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<br />COLORADO DEPARTMENT OF HEALTH <br />Water Quality Control Division <br />Addendum - Page 3 <br />Permit Number: CO-0027154 <br />Applicable Rules and Regulations: (Cont'd.) <br /> <br />~!~ ~`~ \ <br />PP 9 it ~~ (~q„ ~~^ <br />~, .. ,; ; G;~ 6 tli~i{T6flM <br />With regard to copper, the one time analysis showed a maximum of .02 mg/1, the <br />average copper value from the data submitted was .016 mg/1 which is still <br />above the stream standard of .O1 mg/1. <br />Dissolved manganese in the one time analysis also exceeds the stream <br />standard. However, the average manganese value is below the stream standard. <br />For silver, the detection limit is above the stream standard and thus it <br />cannot be determined if the standard can be achieved. <br />In the case of zinc, the maximum one time analysis value is greater than the <br />stream standard but the average value is less . <br />Sulfate concentrations in the aquifer water also exceed water quality standard <br />values. However, a sulfate limitation will not be placed in the permit for <br />the following reasons. Based on the information provided by the Water Quality <br />Control Commission in setting stream standards, the 250 mg/1 sulfate standard <br />has been established by EPA for a "finished" drinking water supply. The <br />Commission, in order to maintain the water supply use, has suggested <br />application of this standard at water supply intakes. The nearest downstream <br />community water supply is on the Yampa River at Craig, Colorado. <br />No reports of excessive sulfate concentrations have been received by the <br />Division. Thus, there is no need to impose a sulfate limitation at the point <br />of discharge. Should future reports indicate a sulfate problem in drinking <br />water, this permit may be reopened and modified. <br />tJhen effluent limitations are calculated the stream standard converts to a <br />30-day average. The daily maximum concentration is generally twice the 30-day <br />average value. <br />The annual seven day ten year low flow (Q7_lp) for Foidel Creek is zero. <br />This information is based on USGS stream gage 09243800 located on Foidel Creek <br />approximately 6.5 river miles upstream from the confluence of Foidel Creek and <br />Trout Creek. <br />In addition to an annual low flow determination, seasonal low flows were <br />calculated for the periods of March-June, July-October and November-February. <br />All seasonal low flows were found to be zero. The period of record was 1976 <br />to 1979. Since the Q7_lp is zero for all seasons, instream water quality <br />standard (WQS) values become the effluent limitations for the permit for <br />discharge point 005. <br />For the other discharge points associated with sedimentation ponds, new <br />effluent limitations will also be added. These effluent limitations are the <br />result of promulgation of Federal Best Available Technology Economically <br />Achievable (BAT) rules. <br />