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EBMUD <br /> Page 2 <br /> -monitoring well data including groundwater elevation, <br /> pH, conductivity, gradient; <br /> -analytical results of groundwater or soil sampling; <br /> and <br /> -site map showing the "zero line" of contamination, if <br /> known, and changes in the above measurements over the <br /> last quarter. <br /> During the construction of monitoring wells 14, 15, 16, and #7, <br /> soil samples collected at 10 feet detected petroleum hydrocarbons <br /> and total lead. The constituents remaining in the soil pose a <br /> potential threat to groundwater quality. (Refer to Table 1 of <br /> Weston's report, page 12. ) Seasonal high groundwater (Spring <br /> 1986, San Joaquin County Flood Control) can fluctuate to depths <br /> of ten feet below grade. Based upon this information, it will be <br /> necessary for the District to address the remaining soil <br /> contamination with an appropriate mitigation measure. No action <br /> is not an acceptable mitigation measure for this site. <br /> The levels of total lead detected during the construction of <br /> monitoring wells 14 - #7 exceed acceptable water quality• <br /> concentrations.l Further remedial action will necessitate <br /> performing the WET analysis using deionized water to determine <br /> the soluble concentration. Subsequent sampling of all the <br /> monitoring wells shall be analyzed for soluble lead using methods <br /> EPA 239.2 or EPA 200.8. <br /> The Weston report alludes to "daily tidal flux" that may be <br /> influencing the gradients. The District should make arrangements <br /> to perform monthly measurements of the groundwater depths and <br /> compare these to the tide tables. This data should be presented <br /> in a tabular format within the next quarterly report. The <br /> quarterly report shall be submitted to PHS-EHD and Central Valley <br /> Regional Water Quality Control Board (CVRWQCB) by July 15, 1992 <br /> for the months of April, May, and June. <br /> The District shall interpret the quarterly monitoring information <br /> and prepare a Final Remedial Plan by July 24, 1992. <br /> 1Marshack's "The Designated Level Methodology for Waste <br /> Classification Cleanup Level Determination", October 1986, updated <br /> June 1989. <br />