SITE INFORMATION AND CORRESPONDENCE

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vow, e BIOSYSTEMS MANAGEMENT INTERNATIONAL 883 SNEATH LANE,SUITE 224• SAN BRUNO,CALIFORNIA 94066•(415)589-7171 June 21, 1988 all, Mr. Dave Carls L San Joaquin Local Health District JUN .13 1601 E. Hazelton P.O. Box 2009 ENVIROMENTAL H"ALTH Stockton, CA 95201 PERMIT/SEtiVILtS Dear Mr. Carls: This letter will serve as a formal request to your department and the Regional Water Quality Control Board for a variance in the number of monitoring wells to be installed at the Stockton Scav- enger operations facility located at 1240 Navy Drive in Stockton, CA (Fig 1) . The purpose of the monitoring wells is to detect pos- sible groundwater contamination as a result of two underground storage tanks which have leaked and since been removed. It is understood that 3 monitoring wells are usually installed to ascer- tain the existence of contamination and determine the direction of subsurface flow at sites suspected of having contaminated groundwater. A variance is being requested because it is felt that the availability of information concerning groundwater flow, the depositional character of the sediments in the area, and the drainage characteristics of the valley provide sufficient infor- mation about the flow of groundwater in the area. The following information outlines Biosystems Management International's (BMI) basis for requesting a variance. The site is located on the gentle alluvial slope of the western flank of the Sierra Nevada range. The slope has been built up by material carried out of the Sierra by various streams and rivers which drain to the northwest into the upper reaches of the Delta. The topography of the area follows a similar trend with the ground surface reaching sea level approximately 2 miles west of the site. Recharge to the shallow groundwater under concern occurrs where the alluvial strata outcrop at the base of the Sierra Range. From here the groundwater flows to topographical low spots where it becomes effluent and contributes to flow in rivers (for the area under concern the major drainage pathway is the San Joaquin River) . Note that the reasoning for stating of the groundwater being ef- fluent into the San Joaquin River is the fact that the river is a deep water channel. With depth to groundwater at approximately 18 ft. and becoming shallower to the NW towards the river, it is felt that the water table intersects the channel bottom and serves as recharge to flow in the river.