2009-03-06_PERMIT FILE - C1981012A (6)

Home Browse Search

COLORADO DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT, Water Quality Control Division Rationale - Page 12, Permit No. CO-0000906 • effective immediately. At Outfalls 001A and 009A, settleable solids limitations do not apply. ThepH limits are not the most stringent as discussed in later subsections. The paragraphs that follow discuss other conditions that also apply based on 40 CFR Part 434. Sediment Control Plan: In accordance with 40 CFR Part 434.82, the permittee is required to submit a Sediment Control Plan as outlined below. This requirement is applicable only to reclamation areas, brushing and grubbing areas, topsoil stockpiling areas, and to regraded areas. Outfalls that accept runoff from these areas may include Outfalls 004A, 007A and 008A. Once this requirement is met, the settleable solids limitations at these outfalls will be replaced with the approved Sediment Control Plan. This has been included as a compliance schedule item in Section VI.D.2 of this rationale, and Part LA of the permit. (a) The operator must submit a site-specific Sediment Control Plan to the permitting authority that is designed to prevent an increase in the average annual sediment yield from pre-mined, undisturbed conditions. The Sediment Control Plan must be approved by the permitting authority and be incorporated into the permit as an effluent limitation. The Sediment Control Plan must identify best management practices (BMPs) and also must describe design specifications, construction specifications, maintenance schedules, criteria for inspection, as well as expected performance and longevity of the best management practices. (b) Using watershed models, the operator must demonstrate that implementation of the Sediment Control Plan will result in average annual sediment yields that will not be greater than the sediment yield levels from pre- mined, undisturbed conditions. The operator must use the same watershed model that was, or will be, used to acquire the Surface Mining Control and Reclamation Act (SMCRA) permit. (c) The operator must design, implement, and maintain BMPs in the manner specified in the Sediment Control Plan. • Alternate Limitation Burden o Proof Requirements: In conformance with 40 CFR 434.63, the permittee has the burden of proof when requesting relief from total suspended solids (TSS), total iron and/or settleable solids limitations, as appropriate. Relief shall be granted only when necessary and shall not be granted when the permittee has control over the discharge. The permittee should endeavor to meet the primary limitations whenever possible. Relief is not available for mine drainage and therefore the alternate limitations do not apply at Outfalls 001 and 009. For rainfall, to waive TSS and total iron limitations, it is necessary to prove that discharge occurred within 48 hours after measurable precipitation has stopped. In addition, to waive settleable solids limitations, it is necessary to prove that discharge occurred within 48 hours after precipitation greater than the 10 year, 24-hour event has stopped. For snowmelt, to waive TSS and total iron limitations, it is necessary to prove that discharge occurred within 48 hours after pond inflow has stopped. In addition, to waive settleable solids limitations, it is necessary to prove that discharge occurred within 48 hours after pond inflow volume greater than the 10-year, 24-hour event has stopped. Documentation that the treatment facilities were properly operated and maintained prior to and during the storm event must be submitted with any request for relief. The Division shall determine the adequacy ofproof. As part of this determination, the Division shall evaluate whether the permittee could have controlled the discharge in such a manner that primary limitations could have been met, whether proper sediment storage levels were maintained and the ponds had sufficient water and sediment capacityfor the storm event plus other relevant factors. All manual pond dewatering must meet TSS and total iron limitations unless previous approval has been granted for ponds that have no other method of dewatering. Post-Minim: In conformance with 40 CFR 434.50, commencing at the time active mining has ceased and all surface areas served by a sedimentation pond have been returned to the required contour and revegetation has commenced, applicable discharges may be eligible for limitations other than those specified in Part I.A. 1. In most cases, these post-mining limitations shall remain in effect until bond release. The permittee shall notify the Division • at the appropriate time so that consideration of permit modifications can be made. Prior to notification and subsequent permit modification, active mining limitations will apply regardless of actual mine status. b. pH -This parameter is limited by Water Quality Standards as the water quality standards of 6.5-9.0 s. u. range are more stringent than those specified under the Regulations or Effluent Limitations.