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HomeMy WebLinkAbout; 470 Chinquapin Avenue; Final Compaction Report of Grading; 2004-03-22FINAL COMPACTION REPORT OF GRADING 470 CHINQUAPIN AVENUE CITY OF CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA FOR MR. ED HENDRIX 470 CHINQUAPIN AVENUE CARLSBAD, CALIFORNIA 92008 W.O. 3344-B-SC MARCH 22, 2004 Geotechnical - Geologic * Environmental 5741 PalmerWay • Carisbad, California 92008 • (760)438-3155 • FAX (760) 931-0915 March 22, 2004 W.O. 3344-B-SC Mr. Ed Hendrix 470 Chinquapin Avenue Carlsbad, California 92008 Subject: Final Compaction Report of Grading, 470 Chinquapin Avenue. City of Carlsbad, San Diego County, California Dear Mr, Hendrix: This report presents a summary of the geotechnical testing and observation services provided by GeoSoils, Inc. (GSI) during the rough earthwork phase of development for the new construction at the subject site. Earthwork commenced March 9, 2004, and was generally completed on March 10, 2004. Sun/ey of line and grade and locating of the building footprint was performed by others, and not performed by GSI. The purpose of grading was to prepare a relatively level pad for the construction of a single-family residence. Based on the observation and testing services provided by GSI, it is our opinion that the footprint ofthe proposed building appears suitable for its intended use. ENGINEERING GEOLOfiV The geologic conditions exposed during grading were regularly observed by a representative from our firm. The geologic conditions encountered generally were as anticipated and presented In the referenced report (GSI, 2002b). GEOTECHNICAL ENGINEERING Preparation of Existing Ground 1. Prior to grading, the major surficial vegetation was stripped and hauled offsite. 2. Removals consisted of topsoil/colluvium and near-surface weathered terrace deposits within the bulldlng pad area. Removals were performed to a minimum of ±5 feet outside the building footprint. Removals depths were on the order of ± 1 to ±3 feet below pre-construction grades. Once removals were completed, the exposed bottom was reprocessed, moisture conditioned, and recompacted prior to fill placement. The actual location of the proposed footprint of the building was provided by others. Overexcavation Portions of the bullding pad area were overexcavated In order to maintain a minimum 3-foot thick fill blanket across the lot. Overexcavation was completed to at least ±5 feet outside for the building footprint. The actual location of the proposed footprint of the building was provided by others. Fill Placement Fill, consisting of native soils, was placed in 6- to 8-inch lifts, watered, and mixed to achieve at least optimum moisture content. The fill was then compacted to 90 percent of the laboratory standard via mechanical means. The approximate limits of fill, placed under the purview of this report, are indicated on Plate 1. FIELD TESTING 1. Field density tests were performed using nuclear densometer (ASTM Test Methods D-2922 and D-3017). and sand cone (ASTM Test Method ASTM D-1556). The test results taken during grading are presented in the attached Table 1, and the locations of the tests taken during grading are presented on Plate 1. 2. Field density tests were taken at periodic intervals and random locations to check the compactive effort provided by the contractor. Based upon the grading operations observed, the test results presented herein are considered representative ofthe compacted fill. 3. Visual classification of the soils in the field was the basis for determining which maximum density value to use for a given density test. LABORATORY TESTINfi Maximum Densitv Testinq The laboratory maximum dry density and optimum moisture content for the major soil type within this construction phase were determined according to test method ASTM D-1557 The following table presents the results: Mr. Ed Hendrix * WO 3344-A-SC 270 Chinquapin Avenue, Carlsbad I^a^ch 22 2004 File:e:\wp9\3200\3288.3b.fcr p'^g^ ^ GeoSotUf Inc. SOIL TYPE MAXIMUM DENSITY (PCF) MOISTURE CONTENT (PERCENT) A - Reddish Brown. SILTY SAND 133.5 9.5 Expansion Index Expansive soil conditions have been evaluated forthe site. A representative sample ofthe soils near pad grade was recovered for expansion index testing. Expansion Index (E.l.) testing was performed in general accordance with Standard 18-2 ofthe Uniform Building Code ([UBC], International Conference of Building Officials [ICBO], 1997). The test results indicate an E.l. of less than 5, and the corresponding expansion classification of very low. Corrosion/Suifate Typical samples ofthe site materials were analyzed for corrosion/soluble sulfate potential. The testing included determination of pH, soluble sulfates, and saturated resistivity. At the time of this report the results were not available. An addendum to this report will be Issued when the testing is complete. CONCLUSIONS AND RECOMMENDATIONS Unless superseded by recommendations presented herein, the conclusions and recommendations contained In (GSI; 2003. 2002a, and 2002b) remain valid and applicable, and should be properly implemented. FOUNDATION RECOMMENDATIONS General In the event that the information concerning the proposed development concept Is not correct, or any changes in the design, location, or loading conditions of the proposed structure are made, the conclusions and recommendations contained In this report shall not be considered valid unless the changes are reviewed and conclusions ofthis report are modified or approved in writing by this office. Laboratory testing of soils exposed at finish grade indicates that the proposed foundation system will be founded into very low expansive compacted fill. The information and recommendations presented in this section are not meant to supersede design by the project structural engineer. Upon request. GSI could provide additional input/consultation regarding soil parameters, as related to foundation design. Mr. Ed Hendrix VV.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 File:e:\wp9\3200\3288.3b.fcr Pagg 3 OeoSotUf Inc. Foundation Desiqn 1. Conventional spread and continuous footings may be used to support the proposed residential structures provided they are founded entirely into compacted fill. Footings should not simultaneously bear directly on formational material and fiil soils. 2. Analyses Indicate that an allowable bearing value of 1,500 pounds per square foot (psf) may be used for design of continuous footings 12 inches deep by 12 Inches wide, and design of isolated pad footings 24 inches square and 18 inches deep. This value may be increased by 20 percent for each additionai 12 inches in depth, to a maximum of 2,500 psf. The bearing value may be increased by one-third for seismic or other temporary loads. 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. 4. Passive earth pressure may be computed as an equivalent fluid having a density of 250 pounds per cubic foot (pcf) with a maximum earth pressure of 2,500 psf. 5. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 6. 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. The horizontal setback should not be less than 7 feet, nor need not be greaterthan 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 utilities setbacks should be constructed in accordance with distances Indicated in this section, and/or the approved plans. Foundation Settlement Foundation systems should be designed to accommodate differential settlement ofat least ^4 inch in a 40-foot span. Foundation Construction The following preliminary foundation construction recommendations are presented as a minimum criteria from a soils engineering standpoint. The onsite soil expansion potential, of soils exposed at finish grade, is generally very low (E.l. 0 to 20). Foundatiori construction recommendations for very low expansive soil conditions are presented herein. Mr. Ed Hendrix VV.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 R[a:e:\wp9\3200\3288.3b.fcr Page 4 GeoSoils, Inc. Recommendations by the project's design-structural engineer or architect, which may exceed the soils engineer's recommendations, should take precedence over the following minimum requirements. Very Low Expansion Potential (E.l. 0 to 20) 1. Conventional continuous footings may be constructed per UBC guidelines regarding width for very low expansive soil conditions. Footings should be embedded at least 12 inches for one-story floor loads or 18 inches for two-story floor loads into compacted fill. Footings should be reinforced with two No. 4 reinforcing bars, one placed near the top and one placed near the bottom of the footing. 2. Detached Isolated exterior piers and columns are not recommended along the eastern portion ofthe building pad. However, if required, detached isolated exterior piers and columns should be founded at least 18 inches Into compacted fill, and tied to the main foundation in at least two directions with a grade beam. Detached isolated exterior piers and columns, if any, located on the northern, western, and southern portions of the building pad should be embedded 18 inches into compacted fill and be tied to the main foundation in at least one direction. Reinforcement should be properly designed by the project structural engineer. 3. A grade beam, reinforced as above and at least 12 inches square, should be provided across the garage entrances (if any). The base of the reinforced grade beam should be at the same elevation as base of the adjoining footings. 4. Concrete slabs, where moisture condensation is undesirable, should be underiain with a vapor barrier consisting of a minimum of 10 mil polyvinyl chloride, or equivalent membrane, with all laps sealed. This membrane should be covered above with a minimum of 2 inches of sand to aid in uniform curing of the concrete, and to protect the membrane from puncture. 5. Concrete floor slabs should have a minimum thickness of at least 4 inches. Slabs should be reinforced with No. 3 reinforcing bars placed 18 inches on center each way. All slab reinforcement should be supported to ensure proper mid-slab height positioning during placement ofthe concrete. "Hooking" of reinforcement is not an acceptable method of positioning. Concrete used in floor slab construction should have a minimum compressive strength of 2,500 psi. 6. The moisture content of the subgrade soils should be equal to, or slightly greater than, optimum moisture to a depth of 12 inches below the adjacent ground grade in the slab areas for very low expansive soil conditions. Verification of slab subgrade presaturation is not a geotechnical requirement, but should be considered. Mr. Ed Hendrix W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 File:e:\wp9\3200\3288.3b.fcr Page 5 GeoSoils, Inc. WALL DESIGN PARAMETERS Conventional Retaining Walls The design parameters provided below assume that either non expansive soiis (Class 2 permeable filter material or Class 3 aggregate base) or native materials (up to and including an E.l. of 65) are used to backfill any retaining walls. The type of backfill (i.e., select or native), should be specified by the wall designer, and cleariy shown on the pians. Building walls, below grade, should be water-proofed or damp-proofed, depending on the degree of moisture protection desired. The foundation system forthe proposed retaining walls should be designed in accordance with the recommendations presented in this and preceding sections of this report, as appropriate. Footings should be embedded a minimum of 18 inches below adjacent grade (excluding landscape layer, 6 inches) and should be 24 inches in width. There should be no increase in bearing for footing width. Recommendations for specialty walls (i.e., crib, earthstone. geogrid, etc.) can be provided upon request, and would be based on site specific conditions. Restrained Waiis Any retaining walls that will be restrained priorto placing and compacting backfill material or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressure (EFP) of 65 pounds per cubic foot (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. Cantilevered Walls The recommendations presented below are for cantilevered retaining walls up to 10 feet high. Design parameters for walls less than 3 feet in height may be superseded by City and/or County standard design. Active earth pressure may be used for retaining wall design, provided the top ofthe wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are given below for specific slope gradients of the retained material. These do not include other superimposed loading conditions due to traffic, structures, seismic events or adverse geologic conditions. When wall conflguratlons are finalized, the appropriate loading conditions for superimposed loads can be provided upon request. Mr. Ed Hendrix W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 File:e:\wp9\3200\3288.3b.fcr Page 6 GeoSoils, Inc. SURFACE SLOPE OF RETAINED MATERIAL (HORIZONTAUVERTICAL) EQUIVALENT FLUID WEIGHT P.C.F. (SELECT BACKFILL) EQUIVALENT FLUID WEIGHT P.C.F. (NATIVE BACKFILL) Level* 2 to 1 35 50 45 60 * Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall. Retaining Wail Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1.2, and 3, present the back drainage options discussed beiow. Backdrains should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or Vz-inch to y4-inch gravel wrapped in approved filter fabric (Mirafi 140 or equivalent). For low expansive backflll, the filter material should extend a minimum of 1 horizontal foot behind the base ofthe walls and upward at least 1 foot. For native backfill that has up to medium expansion potential, continuous Class 2 permeable drain materials should be used behind the wall. This material should be continuous (i.e., full height) behind the wall, and It should be constructed in accordance with the enclosed Detail 1 (Typical Retaining Wall Backfill and Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall may be constructed in accordance with Detail 2 (Retaining Wall Backfill and Subdrain Detail Geotextile Drain). Materials with an E.l. potential of greater than 65 should not be used as backfill for retaining walls. For more onerous expansive situations, backflll and drainage behind the retaining wall should conform with Detail 3 (Retaining Wall And Subdrain Detaii Clean Sand Backfill). Outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than ± 100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes in walls higher than 2 feet should not be considered. The surface ofthe backfill should be sealed by pavement or the top 18 inches compacted with native soil (E.l. ^90). Proper surface drainage should also be provided. For additional mitigation, consideration should be given to applying a water-proof membrane to the back of all retaining structures. The use of a waterstop should be considered for all concrete and masonry joints. Wail/Retaining Wail Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Should wall footings transition from cut to fill, the civil designer may specify either: Mr. Ed Hendrix 270 Chinquapin Avenue. Carlsbad File: e:\wp9\3200\3288.3b.fcr W.O. 3344-A-SC March 22, 2004 Page 7 GeoSoils, Inc. DETAILS N.T.S. Provide Surface Drainage +12" (Dwaterproofing Membrane (optional) (D Weep Hole Finished Suri'ace Native Backfill CD Rock Native Backfill ® Pipe 1 or Flatter (D WATERPROOFING MEMBRANE (optional): Liquid boot or approved equivalent. <2) ROCK: 3/4 to 1-1/2" (inches) rock. ® FILTER FABRIC: Mirafi 140N or approved equivalent; place fabric flap behind core. ® PIPE: 4" (inches) diameter perforated PVC. schedule 40 or approved altemative with minimum of 1% gradient to proper outlet point. ® WEEP HOLE: Minimum 2" (Inches) diameter placed at 20' (feet) on centers along the wall, and 3" (inches) above finished surface. (No weep holes for basement walls.) TYPICAL RETAINING WALL BACKFILL AND DRAINAGE DETAIL DETAIL 1 Geotechnical • Geologic • Environmentai DETAILS N.T.S. Provide Surface Drainage ©Waterproofing Membrane (optional) ® Weep Hole Finished Surface 1 or Flatter 0 WATERPROOFING MEMBRANE (optional): Liquid boot or approved equivalent. (3) DRAIN: Miradrain 6000 or J-drain 200 or equivalent for non-waterproofed walls. Miradrain 6200 or 3-drain 200 or equivalent for waterproofed walls. ® FILTER FABRIC: ® PIPE: Mirafi 140N or approved equivalent; place fabric flap behind care. 4" (inches) diameter perforated PVC. schedule 40 or approved alternative with minimum of 1% gradient to proper outlet point. ® WEEP HOLE: Minimum 2" (inches) diameter placed at 20' (feet) on centers along the wall, and 3" (inches) above finished surface. (No weep holes for basement walls.) RETAINING WALL BACKFILL AND SUBDRAIN DETAIL GEOTEXTILE DRAIN DETAIL 2 Geotechnical • Geologic • Environmental DETAILS N.T.S. Provide Surface Drainage Clean Sand Backfill CD WATERPROOFING MEMBRANE (optional): Uquid boot or approved equivalent. ® CLEAN SAND BACKFILL: Must have sand dequivalent value of 30 or greater; can be densified by water jetting. CD FILTER FABRIC: Mirafi 140N or approved equivalent. ® ROCK: 1 cubic foot per linear feet of pipe or 3/4 to 1-1/2" (inches) rock. CD PIPE: 4" (Inches) diameter perforated PVC. schedule 40 or approved alternative with minimum of 1% gradient to proper outlet point. ® WEEP HOLE: Minimum 2" (inches) diameter placed at 20' (feet) on centers along the wall, and 3" (inches) above finished surface. (No weep holes for basement walls.) RETAINING WALL AND SUBDRAIN DETAIL CLEAN SAND BACKFILL DETAIL 3 Geotechnicai • Geologic • Environmentai a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 2H, from the point of transition. b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1 /360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints shouid be sealed with a flexible, non-shrink grout. c) Embed the footings entirely into native formational material (i.e., deepened footings). If transitions from cut to fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation "a" (above) and until such transition is between 45 and 90 degrees to the wall alignment. DRIVEWAY, FLATWORK, AND OTHER IMPROVEMENTS The soil materials on site may be expansive. The effects of expansive soils are cumulative, and typically occur over the lifetime of any improvements. On relatively level areas, when the soils are allowed to dry, the dessication and swelling process tends to cause heaving and distress to flatwork and other improvements. The resulting potential for distress to improvements may be reduced, but not totally eliminated. To that end, it is recommended that the developer should notify any homeowners or homeowners association of this long-term potential for distress. To reduce the likelihood of distress, the following recommendations are presented for all exterior flatwork: 1. The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction, and then be presoaked to 2 to 3 percentage points above (or 125 percent of) the soils' optimum moisture content, to a depth of 18 inches below subgrade elevation. If very low expansive soils are present, only optimum moisture content, or greater, is required and specific presoaking is not warranted. The moisture content ofthe subgrade should be verified within 72 hours pnor to pouring concrete. 2. Concrete slabs should be cast over a non-yielding surface, consisting of a 4-inch layer of crushed rock, gravel, or clean sand, that should be compacted and level priorto pouring concrete. If very low expansive soils are present, the rock or gravel or sand may be deleted. The layer or subgrade should be wet-down completely prior to pouring concrete, to minimize loss of concrete moisture to the surrounding earth materials. 3. Exterior slabs should be a minimum of 4 inches thick. Driveway slabs and approaches should additionally have a thickened edge (12 inches) adjacent to all landscape areas, to help impede infiltration of landscape water underthe slab. Mr. Ed Hendrix W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 File:e:\wp9\3200\3288.3b.fcr Rage 11 GcoSoilSy Inc. 4. The use of transverse and longitudinal control joints are recommended to help control slab cracking due to concrete shrinkage or expansion. Two ways to mitigate such cracking are: a) add a sufficient amount of reinforcing steel, increasing tensile strength of the slab; and, b) provide an adequate amount of control and/or expansion joints to accommodate anticipated concrete shrinkage and expansion. In order to reduce the potential for unsightly cracks, slabs shouid be reinforced at mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each direction. If very low expansive materials are present at finish grade, the reinforcement may consist of 6x6-W1.4xW1.4 welded-wire mesh. The exterior slabs should be scored or saw cut, to % inches deep, often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or narrow slabs, control joints should be provided at inten/als of every 6 feet. The slabs should be separated from the foundations and sidewalks with expansion joint filler material. 5. No traffic should be allowed upon the newly poured concrete slabs until they have been properly cured to within 75 percent of design strength. Concrete compression strength should be a minimum of 2,500 psi. 6. Driveways, sidewalks, and patio slabs adjacent to the house should be separated ft-om the house with thick expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., Irrigafion, planters, etc.), all joints should be additionally sealed with flexible mastic. 7. Planters and walls should not be tied to the house. 8. Overhang structures should be supported on the slabs, or structurally designed with continuous footings tied in at least two directions. If very low expansion soils are present, footings need only be tied in one direction. 9. Any masonry landscape walls that are to be constructed throughout the property should be grouted and articulated in segments no more than 20 feet long. These segments should be keyed or doweled together. 10. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible connections to accommodate differential settlement and expansive soil condifions. 11. Positive site drainage should be maintained at all times. Rnish grade on the lots should provide a minimum of 1 to 2 percent fall to the street, as indicated herein, it should be kept in mind that drainage reversals could occur, including post- construction settlement, if relafively flat yard drainage gradients are not periodically maintained by the homeowner or homeowners association. Mr. Ed Hendrix WO 3344-A-SC 270 Chinquapin Avenue, Carlsbad \AQSZ\\ 22 2004 File:e:\wp9\3200\3288.3b.fcr p^gg GeoSoils, Inc. 12. Air conditioning (A/C) units should be supported by slabs that are Incorporated into the buliding foundation or constructed on a rigid slab with fiexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. 13. Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. DEVELOPMENT CRITERIA 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 would recommend that any proposed open-bottom planters adjacent to proposed structures be eliminated for a minimum distance of 10 feet. As an alternative, closed- bottom type planters could be utilized. An outlet placed in the bottom ofthe planter, could be installed to direct drainage away from structures or any exterior concrete flatwork. If planters are constructed adjacent to structures, the sides and bottom ofthe 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 fi'om 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 the type of vegetation chosen and their potenfial effect upon surface improvements (i.e., 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. Ifthe surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Gutters and Downspouts As previously discussed in the drainage section, the installafion of gutters and downspouts should be considered to collect roof water that may othenwise infiltrate the soils adjacent to the structures. If utilized, the downspouts should be drained into PVC collector pipes or non-erosive devices that will carry the water away ft-om the house. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, provided that posifive drainage is incorporated Into project design (as discussed previously). Mr Ed Hendrix W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22 2004 File:e:\wp9\3200\3288.3b.fcr pggg ^3 GcoSoilSy Inc. Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided that 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 construcfion 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(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors. Site improvements Recommendations for exterior concrete flatwork design and construction can be provided upon request. If in the ftjture, any additional improvements (e.g., pools, spas, etc.) are planned forthe 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. Tiie 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. Therefore, the designer should consider additional steel reinforcement for concrete slabs-on-grade where tile will be placed. The tile installer should consider installation methods that reduce possible cracking of the tile such as slipsheets. Slipsheets or a vinyl crack isolation membrane (approved by the Tile Council of America/Ceramic Tile Institute) are recommended between tile and concrete slabs on grade. Additional Gradina 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. Footina Trench Excavation All footing excavations should be obsen/ed by a representative of this firm subsequent to trenching and prior to concrete form and reinforcement placement. The purpose ofthe Mr. Ed Hendrix ' ' W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 File:e:\wp9\3200\3288.3b.fcr Page 14 GeoSoils, Inc. 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 ofthe 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. Trenching Considering the nature ofthe 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. 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 ofthe laboratory standard. As an alternative for shallow (12-inch to 18-inch) under-slab trenches, sand having a sand equivalent vaiue of 30 or greater may be utilized and jetted or flooded into place. Obsen/ation, probing and testing should be provided to verify the desired results. 2. Exterior trenches adjacent to. and within areas extending below a 1:1 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. 3. All trench excavations should conform to CAL-OSHA and local safety codes. 4. 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. Mr. Ed Hendrix W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 Rle:e:\wp9\3200\3288.3b.fcr Page 15 GeoSoils, Inc. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNiCAL OBSERVATION AND TESTING We recommend that obsen/ation and/or testing be performed by GSI at each of the following construction stages: • During grading/recertification. • During significant excavation (i.e., higher than 4 feet). • During placement of subdrains. toe drains, or other subdrainage devices, prior to placing fill and/or backfill. • After excavation of buiiding footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. • 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, priorto backfill placement. During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wail backfill. During slope construction/repair. When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance ofthis report. When any developer or homeowner improvements, such as flatwork, spas, pools, walls, etc., are constructed. A report of geotechnical obsen/ation 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., shouid review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit Mr. Ed Hendrix ~ W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 Rle:e:\wp9\3200\3288.3b.fcr Page 16 GeoSoils, Inc. reference, make this report part of their project plans. In order to mitigate potential distress, the foundation and/or improvement's designer should confirm to GSI and the governing agency, In writing, that the proposed foundations and/or improvements can tolerate the amount of differential settlement and/or expansion characteristics and design criteria specified herein. PLAN REVIEW Final project plans should be reviewed by this office prior to construction, so that construction is in accordance with the conclusions and recommendations ofthis report. Based on our review, supplemental recommendations and/or further geotechnical studies may be warranted. UMITATIONS 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. 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. REGULATORY COMPLIANCE Processing of original/existing ground and placement of compacted fills underthe purview ofthis report have been completed under the obsen/afion of, and with selective testing provided by, representatives of GSI and are found to be in general compliance with the requirements of the City. Our findings were made in conformance with generally accepted professional engineering practices, and no ftjrther warranty is implied or made. GSI assumes no responsibility or liability for work, testing, or recommendations performed or provided by others. This report is subject to review by the controlling authorities for this project. Mr. Ed Hendrix W.O. 3344-A-SC 270 Chinquapin Avenue, Carlsbad March 22, 2004 File:e:\wp9\3200\3288.3b.fcr Page 17 GeoSoils, Inc. We appreciate this opportunity to be of service. If you have any questions, please call us at (760) 438-3155. Respectfully submitted, GeoSoils, Inc. Bryan*^^oss Staff Geologist Reviewed by: ohn P. Franklin N>^^r^M r 'Engineering Geologist, CES454(' RB/JPF/DWS/jk Attachments: Distribution: David W. Skelly Civil Engineer, RCE 4 857 Table 1 - Field Density Test Results Appendix - References Plate 1 - Field Density Test Location Map (4) Addressee Mr. Ed Hendrix 270 Chinquapin Avenue, Carlsbad File:e;\wp9\3200\3288.3b.tcr GeoSoils, Inc. W.O. 3344-A-SC March 22. 2004 Page 18 APPENDIX REFERENCES GeoSoils, Inc., 2003. Geotechnical plan review. 470 Chinquapin Avenue, City of Carlsbad, San Diego County, California, W.O. 3344-A-SC, dated September 15. , 2002a, Soil corrosivity test results, 470 Chinquapin Avenue, City of Carlsbad, San Diego County, California, W.O. 3344-A-SC, dated August 8. , 2002b, Preliminary geotechnical evaluation, 470 Chinquapin Avenue, City of Carlsbad, San Diego County, California, W.O. 3344-A-SC, dated July 29. International Conference of Building Officials, 1997. Uniform building code: Whittier, California, vol. 1,2. and 3. GeoSoils, Inc.