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originally in soil, 12,000 pounds were removed by soil vapor extraction and 10,000 pounds were <br /> remediated by natural biological activity. The evaluation of intrinsic bioremediation parameters performed <br /> by CRTC found that present subsurface conditions are conducive to natural biodegradation of existing <br /> groundwater contamination. Furthermore, their evaluation concluded that the existing groundwater <br /> contaminant plume is stable(not inigrating)and is of finite extent largely due to biodegradation processes. <br /> Based on their evaluation of site data, CRTC recommended that natural biodegradation be used as the <br /> primary method for attaining water quality goals and that a periodic monitoring plan be implemented to <br /> manage residual hydrocarbon contamination until the required goals have been met. Their <br /> recommendation is consistent with those made by Lawrence Livermore Laboratory in their report issued, <br /> October 16, 1995, the guidance provided by the State Water Resources Control Board(12/8/95), and the <br /> position stated by the U.S.EPA,Region IX in their comments to the Lawrence Livermore Lab report <br /> (2/6/96). <br /> During our meeting on April 25, 1996, we discussed the findings and recommendations presented in <br /> CRTC's summary report At that time, Chevron and Pacific Environmental Group were interested in your <br /> response to the proposal to adjust our current remediation strategy(Pacific Environmental Group, <br /> Remedial Action Plan, 12/27/95)to one more similar to that recommended by CRTC. I understood your <br /> response to be that, natural biodegradation and continued groundwater monitoring would not be <br /> acceptable because the groundwater cleanup goals would not be achieved in a"reasonable"amount of <br /> time and that the proposed strategy would not affect residual contamination in vadose zone soils. <br /> Furthermore,you stated that you would pursue enforcement action toward Chevron if progress toward <br /> remediating the subject site was not implemented within ninety days. <br /> Chevron is committed to doing what is right at the subject site in terms of attaining cleanup goals and <br /> facilitating the proposed property development. However, there appears to be a difference in policy <br /> direction that San Joaquin County Public Health Services is taking when compared to the State Water <br /> Resources Control Board and the scientific community. We would appreciate your assistance in helping us <br /> to understand why. In particular, it would be helpful to understand what would be considered a <br /> "reasonable"amount of time to attain cleanup goals at the subject site and what makes the cleanup time <br /> associated with active remediation more reasonable than that which would be associated with natural <br /> biodegradation?Also,your specific comments as to why your agency cannot approve a plan which <br /> includes natural biodegradation and groundwater monitoring as a supplement to active remediation to <br /> attain cleanup goals would be very much appreciated. <br /> Chevron strongly believes that any further application of active remediation at the subject site would be <br /> inappropriate. The recommended proposal using natural biodegradation and groundwater monitoring is <br /> not only practical but, is also cost effective. <br /> If you have any questions or comments, I can be reached at(510) 842-8695. <br /> Sincerely, <br /> Brett L. Hunter <br /> Environmental Engineer <br /> Site Assessment and Remediation <br />