ARCHIVED REPORTS_1990 - Laserfiche WebLink

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kn KLEINFELDER 1.3.2 Ground Water Quality The San Joaquin hydrologic basin has experienced overdraft for many years. Subsequently, declining water levels have induced the eastward movement of poor-quality water from the delta sediments6. Migration of these saline waters has impacted the utility of ground water in the vicinity of Stockton. According to the United States Geologic Survey? (USGS), there is generally better water quality in the northern and eastern parts of San Joaquin County than in other parts of the County. The water in the vicinity of Foothill Sanitary Landfill is characterized by a calcium-magnesium/bicarbonate water. The electrical conductivity of water in the region was less than or equal to 500 umbos/cm; the chloride concentration was less than or equal to 100 mg/L; and the nitrate concentration was less than or equal to 5 mg/L at the time of the USGS study. The USGS report stated that arsenic was less than or equal to 0.05mg/L; boron was less than or equal to 1 mg/L; and manganese was less than or equal to 0.05mg/L. The report stated that the concentrations of other trace elements in the water were probably low, except for iron. Mineral analysis of ground water from the Hatler well (5A) in 1978 by the Department of Water Resources indicates that the water is a calcium/bicarbonate water, with a TDS of approximately 300 mg/1. 1.3.3 Hydrogeology The Foothill Landfill site is located at the eastern side of the San Joaquin hydrologic basin. The basin is predominantly filled with clay, silt, and sand layers. In the area of Foothill Landfill the first water bearing zone encountered was within the Mehrten formation. As already stated, the Merhten formation is dominated by sands and gravels. The first water bearing zone occurs at the contact between sandstone and gravel at a depth of approximately 200 feet. The general water bearing characteristics of clay, silt, sand and gravel are presented below$: FOOTHILL 9