WORK PLANS - Laserfiche WebLink

Home Browse Search

1. �6RO Ms. Mary Meays September 29, 1995 (9347-3011) • The analytical data indicates the system has removed all of the petroleum hydrocarbons that can be practically remediated by vapor extraction. The most recent extraction rate (July 3, 1995) has dropped to approximately less than one-half of 1% of the initial start- up (April 29, 1992) extraction rate, with a corresponding decrease in the efficiency of the VES. • No sources of petroleum hydrocarbons have been present onsite since the former underground storage tanks (USTs) were removed in 1981. • The continued operation of the GWO system, designed specifically to increase the dissolved oxygen content of ground water, will provide an effective and feasible method to enhance the natural biodegredation of the remaining dissolved- and adsorbed-phase petroleum hydrocarbons. • Petroleum hydrocarbon concentrations in the water samples collected from six of the seven monitoring wells are consistently below the respective method detection limits or contain only low concentrations. Therefore, Fugro recommends that the sampling frequency of these wells be reduced to a semi-annual basis. • An estimated 5,772,087 gallons of ground water have been removed from the water- bearing zone beneath the site to date. However, the extracted ground water only contained approximately 5.8 gallons of petroleum hydrocarbons. Therefore, petroleum hydrocarbons have comprised 0.0001 percent of the total volume of the fluids removed from the water-bearing zone beneath the site. Background The following brief discussion of the site background is based, in part, on information from reports prepared by others: Four 4,000-gallon steel gasoline USTs and one used oil UST were installed at the site in 1955. In 1963, one 4,000-gallon UST was removed and two 7,500-gallon gasoline USTs were installed at the site. The five gasoline USTs were removed in 1981 (RESNA, 1991a) and the used oil UST was removed in 1991 (SJCPHS/EHD, 1993). Soil gas samples were collected from 15 sampling points during a soil gas survey performed at the site in May 1990. Petroleum hydrocarbons were detected in the soil gas samples collected in or near the former gasoline UST cluster (Kleinfelder, 1990). 93473011.ARP -2-