Appendix E - Geology and Soils Geotechnical Supporting Information COMBINED

Shea Homes 1080-6B, Lester Property Residential Development Bedrock: Sandstone -Gray, highly weathered, friable, fi n e lO medium sand TP-17 0-2 Colluvium: Silty Clay (CL -CH) -Brown, dry, trace rootlets 2-4 Colluvium: Silty Clay (CL-CH) -Dark h rown , moist, trace sand , trace weathered sandstone 4-8½ Bedrock: Sandstone -Mottled hrown, reddish-brown and gray , highly to completely weathered, very friable , highly fractured , less weathe ring with depth TP-18 O-Y2 Colluvium: Silty Clay (CL-CH) -Brown, moist, trace sand, trace weathered hedrock ½-3 Bedrock: Sandstone -Brown and reddish-brown, slightly to moderately weathered, strong, fractured , interbe dded s ilt stone TP-19 0-1½ Colluvium: Silty Clay (CL-CH) -Brown, moist, trace s and, tra ce weathered bedrock 1 ½-3 Bedrock: Sandstone -Brown a nd reddish-brown, s li ghtl y to moderately weathered , strong, fractured, interheddecl siltstone Seismic Refraction Survey: O ur seismic refraction survey was performed on October 18, 1997 to determine the rippabiliry of the existing bedrock. Four seismic lines ranging from 165 to 220 feet long were performed across the northeast portion of the s it e , as sh own on the Site Plan, Figure 2. A seismic re fr acti o n survey is performed by introducing an energy sou rce at one loca ti o n , known as a shot point, a nd measuring the a rri val time o f the waves through e qually-spaced intervals using geophones . O ur seis mi c lines con sis ted of 12 geophones spaced at 2~-foot intervals on Lin es 1, 2, and 3 and at 15-foot inte rval s on Line 4. The energy source con s is te d of a sledge h ammer striking a m e tal plate u sed to create compressio n waves (P-waves). Sign a ls were recorded fr om various shotpoints along each line using a 12-channel Geometrics SmartSe is S-12 Seismograph. The p late was s tru ck repeatedly at each s h o t point and the resu lts were stacked in order to improve the signal-to-noise ra ti o o f the re cord s. Th e seismograph recordings were then u sed to determine the arrival time of the P-wave fr o m each s h ot p oin t to each geoph o ne. The waves would either travel along the surface or be refracted fr o m an inte rfa ce between materials. A refraction would occur if the materials below the interface have a g reater P-wave velocity th an the material above the inte rfa ce. The arrivals times were then inputted into a computer program wi th LOllVNEY~IATES Environmental/ Geotechnical / Enginee ring Services ----------------------Pa ge A -4