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R604 UPDATE 14 12-28-1992 <br /> control the contour between data points This site is presently <br /> being influenced by vapor extraction at MW5 , VSB3 , VSB5 , VSB9 and <br /> VSB11 A vacuum at these wells and surrounding wells will <br /> ° <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 <br /> before removing the cap and the subsequent depth to water <br /> measurement is corrected for the negative vacuum head <br /> (potentzometric head) <br /> RESULTS - WATER <br /> GROUND WATER GRADIENT <br /> Ground water gradient maps have been produced from the November <br /> 17, 1992 depth to water measurements, Figure 4A and from the <br /> December 7, 1992 depth to water measurements, Figure 4B . <br /> The ground water gradient contour map, Figure 4A, was developed <br /> from measurements taken on November 17 , 1992 . These measurements <br /> were corrected for the negative pressure of the vacuum extraction <br /> on ground water that were obtained dust before the depth to water <br /> measurements <br /> Figure 4A shows flow towards MW2 and MW4, from the west to <br /> the northeast and the southeast No depth to ground water <br /> measurements were obtained from MW2 , MW3 and MW6 , they were dry. <br /> Figure 4B represents ground water contours from measurements <br /> obtained on December 7, 1992 (No vacuum extraction - the system <br /> was shut down for carbon change out service by Exceltrans) Flow <br /> is indicated to the east and southeast All the monitor wells <br /> contained enough ground water for measurements, representing a <br /> recharging of the aquifer beneath this site from the rains that <br /> had occurred the prior week <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 , and MW7) <br /> except MW5 which contained 160 parts per billion (ug/L) . MW5 has <br /> tested below 1 ppm for gasoline range hydrocarbons since the June <br /> 24 , 1991 sampling. All other wells have tested below 1 ppm <br /> gasoline range hydrocarbons since the March 29, 1992 sampling. <br /> This analysis substantiates the removal of hydrocarbons <br /> page 3 <br />