2016-10-12_PERMIT FILE - M2016010

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Rationale for Recommendation to Approve 17 September 29, 2016 On March 11, 2016, the Division provided notice of the permit application to the DWR and the CDPHE, Water Quality Control Division (WQCD). The CDPHE WQCD did not provide any comments or recommendations for protection of surface water. On April 21, 2016, the Division received a comment from the DWR, outlining its conditions for approval of the permit application. The Applicant submitted a response to the DWR's comment, which was included in the first adequacy review response submitted to the Division on July 14, 2016. In the July 14th response, the Applicant committed to contacting the DWR if exposure of groundwater occurs during the operation, to importing water legally obtained from a hydrant(s) operated by Colorado Springs Utilities (from which hydrant permits will be obtained), to not diverting or restricting flows in Little Turkey Creek or Deadman Creek, to consulting with the local Water Commissioner regarding any activity that might affect the flow of water to any stream system and/or ditch, and to complying with all applicable rules and regulations regarding water use. Pursuant to Rule 6.4.7(5) and Rule 6.4.13, the application states that a National Pollutant Discharge Elimination System (NPDES) permit from the WQCD will be obtained (stormwater discharge permit) in order to conduct the proposed mining and reclamation operations. 7. Concern regarding Exhibit G—how did the applicant calculate a maximum flow cap of 20.11 cfs for Little Turkey Creek?Is only three data points collected over a three month period sufficient for analyses?Maximum flow in recent floods far exceed 20.11 cfs-May 2015 floods overwhelmed culverts which have capacity of 70 cfs; Given only three data points were collected at station LTC-], how can applicant say it is similar to historic flows at the USGS station 7099220?No data sources are available for the significant flood years of 1921, 1935, 1965, 1995, 1997, 2013, 2015? Are proposed water management structures undersized? What 24-hour rain amount was used for the maximum storm estimate? What damage is expected to Little Turkey Creek Road or property below the quarry if water management structures fail during a flood event? Will the operator compensate owners for damage due to the improperly sized capacity of water management structures to deal with flood events? Table G-2 shows 24-hour storm event data based on NOAA calculations— is this data based on rain figures for Colorado Springs airport? If so, why were no adjustments made to account for higher rain rates in Little Turkey Creek canyon compared to the airport? (N.Reed, C.Kimble) The maximum calculated flow cap demonstrates the Applicant has taken the initiative to monitor flows in Little Turkey Creek by establishing the LTC-1 monitoring station prior to submitting the permit application. This was done to begin characterizing surface water conditions at the site. This value was not used for stormwater structure designs or peak flow determinations. This value was derived from the instantaneous streamflow measurements obtained from the LTC-1 surface water monitoring station established by Norwest Corporation on Little Turkey Creek in June 2015. A total of five sampling events have been conducted since LTC-1 was established, on June 26, 2015, August 26, 2015, November 16, 2015, April 12, 2016, and June 22, 2016. A rating curve for the station was developed using the instantaneous flow measurements and transducer readings. The rating curve was used to calculate flow using the 15-minute stream depth data. Due to the small data set of measured flow, maximum calculated flow was set at the maximum measured flow plus two standard deviations of the data set resulting in the maximum calculated flow cap of 16.53 cfs. 1313 Srewi in Strr.-V— Rory.,-215, Denver, CO e'>703 P 303.866.356'F 3-33,832.8106 John tv. Hicker,loo' Go,ewor I Rorer, V,. Rand,itt, EXOCU:ve D cc:o( I vir�'F-a 8r=anon. Dtrectot .i , % iOt