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R604 .UPDATE 13 11-24-1992 <br /> being <br /> influenced by vapor extraction at MW5 , VSB3 , VSBS, VSB9 and <br /> VSB <br /> 11 A vacuum at these wells and surrounding wells will <br /> ° influence the shape of the ground water surface and subsequent <br /> flow directions of the ground water. To obtain representative <br /> measurements that show the influence by the vacuum extraction at <br /> this site, a vacuum measurement is obtained at the well head prior <br /> to removing the cap and the subsequent depth to water measurement <br /> is corrected for the negative vacuum head (potentiometric head) . <br /> RESULTS - WATER <br /> Ground Water Gradient <br /> Ground water gradient maps have been produced from the September <br /> 11, 1992 depth to water measurements, Figure 4A and the November <br /> 17, 1992 depth to water measurements, Figure 4B <br /> The ground water gradient contour map, Figure 4A, was developed <br /> from measurements taken on September 11, 1992 (no vacuum <br /> extraction - the system was shut down for carbon change out <br /> service by Exceltrans) <br /> Figure 4A shows flow towards MW-4 No depth to ground water <br /> measurements were obtained from MW--3 and MW-6 , they were dry. <br /> Figure 4B represents ground water contours from measurements <br /> obtained on November 17, 1992 . These measurements were corrected <br /> for the negative pressure of the vacuum extraction on ground <br /> water. Flow is indicated to the east and northeast Monitoring <br /> wells MW-2 , MW-3 and MW-6 were dry <br /> TOTAL PETROLEUM HYDROCARBONS <br /> Floating Product: <br /> No floating product has ever been observed in any of the <br /> monitoring wells <br /> Dissolved Petroleum Hydrocarbons in Ground Water (EPA method 5030 <br /> TFH as gasoline) : <br /> Dissolved total fuel hydrocarbons, gasoline range, were below <br /> detection limits for all wells sampled ( MW1, MW4 , MWS and MW7) <br /> This analysis substantiates the steady decline an Hydrocarbons <br /> associated with the ground water and is evident in comparing the <br /> ground water samples obtained on December 16, 1991 to those <br /> obtained on March 5 , 1992 and later, see Table 1 . <br /> Prior to vapor extraction, November 21, 1990 , gasoline range <br /> hydrocarbons were detected in MW1 - 2 mg/L, and MWS - 31 mg/L <br /> Now MW1 and MW5, along with all wells, are below detection limits <br /> ko 05 mg/L) for gasoline range hydrocarbons, as noted during the <br /> September 11, 1992 sample results <br /> page 3 <br />