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Partially to eliminate the risk to waterfowl, CEMEX engaged in a process to reduce the standing <br />surface area under TR-08 and TR-09 by adding inert fill and pumping water from C-Pit into the <br />cement manufacturing process for cooling water. The objective of filling the area with shale <br />("waste overburden") was three-fold: 1) to reduce the elevation of the pit to reduce the migration <br />of stormwater into the area, 2) to provide pore space for the existing water and eliminate <br />standing surface water, and 3) to provide an inert but highly absorptive surface for selenium. <br />The process of filling was closely monitored, including the addition of monitoring wells and <br />piezometers. Filling was halted before a responsive rise occurred in any surrounding aquifers. <br />The result of the fill was reduction of surface area to less than half an acre and a reduction of the <br />pH to a range of 8.0-8.8. Historically, the pH was elevated, at times as high as 12.8 su, selenium <br />was elevated over 500 µg/L, and thallium was elevated to 30 µg/L in the open pit and 22 µg/L in <br />the nearest monitoring well. The level of thallium has reduced to 2.9µg/L. The agreed <br />monitoring methods were 6020 for thallium and selenium, with selenium being tested using <br />dynamically coupled reactive mass spectrometry due to bromide interference. The results <br />reported for thallium are total concentrations. Note that the drinking water standard, if applied, <br />refers to a dissolved concentration where the sample is first filtered to through a 0.45 micron <br />filter. CEMEX can switch to this method if this provides better information to the Division. <br />However, measuring total concentrations was selected for easier correlation to the potential <br />movement of a plume and the TCLP groundwater modeling. <br />At this time, CEMEX is pleased to report that the quality of the water has significantly improved <br />through t he attenuation via t he s hale in aterial a nd s hould n of p resent a s ignificant risk t o t he <br />groundwater in the area. Even so, at this time, CEMEX proposes no reduction in the frequency <br />of monitoring. Quarterly monitoring of C-Pit close well CEM-001 and CEM-004, and <br />compliance well CEM-005, if water is present, will continue to be conducted for the following <br />six analytes: chloride, sulfate, pH, selenium, dissolved thallium, and dissolved solids. <br />The risk presented to wildlife and waterfowl, in particular, is limited. The primary modes of risk <br />are through bioaccumulation within the food chain and impact to nesting birds. There are no <br />algae or aquatic invertebrate life forms present in the ponded area of C-Pit for waterfowl to feed