|
COLORADO DEPARTMENT OF PUBLICHEALTHAND ENVIRONMENT, Water Quality Control Division
<br />Rationale-Page 6, Permit No. CO-0032115
<br />Table VI-3 -Federal Standards (40 CFR 434
<br />Parameter Limuations
<br />30 Day Avg Daily Max.
<br />pH, s.u. (minimum -maximum) -6.0 - 9.0-
<br />Total Suspended Solids, mg/1' 35 70
<br />Total Iron, mgA'
<br />BAT" 3.5 7.0
<br />NSPS'** 3.0 6.0
<br />Settleable Solids, ml/1' N/A 0.5
<br />' These parameters subject to Burden of ProojRequirements, see next section
<br />" Best Available Technology -applies to those ponds constructed prior to 5/4/1984
<br />"' New Source Performance Standards -applies to those ponds constructed after 5/4/1984
<br />Alternate Limitation Burden of ProofReauirements: In conformance with 40 CFR 434.63, the perminee has the
<br />burden ofproof when requesting relief from total suspended solids (7SS), total iron and/or settleable solids
<br />limitations. Reliefshal! be granted only when necessary and shall not be granted when the perminee has control
<br />aver the discharge. The perminee should endeavor to meet the primary limitations whenever possible. The Division
<br />shall have final authority in determining whether relief is granted. Discharges from all outfa/Js are eligible for this
<br />exemption; however, the majority ofthe loadingfrom any discharge has to consist ofstorm runoff for the relief to be
<br />avatlablejor any dscharge. Outfalls 001, 002, OOS, 008, 009, 012, 013, 014, 015, 016, OI B, 022, and 024 consist
<br />entirely of surface runoff' thus all discharges from these thirteen outfal[s should be eligible, providing the proper
<br />demonstration is submitted and approved.
<br />i. For active outfalls.• Far rainfall, to waive TSS and [oral iron limitations, it is necessary to prove that discharge
<br />occurred within 48 hours after measurable precipitation bas stopped. In addition, to waive settleable solids
<br />limitations, it is necessary to prove that discharge occurred within 48 hours after precipitation greater than the
<br />10-year, 24-hour event has stopped. For snowmelt, to waive TSS and total iron limitations, it is necessary to
<br />prove that discharge occurred within 48 hours after pond inflow has stopped. In addition, to waive settleable
<br />solids limitations, it is necessary to prove that discharge occurred within 48 hours after pond inflow volume
<br />greater than the 10-year, 24-hour event has stopped.
<br />ii. Fo~ost-minim outfalls: For rainfall, to waive settleable solids [imitations, it is necessary to prove that
<br />discharge occurred within 48 hours after precipitation greater than the 10 year, 24-hour event has stopped.
<br />For snowmelt, to waive settleable solids limitations, it is necessary to prove that discharge occurred within 48
<br />hours after pond inflow volume greater than the 10 year, 24-hour event has stopped.
<br />Documentation that the treatment facilities were properly operated and maintainedprior to and during the storm
<br />event must be submitted with any request for relief. The Division shall determine the adequacy ofproof. As part of
<br />this determination, the Division shall evaluate whether the permittee could have controlled the discharge in such a
<br />manner thatprimary limitations could have been met, whetherproper sediment storage levels were maintained and
<br />the ponds had su,Jftcient water and sediment capacity for the storm event plus other relevant factors. All manual
<br />pond dewatering must meet TSS and total iron limitations unless previous approval has been granted for ponds that
<br />have no other method ofdewatering.
<br />Post-Mininr Areas: In conformance with 40 CFR 434.50, commencing at the time active mining has ceased and all
<br />surface areas served by a sedimentation pond have been returned to the required contour and revegetation has
<br />commenced, applicable discharges may be eligible for limitations other than those specified in Part I.A.I. In most
<br />cases, these post-mining limitations shall remain in effect until bond release. The perminee shall notify the Division
<br />at the appropriate time so that consideration of permit modifications can be made. Pn'or to notification and
<br />subsequent permit modification, active mining limitations will apply regardless ofactual mine status.
<br />d. Pollutanu Limited by Water Quality Standards: The water quality assessment in Appendix A contains the
<br />evaluation ofpollutanu limited by water quality standards. The mass balance equation shown in Secton IV of
<br />Appendix A was used for all pollutants to calculate the maximum allowable e~Iuent concentration, M,, that could be
<br />discharged without causing the water quality standard to be violated. A detailed discussion of the calculations for
<br />the maximum allowable effluentpo/lutant concentrations for metals are provided in Section IV of the water quality
<br />assessment contained in Appendix A.
<br />Last Revised: 3/12/2004
<br />
|