2011-10-26_REVISION - M1977208 - Laserfiche WebLink

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pH Chloride Sulfate Dissolved Solids Selenium Thallium 6.5 -8.5 250 mg /L 250 mg /L background = X 1.25 0.05 mg/L 0.002 mg /L can be above 400 mg /1 and can range between 108 ppm to 3,680 ppm, according Ground Water Resources of the Bedrock Aquifers of the Denver Basin Colorado. Therefore, per discussions with the Division, CEMEX would like to propose the "middle" CDPHE Water Quality Control Commission (5 CCR 1002 -41 Regulation NO. 41) basic Standards for Ground Water (Table 4) standard of 501- 10,000 mg /1 or 1.25 the background standard if one becomes available. The second exception is the Selenium standard. There is no ground water standard for thallium in the Agricultural Standards Table 3 (CDPHE Water Quality Control Commission (5 CCR 1002 -41 Regulation NO. 41) basic Standards for Ground Water). There is a standard for both selenium and thallium in the drinking water standards Table 1 per the above reference, therefore CEMEX would like to request a standard for selenium of 0.05mg /l. Comment 4. The Operator has requested the removal of streamers around the C -Pit. The Division approved the removal of the net or "other surface water cover" and removal of the condition of daily monitoring for wildlife under Technical Revision - 10. Therefore, the Operator may remove any streamers around the C -Pit. Response: CEMEX appreciates that the Division will allow the removal of the streamer requirement around C -Pit. Comment 5. The Operator has proposed reducing the frequency of sampling from quarterly to semiannually for C -Pit and CEM -004 if the numeric standards have not been exceeded during the first four quarters of sampling. The Division will allow sampling to be reduced to semiannually if the numeric standards have not been exceeded during the first four quarters of sampling. However, if the numeric standards are exceeded during a semi - annual sampling event, then the Operator will be required to resume quarterly sampling. Sampling will continue on a quarterly basis until four quarters are shown to not exceed numeric standards, at which time the Operator may resume semi - annual sampling. Response: CEMEX acknowledges that sampling will continue for four quarters for CEM -001, CEM -004, CEM -005, and C -pit. If the numeric standards have not been exceeded during the four quarters for either CEM -004 or CEM -005 then all sampling, including Page 3 of 5