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Pilot Testing Report and Conceptual Corrective Action Plan July 15, 1994 Manna Pro, 4004 South EI Dorado, Stockton, CA 7 31 Topography The Manna Pro facility is located in southern Stockton between Duck Creek (to the north) and French Camp Slough (to the south) The general area slopes to the west toward French Camp ' Slough and the San Joaquin River The site is an industrial area on graded surface, approximately 15 feet above sea level, and is essentially flat Much of the ground surface at the plant consists of gravel and broken asphalt/concrete pavement There is a large grassy area occupying the southern ' quarter of the site 32 Hydrogeologic Conditions The subsurface materials encountered during drilling in the site vicinity consist of silt and clay from surface grade to approximately 20 feet below grade, interbedded silt and sand units from 20 to 46 feet below grade, and silt and clay below 46 feet below grade To enhance the understanding and interpretation of the site geology, a generalized geologic cross section was developed Data from the previous investigations and from the recent drilling conducted by Groundwater Technology were used to develop this cross section The location of the cross section is illustrated in Figure 3 Cross section A-A' is presented as Figure 4 ' Cross section A-A' traverses the site approximately from the north to the south beginning at MP-20 and ending at MW-4 The cross section passes through the area where the former USTs were located, as well as the area where the pilot test was performed The former USTs were located between monitoring wells MW-4 and MW-1 (see cross section A-A') The extraction well (EW-1) and observation wells (013-1, 013-2, and 013-3) were installed in this location because higher TPH and ' BTEX concentrations in the sod and groundwater were identified in this area by the previous investigations Four relatively distinct intervals of geologic strata are illustrated on cross section A-A' The uppermost horizon consists of approximately 20 feet of brown clay and silt The former UST excavation is located within this clay between MP-1 and MP-2 A fine to medium sand exists directly beneath the clay layer This layer is apparently thickest near monitoring point MP-20 (approximately 18 feet thick) and appears to become thinner in the direction of monitoring well MW-4 2819RD34 070 GROUNDWATER TECHNOLOGY, INC