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WASTE DISCHARGE REQUIREMENTS ORDER R5-2015-0058-01 -9- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS FOOTHILL SANITARY LANDFILL, INC. FOOTHILL LANDFILL SAN JOAQUIN COUNTY site is underlain by Laguna alluvial deposits and cemented to partially-cemented Mehrten deposits. Laguna soils generally consist of silty sand, clayey silt, and silty clay to approximately 10 feet bgs.2 Underlying Mehrten deposits generally include clay/claystone, silt/siltstone, sand/sandstone, and conglomerates. 42. Laboratory analysis of soil samples obtained during soil boring investigations of the site have indicated in-place hydraulic conductivities ranging from 1 x 10-3 cm/sec (sand/sandstone) to 1 x 10-7 cm/sec (clay/claystone). Remolded laboratory samples had lower conductivities. 43. The nearest historically active fault systems to the site include the Foothills Fault System 11 miles to the northeast; the Great Valley Fault Zone 38 miles to the south- southwest; the Clayton-Marsh Creek-Greenville Fault System 60 miles to the west; and the Calaveras Fault Zone 60 miles to the SW. a. The Foothills Fault System trends NW-SE along the western foothills of the Sierra Nevada Mountains. The highest magnitude earthquake historically recorded along the Foothills Fault system was a 1975 earthquake along the Cleveland Hills Fault near Oroville, which registered 5.8 on the Richter scale. b. The Great Valley Thrust Zone is a submerged, NW-SE trending fault system along the eastern foothills of the Coast Range. In 1892, an earthquake registering 6.5 on the Richter scale occurred in Winters and Vacaville along the Vaca Fault in this fault zone. Similar magnitude earthquakes have occurred along other segments of the Great Valley Thrust Zone. c. The Clayton-Marsh Creek-Greenville Fault System is a NW-SE trending, near- surface fault system extending north about 60 miles from the San Antonio Valley to Concord. This fault system is on the east-southeast side of Mt. Diablo, which is west of Foothill LF. In 1980, a 5.8 magnitude earthquake causing minor surface rupture occurred along the Greenville Fault near Mount Diablo. d. The Calaveras Fault Zone is a NW-SE trending, strike-slip fault zone extending north about 100 miles from south of Hollister to Danville. It is part of the larger San Andreas Fault System. In 1911, a 6.5 magnitude earthquake occurred along the fault in the Morgan Hill area, and in 2014, a 6.0 magnitude earthquake occurred along a northern extension of the fault near Napa. Quaternary faults in the above fault systems and other fault systems potentially relevant to the site are identified in the Information Sheet. There are no known Holocene faults within 1,000 feet of the facility. 2. Soil Conservation Service Survey descriptions indicate that surface soil at the site consists primarily of Peters Clay and various loam soils (i.e., Pentz sandy loam, Pentz-Bellota Complex, Keyes-Redding, Keyes-Bellota Complex, Lithic Xerorthents-Toomes Complex). The clay soils generally occur in flat areas.