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A Y s� ments consist of the gray, plastic, organic clays and very fine grained sands mentioned in the previous section. The direction of groundwater flow in the area is estimated to trend towards the northwest. This estimate is based upon review of data from work performed previously in the area as well as inference from topographic and geologic characteristics. It is felt that subsurface flow trends towards the northwest. This information is presented due to its relevance to the transport of contaminants and placement of the monitoring wells. Verification of flow direction will be made upon installation of groundwater monitoring wells at the site. Groundwater investigations being conducted in the vicinity of the Stockton Scavenger facility have ascertained the flow direction to be towards the NW. More specifically, in September of 1987, the subsurface flow at 1111 Navy Drive, one block east of the site, was deter; ined to be flowing towards the northwest and located at 18 ft. below groulid surface. July 1987 measurements of groundwater levels at 3515 Navy Drive, west of the site, were found to be 11 feet below ground surface with subsurface flow trending to the NW. This data was obtained from monitoring wells installed at these sites designed to address similar concerns as those at the Stockton Scavenger site. Inference of subsurface flow can be made from interpretation of to- pographical and geologic framework of the area. The site is located on the gentle alluvial slope of the western flank of the Sierra Navada 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 fol- lows a similar trend with the ground surface reaching sea level approx- imately 2 miles west of the site. Recharge to the shallow groundwater under concern occurrs where the alluvial strata outcrop at the base of I the Sierra Range. From here the groundwater flows to topographical low spots where it becomes effluent and contrioutes to flow in rivers (for the area under concern the major drainage pathway is the San Joaquin River; . It should be noted that during dry years groundv.ater may not be emergent in stream channels and is recharged via infiltra- from channel bottoms. Hydrogeologic properties such as conductivity and permeability have riot been ascertained as of yet. Judging from the character of the water bearing sediments one could estimate permeabilities to be low as a result of the small grain size and hydraulic conductivities fal- ling in the range of 10_q - 10"6 cm/sec. ? 4.0 SOILS INVESTIGATION 4.1 Soil Sampling Procedure The initial investigative stage at the facility consisted of obtain- __ __ing soil samples from various depths to determine the extort of can