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deep in July 1986. The borings were logged according to the Unified Soil Classi- <br />fication System (USCS). The locations of all borings are shown on Figure 3. <br />Soils encountered in the borings between the ground surface (approximately <br />120 feet MSL) and 100 feet generally consist of medium dense silty sands (SM) <br />and clayey sands (SC) with occasional medium stiff sandy silt (ML) and sandy <br />clay (CL) interbeds. The Standard Penetration Test (SPT) blow counts are 19 to <br />68 with an average of 40. Below 100 feet (approximately 20 feet MSL), the soils <br />generally consist of medium dense to dense, poorly graded sand (SP), and grav- <br />elly sand (SP -GP) with average SPT blow counts of about 50 for 2 inches pene- <br />tration. <br />2.4.2 Ground Water <br />Ground -water level data obtained by EMCON from the monitoring wells indicate <br />a ground -water level of 125 to 150 feet below ground surface (-19 to -27 feet <br />MSL). The local gradient is very flat over most of the site area. <br />9 2.5 SEISMIC CONDITIONS <br />A separate study addressing the requirements of Subchapter 15, Section 2547, <br />"Seismic Design," and 2595(f)(5) has been completed to identify sources and <br />magnitudes of seismic events that could affect final landfill slopes. Appendix C of <br />EMCON's Geologic and Hydrogeologic Report details the procedures used in <br />determining the maximum probable earthquake (MPE) projected for the North <br />County Sanitary Landfill site. <br />2.5.1 Maximum Probable Earthquake (MPE) <br />The results of the evaluation indicate that peak horizontal accelerations could re- <br />sult from earthquakes occurring on the Bear Mountain fault zone. This fault zone <br />is located 17.4 miles east of the site. A maximum probable earthquake (MPE) of <br />magnitude 5.7 has been assigned for the North County Sanitary Landfill site. <br />.'IJ9 9390217.00W 4 Rev. 0 May 23, 1989 <br />