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Proposed Plan A • r <br /> Based on the above, UNOCAL proposes to reduce the monitoring and sampling <br /> frequency to annually. We believe this is a sound approach for this site based on the <br /> following: <br /> a) The source has been removed and only residual concentrations remain <br /> in the groundwater system. <br /> b) Sixteen consecutive quarters of groundwater analytical data already exist <br /> for the site. <br /> d) Recent State Water Resources Control Board guidance suggests that <br /> "passive bioremediation should be considered as the primary <br /> remediation tool in most cases once the fuel leak source has been <br /> removed" (see attached letter from Walt Pettit dated December 8, <br /> 1995). <br /> e) Our investigative files show that the nearest downgradient"receptor"well is <br /> located in excess of 2,500 feet from the site. Based on the <br /> configuration of the groundwater plume, it is highly improbable that <br /> hydrocarbons from the site could impact this well. <br /> f) It is anticipated that State policies and additional guidance documents will <br /> be available during the 1997 calendar year that will enable <br /> determination of appropriate remedial alternatives including, but not <br /> limited to, Risk Based Corrective Action(RBCA) options. <br /> UNOCAL considers Plan A to be the best alternative for this site and requests <br /> concurrence to implement said plan. Should your office deny this request, a letter <br /> explaining your rationale would be most appreciated. <br /> Proposed Plan B <br /> As an alternative to Plan A, UNOCAL proposes to reduce the monitoring and <br /> sampling activities to semi-annually, commencing with the June 1996 field event. <br /> Justification for the reduced monitoring is the same as provided above under Proposed <br /> Plan A. Again, correspondence from you approving or denying this proposed plan is <br /> welcomed. <br /> 2 <br />