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1 <br /> 2 .5.2 Groundwater Contamination <br /> ' Both gasoline and diesel contamination were detected in the initial <br /> sample collected from MW-1 in June of 1992 (260 ppb and 310 ppb, <br /> respectively) . Only gasoline was detected in the sample collected <br /> in November of 1992 . <br /> ' Benzene has been detected in samples from MW-1 and MW-4 . Toluene <br /> was detected only in the initial sample from MW-1. No contamination <br /> ' has been detected in samples from MW-2 , MW-3 or 14W-5. In the June <br /> 1993 Quarterly Report, GeoAudit recommended that quarterly <br /> monitoring continue in October, 1993 . <br /> ' 3. 0 PROCEDURES <br /> 3 . 1 Monitoring Well Purge Procedures <br /> i <br /> On October 8 , 1993 , a Solinist water level meter was used to <br /> measure the depth to groundwater in the five monitoring wells. <br /> ' After water levels were measured, a PVC bailer was used to purge <br /> approximately 7 to 8 gallons of water from monitoring wells MW-1, <br /> MW-4 and MW-5 . Temperature, pH and conductivity were measured at <br /> one-gallon intervals and recorded (Table 1) . The purge water was <br /> placed in DOT-approved drums and stored on-site. <br /> ' 3.2 Groundwater sample Collection <br /> Water samples were collected from MW-1, MW-4 , and MW-5 using new <br /> ' disposable plastic bailers. Three 40 ml EPA vials and one I-liter <br /> amber bottle of water were collected from each well and transported <br /> in a chilled container to WEST Laboratory in Davis. Each sample was <br /> analyzed for TPH as gasoline and diesel and BTE&X in accordance <br /> ' with EPA methods 8015m and 602 . <br /> I <br /> ' 4 .0 FINDINGS <br /> 4.1 Groundwater Elevation <br /> The relative groundwater elevations for the monitoring wells were <br /> calculated by subtracting the water depth from the casing elevation <br /> (Table 2) . Comparison of the June and October measurements <br /> indicates that water levels have fallen approximately 3 feet at the <br /> site. This drop in water levels probably reflects the normal <br /> seasonal variation of regional groundwater depths. <br /> 4.2 Groundwater Flow Direction and Gradient , <br /> Based on depth-to-groundwater measurements from monitoring wells <br /> MW-1, MW-2 and MW-3 , the hydraulic gradient was calculated to be <br /> 0. 0091 ft/ft directed N 190 E. The gradient is slightly curved, and <br /> 5 , <br />