09 ATTACHMENTS - Laserfiche WebLink

C CORNERSTONE EARTH GROUP slope would likely be adequate if the slope were graded to a consistent 2:1 slope inclination. This would eliminate over-steepened portions of the slope and reportedly increase long-term slope instability. Their conclusion regarding the stability of the southwestern slope was based on data contained in two other reports (Miller Pacific, 2004 and Treadwell & Rollo, 2007). In addition, a geotechnical investigation was performed by TRC (formerly Lowney Associates) for the adjacent Ironwood residential development and summarized in a report dated June 11, 2002. The results contained in this report were used to develop grading, foundation and pavement recommendations for the recently completed Ironwood development. 1.2 SCOPE OF SERVICES Our scope of services was presented in our proposal dated December 20, 2007, and consisted of field and laboratory programs to evaluate physical and engineering properties of the subsurface soils, engineering analysis to prepare recommendations for site work and grading, building foundations, flatwork, retaining walls, and pavements, and preparation of this report. Brief descriptions of our exploration and laboratory programs are presented below. 1.3 EXPLORATION PROGRAM Field exploration consisted of six borings drilled on December 19, 2007, with truck-mounted hollow-stem auger drilling equipment. The borings were drilled to depths of approximately 20 to (" 40 feet. The approximate locations of the boring drills for this investigation, as well as those \. drilled for previous investigation, are shown on the Site Plan, Figure 2. The borings were backfilled with in accordance with local requirements; exploration permits were obtained as required by local jurisdictions. Details regarding our field program are included in Appendix A. 1.4 LABORATORY TESTING PROGRAM In addition to visual classification of samples, the laboratory program focused on obtaining data for foundation design and seismic ground deformation estimates. Testing included moisture contents (ASTM D2216), dry densities (ASTM D2937), grain size analyses (ASTM D 422), washed sieve analyses (ASTM D1140), Plasticity Index tests (ASTM D4318), percent collapse (ASTM D5333), and unconsolidated-undrained triaxial strength (ASTM DD2850) tests. Details regarding our laboratory program are included in Appendix B. 1.5 CORROSION EVALUATION Preliminary soil corrosion tests were also performed on six soil samples collected at depths ranging from 2'/z to 9 feet. These tests included pH (ASTM G51), sulfate (Caltrans 417), chloride (Caltrans 422), and resistivity at 100 percent saturation (ASTM G57). The results of these tests, as well as a brief discussion of the soil corrosion potential prepared by JDH Corrosion Consultants, are presented in Appendix C. Ponderosa Active Adult Community Page 2 132-2-1