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New West Petroleum #100 2 3 February zu i i ' <br /> 6437 N. Banner Street, LoMV <br /> San Joaquin County <br /> Discontinue R5-2008-0085-013 monthly sampling of the GWETS Influent port and <br /> bove operating extraction wells, in order to evaluate <br /> substitute monthly sampling of the a <br /> remedial progress and to assist with reconfiguration of the GWETS extraction wells for <br /> optimization of the GWETS. <br /> Comments: <br /> 1. Currently semi-annual monitoring is in effect for your Site for a limited number of wells an <br /> analyses. Groundwater monitoring for EW-4 and EW-5 was reduced from semi-annual to <br /> annual in my 3 November 2010 letter. Monitoring all wells annually does not resolve the <br /> issue that some wells have reported maximum concentrations during the second quarter, <br /> while other wells have reported maximum concentrations during the fourth quarter. Annual <br /> sampling of the wells may not fevlecapture wo years)cmay be more ation appropriate for wellends for some s that <br /> However, bi-annual sampling <br /> have historically remained non-detect over a like period of time, with annual monitoring for <br /> the wells that are showing steady declining trends, and semi-annual monitoring for wells <br /> that are showing variable trends or for wells tl aware are necessary a 2) The CSA 3guard wells 1vW el 2 <br /> MW-9C, and MW-9D) for the municipal supply <br /> sampling frequency could also be reduced to semi-annual monitoring. Please make <br /> specific recommendations in a table with the rationale for the proposed changes to the <br /> monitoring program in the next quarterly status letter report, which is due on 15 April 2011. <br /> 2. You shall discontinue sampling for TPHg, benzene, toluene, ethylbenzene, and xylenes <br /> and focus on MTBE for the GWETS. <br /> 3. You shall conduct monthly analysis for MTBE in operating extraction wells EW-6A <br /> (23 ug/L), EW-7A (7.1 ug/L), EW-8B (9 ug/L) and EW-913 (21 ug/L) for two months <br /> (February and March of 2011), with concurrent analysis of the influent samples on the <br /> GWETS, to demonstrate that the mass removed by the GWETS can be calculated by the <br /> recommendation's change to extraction well sampling, and to optimize the extraction wells <br /> for more cost effectively treatment of the MTBE plume. The mass removal calculations, <br /> .comparison sampling results and further recommendations for optimization of GWETS <br /> shall be included in the next quarterly status letter report due 15 April 2011. <br /> If you have any questions, you can contact me at (916) 464-4615 or I can be reached by e- <br /> mail at ibarton(a waterboards.ca.gov. <br /> James L.L. Barton, P.G. <br /> Engineering Geologist <br /> cc: <br /> Mr. Michael Infurna, San Joaquin County Environmental Health Department, Stockton <br /> Mr. Bill & Mrs. Rupinder Padda, 236 N. Ham Ln., Lodi 95242 <br /> Mr. Timothy Cuellar, Advanced GeoEnvironmental Inc., 837 Shaw Rd., Stockton 95215 <br />