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i <br /> Mr. Robert Garcia 29 May 2002 <br /> Leprino Foods,Inc. 3 <br /> quarter. The semi-annual report(October 26, 2001) laboratory sheet for MW-17 shows a non- <br /> detect on September 7, 2001. <br /> Please check for consistency and typographic errors in future reports. <br /> 2. Section 5.0 Conclusions: The Report states that one recommendation should include negotiations for <br /> termination of groundwater extraction from well RW-4A. Termination of any groundwater extraction <br /> system is contingent upon full characterization of the extent of the plume and either of the following: <br /> • Groundwater cleanup has reduced contaminant concentrations to levels consistent with the <br /> water quality objectives, which supports site closure, or <br /> • Natural attenuation has been shown to reduce contaminant levels to the point where the plume <br /> is stable, and cleanup to the water quality objectives will occur in a reasonable time frame. <br /> However, the data and other statements in the Report do not support the recommendation for discussion <br /> of terminating groundwater extraction from RW-4A at this time. <br /> 3. Section 5.0 Conclusions: The Report states that the MW-6 TPH-d concentration increase is due to <br /> another petroleum hydrocarbon groundwater plume moving onsite from the upgradient Mobil property. <br /> The data for 2001 does not support the statement (page 11) that pollution at MW-6 is from the Mobile <br /> plume,nor does it provide proof that the Mobil plume is being drawn across the site. MW-6 is <br /> upgradient of RW-4A, and downgradient of Mobil monitoring wells MW-16, MW-17, and MW-18. <br /> TPH-d concentrations in the Mobil groundwater plume declined to the 50 to 120 µg/L range during the <br /> first (June 2001) and second(September 2001) quarters, and have continued to decline or stabilize in the <br /> <50 to 60 µg/L range during the third(December 2001) and fourth (March 2002) quarters. <br /> As a result of the expanding plume and increasing SPP, additional remedial actions are necessary: <br /> 1) Submit Work Plans by 15 July 2002 for: <br /> a) An additional groundwater investigation downgradient and offsite from RW-1 and RW-2, <br /> and <br /> b) Groundwater sampling and analysis of existing and new wells for evidence of natural <br /> attenuation, including bioremediation. <br /> 2)By 1 August 2002,begin extracting and treating groundwater from monitoring wells RW-1 and <br /> RW-2. <br /> 3) Resume sampling TPH-d quarterly for two quarters in all perimeter and offsite wells that do not <br /> contain SPP. <br /> If you have any questions, you may contact me at(916) 255-3050. <br /> James L. Barton, R.G. <br /> Federal/Private Sites Cleanup Unit <br /> cc: Mr. Michael Infurna, San Joaquin County Environmental Health Services, Stockton <br /> Mr.Brendan Shine, HSI GeoTrans, Westminster, CO <br />