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COLORADO DEPARTMENT OF PUBLIC HEALTHAND ENVIRONMENT, Water Quality Control Division <br />Rationale, Page 10, COG-0850000 Coal Mining General Per»tit <br />may have additional constraints placed upon the discharge. These constraints may include accepting end ofpipe limitations (no <br />dilution), moving the discharge point to a d~erent location, or using a diffuser to obtain an instantaneous mixing of the effluent <br />and the receiving water. This last option may allow for a portion of the available assimilative capacity (dilution) to be <br />incorporated into the permit. However, as this is a general permit, all limitations are imposed as end ofpipe limits, and <br />therefore, the first option is met. Generally, it will be assumed that the end ofpipe limitations will satisfy the MOA, and no <br />further consideration is needed. On a case-by-case basis, additional constraints may need to be evaluated. <br />i. MIXZnQ Zones -Under this general permit mixing zone regulations do not apply, as the water quality standards are applied as <br />the effluent limits(i.e., no dilution is allowed.). <br />Discharges to 303(d) Listed Waters -Where the receiving water is included on the state's 303(d) list, total maximum daily <br />loads (TMDLs) are being developed in accordance with the Division's schedule for TMDL completion. Once a TMDL has <br />been established, if it is necessary to incorporate limitations for a facility certified under this general permit, based upon the <br />outcomes of the TMDL or the results of the data analysis, a modification to the certification to discharge, or an individual <br />permit may be required to regulate discharges from a facility. The facility would continue to be covered under this general <br />permit certification until the individual permit is issued. <br />Compliance Schedules- Existing dischargers may be granted compliance scheda~les for any new effluent limitations applicable <br />to the discharge. Some items requiring a compliance schedule may require an individual permit. Note that compliance <br />schedules cannot be granted for limitations based upon the federal ELGs. <br />V. STORMWATER DISCHARGES <br />Stormwater requirements have been included in this general permit and are outlined in Part I. C of the permit. <br />VI. PUBLICNOTICE COMMENTS <br />No comments were received during the public notice period. Note that the Division eliminated the 2 year maximum compliance <br />schedule requirement. <br />Andrew J. Neuhart <br />May 28, 2008 <br />• <br />