2009-10-23_PERMIT FILE - M2009076 (19)

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PHS - South Platte June 2009 Reg 38 RMH Segment WBID: COSPCL02c Segment Number & Description: 2c. Mainstem of Clear Creek, including all tributaries and wetlands, from a point just below the confluence with Mill Creek to a point a point just above the Argo Tunnel discharge, except for specific listings in Segments 9a- 9b, and 10. Antideg. Designation: Reviewable. "9/30/2000 Baseline_ does not apply" Use Classifications: Aquatic Life Cold I Recreation E Agriculture Water Supply Special Conditions: Zn(ch)=200 lig/l. Temporary Modifications: u(ch)=11.9 11g/1(dis). Zn(ch)=234 ug/1(dis)Zn(ac)=304_ _u_g/_1(disl type" expiration date of 7/01/2014 Proposed Changes 2008: The Division is proposing to split this segment from Segment 2. A note that the "9/30/2000 Baseline does not apply" was added for antidegradation analysis. Rationale for Changes 2008: The Division is proposing to split this segment from Segment 2 in order to better capture differences in water quality along the length of Clear Creek. Current conditions of this segment have been evaluated and summarized in this rationale. The figures below show zinc concentrations at a station above Mill Creek and below Mill Creek, the lower bound of Segment 2b and the upper bound WQCD Exhibit 38-5 Clear Creek Basin Rationale Water. Quah ..Data COSPCl 0 c ?Paramctcr TVS=- DOW, RW, UCCWA' 2002 - 2.008 n H, s.u. 6.5- 9.0 7.5-8.4 60 D.O., mg/L 6 8.82 5 Hardness*, mg/L NA 83.5 113 E. coli, #/100 mL 126 - 0 As-D**, pg/L 0.02 0.00 107 Cd-D, pg/L 0.37 0.70 142 Cu-D, pg/L 7.68 8.59 142 Fe-D, pg/L 300 55 142 Fe-Trec, pg/L 1000 161 137 Pb-D, pg/L 2.07 0.45 119 Mn-D, pg/L 50.0 162.4 142 Se-D, /L 4.60 0.00 133 A -D, pg/L 0.06 0.00 72 Zn-D, pg/L 106.6 203.4 142 U-D, pg/L 30 - 0 NH3, Mg/L TVS 0.010 23 N05, 1119/L 10 0.349 23 S04i m 250 45.8 3 * Hardness measured as CaCO3 mg/L ** Standard is Tree of Segment 2c. Ambient-based standards remain unchanged until further investigation can prove what the appropriate underlying standards should be. The Division has also modified the temporary modifications applied to this segment based upon data from within the segment from 1998 forward (WQCD Exhibit 15). A temporary modification was added for the acute zinc standard because acute zinc TVS which currently applies to the stream is lower than both the current site-specific chronic standard and the chronic temporary modification. The Division is proposing to add the note to the tables regarding the antidegradation baseline as it is not clear that the default baseline is appropriate in consideration of remediation efforts. An adjustment of the baseline may not be appropriate for all parameters (i.e., non-metals). Aquatic Life: Along the mainstem, between Georgetown Lake and Idaho Springs, rainbow (CS-2) and brown trout (CS-2) generally dominate the total catch in terms of abundance. Although brook and cutthroat trout (CS-1) occasionally comprise a high percentage of the total catch, generally, their numbers are substantially reduced relative to the surveys above Georgetown. CDOW data indicate the presence of the following species in the segment's tributaries: brook trout (CS-1). These data derive from survey sites in a single tributary, Mill Creek. Water Supply: None identified. Recreation: Fishing, boating, kayaking, and swimming are practiced activities in these waters. Commercial rafting