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The cohesionless materials can be characterized as dense to very dense. Because the sediments at the site were deposited as fluvial floodplain and channel deposits, the soil deposits at the site were found to be heterogeneous and laterally and vertically discontinuous. It is therefore difficult to characterize the subsurface soils into distinct units. Results of the most recent site investigation (GLA, 2008) indicate that under the loading of the site's design Maximum Credible Earthquake horizontal acceleration, the subsurface soils at the site are too dense to liquefy. In addition, the maximum differential settlement of subsurface soils under the proposed landfill expansion is on the order of only 0.3 percent, and dynamic settlement of subsurface soils due to a design earthquake is 0.01 to 0.2 inches with a differential settlement on the order of 0.1 inches. Two soil borrow studies (Twining, 1991 and Lewis Engineering, 2000) were conducted in a former borrow pit area within the landfill footprint. The results of these studies indicate that soils at elevations of approximately 15 to 25 feet amsl are classified as low plasticity clays (CL) based on the Unified Soil Classification System (USCS) and have laboratory permeabilities ranging from 1 x 10' to 1 x 10"$ cm/sec when compacted to above 90 percent relative compaction based on American Society for Testing Materials Method D1557 (ASTM D1557). The other soil borrow study (Twining 1996) was conducted in the borrow area north of the FL. The results of this study indicate that the soils encountered at a depth of approximately 4 to 11 feet below ground surface are classified as sandy clay and have a laboratory permeability of approximately 3 x 10-' cm/sec when compacted to above 90 percent relative compaction based on ASTM D1557. 2.5 CLIMATE The climate of the region is typical of the California Central Valley. Winters are generally cold and wet with fog, while summers are hot and dry. Representative climatologic stations were selected based on their proximity to the site and reliable period of records for the station (30 years or more). Forward Landfill-Project Description 2-6 BRYAN A.STIRRAT&ASSOCIATES j:\Allied\Forward\2007.0018 Lateral Expansion\Reports\Prof Descrip\021308 Final Proj Des\Sec 2.doc:2/13/2008)