Laserfiche WebLink
may be granted for each discharge occurrence only when necessary and shall not be granted when <br />the permittee has control over the discharge. The permittee should endeavor to meet the primary <br />limitations whenever possible. <br />a) For rainFall to waive TSS and total iron limitations, it is necessary to prove that discharge <br />occurred within 48 hours after measurable precipitation has stopped. In addition, to waive <br />settleable solids limitations, it is necessary to prove that discharge occurred rovithin 48 hours after <br />precipitation greater than the 10-year, 24-hour event has stopped. <br />Relief from primary TSS and Total Recoverable Iron limitations at Outfalls 001 and 004A: <br />Please see OOlA and 004A Exceedence Report attached to this submittal for more detail and <br />back-up information. <br />Rainfall was recorded at Colowyo on Febmary 11 and 12, 2007, the day prior to and the day <br />sampling was completed at this location. Inflow into this pond is primarily in the form of <br />stormwater runoff at this time. Temperatures on the two prior stated dates reached highs of 41.4°F <br />on February 11, 2007 and 35.3°F on February 12, 2007. This accumulated precipitation combined <br />with unseasonable warm temperatures created severe snow melt and runoff from sun•ounding <br />slopes. It is Colowyo's firm belief that the discharges occurring on February 13, 2007 were a <br />direct result of precipitation events (rain) and warm temperatures creating snow melt and surface <br />runoff. Additionally, please see the attached climatological data for additional information. <br />Colowyo believes this specific incident of exceeding primary TSS and Total Recoverable Iron <br />limitations is due primazily to increased stormwater runoff caused by a storm events and snowmelt <br />the day prior to and the day of sampling. <br />Colowyo performs PE reviewed pond inspections of all NPDES ponds on a quarterly basis as <br />mandated by CDRMS/Colowyo Permit requirements. These quarterly inspections are reviewed by <br />CDRMS staff and specific guidance, maintenance issues, and improvements aze discussed as <br />necessary with Coloywo's assigned CDRMS inspector (currently James Stazk). <br />Outfalls OOIA and 004A were cleaned out in November 2006, and all sediment accumulation was <br />removed at that time. The available sediment volume storage capacity for the ponds during the <br />first quarter was well below any tilt level for permit compliance. Ponds are tazgeted for cleanout in <br />the event one of two criteria are met; either the pond approaches 60% available storage capacity, or <br />the rate of sedimentation suggests the pond will receive enough sediment to reach 60% available <br />capacity during the course of the following year. As a matter of convenience, sediment was <br />removed from this ponds during November 2006 even though no thresholds requiring cleanout <br />were reached. <br />In an effort to further minimize issues with TSS limitations, Colowyo is in communication with GE <br />Betz in order to identify any acceptable products on the mazket that could be more effective at <br />settling out suspended materials. Testing is in progress to evaluate the relative effectiveness of <br />these products. <br />Colowyo is currently evaluating opportunities for improving the manner in which stormwater <br />enters the pond. Modifications to in-pit drainage structures and conveyance ditches may be <br />warranted if opportunities for minimizing particle/sediment loading are discovered. This is an on- <br />going process and improvements will be implemented as they aze identified. <br />Colowyo Mine • 5731 State Highway 13 • Meeker, Colorado 81641 <br />T +1 970 824 1500 • F +1 970 824 1504 • www.nea.rom <br />