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HomeMy WebLinkAbout3889B; Calavera Hills II Pump Station; Report of Rough Grading; 2004-10-11 (2)REPORT OF ROUGH GRADING CALAVERA HILLS II, VILLAGE X, LOT 118 (PUMP STATION) CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA CARLSBAD TRACT 01-06, DRAWING 4054 FOR CALAVERA HILLS II, LLC 2727 HOOVER AVENUE NATIONAL CITY, CALIFORNIA 91950 W.O. 3459-B1-SC OCTOBER 11,2004 W@He Geotechnical - Geologic - Environmental 5741 Palmer Way * Carlsbad, California 92008 (760) 438-3155 - FAX (760) 931-0915 October 11,2004 W.O. 3459-B1-SC Calavera Hills II, LLC 2727 Hoover Avenue National City, California 91 950 Attention: Mr. Don Mitchell Subject: Report of Rough Grading, Calavera Hills II, Village X, Lot 118 (Pump Station), Carlsbad Tract 01-06, Drawing 405-4A, Carlsbad, San Diego County, California Dear Mr. Mitchell: This report presents a summary of the geotechnical testing and observation services provided by GeoSoils, Inc. (GSI) during the rough earthwork construction phase of development at the subject site. Earthwork for the subject site was completed as part of the larger Calavera Hills development. Grading for the larger development generally commenced in January 2003, and was generally completed in April 2004. Unless specifically superceded in the text of this report, the findings and conclusions presented within the compaction report of rough grading for Village X, of which this lot is a part, remain valid and applicable. PURPOSE OF EARTHWORK The purpose of grading was to prepare a relatively level pad for the construction of a planned sewer pump station, servicing the surrounding residential development. Cut-and-fill grading techniques were utilized to attain the desired graded configurations. The lot is a plan transition lot; however, removal operations completed during grading resulted in an as-built fill pad. Existing topsoils and colluvium were removed to suitable bedrock material and recompacted. The grading plan for this portion of Calavera Hills II, Village X (including Lot 118), prepared by O’Day Consultants, dated December 5,2002, is included with this report as Plate 1. EARTH MATERIALS Subsurface geologic conditions exposed during the process of rough grading were observed by a representative of GSI. Earth materials onsite generally consist of dense graniticlmetavolcanic rock with a thin, discontinuous surficial veneer of topsoil/colluvium. Existing topsoils and colluvium were removed to suitable bedrock material and recompacted. The lot was then brought to grade with compacted fill. It is our understanding that subsequent to the mass grading and final compaction of Lot 11 8, several excavations were advanced into the pad by others, then backfilled with loose soil. Their specific locations are unknown. This backfill is loose and not suitable for the support of settlement-sensitive improvements, unless the backfill is removed and properly compacted. GROUNDWATER Naturally occurring groundwater was not encountered during rough grading of the pad and should not significantly affect the proposed building construction, provided that the recommendations contained in this report, and/or provided by GSI, are incorporated into final design and construction, and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Based on the fractured and dense nature of the granitic/metavolcanic bedrock, perched groundwater conditions may develop in the future due to excess irrigation, homeowner altered drainage, or damaged utilities, and should be anticipated. Should manifestations of perched conditions (i.e., seepage) develop in the future, this office could assess the conditions and provide mitigative recommendations, as necessary. A discussion of near surface slope subdrainage is presented in our referenced report on toe drains (GSI, 2004c), and is considered applicable with respect to this site. A discussion of other subdrainage is presented in a later section of this report. EARTHWORK CONSTRUCTION Earthwork operations have been completed in general accordance with the City grading ordinance and the guidelines provided in the field by this office. Observations during grading included removals, overexcavation, and subdrain construction along with general grading procedures and placement of compacted fills by the contractor. Calavera Hills II, LLC W.O. 3459-81-SC Calavera Hills 11, Village X, Lot 118 (Pump Station) October 11, 2004 File:e:\wp9\3400\3459bl .x.rorll8 Page 2 GeoSoils, Inc. Rouah Grading Preparation of Existing Ground 1. Deleterious material, such as concentrated organic matter and miscellaneous debris, were stripped from the surface and disposed of beyond the limits of grading for the subject area, prior to placing any fill. Loose surficial materials (i.e., existing topsoils and colluvium) were removed to expose competent bedrock in all areas to receive fill. Subsequent to completing removals, areas to receive compacted fill were scarified to a minimum depth of 12 inches, moisture conditioned to at least optimum moisture content, and then compacted to attain a minimum relative compaction of 90 percent. These areas were then brought to grade with fill compacted to a minimum 90 percent relative compaction. All processing of original ground in areas to receive fill was observed by a representative of GSI. 2. 3. 4. Fill Placement Fill consisted of onsite and import materials, which were placed in thin lifts, approximately 4 to 8 inches in thickness, brought to at least optimum moisture content, and compacted to attain a minimum 90 percent relative compaction. Compaction test results of fills are presented in the attached Table 1. Fill depths across the site generally vary from approximately 7 feet in the south, to approximatety 20 feet at the north end of the pad. The preparation of some of these fill materials included processing of shot rock and oversize rock through a rock crusher. This process generally produced “4- to 5-inch minus” (in one direction) material, in general accordance with guidelines presented in GSI (2002b and 2003~). Compacted fills containing rock fragments in excess of 12 inches in diameter were placed within the lot, routinely no closer than about 10 feet from finish grade. Fill materials generated onsite, or within the larger Calavera Hills development, from either raw excavation or produced at the crusher site, have been placed in general accordance with recommendations presented in GSI (2002b). An additional criteria, developed for this project during grading, has included gradation testing (in general accordance with ASTM D-422) of stockpiled materials produced from the rock crusher (GSI, 2003~). This testing has been performed in order to evaluate the percentage of “fines” included in the stockpile material. For this project, “fines” are considered to be earth materials that are ?4 inch in diameter, or finer. Suitable soil fills are considered to consist of earth materials generally with at least 240 percent finer than %of an inch (GSI, 2002b and 2003~). Based on our testing and observation, a suitable material gradation appears to have been produced and utilized onsite. Calavera Hills 11, LLC W.O. 3459-81-SC Calavera Hills 11, Village X, Lot 11 8 (Pump Station) October 11,2004 File:e:\wp9\3400\3459bl .x.rorl18 Page 3 CeoSoils, Inc. Subdrainaae Canyon Subdrains Prior to placement of fill, a canyon subdrain, consisting of 6-inch diameter (Schedule 40) PVC pipe, was placed within a canyon/natural drainage area traversing the northern end of Lot 118, and is part of a larger drain system which extends offsite beneath College Boulevard and Village W, to a outlet on the east side of Village W. Subdrain construction was performed in general accordance with GSI guidelines. The approximate locations of all subdrains are shown on Plate 1. Toe Drains Toe drains were not warranted on Lot 118 at the time of grading. Graded Slopes In general, graded slopes constructed under the purview of this report should perform satisfactorily with respect to gross and surficial stability, provided that these slopes are properly maintained, and are subject to the prevailing semi-arid climatic conditions. Fill slopes, constructed under the purview of this report, were provided with a keyway excavated into suitable bedrock material in general accordance with GSI recommendations. Cut slopes are not associated with this building pad. Temporary Slopes Temporary construction slopes may generally be constructed at a gradient of 1 :1 (horizonta1:vertical [h:v]), or flatter, in compacted fill, and %:1 (h:v) in suitable bedrock material (provided adverse geologic structures are not present, as evaluated by GSI prior to workers entering trenches). Utility trenches may be excavated in accordance with guidelines presented in Title 8 of the California Code of Regulations for Excavation, Trenches, and Earthwork, with respect to Type B soil (compacted fill) and stable rock (bedrock). Construction materials and/or stockpiled soil should not be stored within 5 feet from the top of any temporary slope. Temporarylpermanent provisions should be made to direct any potential runoff away from the top of temporary slopes. Field Testinq 1. Field densitytests were performed using thesand cone method (ASTM D-1556) and nuclear method (ASTM D-2922). Tests taken for the entire Calavera Hills project were taken in consecutive numerical order. Only the test results for Village X (including Lot 118) are presented in Table 1 at the end of this report. The Calavera Hills II, LLC W.O. 3459-81-SC Calavera Hills II, Village X, Lot 11 8 (Pump Station) October 11,2004 File:e:\wp9\3400\345Sbl mor1 18 Page 4 CeoSoifs, Inc. 2. 3. 4. 5. C - Light Brown, Silty SAND 126.0 11.0 D - Light Gray, Silty SAND 125.5 10.5 . E - Dark Brown, Silty GMVEL 130.0 11 .o . approximate locations of field density tests are shown on the Field Density Test Location Maps, Plate 1, which utilize the 40-scale grading plans, prepared by O’Day Consultants (2003), as a base map. Field density tests were taken at periodic intervals and random locations to check the compactive effort provided by the contractor. Based on the operations observed, test results presented herein are considered representative of the fills observed under the purview of this report. Visual classification of the soils in the field, as well as random laboratory testing, was the basis for determining which maximum dry density value to use for a given density test. Fills containing large amounts of rock, but suitable for placement as engineered fill (GSI, 2002 and 2003c) were periodically observed using dozer pits in order to evaluate adequate moisture content and relative compaction. Testing and observations were performed on a full-time basis. LABORATORY TESTING The laboratory maximum dry density and optimum moisture content for each major soil type was determined according to test method ASTM D-1557. The following table presents the test results: SOIL TYPE DENSITY I 1 I A - Dark Brown, Silty SAND 120.5 13.0 B - Light Brown, Silty SAND 128.0 10.0 F - Brown, Sandy GRAVEL (processed material) I 126.5 I 10.5 It G - Brownish Grav. Gravellv SILT 131.0 10.0 Calavera Hills II, LLC W.O. 3459-81-SC Calavera Hills 11, Village X. Lot 118 (Pump Station) October 11,2004 File:e:\wp9!34W!3459bl .x.rorl18 GeoSoils, Inc. Page 5 ExDansive Soils Expansive soil conditions have been evaluated for the site. A representative sample of soil near pad grade was recovered for classification and expansion testing. Expansion Index (El) testing was performed in general accordance with Standard 18-2 of the Uniform Building Code ([UBC], International Conference of Building Officials [ICBO], 1997). Testing indicates that site soils near pad grade, within the subject lot, are very low expansive (E.I. ~20). Corrosion/Sulfate Testinq Typical samples of the site materials were analyzed for corrosion/soluble sulfate potential. Soil sulfate testing indicates that the sulfate exposure to concrete is negligible, in accordance with Table 19-A of the UBC (ICBO, 1997). Site soils are considered corrosive to ferrous materials when wet or saturated. While it is our understanding that standard concrete cover is sufficient mitigation, alternative methods and additional comments should be obtained from a qualified corrosion engineer. Sieve Anahrsls Sample gradation for various representative samples was determined in general accordance with ASTM Test Method D-422. Test results generally indicated that at least 40 percent of each sample was finer than the %-inch sieve in accordance with GSI (2002b and 2003~). RECOMMENDATIONS - FOUNDATIONS Foundation systems should be designed and constructed in accordance with the guidelines contained in the UBC (ICBO, 1997). All footing designs should be reviewed and approved by the project structural engineedfoundation designer. Based on soil expansion potential and the as-built fill thicknesses (Le., differential fill thickness less than 3:1, maximum to minimum, across the lot), conventional foundations may be constructed. For the purposes of preliminary design, the following design parameters are provided. Construction plans should be reviewed by this office once they are developed, in order to verify that the intent of the soils report has been properly incorporated into the design and construction of any planned improvements. 1. Conventional spread and continuous footings may be used to support the proposed structure@), provided they are founded entirely in properly compacted fill or other Calavera Hills II, LLC W.O. 3459-B1-SC Calavera Hills II, Village X, Lot 118 (Pump Station) October 11,2004 File:e:\wp9\3400\3459bl .x.rorll8 Page 6 GeoSoils, Inc. competent bearing material (i.e., bedrock). Footings should not simultaneously bear directly on bedrock and fill soils. Analyses indicate that an allowable bearing value of 2,000 pounds per square foot (ps9 may be used for design of continuous footings per Table 3, and for design of isolated pad footings 24 inches square and 18 inches deep into properly compacted fill or bedrock. The bearing value may be increased by one-third for seismic or other temporary loads. This value may be increased by 20 percent for each additional 12 inches in depth, to a maximum of 2,500 psf. 2. 3. . For lateral sliding resistance, a 0.35 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. Passive earth pressure may be computed as an equivalent fluid having a denslty of 300 pounds per cubic foot (pc9 with a maximum earth pressure of 2,500 psf. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Footings should maintain a horizontal distance or setback between any adjacent slope face and the bottom outer edge of the footing. The horizontal distance may be calculated by using h/3 (where h is the height of the slope). The horizontal setback should not be less than 7 feet, nor need not be greater than 40 feet (per code). The setback may be maintained by simply deepening the footings. Flatwork, utilities, or other improvements, within a zone of h/3 from the top of slope, may be subject to lateral distortion. Footings, flatwork, and utility setbacks should be constructed in accordance with distances indicated in this section, and/or the approved plans. Provided that the recommendations contained in this report are incorporated into final design and construction phase of development, amajority (250 percent) of the anticipated foundation settlement is expected to occur during construction. Maximum settlement is not expected to exceed approximately 1% inches and should occur below the heaviest loaded columns. Differential settlement is not anticipated to exceed 0.9 inch between similar elements in a 40-foot span. Foundation plans should be reviewed by this office in order to verify that the intent of the soils report has been properly incorporated into the design and construction of the planned structure@). 4. 5. 6. 7. 8. Calavera Hills II, LLC W.O. 3459-81-SC Calavera Hills 11, Village X, Lot 11 8 (Pump Station) October 11,2004 File:e:\wp9\3400\3459bl .x.rorllB CeoSoSls, Inc. Page 7 EXTERIOR FLATWORK Exterior driveways, walkways, sidewalks, or patios, using concrete slab-on-grade construction, should be designed and constructed in accordance with the following criteria: 1. 2. 3. 4. 5. 6. Driveway slabs should be a minimum 4 inches in thickness; all other exterior slabs may be a nominal 4 inches in thickness; however, such nominal slabs will be at increased risk for distress. A thickened edge should be considered for all flatwork adjacent to landscape areas. Slab subgrade should be compacted to a minimum 90 percent relative compaction and moisture conditioned to at, or above, the soils optimum moisture content. The use of transverse and longitudinal control joints should be considered to help control slab cracking due to concrete shrinkage or expansion. Two of the best ways to control this movement are: 1) add a sufficient amount of properly placed reinforcing steel, increasing tensile strength of the slab such as 6x6, W1.4xW1.4); and/or, 2) provide an adequate amount of control and/or expansion joints to accommodate anticipated concrete shrinkage and expansion. We would suggest that the maximum control joint spacing be placed on 5- to 8-foot centers, or the smallest dimension of the slab, whichever is least. No traffic should be allowed upon the newly poured concrete slabs until they have been properly cured to within 75 percent of design strength. Positive site drainage should be maintained at all times. Adjacent landscaping should be graded to drain into the street/parking area, or other approved area. All surface water should be appropriately directed to areas designed for site drainage. Concrete compression strength should be a minimum of 2,500 psi. CONVENTIONAL RETAINING WALLSMALLS Foundations may be designed using parameters provided in the Design section of Foundation Recommendations presented herein. Wall sections should adhere to the County and/or City guidelines. All wall designs should be reviewed by a qualified structural engineer for structural capacity, overturning, and seismic resistance stability per the UBC. The design parameters provided assume that onsite or equivalent low expansive soils are used to backfill retaining walls. If expansive soils are used to backfill the proposed walls Calavera Hills II, LLC File:e:\wp9\3400\3459bl .x.rorllB W.O. 3459-B1-SC October 1 1, 2004 Page 0 Galavera Hills II, Village X, Lot 118 (Pump Station) GeoSoSls, Inc. within this wedge, increased active and at-rest earth pressures will need to be utilized for retaining wall design. Heavy compaction equipment should not be used above a 1 :1 projection, up and away from the bottom of any wall. The following recommendations are not meant to apply to specialty walls (cribwalls, loffel, earthstone, etc.). Recommendationsfor specialty walls will be greaterthan those provided herein, and can be provided upon request. Some movement of the walls constructed should be anticipated as soil strength parameters are mobilized. This movement could cause some cracking dependent upon the materials used to construct the wall. To reduce wall cracking due to settlement, walls should be internally grouted and/or reinforced with steel: Any retaining walls that will be restrained prior to placing and compacting backfill material, or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressures of 60 pcf, plus any applicable surcharge loading. For areas of male or re-entrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall (2H) laterally from the corner. Building walls below grade should be water-proofed or damp-proofed, depending on the degree of moisture protection desired. Refer to the following section for preliminary recommendations from surcharge loads. These recommendations are for cantilevered retaining walls up to 15 feet high. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An empirical equivalent fluid pressure (EFP) approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are provided for specific slope gradients of the retained material. These do not include other superimposed loading conditions such as traffic, structures, seismic events, or adverse geologic conditions. SURFACE SLOPE OF I EQUIVALENT FLUID The equivalent fluid density should be increased to 60 pcf for level backfill at the angle point of the wall (corner or male re-entrant) and extended a minimum lateral distance of 2H on either side of the corner. Traffic loads within a 1 :1 projection up from the wall heel, due to light trucks and cars, should be considered as a load of 100 psf per foot in the Calavera Hills 11, LLC W.O. 3459-Bl-SC Calavera Hills II, Village X, Lot 11 8 (Pump Station) October 11,2004 File:e:\wp9\340o\3459b1 .x.rorl18 Page 9 GeoSofls, Inc. upper 5 feet of wall in uniform pressure. For preliminary design purposes, footing loads within a 1:l backfill zone behind wall will be added to the walls as 'h of the bearing pressure for one footing width, along the wall alignment. Sound Walls/ToD-of-Slope Walls Sound wall plans have been reviewed for this project (GSI, 2003a) and were evaluated to be in general conformation with the intent of the referenced reports (see the Appendix). Wall Backfill and Drainaae All retaining walls should be provided with an adequate gravel and pipe back drain and outlet system to prevent buildup of hydrostatic pressures, and be designed in accordance with the minimum standards presented herein. Retaining wall drainage and outlet systems should be reviewed by the project design civil engineer, and incorporated into project plans. Pipe should consist of schedule 40 perforated PVC pipe. Gravel used in the back drain systems should be a minimum of 1 cubic foot per lineal foot of 3/8- to 1 %-inch clean crushed rock encapsulated in filter fabric (Mirafi 140 or equivalent). Additional gravel may be warranted depending on wall height and the nature of the wall backcut. Perforations in the pipe should face down. The surface of the backfill should be sealed by pavement, or the top 18 inches compacted to 90 percent relative compaction with native soil. Proper surface drainage should also be provided. As an alternative to gravel back drains, panel drains (Miradrain 6000, Tensar, etc.) may be used. Panel drains should be installed per manufacturers' guidelines. Regardless of the back drain used, walls should be water-proofed where they would impact living areas, or where staining would be objectionable. DEVELOPMENT CRITERIA General Compacted fill slopes, designed using customary factors of safety for gross or surficial stability and constructed in general accordance with the design specifications, should be expected to undergo some differential vertical heave, or settlement, in combination with differential lateral movement in the out-of-slope direction, after grading. This post-construction movement occurs in two forms; slope creep and lateral fill extension (LFE). Calavers Hills II, LLC W.O. 3459-Bl-SC Calavera Hills II, Village X, Lot 118 (Pump Station) October 11,2004 File:e:\wp9\3400\3459bl xrorl18 Page 10 GeoSoSls, Inc. Slope Creep Slope creep is caused by alternate wetting and drying of the fill soils, which results in slow downslope movement. This type of movement is expected to occur throughout the life of the slope, and is anticipated to potentially affect improvements or structures (Le., separations and/or cracking), placed near the top-of-slope, generally within a horizontal distance of approximately 15 feet, measured from the outer, deepest (bottom outside) edge of the improvement to the face of slope. The actual width of the zone affected is generally dependant upon: 1) the height of the slope; 2) the amount of irrigationlrainfall the slope receives; and, 3) the type of materials comprising the slope. This movement generally results in rotation and differential settlement of improvements located within the creep zone. Suitable mitigative measures to reduce the potential for distress due to lateral deformation typically include: setback of improvements from the slope faces (per the 1997 UBC and/or CBC); positive structural separations (i.e., joints) between improvements; and, stiffening and deepening of foundations. Per Section 1806.5.3 of the UBC, a horizontal setback (measured from the slope face to the outside bottom edge of the building footing) of H/3 is provided for structures, where H is the height of the fill slope in feet and H/3 need not be greaterthan 40feet. Alternatively, in consideration of the discussion presented above, site conditions and Section 1806.5.6 of the UBC, H/3 generally need not be greater than 20 feet for the Calavera Hills II development. As an alternative to a deepened footing, where the adjacent slope is greater than 45 feet in height and the buildinglfooting is within 20 feet from the slope face, a differential settlement of Yi inch (additional) may be applied to the design of that portion of the structure@). Any settlement-sensitive improvements (i.e., walls, spas, flatwork, etc.) should consider the above. Proper disclosure to homeowners and/or homeowners associations is recommended. Lateral Fill Extension (LFE) LFE occurs due to deep wetting from irrigation and rainfall on slopes comprised of expansive materials. Based on the generally very low expansive character of onsite soils, the potential component of slope deformation due to LFE is considered minor, but may not be totally precluded. Although some movement should be expected, long-term movement from this source may be minimized, but not eliminated, by placing the fill throughout the slope region, wet of the fill's optimum moisture content. During grading of the site, GSI observed fill soil moisture contents during fill placement and compaction. Our observations indicate that the moisture content of the fill is generally above the soils optimum moisture content, in accordance with our recommendations. Summary It is generally not practical to attempt to eliminate the effects of either slope creep or LFE. Suitable mitigative measures to reduce the potential of lateral deformation typically include: Calavera Hills II, LLC W.O. 3459-81-SC Calavera Hills II, Village X, Lot 11 8 (Pump Station) October 11, 2004 FIle:e:\wp9\34W\3459bl .x.rorl18 Page 11 GeoSoils, Inc. setback of improvements from the slope faces (per the 1997 UBC and/or CBC); positive structural separations (Le., joints) between improvements; stiffening; and, deepening of foundations. All of these measures are recommended for design of structures and improvements and minimizing the placement of “dry” fills. The ramifications of the above conditions, and recommendations for mitigation, should be provided to each homeowner and/or any homeowners association. Slope Malntenance and Plantlnq Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Positive surface drainage, away from slopes, should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Over-watering should be avoided as it can adversely affect site improvements and cause perched groundwater conditions. Graded slopes constructed utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for landscaping should be light weight, deep rooted types that require little water and are capable of surviving the prevailing climate. Jute-type matting, or other fibrous covers, may aid in allowing the establishment of a sparse plant cover. Utilizing plants other than those recommended above will increase the potential for perched water, staining, mold, etc. to develop. A rodent control program to prevent burrowing should be implemented. Irrigation of natural (ungraded) slope areas is generally not recommended. These recommendations regarding plant type, irrigation practices, and rodent control should be provided to each homeowner. Over-steepening of slopes should be avoided during building construction activities and landscaping. Adequate lot surface drainage is a very important factor in reducing the likelihood of adverse performance of foundations, hardscape, and slopes. Surface drainage should be sufficient to prevent ponding of water anywhere on a lot, and especially near structures and tops of slopes. Lot surface drainage should be carefully taken into consideration during fine grading, landscaping, and building construction. Therefore, care should be taken that future landscaping or construction activities do not create adverse drainage conditions. Positive site drainage within lots and common areas should be provided and maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and not allowed to pond and/or seep into the ground. In general, the area within 3 feet around a structure should slope away from the structure (GSI, 2003d). We recommend that unpaved lawn and landscape areas have a minimum gradient of 1 percent sloping away from structures, and whenever possible, should be above adjacent paved areas. Consideration should be given to avoiding construction of planters adjacent to structures (buildings, pools, spas, etc.). Pad drainage Calavara Hills 11, LLC W.O. 3459-81-SC Calavera Hills 11, Village X, Lot 118 (Pump Station) October 11,2004 File:e:\wp9\3400\3459bl .x.rorllB Page 12 GsoSoils, rnc. should be directed toward the street or other approved area@). Although not a geotechnical requirement, roof gutters, down spouts, or other appropriate means may be utilized to control roof drainage. Down spouts, or drainage devices, should outlet a minimum of 3 feet from structures (GSI, 2003d) or into a subsurface drainage system. Areas of seepage may develop due to irrigation or heavy rainfall, and should be anticipated. Minimizing irrigation will lessen this potential. If areas of seepage develop, recommendations for minimizing this effect could be provided upon request. Erosion Control Cut and fill slopes will be subject to surficial erosion during and after grading. Onsite earth materials have a moderate to high erosion potential. Consideration should be given to providing hay bales and silt fences for the temporary control of surface water, from a geotechnical viewpoint. Landscape Maintenance Only the amount of irrigation necessary to sustain plant life should be provided. Over-watering the landscape areas will adversely affect proposed site improvements. We recommend that any open-bottom, raised box planters adjacent to proposed structures be restricted for a minimum distance of 10 feet. As an alternative, closed-bottom type raised planters could be utilized. An outlet placed in the bottom of the planter could be installed to direct drainage away from structures or any exterior concrete flatwork. If raised box planters are constructed adjacent to structures, the sides and bottom of the planter should be provided with a moisture barrier to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Graded slope areas should be planted with drought resistant vegetation. Consideration should be given to thetype of vegetation chosen and their potential effect upon surface improvements (Le., some trees will have an effect on concrete flatwork with their extensive root systems). From a geotechnical standpoint, leaching is not recommended for establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided the recommendations contained in this report are incorporated into final design and construction, and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions, along zones of contrasting permeabilities, may not be precluded from occurring in the future due to site irrigation, poor drainage conditions, or damaged utilities, and should be anticipated. Should perched groundwater conditions develop, this office could assess the affected area@) and provide the appropriate recommendations to mitigate the observed groundwater Calavera Hills II, LLC W.O. 3459-81-sc Calavera Hills 11, Village X, Lot 118 (Pump Station) October 11,2004 File:e:\wp9\3400\3459bl .x.rorll8 Page 13 GeoSoiIs, Inc. conditions. Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors. Tile Flooring Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small cracks in a conventional slab may not be significant. The tile installer should consider installation methods that reduce possible cracking of the tile such as slipsheets, a vinyl crack isolation membrane, or other approved method by the Tile Council of AmericaKeramic Tile Institute. Slte IrnrJrovernents Recommendations for exterior concrete flatwork construction are provided in a previous section of this report. If in the future, any additional improvements (e.g., pools, spas, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. This office should be notified in advance of any fill placement, grading of the site, or trench backfilling after rough grading has been completed. This includes any grading, utility trench, and retaining wall backfills. Additional Grading This office should be notified in advance of any fill placement, supplemental regrading of the site, or trench backfilling after rough grading has been completed. This includes completion of grading in the street and parking areas and utility trench and retaining wall backfills. As noted in a previous discussion, several pits have been excavated into the pad, then backfilled, by others. This backfill is considered to be loose and not suitable for the support of settlement sensitive improvements, unless the backfill is removed and properly compacted. Footing Trench Excavatlon All footing excavations should be observed by a representative of this firm subsequent to trenching and to concrete form and reinforcement placement. The purpose of the observations is to verify that the excavations are made into the recommended bearing material and to the minimum widths and depths recommended for construction. If loose or compressible materials are exposed within the footing excavation, a deeper footing or removal and recompaction of the subgrade materials would be recommended at that time. Footing trench spoil and any excess soils generated from utility trench excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Calavera Hills 11, LLC W.O. 3459-81-SC Calavera Hills (I, Village X. Lot 11 8 (Pump Station) October 11,2004 File:e:\wp9\3400\3459b1 .x.rorl18 Page 14 ~eosoils, Inc. Trenchinq Considering the nature of the onsite soils, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls at the angle of repose (typically 25 to 45 degrees) may be necessary and should be anticipated. All excavations should be observed by one of our representatives and minimally conform to CAL-OSHA and local safety codes. Utilitv Trench Backfill 1. 2. 3. 4. All interior utility trench backfill should be brought to at least 2 percent above optimum moisture content and then compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. As an alternative for shallow (12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of 30 or greater may be utilized and jetted or flooded into place. Observation, probing and testing should be provided to verify the desired results. Exterior trenches adjacent to, and within areas extending below a 1:l plane projected from the outside bottom edge of the footing, and all trenches beneath hardscape features and in slopes, should be compacted to at least 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used in these backfill areas. Compaction testing and observations, along with probing, should be accomplished to verify the desired results. All trench excavations should conform to CAL-OSHA and local safety codes. Utilities crossing grade beams, perimeter beams, or footings should either pass below the footing or grade beam utilizing a hardened collar or foam spacer, or pass through the footing or grade beam in accordance with the recommendations of the structural engineer. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that observation and/or testing be performed by GSI at each of the following construction stages: . During grading/recertification. . After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. Calavera Hills 11, LLC W.O. 3459-B1-SC Calavera Hills II, VillageX, Lot 118 (Pump Station) October 11,2004 ~ File:e:\wp9\3400\3459bl .x.rorllB GeoSoils, he. Page 15 Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor barriers (i.e., visqueen, etc.). During retaining wall subdrain installation, prior to backfill placement. During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wall backfill. During slope construction/repair. When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. When any developer or homeowner improvements, such as flatwork, spas, pools, walls, etc., are constructed. A report of geotechnical observation and testing should be provided at the conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and/or to comply with code requirements. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, post-tension designer, architect, landscape architect, wall designer, etc. should review the recommendations provided herein, incorporate these recommendations into all their respective plans, and by explicit reference, make this report pari of their project plans. PLAN REVIEW Any additional project plans generated for this project should be reviewed by this office, prior to construction, so that construction is in accordance with the conclusions and recommendations of this report. LI M lTATl0 NS The materials encountered on the project site and utilized for our analysis are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Calavera Hills II, LLC W.O. 3459-81-SC Calavera Hills 11, Village X, Lot 118 (Pump Station) October 11,2004 Fiie:e:\wp9\3400\3459bl .x.rorllB GeoSoils, Inc. Page 16 Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is expressed or implied. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this project. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hem call our office. Respectfully GeoSoils, Inc. C”_ m-t Robert G. Crisman Engineering Geologist, CEG 1934 RGC/JPF/BBS/jk Geotechnical Engineer, GE 2296 Attachments: Table 1 - Field Density Test Results Appendix - References Plate 1 - Field Density Test Location Map Distribution: (4) Addressee Calavera Hills II, LLC W.O. 3459-B1-SC Calavera Hills II, Village X, Lot 118 (Pump Station) October 11,2004 File:e:\wpSWW\345Sbl x.rotl18 Page 17 GeoSoils, Inc. Table 1 Calavera Hills 11, UC Calavera Hills 11, Village X, Lot 118 (Pump Station) File: C:\excaRtables\34MW45Sbl x.rorl18 GeoSoils, Inc. W.O. 3459-81-SC October 2004 Page 1 Table 1 FIELD DENSITY TEST RESULTS Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C\excel\tableslMOW459bl .xrorl18 GeoSoils, he. W.O. 3459-BISC October 2004 Page 2 Table 1 Cslavera Hills II, LLC Calavera Hills 11, Village X, Lot 118 (Pump Station) File: C\exceRlables\340O\W\3459bl .x.rcfl18 GeoSoils, Inc. W.O. 3459-81-50 October 2004 Page 3 Table 1 FIELD DENSITY TEST RESULTS Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C:\excahlables\34CO~l .x.rorl18 GeoSoils, he. W.O. 3459-81-SC October 2004 Page 4 Table 1 FIELD DENSITY TEST RESULTS Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C:\excahiables\~3459bl .x.rorlIB GeoSoils, he. W.O. 3459-61-SC October 2004 Page 5 Table 1 Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C\exce\tablesW4Qbl .x.rorll8 GeoSoils, he. W.O. 3459-B1-SC October 2004 Page 6 Table 1 Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C:\exml\tablesl34W34Sbl.x.rorllB GeoSoils, Inc. W.O. 3459-B1-SC October 2004 Page 7 Table 1 Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C:\exceRtablesU45Qbl .x.rorl18 Geosoils, Inc. W.O. 3459-81-SC October 2004 Page 8 Table 1 Calavera Hills II, LLC Calavera Hills II, Village X, Lot 118 (Pump Station) File: C:\ermRtablebl.x.rorl18 GeoSoils, Inc. W.O. 3459-B1SC October 2004 Page 9 Table 1 Calavera Hills II, UC W.O. 3459-B1-SC Calavera Hills 11, Village X. Lot 118 (Pump Station) October 2004 File: C:\exceRtable.s-bl .x.rorll8 GeoSoils, fnc. Page 10 Table 1 Calavera Hills II, LLC Calavera Hills 11, Village X, Lot 118 (Pump Station) File: C\excehtablesW4M)\3459b1 .x.rorllB GeoSoils, Inc. W.O. 3459-81-SC October 2004 Page 11 Table 1 LEGEND: ' = Indicates Repeated Test Number * = Indicates Failed Test A = Indicates Retest FG = Finish Grade FS = ND = Nuclear Densometer SC = Sand Cone Calavera Hills 11, LLC Calavera Hills 11, Village X, Lot 118 (Pump Station) File: C:\excal\tables\3400\3459b1 .x.rorl18 GeoSoils, Inc. W.O. 3459-81-SC October 2004 Page 12 APPENDIX REFERENCES APPENDIX REFERENCES California Building Standards Commission, 2001 , California building code, California Code of Regulations, Title 24, Part 2, Volume 2, Adopted November 1,2002. GeoSoils, Inc., 2004a, Report of rough grading, Calavera Hills, Village X, Building Lots 1 through 115, and Recreation Lots 116 and 117, Carlsbad tract 01-06, Drawing 405-4A, Carlsbad, San Diego County, California, W.O. 3459-B1 -SC, dated August 4. -, 2004b, Development criteria for Calavera Hills II, City of Carlsbad, San Diego County, California, W.O. 3459-81 -SC, dated March 29. -, 2004c, Geotechnical review of documents, Village X of Calavera Hills II, Carlsbad, San Diego County, California, W.O. 3459-81 -SC, dated January 7. -, 2004d, Revised pavement design report, Calavera Hills 11, Village X, City of Carlsbad, San Diego County, California, W.O. 3459-E-SC, dated May 3. -, 2004e, Revised toe drain recommendations, Calavera Hills II, Village X, Carlsbad, San Diego County, California, W.O. 3459-Bl-SC, dated March 5. -, 2003a, Geotechnical plan review, Wall construction plans for Calavera Hills II, Village X, City of Carlsbad, San Diego County, California, W.O. 3459-Bl-SC, dated December 23. -1 2003b, Supplemental evaluation of allowable bearing value, Calavera Hills 11, City of Carlsbad, San Diego County, California, W.O. 3459-Bl-SC, dated July 1. -, 2003c, Memorandum: general discussion of fill quality, Calavera Hills 11, Carlsbad, California, W.O. 3459-B2-SC, dated May 20. -, 2003d, Recommendations regarding sideyard drainage swales, Villages E-1, H, K, L-2, U, W, X, Y and 2, Calavera Hills II, City of Carlsbad, San Diego County, California, W.O. 3459-B1 -SC, dated June 18. -, 2002a, Preliminary segmental retaining wall soil parameters and wall design criteria, Calavera Hills 11, City of Carlsbad, San Diego County, California, W.O. 3459-Bl-SC, dated November 27 -, 2002b, Review of grading and trench backfill recommendations, Calavera Hills II, Carlsbad tract 00-02, Drawing 390-90, City of Carlsbad, San Diego County, California, W.O. 2863-A-SC, August 16. CeoSoils, Inc. -, 1999, Update of geotechnical report, Calavera Hills, Village X, City of Carlsbad, California, W.O. 2751 -A-SC, dated October 22. -9 1998a, Lack of paleontological resources, Carlsbad tract nos. 83-19, PUD 56, and 83-32, PUD 62, Carlsbad, San Diego County, California, W.O. 2393-B-SC, dated January 21. -8 1998b, Preliminary review of slope stability, Calavera Hills, Villages “Q” and “T”, City of Carlsbad, California, W.O. 2393-B-SC, dated February 16. -7 1998c, Review of slope stability, Calavera Hills, Villages “Q and “T,” City of Carlsbad, California, W.O. 2393-B-SC, dated June 24. International Conference of Building Officials, 1997, Uniform building code. O’Day Consultants, 2003, Grading plans for: Calavera Hills II, Village X, Carlsbad tract C.T. 01-06, Job No. 9820, Drawing No. 405-4A, print date August 22. Southern California Soil and Testing, Inc., 1990, Interim report of geotechnical investigation, Calavera Heights, Village W-X-Y, Tamarack Avenue and College Boulevard, Carlsbad, California, W.O. 9021 049, dated May 15. -9 1984, Summary of geotechnical investigation for Lake Calavera Hills, Villages E-1 , E-2, H, K, L-2, L-3, Q, R, S, T, U and W-X, Carlsbad, California, W.O. 141 12, report no. 6., dated August 6. Southern California Soil and Testing, Inc., 1992, Interim report of as built geology field observations and relative compaction tests, proposed College Boulevard improvements and Village El, Carlsbad, California, SCS&T 9121081 -, 1988, Supplemental soil investigation, Calavera Hills Village Q and T, College Boulevard, Carlsbad, California, Job no. 8821 142, Report no.1, dated October 6. -, 1984, Summary of geotechnical investigation for Lake Calavera Hills, Villages E-1 , E-2, H, K, L-2, L-3, Q, R, S,T, U, and W-X, Carlsbad, California,” W.O. 141 12, Report No. 6., dated August 6. -, 1983, Report of preliminary geotechnical investigation for the Calavera Hills areas El, E2, H, I, K, and P through 22, Carlsbad, Job no. 14112, Report no.1, dated July 29. Calavera Hills Ii, LLC Appendix Flle:e:\wp9\34W\3459bl .x.rorl18 Page 2 GeoSoils, Inc.