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<br /> <br />COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale - Page 6. PERMIT NUMBER: COG-850000 <br />EFFLUENT LIMITATIONS: (Continued) <br />Table 4 <br />(Final LimitatiSne) <br />Parameter Limitation <br />Flow (MGD) <br />pH (s.u.) <br />011 and Crease (mg/1) <br />Settleable Solids (ml/1) <br />Total Dissolved Solids (mg/1) <br />(Colo. River Basin) <br />Total Phosphorus, ae P (mg/1) <br />(Dillon Reservoir basin only) <br />Active Mining <br />Basis <br />Report Monitoring Only <br />6.5-9.0 WQS <br />10 SES <br />0.5 BAT/NSPS <br />Report Monitoring Only <br />Report Monitoring Only <br />Limitations for pH and oil and grease apply to all discharges, regardless of <br />precipitation conditions. Additionally, TSS and total iron limitations apply <br />unless ezempted as described herein. The permittee may submit documentation <br />proving that discharge was precipitation induced. Upon acceptance by the <br />division. of said proof, the settleable solids limitation will apply in place <br />of the TSS and total Sron limitations. Similarly, upon acceptance of proof <br />that discharge was caused b}• precipitation greater than the 10-year, 24-hour <br />event (or equivalent anowmelt volume) compliance with TSS, total iron and <br />settleable solids limitations will be ezempted. This means such a discharge <br />would be subject to pH and oil aadrgrease limitations only. The division <br />allows these exemptions fora period up to 48 hours after measurable rainfall <br />has stopped or, for snowmelt, within 48 hours after inflow to the <br />sedimentation pond has ceased. After such time, TSS and total iron <br />limitations shall be met. e,~ <br />Example 1: The area se=ved by sedimentation pond and outfall 002 <br />receives 1.4 inches of rainfall during one 24-hour period (the 10-year, <br />24-hour event for this site is 1.7 inches). The permittee collects <br />samples at the outfall 18 hours after rainfall has ceased. The permittee <br />submits rain gauge data with the sample results to the division and <br />requests that the settleable solids limitation be substituted for TSS and <br />total iron limitations. Upon acceptance of the proof, the division will <br />determine compliance with settleable solids limitation and disregard TSS <br />and total iron results. The division requires monitoring for all <br />parameters regardless of whether an exemption is sought. <br />