SITE INFORMATION AND CORRESPONDENCE_FILE 2

Home Browse Search

:..:, MEMORANDUM.-., 2 _ 8 June .1992 ... Table 3- -in the LUFT Manual to prove this contention.' Based .on this opinion, he stated that the operation of the soil venting system installed in the base of the tank excavation was not necessary. Quarterly reports have not been submitted every quarter. From June 1987 through April 1992, the 4 wells have been sampled only 7 times (sampling once per quarter would have resulted in 19 sampling events) . From June 1987 to July 1988 all four wells contained contamination at about the same orders of magnitude. By September 1990, all weds had non-detectable levels of contamination and in April 1991 only MW2 contained 1.3 ppb benzene and 1.4 ppb toluene. The ground water level has dropped 10 feet. During the meeting, Mr. Nations reported his interpretation of the data and stated that based on his interpretation, no further investigation and cleanup of the site is necessary. County staff and I informed Mr. Nation and Ms. Uram that our interpretation of the site information is as follows: 1. An unauthorized release of petroleum hydrocarbons occurred at the site; 2. The borings drilled and wells installed by AGS detected the contamination resulting from the unauthorized release; 3. In the Central Valley, in general , as the water level drops so do the concentrations of contaminants in ground the water, including benzene; 4. At least one of the borings, MW2, had soil contamination to ground water; 5. The extent of ground water contamination was not defined; 5. The extent of soil contamination has not been defined; 7. The ground water level has dropped about 10 feet since 1987, which has resulted in the adsorption of substantial amounts of gasoline to the soil . 8. A rise in ground water elevation, will recontaminate the ground water due to desorption of contaminants from the soil to ground water; 9. Numerous areas in San Joaquin County have experienced a rise in the water table this spring; 10. If Mr. Phillips would like to close the site, additional soil investigation and ground water monitoring are necessary; 11. Because ground water has been impacted, leaching potential analysis cannot be used to determine what concentration of soil contamination will not impact ground water. 12. San Joaquin County does use the LUFT Manual for soil cleanups;