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Minrec, Incorporated Water Quality Assessment CO- 0048233 The Minrec facility is the sole known point source industrial contributor to North Thompson Creek. No other point sources were identified as dischargers to North Thompson Creek upstream or downstream of the confluence with Thompson Creek. Pollutants of Concern Pollutants of concern may be determined by one or more of the following: facility type; effluent characteristics and chemistry; effluent water quality data; receiving water quality; presence of federal effluent limitation guidelines; or other information. Parameters evaluated in this WQA may or may not appear in a permit with limitations or monitoring requirements, subject to other determinations such as a reasonable potential analysis, mixing zone analyses, 303(d) listings, threatened and endangered species listings or other requirement as discussed in a permit rationale. The following parameters were identified by the Division as pollutants to be evaluated for this facility: • Metals • Sulfide • Boron • Temperature There are no site - specific in- stream water quality standards for TSS and oil and grease for this receiving stream. Thus, assimilative capacities were not determined for these parameters. The applicable limitations for these pollutants can be found in Regulation No. 62 and will be applied in the permit. Stream segment COUCRF 10 is designated a water supply for future uses. There are surface water intakes downstream of the discharge. However, due to the distance (greater than 5 miles) and the significant dilution of both the Crystal River and the Roaring Fork River, drinking water uses are not considered. During assessment of the facility, nearby facilities, and receiving stream water quality, no additional parameters were identified as pollutants of concern. VI. Determination of Water Quality Based Effluent Limitations (WQBELs) Technical Information Note that the WQBELs developed in the following paragraphs, are calculations of what an effluent limitation may be in a permit. The WQBELs for any given parameter, will be compared to other potential limitations (federal Effluent Limitations Guidelines, State Effluent Limitations, or other applicable limitation) and typically the more stringent limit is incorporated into a permit. If the WQBEL is the more stringent limitation, incorporation into a permit is dependent upon a reasonable potential analysis. In- stream background data and low flows evaluated in the previous sections are used to determine the assimilative capacity of North Thompson Creek near the Minrec facility for pollutants of concern, and to Appendix A (WQa v 7.0) Page 12 of 25 Last Revised Sept 14, 2009 /ES