Appendix E - Geology and Soils Geotechnical Supporting Information COMBINED

Shea Homes 1080-6B, Lester Property Residential Development e levation , locati o n , a nd layer control information to determine the average velociti es of each layer. The results o f the compute r analysis of the r efraction data indicate that we en countered three seismic layers beneath each line . The approximate depth co interface a nd range of P-wave velocities for each layer are summari zed in Tabl e A-2 helow. TABLE A -2. SUMMARY OF REFRACI10N REsULTS uiyer Approximate Depth Estimated uiyer Velocity Number to Interface (feet) (feet oer second) 1 5-10 1,300 -1 ,800 2 10-20 3 ,200 -4,200 3 > 20 6,900 - 8,900 According to the Caterpillar© Performance H a ndbook, bedrock with velocities less than 7,000 feet per second (fps) is considered rippable hy a Ca terpill a r D-9N tract o r with Sing le Shank No. 9 rippers. Sandstone, siltstone, and shale bedrock with velocities up to 8,500 fps is con sidered rippable with a Caterpillar D-lON t ractor w ith Single Sh ank No. 10 rippers. Once bedrock velocities begin approaching 9 ,000 to 10,000 fps, the bedrock would be marginally to non-rippable h y the above m entioned equipm e nt. The anached test pit s ummary, seismic re fraction data , and related information d epict s ubs urfa ce conditions only at the locations indicated a nd at the particular date designated above. Subsurface conditions at oth e r locati ons may differ from conditions occurring a t these test pit locati ons. The passage of time may res ult in altered su bsurface conditio ns due to environmental chan ges. In addition, a ny stratifi cation lines in the table represent the approximate boundary between soil types and the tra n s iti on may be gradua l. * * * * LOWNEY~IAlES Environmental/ Geotechmcal / Engineering Services ---------------------Page A -5