Laserfiche WebLink
1 <br /> ' 2.2 Estimates of Liquid Quantity and Composition Leaked: <br /> No estimate of the quantity of liquid contaminant leakage can be determined from existing information <br /> Based on analytical results, the soil contamination appears to be comprised of diesel and gasoline <br /> constituents <br /> 2.3 Topography, Geology, Hydrology <br /> The site is situated in central Escalon in Section 4, 72S, R9E, San Joaquin County, California <br /> 1 Regionally the property is located in the San Joaquin Valley physiographic province The valley is <br /> a topographic and structural basin bounded on the east by the Sierra Nevada and on the west by the <br /> Coast Ranges Locally the topography slopes gently toward the west at approximately 5 feet per mile <br /> ' The near surface geology underlying the site is comprised of unconsolidated alluvial deposits of <br /> Pleistocene to Holocene age These deposits, sometimes referred to as the "older alluvium", consist <br /> of intercalated beds of gravel, sand, silt and clay The thickness of the older alluvium in the Escalon <br /> area averages approximately 450 feet Underlying the older alluvium are Plio/Pleistocene continental <br /> deposits of similar derivation and lithology The older alluvium functions as the most important <br /> aquifer in the site area (USGS Professional Paper, 1401-C, 1986) <br /> Soils developed on the alluvium are generally well drained, differing from the parent material only <br /> in the increased volume of organic matter (DWR Bulletin No 146, 1967) The important bodies of <br /> surface water in proximity to the site are the Stanislaus, Tuolumne, and San Joaquin rivers. The <br /> Stanislaus and Tuolumne, respectively, are located approximately 2 112 and 10 112 miles to the south <br /> of the site area These two rivers flow in a westerly direction and are tributaries to the San Joaquin, <br /> located approximately 14 miles west of the site The northerly flowing San Joaquin drains the San <br /> Joaquin Valley All three of these are gaining streams over portions of the year and derive a portion <br /> of their flow from groundwater influx (USGS Professional Paper, I401-C, 1986) <br /> The primary uses of groundwater in the area include irrigation and both private and municipal water <br /> supply The "older alluvium" is the most extensively developed geologic unit in the Modesto area and <br /> hosts both unconfined and confined zones The unconsolidated, mostly coarse grained nature of the <br /> R 042992 TIL 2 <br />