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..~~ ,.~ <br />. • Part <br />Page lj of 19 <br />Permit No. CO-0042562 <br />B. MONITORING REQUIREMENTS <br />13. Mining Impacts to the Roosevelt Tunnel: In the event of resumed mining <br />activity in the Carlton Tunnel, the permittee shall observe monthly for <br />any discharge from the Roosevelt Tunnel to determine whether the <br />activity has any impact on the Roosevelt Tunnel drainage area. If any <br />impact is observed, the permittee shall immediately apply for a <br />discharge permit for the Roosevelt Tunnel drainage. <br />14. Low Flow Determination: Instream monitoring requirements are being <br />added to verify the assumptions made for determining the effluent <br />limitations in this permit. The permittee has the option to either <br />develop and implement a monitoring plan or to install a gauge upstream <br />from the discharge to measure flow. If the permittee chooses to <br />perform a monitoring study, the three (3) year study should include, at <br />a minimum: a determination of variability on a daily basis by <br />measuring flow over the period of a day for at least five (5) days <br />during the study period, a determination of variability over a week by <br />measuring flow daily over the period of a week for at least one summer <br />and one winter week during the study period, a determination of <br />variability over a month by measuring flow weekly for at least six (6) <br />months (if variability is seen, weekly flow measurements should be <br />taken for the entire study period). The final monitoring location and <br />the study plan or the location of a gauge shall be submitted to the <br />Division withing 180 days of the permit effective date. The final <br />results and data from the study shall be submitted to the Division with <br />the permit renewal application 180 days prior to the permit expiration <br />date. <br />15. One Time Analysis: In the event of resumed mining activity in the <br />Carlton Tunnel, the permittee shall conduct a one time analysis of the <br />discharge for Potentially Dissolved Arsenic, Trivalent Chromium, <br />Hexavalent Chromium and Nickel, and for Total Recoverable Iron and <br />Manganese. Results of this analysis shall be submitted to the Division <br />within 45 days of resuming mining activity. The Division may impose <br />additional monitoring and/or effluent limitations based on the results <br />of this analysis. <br />