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few silt and clay interbeds. Contacts between these three subunits are not distinct and are therefore subject to interpretation. By their nature these sedimentary units interfinger and are discontinuous on an individual basis. 2.3.3 FAULTING AND SEISMICITY The Forward Landfill is located in an area of relatively low seismic activity. No evidence of Holocene-age faulting on the property has been found either through a review of available literature or through site investigations and the site in not within or near any State of California Earthquake Fault Zones (as mandated by the Alquist-Priolo Earthquake Fault Zoning Act passed in 1974 and updated through 1999). The nearest known fault to the site, the Tracy-Stockton Fault Zone, passes through the City of Stockton, 6.5 miles northwest of the site. This fault zone is the closest known to the landfill and does not show evidence of Holocene displacement. The nearest active fault is the Great Valley 7 fault located approximately 19.8 miles (31.9km) southwest of the site. The seismic exposure of FL was evaluated by Geologic Associates (2007). Since the Forward Landfill is a Class II facility, the landfill design is based on the anticipated peak horizontal ground acceleration (PHGA) from a Probabilistic Seismic Hazard Assessment (PSHA) approach or the Maximum Credible Earthquake (MCE). Therefore, GLA proposed the MCE magnitude of 6.7 on the Great Valley 7 fault as a design-level earthquake. Using this magnitude, GLA used a variety of attenuation relationships from Blake (2004a) to evaluate the PHGA at the site. The attenuation relationship by Campbell and Bozorgnia (1994, revised 1997) for alluvial sites assuming a reverse fault event was concluded to be the most appropriate for the site conditions. Using this attenuation relationship, a PHGA of 0.13g was calculated for the MCE event of 6.7 on the Great Valley 7 fault at a distance of 19.8 miles (31.9 km). However, the family of attenuation curves for reverse faulting (Ord6nez, 2006; SHAKE 2000) indicates an upper bound horizontal ground acceleration of 0.15g. Forward Landfill-Project Description 2-4 BRYAN A.STIRRAT&ASSOCIATES j:\Allied\Forward\2007.0018 Lateral Expansion\Reports\Proj Descrip\021308 Final Proj Des\Sec 2.doc:2/13/2008)