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UPDATE 28 8-02-94 Vacuum Influence As was stated earlier, vapor recovery has removed the lighter fractions of gasoline range (through ethylbenzene) petroleum hydrocarbons from the soil and has greatly reduced the petroleum hydrocarbons dissolved in the ground water beneath this site Figure 3A represents the vacuum influence generated from the vapor recovery system, as measured on July 21, 1994 System Operation. Prior to turning the system off on December 30, 1993 a flow rate of 51 cubic feet per minute was maintained by the two blowers that are placed in series, that exhaust through 2 (in series) 110 gallon and one 85 gallon activated carbon vapor scrub units The vapor scrub units are serviced by Exceltran and Cameron Yakima for change-out and rejuvenation Prior to turning the system off on December 30, 1993 the system had operated 12847 hours and recovered an estimated 18 , 191 pounds of gasoline range hydrocarbons Since turning the system back on on February 16, 1994 until the last sampling of the system on July 21, 1994 an additional 131 pounds of gasoline range hydrocarbons has been recovered Pounds per day recoveries have been reduced to approximately 0 8 pounds per day, which is approximately 43% of the production rate prior to the turning the system off on December 30 , 1993 (1 85 pounds per day) METHODS AND QA/QC WELL SAMPLING AND ANALYTICAL TECHNIQUES Depth to ground water and ground water samples were obtained from all of the ground water monitoring wells on September 15 , 1993 Vacuum and depth to water measurements were obtained from all of the wells on October 27 , 1993 Depth to top of fluid and ground water measurements were obtained using a clean product water interface probe The probe, lowered into the well , by an attached tape calibrated in 0 02 foot intervals, signals at the contact of floating product and at the top of ground water The measurement is obtained from the calibrated tape reading adjacent to a reference point on the casing The probe is cleaned with trssodium phosphate water followed by a distilled water rinse before measuring the next well Measurements are started at the historically cleanest wells and progress to the dirtiest well All depth to ground water measurements were obtained before purging the wells for sampling The depth to water is then subtracted from the elevation of the casing' s reference point for a corrected ground water elevation A computer generated gradient program was not utilized The more interpretive gradient map was developed by calculating the gradient from each well to all surrounding wells (difference in ground water elevations/distance between wells) , "l e It MW1 to MW2 , MW1 to MW3 , MW1 to MW4 , and MW1 to MW6 Depth to ground water data from MW5 is not used, this well was installed in a slant boring and page?