Laserfiche WebLink
monitoring wells, wells LM3, LM15, LM16, LM28, LM29, LM49, and LM55 have had hits of <br /> organochlorine pesticides for at least two quarters of monitoring during the past year. <br /> (Note that the September 1992 monitoring round was the first to monitor the extraction and <br /> injection monitoring wells, 100 series, for these analyses.) <br /> EPA has previously constructed plume maps of arsenic and dieldrin from September <br /> 1992 monitoring round data, that shows plumes of these contaminants that appear to <br /> emanate from the IWPs.t Also, arsenic concentrations from the September 1992 monitoring <br /> round were at or near their California Action Level of 5.0 Erg/L for arsenic in these <br /> monitoring wells: LM3, LM15, LM101, and LM104. Note that wells LM27A, LM28, LM49, <br /> LM62, and LM103 all had groundwater concentrations of arsenic, both filtered and <br /> unfiltered, above potential concentrations from monitoring wells LM11 and LM12. <br /> Furthermore, EPA feels that the injection monitoring wells (LM106, LM107, LM108, LM109, <br /> and LM110) should also be monitored semiannually for arsenic as well as for dieldrin when <br /> the injection wells are operational, since both of these ccnstituents are being extracted with <br /> the groundwater in the extraction monitoring wells and are probably not being adequately <br /> treated in the present IRM system. <br /> Similarly, chromium concentrations above potential background values, both filtered <br /> and unfiltered, were consistently detected in monitoring wells LM25, LM32, LM37, LM41, <br /> and LM43. Manganese concentrations, both filtered and unfiltered, above potential <br /> background values were detected in wells LM3, LM15, LM27A, and LM30. We feel that <br /> DDRW-Tracy should continue to monitor for these constituents on at least a semiannual <br /> basis. <br /> Should you have any questions, please contact me at (415) 744-2392. <br /> Sincerely, <br /> Michael Work <br /> Federal Enforcement Section I (H-9-1) <br /> Office of Superfurd <br /> cc: (See Distribution List) <br /> t DDRW-Tracy may desire continuo .s monitoring at selected wells to observe potential <br /> movement of these contaminants. <br /> 2 <br />