SUMMARY OF EARTHWORK OBSER VATIONS AND DENSITY TESTING 3.1 3.2 3.3 3.4 Site C[eariftQ and Grubbin~ Prior to grading, all grasses and weeds were stripped and removed from the site. Ground Preparation The purpose of this grading operation was to provide a compacted fill mat under each of the individual building sites. In proposed azeas where fills and/or shallow cuts less than 3 feet below original ground surface were planned, overexcavation of existing ground surfaces extended into the underlying bedrock to remove the existing topsoil, alluvium and/or colluvium. Removals throughout most ofthe subject site varied from approximately 7 to 12 feet below original grades, with locally deeper removals. Prior to placing fill, the exposed bottom surfaces were scarified to depths of 6 to 8-inches, watered or air- dried as necessary to achieve at or slightly above optimum moisture content and then recompacted in-place to a minimum relative compaction of 90 percent. Disposal of Oversize Xock Oversize rock (rock generally greater than 1 foot in maximum dimension) was not encountered during the removal operations. Fill P[acement and Testin2 Fill materials consist of onsite soils. All fills were placed in lifts restricted to approximately 6 to 8 inches in maximum thickness, watered or air-dried as necessary to achieve near optimum moisture conditions, then compacted in-place to a minimum relative compaction of 90 percent by rolling with an 834 rubber-tired bulldozer or loaded scrapers. The maximum vertical depth of fill placed within the subject building pads as a result of grading is approximately 12 feet. A summary of maximum and minimum fill thickness is provided in Table 2- Lot Summary. ~ Pi~ojec~ Na I04629-30 Page 2 July 38, 2006 ~ ~ Field density and moisture content tests were performed in accordance with ASTM Test Methods D2922 and D3017 (nuclear gauge). Test results are presented on Table l(attached) and test locations are shown on the enclosed As-Graded Geotechnical Map (Plate 1). Field density tests were taken at vertical intervals of approximately I to 2 feet and the compacted fills were tested at the time of placement to verify that the specified moisture content and minimum required relative compaction of 90 percent had been achieved. At least one in-place density test was taken for each 1,000 cubic yards of fill placed and/or for each 2 feet in vertical height of compacted fi1L The actual number of tests taken per day varied with the project conditions, such as the number of earthmovers (dozers) and availability of support equipment. When field density tests produced results less than the required minimum relative compaction of 90 percent, the approximate limits of the substandard fill were established. The substandard area was then reworked or removed, moisture conditioned, re-compacted, and retested until the minimum relative density was achieved. Visual classification of earth materials in the fiefd was the basis for determining which maximum dry density value, summarized in Appendix B, was appticable for a given density test. 3.5 SIOp¢S Stopes were not constructed within the project pad area. 4.0 LABORATORY TESTlNG 4.1 Maximum Drv Densitv Maximum dry density and optimum moisture content for the major soil types observed during grading were determined in our laboratory in accordance with ASTM Test Method D 1557-00. Pertinent test values are summarized in Appendix B. 4.2 Expansion Index Tests Expansion index tests were performed on representative samples of soil existing at or near finish-pad grade within select building pads. These tests were performed in accordance with ASTM D 4829-03. Test results are summarized in Appendix B. 4.3 Solub[e Sulfate Analvses Water-solubie sulfate contents were also determined for representative samples of soil existing at or near pad grade of select building pads in accordance with Califomia Test Method (CTM) No. 417. Test results are summarized in Appendix B. 4.4 Chlnride/nH/Resistivitv Samples of soil considered representative were tested for corrosion potential by testing for chlorides (CTM 422) and pH and resistivity (CTM 643). Test results are presented in Appendix B. ~ Project No. I04629-30 Page 3 Ja~[y 28, 2006 ' ' ~ ~ 5.0 POST-GItADlNG CONS[DERATIONS 5.1 Landscapinp and Maintenance of Graded S[ones Unless long-term mitigation measures are taken, slopes may be subject to a low to moderate degree of surficial erosion or degradation during periods of heavy rainfall. Therefore, it is recommended that fill slopes be landscaped with a deep-rooted, drought-resistant, woody plant species. To provide temporary slope protection while the woody materials mature, the slopes should be planted with an herbaceous plant species that will mature in one season or provided with some other protection, such as jute matting or polymer covering. The temporary protection should be maintained until the woody material has become fully mature. A landscape azchitect should be consulted to determine the most suitable plant materials and irrigation requirements. To mitigate future su~cial erosion and slumping, a permanent slope-maintenance program should be initiated. Proper slope maintenance must include regular care of drainage- and erosion-control provisions, rodent control, prompt repair of leaking irrigation systems and replacement ofdying or dead plant materials. The irrigation system should be designed and maintained to provide constant moisture content in the soils. Over-watering, as well as over-drying, of the soils can lead to surficial erosion and/or slope deterioration. The owners should be advised of the potential problems that can develop when drainage on their pads and adjacent slopes is altered in any way. Drainage can be adversely altered due to the placement of fill and construction of garden walls, retaining walls, walkways, patios, swimming pools and planters. 5.2 Pad Drainape Drainage on the pads should be designed to carry surface water away from all graded slopes and structures. Pad drainage should be designed for a minimum gradient per the UBC with drainage directed to the adjacent drainage facilities or other location approved by the building official. Ground adjacent to foundations shall also be graded at the minimum gradient per the UBC to divert water from the foundation. After dwellings are constructed, positive drainage away from the structures and slopes should be provided on the lots by means of earth swales, sloped concrete flatwork and area drains. 5 Project No. 704629-30 Page 4 July 28, 2006 ~._.~ -- _ ~ __ ~ ~ i 5.3 Utilitv Trenches All utility-trench backfili within street right-of-ways, utility easements, under sidewalks, driveways ar~d building-floor slabs and within or in proximity to slopes, should be compacted to a minimum relative compaction of 90 percent. Where onsite soils aze utilized as backfill, mechanical compaction will be required. Density testing, along with probing, should be performed by a LGC representative to vedfy adequate compaction. Excavations for trenches should be made in accordance with OSHA requirements and when excavations exceed 4 feet in depth they should be laid-back at a gradient no steeper than 1:1 (h:v). For deep trenches with vertical walls, backfills should be placed in lifts no greater than 8 inches in thickness and then mechanically compacted with a hydra-hammer, pneumatic tampers or similar equipment. For deep trenches with sloped walls, backfill materials should be placed in lifts no greater than 6 to 8 inches and then compacted by roliing with a sheepsfoot tamper or similar equipment. Wherc utility trenches are proposed parallel to any building footing (interior and/or exterior trenches), the bottom of the trench should not be located within a l:l (h:v) plane projected do~unward from the outside bottom edge of the adjacent footing. 6.0 FOUNDATIONDESIGNRECOMMENDATIONS 6.1 General Conventional shallow foundations are considered feasible for support of the proposed residential structures. Foundation recommendations are provided below. 6.2 AllorvableBearinr [~a[ues An allowable bearing value of 1,500 pounds per square foot (ps~ is recommended for design of 36-inch- wide continuous footings founded at a minimum depth of 36-inches below the lowest adjacent final grade. These values may be increased by 20 percent for each additional 1 foot of width and/or depth to a maximum value of 3,000 pounds per square foot. Recommended allowable-bearing values include both dead and live loads and may be increased by one-third when designing for short-duration wind and seismic forces. 6.3 Settlement Based on the general settlement characteristics of the soil types that underlie the building sites and the anticipated loading, it has been estimated that the maximum total settlement ofconventional footings will be less than approximately'/< inch. Diffe~ential settlement is expected to be about one-ha(f the total settlement over a horizontal distance of approximately 30 feet, for an angular distortion ratio of 1:960. It is anticipated that the majority of the settlement will occur during construction or shortly thereafter as building loads are applied. The above settlement estimates are based on the assumption that the project geotechnical consultant will observe or test the soil conditions in the footing excavations. ~ '7'OiectNo. f04629-30 P..~o S ~..i.. ~o ~nn~ ,. ~ ~ 6.4 Lateral Resistance A passive earth pressure of 250 psf per foot of depth to a maximum value of 2,500 psf may be used to determine lateral-bearing resistance for footings. Where shuctures are planned in or near descending slopes, the passive earth pressure should be reduced to I50 psf per foot of depth to a maximum value of 1,500 psf. In addition, a coefficient of friction of 0.40 times the dead-load forces may be used between concrete and the supporting soils to determine lateral sliding resistance. The above values may be increased by one-third when designing for short-duration wind or seismic forces. When combining passive and friction for lateral resistance, the passive component should be reduced by one third. The above values are based on footings placed directly against compacted fill. In the case where footing sides are formed, all backfill placed against the footings should be compacted to a minimum of 90 percent of maximum dry density. 6.5 Fnotinp Observations Alf foundation excavations should be observed by the project geotechnical engineer to verify that they have been excavated into competent bearing materia(s. The foundation excavations should be observed prior to the placement of forms, reinforcement or wncrete. The excavations should be trimmed neat, level and square. All loose, sloughed or moisture-softened soil should be removed prior to concrete placement. Excavated materials from footing excavations should not be placed in slab-on-grade areas unless the soi(s are compacted to a minimum 90 percent of maximum dry density. 6.6 ExnansiveSoiLConsiderations Results of the laboratory tests indicate onsite earth materials exhibit expansion potentials of VERY LOW as classified in accordance with 1997 UBC Table 18-I-B. The design and construction details herein are intended to provide recommendations for this level of expansion potential. 6.6.1 Verv Low Exnansion Potential (Exoansion Index of20 or Lessl Results of our laboratory tests indicate onsite earth materials exhibit a VERY LOW expansion potential as classified in accordance with Table 18-I-B of the 1997 Uniform Building Code (UBC). Since the onsite soils exhibit expansion indices of 20 or less, the design of slab-on-ground foundations is exempt from the procedures outlined in Section 1815. Based on the above soil conditions, it is recommended that footings and floors be constructed and reinforced in accordance with the following minimum criteria. However, additional slab thickness, footing sizes and/or reinforcement should be provided as required by the project architect or structural engineer. 1 'i'oject No. I04629-30 Pnve 6 ~.,~., ~o ~nn~ ---- _--,•, 5 ~ .: 1 F--- • --= • ,_--- _,_~, 6.6.1.1 Footines • Exterior continuous footings may be founded at the minimum depths indicated in UBC Table 18-I-C (i.e. 12-inch minimum depth for one-story and l 8-inch minimum depth for two-story construction). Interior continuous footings for both one- and two-story construction may be founded at a minimum depth of 12 inches below the lowest adjacent grade. All continuous footings should have a minimum width of 12 and 15 inches, for one-story and two-story buildings, respectively, and should be reinforced with a minimum of two No. 4 bars, one top and one bottom. • Exterior pad footings intended for the support of roof overhangs, such as second story decks, patio covers and similar construction should be a minimum of 24 inches square and founded at a minimum depth of 18 inches below the lowest adjacent final grade. No special reinforcement of the pad footings will be required. 6.6.1.2 Buildine Floor S[abs • Concrete floor slabs should be 4 inches thick and reinforced with No. 3 bars spaced a maximum of24 inches on center, both ways. All slab reinforcement should be supported on concrete chairs or bricks to ensure the desired placement near mid-depth. • Interior floor slabs with moisture sensitive floor coverings should be underlain by a I S-mil thick moisture/vapor barrier to heip reduce tUe upward migation of moisture from the underlying subgrade soils. The moisture/vapor barrier .product used should meet the performance standazds of an ASTM E 1745 Class A material, and be properly installed in accordance with ACI publication 302. It is the responsibility of the contractor to ensure that the moisture/vapor barrier systems are placed in accordance with the project plans and specifications, and that the moisture/vapor retarder materials are free of tears and punctures prior to concrete placement. Additional moisture reduction and/or prevention measures may be needed, depending on the performance requirements of future interior floor coverings. Recommendations are traditionally included with geotechnical foundation recommendations for sand layers to be placed below slabs and above/below vapor barriers and retarders for the purpose of protecting the barrier/retarder and to assist in concrete curing. Sand layer requirements are the purview of the foundation engineer/structural'engineer, and should be provided in accordance with ACI Publication 302 "Guide for Concrete Floor and Slab Constructiod'. From a geotechnical perspective, a 1-inch layer of sand over the moisture barrier is considered to be the minimum. These recommendations rriust be confirmed (and/or altered) by the foundation engineer, based upon the performance expectations of the foundation. Ultimately, the design of the moisture retarder system and recommendations for concrete placement and curing are the purview of the foundation engineer, in consideration of the project requirements provided by the architect and developer. ~ ~ ~ ~ • Garage area floor slabs should be 4 inches thick and should be reinforced in a similar manner as living-area floor slabs. Garage area floor slabs should also be placed separately from adjacent wall footings with a positive separation maintained with 3/8-inch-minimum felt expansion-joint materials and quartered with weakened-planejoints. A 12-inch-wide grade beam founded at the same depth as adjacent footings should be provided across garage entrances. The grade beam should be reinforced with a minimum of two No. 4 bars, one top and one bottom. • Prior to placing concrete, the subgrade soils below all living-area and garage area floor slabs should be pre-watered to promote uniform curing of the concrete and minimize the development of shrinkage cracks. 6.7 Post Tensioned Slab/Foundation Desien Recommendations In lieu of the proceeding recommendations for conventional footing and floor slabs, post tensioned slabs may be utilized for the support of the proposed structures. We recommend that the foundation engineer design the foundation system using the geotechnical parameters provided in the table below. These parameters have been determined in general accordance with Chapter l8 Section 1816 of the Uniform Building Code (UBC), 1997 edition. Alternate designs are allowed per 1997 UBC Section 1806.2 that addresses the effects of expansive soils when present. In utilizing these parameters, the foundation engineer should design the foundation system in accordance with the ailowable deflection criteria ofapp(icable codes and the requirements of the structural engineer/architect. Please note that the.post tensioned design methodology reflected in UBC Chapter 18 is in part based on the assumption that soil moisture changes around and beneath the post-tensioned slabs are influenced only by climatological conditions. Soil moisture change below slabs is the major factor in foundation damages relating to expansive soil. The UBC design methodology has no consideration for presaturation, owner irrigation, or other nonclimate related influences on the moisture content ofsubgrade soils. In recognition of these factors, we have modified the geotechnical parameters obtained from this methodology to account for reasonable irriQation nractices and prooer homeowner maintenance. [n addition, we recommend that prior to foundation construction, slab subgrades be presoaked to 12 inches prior to trenching and maintained at above optimum moisture up to concrete construction. We further recommend that the moisture content of the soil around the immediate perimeter ofthe slab be maintained near optimum moisture content (or above) during construction and up to occupancy. The following geotechnical parameters provided in the following table assume that if the areas adjacent to the foundation are planted and irrigated, these areas will be designed with proper drainage so ponding, which causes significant moisture change below the foundation, does not occur. Our recommendations do not account for excessive irrigation and/or incorrect landscape design. Sunken planters placed adjacent to the foundation, should either be designed with an efficient drainage system or liners to prevent moisture infiltration below the foundation. Some lifting of the perimeter foundation beam should be expected even with properly constructed planters. Based on the design parameters we have provided, and our experience with monitoring similar sites on these types of soils, we anticipate that if the soils become saturated below tlie perimeter of the foundations due to incorrect landscaping irrigation or maintenance, then up to approximately'/-inch of uplift could occur at the perimeter of the foundation relative to the centra( portion of the slab. ~ ProjeCt IVo. 104629-30 Pnve R r..~.. ,o ,.,.,~ _ . _ . __ --------_r.~._~_~_.~,_: . . ~ ~ Futureowners should be informed and educated regarding the imporfance ofmaintaining a consistent level of soil moisture. The owners should be made aware of the potential negative consequences of both excessive watering, as well as allowing expansive soils to become too dry. The soil will undergo shrinkage as it dries up, followed by swelling during the rainy winter season, or when irrigation is resumed. This will result in distress to site improvements and structures. TABLE A Geotechnica[ Parameters for Post Tensioned Foundation Slab Desien :~ ~ . ~ 'x ' ~~t.'.R'rT~ET~7t. '„ ` . ~~ :- - Ex ansion Index Ve Low Percent that is Finer than 0.002 mm in the Fraction Passin the No. 200 Sieve. < 20 percent (assumed) Cla Mineral T e Montmorillonite assumed Thomthwaite Moisture Index _20 Depth to Constant Soil Suction (estimated as the depth to constant moisture content over time, but within 7 feet UBC limits Constant Soil Suction P.F. 3.6 Moisture Velocit 0.7 inches/month Center Lift Edge moisture variation distance, e,,, 5.5 feet Center lift, ,,, 1.5 inches Edge Lift Edge moisture variation distance, e,,, 2.S.feet Ed e lift, m 0.4 inches Soluble Sulfate Content for .Design of Concrete Mixtures in Contact with Site Soils in Accordance Negligible with 1997 UBC Table 19-A-4 Modulus of Subgrade Reaction, k(assuming resaturation as indicated below) 200 pci Minimum Perimeter Foundation Embedment 12 15-mil thick moisture retardant in Under slab moisture retarder and sand layer conformance with an ASTM E 1745 Class A materiai overlain 6 1-inch of sand} I. Assumed For design purposes or obtained by labora[ory testing. 2. Recommendations for foundation reinforcement are ultimately the purview of the foundation/structural engineer based upon the geotechnical criteria presen[ed in Ihis report, and structural engineering considerations. 3. Recommendations for sand below slabs are traditionally included with the geotechnical foundation recommendations, although they are not the purview of the geotechnical consultanL The sand layer requirements are the purview of the founda[ion engineedstructural engineer and should be provided in accordance with ACI ' Publication 302, Guide for Concrete Floor and Slab Construction. ~ Proiect No. 104619-30 P„~o 9 .,.. ,~ ,,,,,~ , . ~ ~ 6.8 Corrosivitv to Concrete and Metal The National Association of Corrosion Engineers (NACE) defines conosion as "a deterioration of a substance or its properties because of a reaction with its environment." From a geotechnical viewpoint, the "environment" is the prevailing foundation soils and the "substances° are the reinforced concrete foundations or various buried metallic elements. Some ofthe many factors that can contribute to corrosivity, include the presence of chlorides, sulfates, salts, organic materials, different oxygen levels, poor drainage, different soil types, and moisture content. In general, soil environments that are detrimental to steel include high concentrations of chloride measured per Califomia Test Method (CTM) 422 and/or pH values of less than 5.5 measured per CTM 643. Another major factor contributing to soil corrosivity to buried ferrous metal is low electrical resistivity, which can also be measured using CTM 643. The minimum amount of chloride in the soii environment that is considered corrosive to buried steel is 500 ppm. As the soil resistivity measured in ohm-cm decreases, the corrosion potential increases. Soil resistivity test results less than 1,000 ohm-cm are generally considered very highly corrosive to buried steel. Based on limited preliminary laboratory t~sting and the generally accepted criteria described above, it is our opinion that onsite soils should be considered highly corrosive to buried ferrous metals. Table 19-A-4 ofthe U.B.C., 1997, provides specific guidelines for the concrete mix design when thc soluble sulfate content of the soils exceeds 0.1 percent by weight. Based on limited preliminary laboratory testing performed on samples from the project area using CTM 417, the onsite soils are classified as having a negligible sulfate exposure condition in accordance with Table 19-A-4, of U.B.C., 1997. Therefore, in accordance with Table 19-A-4 structural concrete in contact with earth materials should have cement of Type I or II. Table 19-A-2 refers to corrosion protection for reinforced concrete exposed to chlorides. Based on limited laboratory testing performed on samples from the project area using CTM 422, the onsite soils have chloride contents less than 500 ppm. In accordance with Table 19-A-2, requirements for special exposure conditions are not required due to chloride contents. These test results are based on limited samples of the subsurface soils. Laboratory test results are presented in Appendix B. LGC does not employ a registered corrosion engineer, therefore, we recommencj that you consult with a competent registered conosion engineer and conduct additional testing (if required) to evaluate the actual corrosion potential of the site and provide recommendations to mitigate the corrosion potential with respect to the proposed improvements. The recommendations of the registered corrosion engineer may supersede the above requirements. 6. 9 Structural Setbacks Structural setbacks in addition to those required in the UBC, are not required due to geologic or geotechnical conditions within the site. Building setbacks from slopes, property lines, etc. should conform to 1997 UBC requirements. ~~ ProlectNo. I04629-30 P„~~ l/1 i..r.. ~o ~n.,< ~ zo 7.1 7.2 7.3 Active and At-Rest Earth Pressures RETAINING WALLS ~- -- , An active earth-pressure represented by an equivalent fluid having a minimum density of 40 pounds per cubic foot (pc~ should tentatively be used for design ofretaining walls up to 10 feet high retaining a drained level backfill. Where the wall backfill slopes upward at 2:1 (h:v), the above value should be increased to a minimum of 63 pcf. Ali retaining walis should be designed to resist any surcharge loads imposed by other nearby walls or structures in addition to the above active earth pressures. For design of retaining walls up to 10 feet high that are restrained at the top, an at-rest earth pressure equivalent to a fluid having a minimum density of 60 pcf should tentatively be used for walls supporting a leve( backfill. This value should be increased to a minimum of 95 pcf for ascending 2:1 (h:v) backfill. Drainaee Weep holes or open vertical masonryjoints should be provided in retaining walls to prevent entrapment of water in the backfill. Weep holes, if used, should be 3 inches in minimum diameter and provided at minimum intervals of6 feet along the wall. Open vertical masonryjoints, ifused, should be provided at 32- inch-minimum intervals. A continuous gravel fill, 12 inches by l 2 inches, should be placed behind the weep holes or open masonryjoints. The gravel should be wrapped in filter fabric to prevent infiltration of fines and subsequent clogging. Filter fabric may consist of Mirafi 140N or equivalent. In lieu of weep holes or open joints, a perforated pipe-and-gravel subdrain may be used. Perforated pipe should consist of 4-inch-minimum diameter PVC Schedule 40 or ABS SDR-35, with the perforations laid down. The pipe should be embedded in 1.5 cubic feet per foot of 0.75- or 1.5-inch open-graded gravel wrapped in filter fabric. Filter fabric may consist of Mirafi 140N or equivalent. The backfilled side of the retaining wat] supporting backfill should be coated with an approved waterproofing compound to inhibit infiltration of moisture through the walls. Te~ndorarv E.rcavations All excavations should be made in accordance with OSHA requirements. LGC is not responsible forjob site safety. 7.4 Wa[! Back~[1 All retaining-wall backfill should be placed in 6- to 8-inch maximum lifts, watered or air dried as necessaty to achieve near optimum moisture conditions and compacted in place to a minimum relative compaction of 90 percent. ~~ '~~oject No. 1046?9-30 Paoe l l ,--,_ ~., .,,,,, ~ ~ 8.0 MASONRY GARDEN WALLS Footings for masonry garden walls should also be reinforced with a minimum of four No. 4 bars, two top and two bottom. In order to mitigate the potential for unsightly cracking, positive separations should also be provided in the garden walls at a maximum horizontal spacing of 20 feet. These separations should be provided in the blocks only and not extend through the footing. The footing should be placed monolithically with continuous rebars to serve as an effective "grade beam" below the wall. [n areas where garden walls may be proposed on or near the tops of descending slopes, the footings should be deepened such that a minimum horizontal clearance of 5 feet is maintained between the outside bottom edges of the footings and the face of the slope. 9.0 CONCRETE FLATWORK 9.1 Thickness and Joint Snacinp To reduce the potential of unsightly cracking concrete sidewalks and patio-type slabs should be at least 3'/~ inches thick and provided with construction or expansion joints every 6 feet or less. Any concrete driveway slabs should be at least 4 inches thick and provided with construction or expansion joints every 10 feet or less. 9.2 Subgrade Prenaration As a further measure to minimize cracking of concrete flatwork, the subgrade soils underlying concrete flatwork should first be compacted to a minimum relative compaction of 90 percent and then thoroughly wetted to achieve a moisture content that is at .least equal to or slightly greater than optimum moisture content. This moisture should extend to a depth of 12 inches below subgrade and be maintained in the soils during the placement of concrete. Pre-watering of the soils wiil promote uniform curing of the concrete and minimize the development of shrinkage cracks. A representative of the project geotechnical engineer should observe and verify the density and moisture content of the soils and the depth of moisture penetration prior to placing concrete. 9.3 DrainaPe Drainage from patios and other flatwork areas should be directed to local area drains and/or graded-earth swales designed to carry runoff water to the adjacent streets or other approved drainage structure. Tlie concrete flatwork should also be sloped at a minimum gradient of 1 percent away from building foundations, retaining walls, masonry garden walls, and slopes. 9.4 Tree We[ls Tree wells are not recommended in concrete-flatwork areas since they can introduce excessive water into the subgrade soils or allow for root invasion, both of which can result in uplift of the flatwork. ~ 1"U/L'Cl [VV. lV9VLY-JU n,.,_„ i ~ lJ u 10. 0 PLANTERS AND PLANTER WALLS AND LANDSCAPING 10.1 Planters Planters that are located within 5 feet of building foundations, retaining walls, masonry-garden walls and slope areas should be provided with either sealed bottoms or bottom drains to prevent infiltration of water into the adjacent foundation soils. The surface of the ground in these areas should also be maintained at a minimum gradient of 2 percent and direct drainage to area drains or earth swales. Planters adjacent to a building or structure should be avoided wherever possible or be properly designed (e.g., lined with a membrane), to reduce the penetration of water into the adjacent footing subgrades and thereby reduce moisture related damage to the foundation. Planting areas at grade should be provided with appropriate positive drainage. Wherever possible, exposed soil areas should be above adjacent paved grades to facilitate drainage. Planters should not be depressed below adjacent paved grades unless provisions for drainage, such as multiple depressed area drains are constructed. Adequate drainage gradients, devices, and curbing should be provided to prevent runoff from adjacent pavement or walks into.planting areas. Irrigation methods should promote uniformity of moisture in planters and beneath adjacent concrete flatwork. Over- watering and under-watering of landscape areas must be avoided. Z0.2 Planter bvalls Low height planter walls should be supported by continuous concrete footings constructed in accordance with the recommendations presented for masonry block wall footings. 10.3 Landscaoinp In recognition that the future homeowners will add either sofr-scape or hard-scape after precise grading, the following recommendations may be used as a guide. It is paramount that future homeowners consult with a proFessional engineer to ensure that the construction of future landscaping improvements wiil not cause obstruction of existing drainage patterns or does not cause surface water to collect adjacent to the foundation, creating saturated soils adjacent to the foundation. Area drains should be maintained and kept clear ofdebris in order to properly function. Homeowners should also be made aware that excessive irrigation of neighboring properties can cause seepage and moisture conditions on adjacent lots. Homeowners should be furnished with these recommendations communicating the importance of maintaining positive drainage away from structures towards streets when they design their improvements. The impact of heavy irrigation or inadequate runoffgradients can create perched water conditions. This may result in seepage or shallow groundwater conditions where previously none existed. Maintaining adequate surface drainage and wntrolled irrigation will significantly reduce the potential for nuisance-type moisture problems. To reduce differential earth movements such as heaving and shrinkage due to the change in moisture content of foundation soiis, which may cause distress to a residential structure and associated improvements, moisture content ofthe soils surrounding the structure should be kept as relatively constant as possible. ~~ 1'/~U~L'C! 1V0. [U40LY-JU Pi,oa 14 ..._ _~~ ---- __ _ -- -- -- ---- - ---- I, , -:---- -- --- -- = ~ ------ - -- I 11.0 POST- GRADING OBSERVATIONS AND TESTING LGC should be notified at the appropriate times in order to provide the following observation and testing services I during the various phases of post-grading construction. 11.1 Bui[dine Construction ~ • Observe all footings when first excavated to verify adequate depth and competent soil bearing conditions. • Re-observe all footings, ifnecessary, if excavations are found to be excavated to inadequate depth and/or found to contain significant slough, saturated or compressible soils. ~ 11.2 Retainine Wall Constructian • Observe all foundations when first excavated to verify adequate depth and.competent soil bearing conditions. • Re-observe al( foundations, if necessary, if excavations are found to be at an inadequate depth and/or found to contain significant slough, saturated or compressible soils. • Observe and verify proper installation of subdrain systems prior to placing wall backfill. • Observe and test placement of all wall backfill. 11.3 Masonrv Garden Walls • Observe all footing trenches when first excavated to verify adequate depth and competent soil bearing conditions. . Re-observe all footing trenches following removal of any slough and/or saturated soils and re-excavate to proper depth. 11.4 E.rterior Concrete Flatwork Construction . Observe and test subgrade soils below all concrete flatwork areas to verify adequate compaction and moisture content. 11.5 Utilitv-Trench Backrll • Observe and test placement of all utility trench backfill. 11.6 Re-Gradine Observe and test placement of any fill to be placed above or beyond the finish grades shown on the grading plans. ~~ -..._ --.. . __ __ __---- -- ---- -- - -- - ~ ~ 12.0 LIMITATIONS Our services were performed using the degree of care and skill ordinazily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similaz localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. This report is issued with the understanding that it is the responsibility ofthe owner, or ofhis/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result 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 modification, and should not be relied upon after a period of 3 years. ~~ Project No. I04619-30 p„~~ ~ s ., _„ ~ • This opportunity to be of service is sincerely appreciated. P(ease call if you have any questions pertaining to this report. Respectfully submitted, LCClnland, Inc. Chad E. Welke, CEG 2378, PE 63 Associate Geologist/Engineer CA%Y~/t.~~~GA~~'ccw Andrew Shinnefield Senior Staff Geologist Project Manager SAH/AS/CW/SMP/kg ~~, ~ ~ St hen M. Poole, GE 692 Vice President Principal Engineer Attachments: Appendix A- References (Rear of Text) Appendix B- Laboratory Testing Procedures and Test Results (Renr of Te.rt) Table 1- Summary of Field Density Tests (Rear of Test Table 2- L,ot Summary (Rear of Text) Plate I- As-Graded Geotechnica( Map (In Pocket) Distribution: (4) Addressee ~~ Projecl No. l04629-30 PaQe 16 ~„i„ ~Q ~nn~ . . . ~ ~ APPENDIX B Laboratorv Testinp Procedures and Test Results The laboratory testing program was directed towards providing quantitative and qualitative data relating to the relevant engineeringproperties ofthe soils. Samples considered representative ofsite conditions were tested in general accordance with American Society for Testing and Materials (AST'M) procedures and/or Califomia Test Methods (CTM), where applicable. The following summary is a briefoutline ofthe test type and a table summarizing the test results. Mazin:um Densitv Tests: The maximum dry density and optimum moisture content ofrepresentative samples were determined with ASTM D 1557. The results of these tests are presented in the table below: SAMPLE SAMPLE MA,~lMI/MDRY OPTIMUMMOISTURE No. DESCRIPTION DENSITY (pc~ CONTENT (%) ~ Silty SAND 133.5 2 7.0 Silty SAND 132.0 8.0 Esomzsia~ Index: The expansion potential ofrepresentative samples were evaluated with the Expansion Index Test, ASTM D 4829. The results of these tests are presented in the table below: SAMPLE LOCATION LOT 1 throueh 3 SAMPLE DESCRIPTION Silty SAND LOT 4 and 5 I Silty SAND * Per Table 18-I-B of 1997 UBC. EXPANSIONINDEX 7 1 EXPANSION POTENTIAL * Verv Low Very Low Mini»unn Resistivitv and pH Tests: Minimum resistivity and pH tests were perfo~med with CTM 643. The results are presented in the table below: SAMPLE LOC,9TION LOT 1 throuRh 5 SAMPLE DESCRIPTION Silty SAND pH I MINIMIIMRESISTIVITY 8 4 ~ 1300 ~~ T_h ~ ° ` ~ ~ _---- I I Soluble Suffate: The soluble sulfate content of selected samples were determined with CTM 417. The test results aze presented in the table below: SAMPLE ~ i.SAMPLE • `' ` SULFATE CONTENT ~ _ LOCATION- DESCRIPTION- ~ * ('~o by weight) . , SULFATEEXPOSURE* LOT 1 through 5 Silty SAND 0.013 Negligible M R~ooA .... ~6e t nM _a:."' 'r.v_ ir_ee .. .. ... . ... . .'__ '._ ~..a.~ ..~.,o ~v.n. ~..~, iaoie rvo. iv-n-4, prepared by the Intemational Conference of Building Officials (ICBO, 1997). Chloride Content: Chloride content was tested with CTM 422. The results are presented below: SAMPLE LOCATION SAMPLE DESCRIPTION. ,. , CHLORIDE CONTENT (ppm) LOT 1 through 5 Silty SAND 135 ~\ ~ ( ~ F • • TABLC 1 SUA1D79 R P OF FLELD DEArSfT N TEST 7{ i ~ I ~ ~ ___,_. _ .. _ .Th .'_ ..__.~.I. P~rojecf 11ro. I04619-30 Test No. Test ~ Type Test Date Test of Test Location £levation (feet) Soil Type Dry Density (pc~ Moisture Content (%) ~. Density (pc~ ~ Rel. Comp. (g5) ( N 04/IVOG CP LOTS IOOI.S I (19.5 7.7 132.0 90 Z N 04/tI/OG CF LOTS 1003.'L t 119:; B., [3'Lp qp N 04/li/OG C'F LOTS 1005.0 [ ll9.9 7D Gi2.~ g~ 4~ N 04/12/OG Cf LOT4 1001.Z I [f9.5 7.5 13Z.0 g~ 5 N 04/I'L/OG CC- [pT4 1003.L 1 119.R S,I (3?,p g~ G N 04/I'L/OG CP LOT4 I005.4 I 119.9 7.7 132.0 9( % N 04/i2/OG CP LOT4 1007.0 I 119.f; 7.9 (32.0 9[ 8 f~~ 04/I4/OG CP LQT4 (009.0 1 [Oi.K IZ.4 1;4Y.0 RZ 9 N 04/l4/OG CC Restes[#8 1009D I It9.5 IQO [32.0 91 [0 N 04/14/06 CF LOT3 L007.G 1 1[9.fi 8,2 I;SZ,p g( LC N 04/f4/OG CC LOT3 1009.:~ L 119.3 1QU [32.0 90 IZ N 04/14/OG CF LOT3 [UILI I ([9.5 81 i3'L.0 9L 13 N 04/l4~/OG CF LOT3 (Ol?.1 [ II9.9 S,~ [J2.0 9l t4~ N 07/17/OG -Cf LOT2 IOOi.( t 119? 8.9 [32A 90 I:~ N 07/ t7/Of CF LOT Z I OU9:S I L 1 fl.S 92 L:i'L.0 ~! IG N 07/L7/UG Cf LOTZ ]UILfl t II9., 7.G [3'LA 90 I7 N 07/17/Of, c'F LOT2 IOCf.2 I If9.G £,2 I32.0 91 LS N 07/IF/06 CF LOTI IOOiA i L~9.t g.L C;ZA gp 19 N 07/IS/Of CF LOT 1 L009.3 1 ((9.0 9.S 132A 90 20 N 07/IS/06 CP LOTI IOILG I Lf9.S 9.9 L'32.0 9t 21 IJ OU(S/OG CF LOTS IOOi.I 1 I?0.f 9., [;t'L.0 9t 22 N 07/IS/OF, CF LOT5 L009.f ! 11'~A. 7.9 t3'L.0 90 2: PJ 07/24/OG CF LOT ( P.G I ! t93 &,9 [g?p gp 24 N 07/24/OG CF LOTZ C,G t 119.3 7.C I3Z.0 90 26 N 07/24/OG CF LOT3 F.G I (]9,0 9.3 I32.0 90 2(( N Oi/Z4/UC, CF LCl7'4 P.G 1 120.0 S.( 1~2.0 9I 27 N 07/24/OG CF LOT , EG t II~.F; 29 132.0 9I /~"' ,~~ - .~ `~~~ ~/ctvr 7i :~i : I l~ ~Ur~>ri . ,,. ~ ~ ~ ~ ~ LOT SUMMARY- TRACT 30990 Table 2 LOT NUMBER . MAXIMUM DEPTH OF FILL (jy _ ,,MINIMUMDEPTH OF FlLL (/?J I 9 g Z 9 g 3 8 7 4 ~z g 5 12 I1 ~\