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well. Statistically significant increasing TDS trends are observed. <br /> Surface Water <br /> SPL has a functioning sediment control system diverting, conveying and/or treating <br /> surface water runoff in and around the mine site. The sediment control system <br /> includes seven sedimentation ponds (Ponds 005, 006, 009, 015, 016, 016A and 017). A <br /> more complete discussion of this system is found above, in Section III C of this <br /> document. <br /> The applicant conducts monitoring of surface water in a manner approved by the Division. <br /> The monitoring plan submitted under 2.05.6(3)(b)(iv) comprises Tab 15 and Appendix 15- <br /> 3A of the permit application package. A number of amendments to the surface water <br /> parameter list and analytical techniques for certain parameters were approved in TR69, in <br /> 2010 and TR83 in 2016. SPL included a plan for an alternative water supply in the event <br /> that local water rights are adversely impacted by mining in Tab 16 of the permit. <br /> Hydrologic protection,probable hydrologic consequences, and the hydrologic reclamation <br /> plan constitute Tabs 16, 17,and 18,respectively. <br /> Surface water at the Seneca IIW Mine lies within two watersheds. The primary <br /> affected area lies within the Dry Creek Drainage flowing to Hubberson Gulch and an <br /> unnamed tributary to Dry Creek (the Pond 005 Gulch). A small portion of the eastern <br /> part of the permit area drains to Sage Creek. Both creeks confluence with the Yampa <br /> River near Hayden. Both Dry Creek and Sage Creek exhibit intermittent to perennial <br /> flows, depending on location along the streams, and precipitation trends. Hubberson <br /> Gulch is intermittent. <br /> Surface water quality sampling is described in Tab 15,Appendix 15-3A of the Seneca IIW <br /> mining permit. The CDPHE surface water quality and receiving stream standards appropriate <br /> for the site are: <br /> o CDPHE,Regulation 31,2009 <br /> o Yampa Segment 13d,Regulation No 33,2015 <br /> o Yampa Segment 13e,Regulation No 33,2015 <br /> The stream standards for Sage Creek and Dry Creek are based on aquatic life standards. <br /> Occasional annual exceedances comprise ammonia nitrogen MDL,mercury, sulfide and the <br /> recoverable iron standards. The recoverable iron standard has seasonal limits(1.I I mg/1 from <br /> May—Feb. and 3.04 mg/1 during March and April). The high level mercury test with a <br /> method detection limit of 0.2 ug/1 for streams was run as were tests for ammonia nitrogen and <br /> sulfide. All high level test values were less than the detection limits. <br /> Based on CWQCC reg. 31,the manganese standard of 0.2 mg/l,applies to plants grown in <br /> acidic soils(<6.0 pH). In alkaline soils,as found throughout the Yoast and Seneca II W <br /> region,the EPA standard would be 10 mg/l. Pre mining manganese baseline values exceeded <br /> the 0.2 mg/1 standard. The manganese standard(0.2 mg/1),for agricultural use, is generally <br /> exceeded a couple instances per year. This standard is only appropriate where irrigation is <br /> utilized on soils with a pH lower than 6.0. In the alkaline soils typical of the Seneca II site,a <br /> more appropriate standard would be 10 mg/L,thus the 0.2 mg/1 standard shows occasional <br /> annual excursions. <br /> The Hubberson Gulch Watershed,Dry Creek and Sage Creek <br /> 11 monitoring sites exist within the Sage Creek, and Hubberson Gulch/Dry Creek basins. <br /> These include six NPDES surface water monitoring sites. In TR63 it was determined that <br /> Page 21 of 37 <br />