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f June 15, 1992 R CNP#A . Fire Engine Company No 2, Stockton, California PRESENT GROUND-WATER SAMPLING On April 17, 1992, a technician from RFSNA measured the water-levels in wells MW-1 through MW-4 and collected groundwater samples from the wells for subjective and laboratory analyses The field methods and procedures used are presented as an attachment to this report Water samples from wells MW-1 through MW-4 exhibited no subjective evidence of hydrocarbons during this site visit (Table 1) Purge water from the wells was stored temporarily in 55-gallon steel drums pending the results of laboratory analyses The City of Stockton is responsible for the disposal of the purge water The top of the four monitoring wells were surveyed relative to mean sea level and the ground-water flow direction and gradient were evaluated as described in the attached Field Procedures The ground-water gradient on April 17, 1992, was approximately 0 006 with a flow direction to the north, as shown on Plate 3 The direction of ground-water flow previously ranged from southeast to north-east with gradients of 0 0028 to 0 033 The elevations of the ground-water surface in each well are shown in Table 1 Ground-water samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) and as diesel (TPHd) using Environmental Protection Agency (EPA) Method 8015 • (modified for gasoline and diesel) and for benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using EPA Method 602 These samples were analyzed at RESNA Environmental Laboratories in Rancho Cordova, California (Hazardous Waste Testing Laboratory Certificate No E773) Results of laboratory analyses indicated that dissolved TPHd was not detected in water sampled from the four wells, and dissolved TPHg was not detected in ground water collected from well MW-3 TPHg and benzene were detected in the water sampled from well MW-1 at concentrations of 960 parts per billion (ppb) and 142 ppb, respectively TPHg was detected at concentrations of 1.00 and 54 ppb in water sampled from wells MW-2 and MW-4,respectively,concentrations of BTEX compounds were below maximum contaminant levels recommended for drinking water by the California Department of Health Services. Results of laboratory analyses are summarized in Table 2 Copies of the laboratory analysis reports are attached osoa,esc 2 3soo9-a