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1 , 02 June 1997 _ AGE-NC Project No 95-0105 ' Page 7 of 11 z ' excavations, a volume reduction of approximately 20 percent Approximately 590 cubic yards of hydrocarbon-impacted soil is estimated to remain at the northern edge of the site and under Grant Line Road and Parker Avenue Impacted soil extends an estimated ten to fifteen feet horizontally under the road way to the location of boring P2 The impacted soil is likely vertically limited to a depth range of five to ten feet bsg Assuming an average concentration of 1,100 ppm 2n the soil from samples collected from probe borings P2 and P6, the mass of hydrocarbons remaining in place is estimated to be 744 kilograms of gasoline (262 gallons of gasoline) , ' Approximately 162 cubic yards of impacted soil remain in the area south of the former UST ti dispenser area and under the building on the site The impacted soil is probably limited to a depth range of five to ten feet bsg The mass of gasoline in this area is approximately 1857 kilograms (655 gallons of gasoline) A mass calculation of the remaining hydrocarbons in depicted in Appendix B - ' Mass Balance Calculation 3 0 QUARTERLY GROUND WATER MONITORING, MARCH 1997 3 1 MONITORING WELL PURGE PROCEDURES On 19 March 1997, the water level in each monitoring well was measured relative to the top of the well casing using a Solinst water level meter The depths to ground water and ground water ' elevations are tabulated in Table 3 - Gi ound Water Elevation After water levels were measured, a two-stage submersible pump was used to purge each well of ' standing water A minimum of three well volumes of water were removed from each well ten gallons of water were removed from MW-1, MW-2, MW-3, MW-5 and MW-6, twelve gallons of ' water were removed from MW-4 Ground water parameters were measured at two-gallon intervals' using an ICM water analyzer Temperature, pH and conductivity stabilized during purging (see Appendix C) Purged water was stored on-site in labeled, 55-gallon DOT-approved drums 3 2 COLLECTION OF GROUND WATER SAMPLES ' Water samples were collected from each well using new disposable plastic bailers Each water sample was transferred into two 40-m1 VOA vials containing 0 5 ml of 18%hydrochloric acid as a sample preservative and into a one 1-liter amber bottle without preservative After collection, the samples were properly labeled, placed in a chilled container and transported under chain-of-custody to Alpha Analytical Laboratories (AAL) Each sample was analyzed in accordance with EPA i 1 ,