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Home My WebLink AboutGeotechFineGrading(Aug.30,2000) I I I I I I I I I I I I I I I I I I I ~UI-- ~ === - -:: A GTG Company Leighton and Associates GEOTECHNICAL CONSULTANTS Fine Grading Geotechnical Report, ParkIPool Site, Recreation Center, Lot 7, Tract 23 IO 1-6, Temecula, California Dated August 3D, 2000 Project # 11871347-031 Lennar Homes 24800 Chrisanta Drive, Suite 200 Mission Viejo, California 92691 41715 Enterprise Circle N. Suite 103, Temecula, CA 92590-5661 (909) 296-0530 . FAX (909) 296-0534 . www.lelghlongeo.com \ I I I I I I I I I I I I I I I I I I I ---0' ~ - ~ -- - n-':::; ~ ~ A GTG Company Leighton and Associates GEOTECHNICAL CONSULTANTS August 30, 2000 Project No. 11871347-031 To: Lennar Homes 24800 Chrisanta Drive, Suite 200 Mission Viejo, California 92691 Attention: Mr. Greg Dooley Subject: Fine Grading Geotechnical Report, ParkIPool Site, Recreation Center, Lot 37, Tract 23101- 6, Temecula, California Per your request, Leighton and Associates, Inc. (Leighton) has prepared this fme grading report for the subject site recreation center, Lot 37, Tract 23IOI-6 in Temecula, California. The subject lot was fine graded in general accordance with the recommendations of the referenced reports (Leighton, 1998 and 2000) and our field recommendations. The subject site was rough graded under the geotechnicallesting and observation of Leighton and was found to be suitable for further development (Leighton, 2000). The cut and fills performed during the fine grading operations were on the order of I-foot and were performed between July 26, 2000 and August 7, 2000. The subject lot, where tested, was compacted to a minimum of 90 percent relative compaction of ASTM D1557. Utility trench backfill was tested as necessary for the sewer and storm drain renches that crossed the subject lot. In addition, footing excavations were observed and inspected from a geotechnical perspective during this phase of construction. The subject lot has been graded and is acceptable for further development/construction from a geotechnical viewpoint. The results of our laboratory testing of the near surface finish grade soils are presented in Appendix B attached herewith (expansion index per UBC 18A-I-B, soluble sulfates per UBC Table 19-A-4). The results of our testing indicate the subject lot is underlain by soils that exhibit a very low expansion potential and are negligible in soluble sulfate attack. The proposed foundation and slab systems for the subject lot is conventional type and should be designed in accordance with Section 1815 ofthe UBC and Table 1 for very low expansive soils. The presoaking requirement for the subject lot is a near optimum moisture content to a depth of 6 inches. The lateral resistances, earth pressures, and friction resistance for lateral sliding can be found in the Leighton report: "As-Graded Report of Rough Grading", dated March 14,2000 in section 5.3, as well as the footing setback schedule in section 5.2.3 of the same report. Retaining wall recommendations can be found in section 5.3 in the March 14,2000 report. 41715.Enterprise Circle N. Suite 103, Temecula, CA 92590-5661 (909) 296-0530 . FAX (909) 296-0534 . www.lelghlongeo.com 1,- I I I I I I I I I I I I I I I I I I I 11871347-031 Please note that UBC Chapter 18 is based on certain climatological assumptions with regard to soil-moisture conditions around and beneath the slabs. Soil-moisture change below slabs is the major factor in expansive soil problems. The UBC design method does not contain specific provisions to account for the effects of irrigation, presatnration, or other non-climate-related influences on the moisture content of subgrade soils. In recognition that this method does not take into account such things as planters adjacent to structures, or the influence of landscape watering, we have adjusted our geotechnical design parameters to account for resPOnsible association maintained improvements. Such improvements include properly designed planters and lawn areas. In utilizing these parameters the foundation engineer should design the foundation system to the acceptable deflection criteria detennined by the structnra1 engineer or architect. In our experience, rigid architectural finishes or construction design that utilizes rigid roof trusses will ouly tolerate minima1 deflections. We also recommend that soil moisture around the immediate perimeter of the slab be maintained near optimum-moisture content (or above) during and after construction until landscaping irrigation is started. Future owners of these improvements should be informed and educated. regarding the importance of maintaining a constant level of soil moisture. . The association should be made aware of the potential negative consequences of both excessive watering, as well as allowing expansive soils to become too dry (i.e., the soil will undergo shrinkage as it dries, followed by swelling during the winter, rainy season or when irrigation is resumed, potentially resulting in distress to improvements and structures). Planters should not be located adjacent to foundations unless they are properly designed, and the association should be made aware of the possible problems associated with planters adjacent to foundations as noted in this letter. Our recommendations assume a reasonable degree of association responsibility, if the association does not adequately maintain correct irrigation and drainage, some degree of foundation movement should be expected. However, this movement typically does not cause structural damage, but will cause such things as stucco cracking and dry wall separation. Maintenance guidelines for this park and pool site should be provided by the developer. Future moisture sensitive interior slabs should be underlain by aiD-mil Visqueen moisture barrier (or equivalent) covered by a 2-inch layer of sand (SE of 30 or greater) above the Visqueen and an additional 2-inch layer below the Visqueen for total sand thickness of 4 inches. Visqueen membrane should be placed with all laps/openings sealed. Visqueen protected areas should be separated from areas not similarly protected. This separation could be provided with a concrete cut-off wall extending at least 18 inches into subgrade soil, below the sand layer. Due to the nature of site soils, the sand above the Visqueen or in direct contact with foundations, should be imported neutral sand (SE > 30). Concrete in contact with onsite soil should be designed in accordance with Table 19-A-4 of Uniform Building Code (UBC, 1997) for soils with moderate sulfate concentrations. The project structural engineer should consider the use of transverse and longitudinal control joints to help control slab cracking due to concrete shrinkage or expansion. -2- -01 ;::; ~ -- ~ ~=:. -...:!' .;:? I I I I I I I I I I I I I I I I I I I Geotechnical Review - Construction 11871347-031 Observation and testing should continue to be performed by Leighton and Associates representatives during the remaining construction at this site. Substrata exposed during construction may vary from that encountered in the lest borings or trenches. Reasonably continuous construction observation and review during foundation installation allows for continued evaluation of the exposed soil conditions and the ability to provide appropriate revisions if required during construction. If you have any questions regarding this letter, please do not hesitate to contact this office. We appreciate this opportunity to be of service. Respectfully submitted, Attachment: Appendix A - References Appendix B - Testing Procedures and Test Results In Pocket - Density Test Location Map Distribution: (2) Addressee (4) Lightfoot Planning, Attention: Phil Armstrong - 3 - Q:R46, Senior Staff Engineer -iii =:::::: - ~ -- =- -=--=.= L ~ --~ I I I I I I I I I I I I I I I I I I I 11871347-031 Appendix A References Leighton and Associates, Inc., 1998a, Geotechnical Review of Site Conditions and Update of Geotechnical Report, Tract 23101-5 (Lots 1-27) and Tract 23101-6 (Lots 1-37), Chardonnay Hills, City of Temecula, California, Project No. 11871347-028, dated August 27, 1998. , 2000, As-Graded Report of Rough Grading, Chardonnay Hills, Tracts 23101-5 and 23101-6, Temecula, Riverside County, California, Project No. 11871347-031, dated March 14, 2000. ~UI::-- ~ -- -.: ~.::: ~ ~ ---..I I I I .11871347-031 Appendix B Laboratorv Testing Procedures and Test Results I I I Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, ASTM D4829. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared I-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The soluble sulfate contents of selected samples were detenuined by standard geochemical methods (CTM 417). The results ofthese tests are presented in the table below: I I I I I I I I I I I I I Representative Sample Soil Sulfate Expansion Expansion Content Sulfate Tract No. Lots Location Type Attack Index Potential (ppm) 23101-6 37 37 Brown Clayey SAND <150 Negligible 18 Very Low Maximum Densitv Tests: The maximum dry density and optimum moisture content of typical materials were detenuined in accordance with ASTM Test Method D 1557. The results of these tests are presented in the table below: Maximum Optimum Sample Sample Description Dry Density Moisture Content Number (pct) (%) 4 Medium brown silty sand 131.0 9.0 Cp I I I I I I I I I I I I I I I I I I I 11871347-031 " Exvlanation of Sununarv ofField Density Tests I Test No. I I Test or II Test No. I I Test of I Prefix Test or Abbreviations Prefix Test of Abbreviations , (none) GRADING Natural Ground NG (SG) SUBGRADE Original Ground OG (AB) AGGREGATE BASE Existing Fill EF (CB) PROCESSED BASE Compacted Fill CF (PB) ASPHALT CONCRETE Slope Face SF (AC) Finish Grade FG (S) SEWER Cwb C (sq) STORM DRAIN Gutter G (AD) AREA DRAIN Curb and Gutter CG (W) DOMESTIC WATER Cross Gutter XG (RC) RECLAIMED WATER Street ST (SB) SUBDRAlN Sidewalk. SW (G) GAS Driveway D (E) ELECTRICAL Driveway Approach DA (I) TELEPHONE Parking Lot PL (1) JOINT UTIUfY Electric Box Pad EB (I) IRRIGATION Bedding Material B Shading Sand S Main Backfill M Lateral Backfill L Crossing X Manhole MH Hydrant Lateral HL Catch Basin CB Riser R Invert I Check Valve CV MeterBo" MB Junction Box JB (RW) RETAINING WALL (P) PRESATURATION (CW) CRIB WALL (LW) LOFFELL WALL Moisture Content M (SF) STRUCT FOOTING Footing Bottom F (IT) INTERIOR TRENCH Backfill B Wall Cell C Plumbing P Electrical E N represents nuclear gauge tests that were perfonned in general accordance with most recent version of ASTM Test Methods D2922 and mOt? 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