SITE INFORMATION AND CORRESPONDENCE_1

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Steve Ronzone Page 2 vapor extraction wells in the same soil boring. In addition, the complete radius of influence of the vapor extraction and air sparge wells has not been determined. PHS/EHD recommended installation of additional wells that could be used in various ways to investigate remedial options at the site . The wells should be constructed so they can be used as vapor extraction wells, air inlet wells, or i observation points for determining the radius of influence of the current vapor extraction wells . CH2M Hill felt there may be existing information to establish the radius of influence of the air sparge and vapor extraction wells . PHS/EHD requested that this information be submitted for their review and comment . CH2M Hill stated that the decreasing levels of toluene in monitoring well DIS-2 prior to the start of the air sparging and vapor extraction was evidence of intrinsic bioremediation occurring at the site . Also respiration tests which consisted of injecting oxygen and then measuring the decreasing oxygen levels indicated that the oxygen was being used by the naturally occurring bacteria at the site . CH2M Hill proposed performing an intrinsic bioremediation study for one year. There are currently no domestic, agricultural or domestic wells in the area that would be receptors of the site contamination and the use of the Del Monte production wells has been discontinued. In addition, contaminants are well below ground surface. Therefore, human health risks are reduced. Del Monte and the State Water Resources Control Board (SWRCB) are in the midst of legal activities with PARMACEAST. PHS/EHD has identified PARMACEAST as a responsible party, but they have not accepted their responsibility to date . Resolution of the legal issues will take time and human health risks are reduced so PHS/EHD will consider implementation of the "Intrinsic Study" . PHS/EHD requested CH2M Hill submit a proposal for their "Intrinsic Study" . The proposal should have a theory statement and should provide physical parameters that can be used to prove the theory. The proposal should explain how the theory supporting data will be gathered and provide a timetable for gathering the data. Since all the shallow monitoring wells except DIS-1 and DIS-2 have non-detect groundwater sample results, and DIS-1 is being influenced by the air sparge vapor extraction system, confirmation sampling in other areas of .the groundwater contamination plume will be necessary. PHS/EHD has been informed by a certified laboratory that analytical method ASTM G22 can be performed on soil and groundwater to determine if there are hydrocarbon utilizing bacteria present .