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Whetstone' <br />Associates <br />Technical Memorandum <br />intermediate contour lines were created by extrapolating between the existing 6,550, 6,570, and <br />6,590 ft contour lines. <br />SECTION 11. SURFACE WATER QUALITY DATA <br />13) Based on surface water quality data from stations SW-A001 and SW-BPL, the uranium <br />concentration in Ralston Creek increases about two orders of magnitude between the two stations. <br />Knowledge of the concentrations along this reach is important to understanding the system, yet the <br />five surface water sampling stations between these two sites have been discontinued from the <br />monitoring program. The monitoring plan must initially include all of the surface water sampling <br />stations SW-BDIS, SW-PL, SW-OS, SW-BOS, and SW-GS. <br />The monitoring program has been expanded to include sampling at the five "local" surface water <br />stations SW-BDIS, SW-PL, SW-OS, SW-BOS, and SW-GS. Section 12 of the EPP has been revised <br />to include quarterly sampling of the extended surface water analytical suite at these five stations, <br />along with weekly sampling for dissolved uranium, field temperature, field pH, and field <br />conductivity. <br />14) Pursuant to comments provided by CDPHE Water Quality Control Division in their memo of <br />May 10 2010, please ensure that the appropriate and current water quality standards are referenced <br />and apply to the entire stream segment of Ralston Creek. <br />The text of Section 11 of the revised EPP has been modified to reflect the current stream standards <br />identified by CDPHE. <br />SECTION 12. WATER QUALITY MONITORING PLAN <br />15) DRMS supports the proposed locations of future surface and ground water quality monitoring, <br />and requires additional surface water monitoring sites as discussed in item 13 above. With respect <br />to analytes, the plan must include field temperature along with pH and conductivity for all surface <br />and ground water samples. The extended analyte suite for surface water shown on page 5 of 7 <br />should be expanded to include Phosphorus and Nitrate + Nitrite. As recommended by CDPHE, the <br />surface water sampling suite must also include Gross Alpha and Gross Beta. The extended analyte <br />suite for monitoring wells, domestic wells and sumps shown on page 6 of 7 must be expanded to <br />include Phosphorus and Nitrate + Nitrite. As recommended by CDPHE, the sampling suite for <br />monitoring wells, domestic wells and sumps must also include Gross Alpha and Gross Beta. <br />Concurrently with the plan as proposed, all surface water, ground water, and sump monitoring <br />locations must be analyzed for the extended suite on a quarterly basis. <br />The analytical suite has been modified as requested. The revised monitoring plan is included in <br />Section 12 of the revised EPP. <br />SECTION 15. MITIGATION OPTIONS AND CONSTRUCTION SCHEDULE <br />4109C.100731