SITE INFORMATION AND CORRESPONDENCE

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JOHNJOHNSON DRAFTTHE CUSTOMER COMPANY P O BOX 886 BENICIA CA 94510 RE: 15 EAST GRANT LINE ROAD SITE CODE: 1404 TRACY CA San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has completed the review of the "Remedial Action Work Plan Additional Information" letter dated December 15, 1994, submitted by Trans Tech Consultants, and has the following comments for your consideration. To appropriately characterize soil contamination in areas not already investigated at this site, sufficient discrete soil samples must be submitted to a state certified laboratory for analysis. Headspace analysis data can be used in conjunction with the data obtained from the laboratory to "fill in the spaces". However, use of the headspace analysis data must be justified by the analytical data from the laboratory. Assumptions on the full distribution and concentration of contaminants in the subsurface at the site should not be based on headspace data alone. The bioremediation proposal was presented to the PHS/EHD technical staff at a recent meeting. Staff concluded that a small scale pilot study should be conducted at this site. The objective of the pilot study would be to gather physical data to indicate that this type of approach is appropriate for use at this site on a larger scale. The discussion in the letter addendum discusses the use of monitoring vapors in the wells as an indicator of progress of bioremediation and that stable, low levels of hydrocarbons would indicate bioremediation to be complete. Any detection on an organic vapor meter would indicate remediation at the site is not yet complete. As already mentioned in a July 18,1994 letter from PHS/EHD to you, the initial cleanup goal for this site must be the background levels that existed before the release occurred. As petroleum hydrocarbons do not naturally occur in the subsurface at this site, background levels are nondetecable levels using the most stringent detection limits available. Therefore, abating the levels of contamination at this site to any other level than those mentioned above would require additional remedial action and/or a comprehensive feasibility versus cost benefit comparison for justification for no further action. A special permit will have to be issued for the installation of the temporary vapor monitoring points as the construction of these wells are a variance of San Joaquin County Well Standards. In addition, these wells must be constructed to have a sealing cap fitted with a sampling port which extends into the well. A small pump can be used to obtain representative air samples from the well. This construction will provide a more accurate representation of actual subsurface air conditions. In addition to monitoring vapors from the wells for bioremedial progress, the following monitoring parameters will be required: Initial background levels for carbon dioxide, dissolved oxygen, and bacteria in groundwater in the test area; On a weekly basis, monitor air in test wells for gasoline vapors, carbon dioxide, and oxygen. Initially, monitor for methane to show no methane producing bacteria are being applied. On a weekly basis, monitor groundwater in the test area for total petroleum hydrocarbons as gasoline, benzene, toluene, ethylbenzene, xylene, the total number and species of bacteria, and for dissolved oxygen.