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NPDES Effluent Criteria (Permit No. CO-0000221) One excursion of NPDES <br />effluent criteria occurred this year. On April 28, a total recoverable <br />iron (TR) value of 1,490 ug/l was observed at NPDESII. The standard <br />listed on the DMR is 1,000 ug/1. However, a temporary modification <br />applies to this stream segment, 13e, Grassy Creek. The total recoverable <br />iron limit is now "Report", which reflects the temporary modification. <br />Therefore, this excursion should not be considered a NPDES violation. <br />This excursion was most likely caused by a beaver dam found in the <br />discharge culvert the day of sampling. A sample had to be collected that <br />day, as it was getting towards the end of the month. Precipitation was <br />predicted for the last two days of April, and this site is inaccessible <br />when the road is muddy. The total recoverable iron value on a sample <br />collected May 4 was 570 ug/1. <br />Currently there is a Temporary Modification for the TR iron standard on <br />Grassy, Sage and Dry Creeks based on "existing quality". SCC <br />participated in the Colorado Water Quality Control Commission's December <br />13, 2010 Temporary Modification Rulemaking Hearing. The Commission <br />approved SCC's proposals for ambient-based TR iron standards for Sage <br />Creek (Segment 13e). These standards will become effective on June 30, <br />2011. Those standards will be: <br />Lower Sage Creek year round 1.00 mg/l <br />Upper Sage Creek year round 1.25 mg/l <br />The break between Upper and Lower Sage Creek is the west border of <br />Section 18, TSN, R87W. SCC's outfalls for the Seneca II-W Mine discharge <br />into Lower Sage Creek. SCC's outfalls for the Yoast Mine discharge into <br />Upper Sage Creek and Grassy Creek. The Commission did not approve SCC's <br />proposal for an ambient-based TR iron for Grassy Creek, but did extend <br />the Temporary Modification (based on "existing quality") until December <br />31, 2012. <br />Surface Water Summar <br />The Yoast Mine PHC (PAP Tab 17, Attachment 17-5) predicts TDS increases <br />to be observed at various stream sites during the irrigation season <br />14