Laserfiche WebLink
COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Quality Control Division <br />Rationale-Page 6, Permit No. CO-0032638 <br />only when necessary and shall not be grunted when the permit[ee has control over the discharge. Relief is not <br />available for spoils spring water; the permtttee must demonstrate that exceedance was caused by precipitation. The <br />permittee should endeavor [o meet the primary limitations whenever possible. <br />For rainfall, to waive settleable solids limitations, it is necessary to prove that discharge occurred within 48 hours <br />after precipitation ended. For snowmelt, to waive settleable solids limitations, it is necessary to prove that <br />discharge occurred within 48 hours after pond inflow has stopped. <br />Documentation that the treatment facilities were properly operated and maintained prior to and during the storm <br />event must be submitted with any request for relief. The Division shall determine the adequacy of proof. As part of <br />this determination, the Division shall evaluate whether the permtttee could have controlled the discharge in such a <br />manner that primary (imitations could have been met, whether proper sediment storage levels were maintained and <br />the ponds had sufficient water and sediment capacity for the storm event plus other relevantfactors. <br />Sediment Control Plan f40 CFR 434.821: In accordance with 40 CFR Part 434.81, the permtttee is required to <br />submit a Sediment Control Plan as outlined below. This requirement is applicable only to reclamation areas, <br />brushing and grubbing areas, topsoil stockpiling areas, and to regarded areas. Both Outfa11004A and 007A meet <br />this description. Once this requirement is met, the setteable solids limitations at these outfalls will be replaced with <br />the approved Sediment Control Plan. This has been included as a compliance schedule item in Section V/.D.2 of <br />this rationale, and Part I.A of the permit. <br />a) The operator must submit asite-speck Sediment Control Plan to the permitting authority that is designed to <br />prevent an increase in the average annual sediment yield from pre-mined undisturbed conditions. The Sediment <br />Control Plan must be approved by the permitting authority and be incorporated into the permit as an effluent <br />limitation. The Sediment Control Plan must ident~ best management practices (BMPs) and also must describe <br />design specifications, construction specifications, maintenance schedules, criteria for inspection, as well as <br />expected performance and longevity of the best management practices. <br />(b) Using watershed models, the operator must demonstrate that implementation of the Sediment Control Plnn <br />will result in average annual sediment yields that will not be greater than the sedimentyie[d levels from pre- <br />mined undisturbed conditions. The operator must use the same watershed model that was, or will be, used to <br />acquire the Surface Mining Control and Reclamation Act (SMCRA) permit. <br />(c) The operator must design, implement, and maintain BMPs in the manner specified in the Sediment Control <br />PJnn, <br />b. The emulations for Effluent Limitations (Regulation No. 62) include efflatent /imitations thatapply m al! discharges <br />of wastewater to State waters. These regulations are applicable to the discharges from the Edna Mine. <br />The oil & grease and total suspended solids (TSS) concentrations from the Regulations for Effluent Limitations are <br />the mast stringent effluent limits and are therefore applied. These limitations are [he same as those contained in fhe <br />previous permit and are imposed effective immediately. <br />c. pH: This parameter is limited by Water Quality Standards as the water quality standards of 6.5-9.0 s.u. range are <br />more stringent than those specified under the Reputations for Effluent Limitations. <br />d. Pollutants Limited by Water Quality Standards: The water quality assessment m Appendix A contains the evaluation <br />of pollutants limited by water quality standards. The mass balance equation shown in Section IV ofAppendix A was <br />used for pollutants to calculate the maximum allowable effluent concentration, M~, that could be discharged without <br />causing the water quality standard to be violated. A detailed discussion of the calculations for the maximum allow <br />able concentrations for metals is provided in Section IV of the water quality assessment contained in Appendix A. <br />The maximum allowable effluent pollutant concentrations determined as part of these calculations represent the <br />calculated effluent limits that would be protective ojwater quality. These are also known as the water quality-based <br />effluent limits (WQBELs). Both acute and chronic WQBELs may be calculated based on acute and chronic <br />standards, and these may be applied as daily maximum (acute) or 30-day average (chronic) limits <br />