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COLORADO DEPARTMENT OFP IC HEALTH AND ENVIRONMENT, Watei rlity Control Division <br />Rationale - Page 2, CO- 0027529 <br />III. RECEIVING STREAM <br />A. Identification, Classification and Standards <br />1. Identification: Discharges to Cement Creek, Segment 7 of the Animas and Florida Sub -basin of the San Juan <br />River Basin. <br />2. Classification: This stream segment is designated as Use Protected and is classified for the following uses: <br />Recreation, Class 2; Agriculture <br />3. Numeric Standards: The standards which have been assigned in accordance with the above classifications <br />can be found in 3.4.0., Classifications and Numeric Standards for the San Juan River Basin (5 CCR 1002 -8), <br />which became effective March 30, 1995. The organic standards which apply to this receiving stream are <br />listed in 3.1.0 Basic Standards and Methodologies for Surface Water (5 CCR 10024), effective March 2, <br />1995. The following numeric standards which have been assigned in accordance with the above <br />classifications will be used to develop effluent limitations. <br />Physical and Biological Standards <br />pH = 3.7 - 9.0 s. u. <br />Fecal Coliforms = 200/100 ml <br />Metals <br />The Classifications and Numeric Standardsfor the San Juan River Basin contain the following narrative <br />standards for metals: "Effective until March 2, 1998, all metals standards have been set equal to existing <br />ambient quality. Effective as ofMarch 2, 1998, as a result offurther Water Quality Control Commission <br />actions, metals standards will be equal to the concentrations of dissolved aluminum, cadmium, copper, iron, <br />lead, manganese and zinc that are directed toward maintaining and achieving water quality standards in <br />segments 3a, 4a, 4b and 9b of the Animas Basin." <br />B. Receiving Water Data <br />1. Quality - The Division, in coordination with other entities, has extensively sampled the upper Animas Basin, <br />including Cement Creek. In general, the results of that sampling indicate that concentrations ofseveral <br />metals exceed certain aquatic life criteria. A more detailed discussion is presented in 3.4.0., Classifications <br />and Numeric Standards for the San Juan River Basin. <br />2. Quantity, Acute and Chronic Low Flows - There are no effluent limitations in this permit that are based upon <br />mass - balance calculations, which would require the estimation of upstream low flows for the receiving <br />stream. <br />3. Impacts on Downstream Water Supplies or Other Receiving Waters: Provided the terms and conditions of <br />this permit are complied with, no adverse impacts on downstream segments should occur. <br />