Laserfiche WebLink
5. The only constituent within the mine water being treated is suspended solids. This is <br />already apparent in the text. While other parameters are addressed within the discharge permit <br />settling out of suspended solids effectively addresses the pertinent water quality issues. <br />6. Maintenance of the B-Seam Dewatering System will primarily entail cleaning out sediment <br />from the first sedimentation pond on an as-needed basis. The specific frequency will depend on <br />operational and hydrologic changes encountered underground. It is anticipated that cleaning this <br />pond will be anywhere from every year to once at the end of the project. During cleanout water <br />from the mine will be discharged to the next pond in sequence. <br />This dewatering system will remain operational until BME has determined that it is no longer <br />needed. We currently anticipate that we can stop discharging to the surface after completing one <br />or two longwall panels on the east side of B-Mains (current estimate of 2023). This will allow <br />room for underground storage of excess water within the sealed workings. <br />Once no longer needed, the treatment facilities will be reclaimed. The Last Chance Pond will be <br />left until phase II bond release. SH-3 will be kept available for alternate uses until BME <br />determines that it is no longer needed. <br />7. The settling of suspended solids is the treatment objective of the proposed system. While <br />the total sediment load on the above ground system is currently unknown a sample collected from <br />BME's current underground excess water handling system (currently being pumped to the mined <br />out D-seam area via underground pipeline) showed TSS in the 650 mg/1 range. Observations from <br />bulk samples collected for testing showed the vast majority of sediment settling in the first few <br />hours with overnight settling resulting in what appeared to be an acceptable sample. While a <br />detailed study was not performed a substantial safety factor was incorporated into the treatment <br />design providing for an extended settling duration. <br />Recent rates of the existing system show average flows of 32.6 gpm. Assuming a higher flow rate <br />of 50 gpm each of the dewatering ponds equates to over 24 hours of retention time. Retention <br />times would be about 40 hours per pond at the current rates. Current system design allows BME <br />plenty of time to monitor treatment effectiveness and make appropriate adjustments if necessary to <br />prepare for higher flow rates. <br />It must be recognized that the system as proposed is over designed and capable of far more <br />treatment than is currently envisioned as being necessary. A substantial safety factor was used to <br />allow for the unknown such as higher periodic flow rates when isolated pockets of water are <br />encountered. <br />The system allows easy maintenance due to its multiple ponds configuration. The dewatering <br />ponds are long and narrow which maximizes their efficiency while keeping sediment within reach <br />of an excavator for cleanout. <br />Applicable effluent limitations found on BME's discharge permit are: <br />Flow, MGD <br />TSS, mg/1 <br />pH, s.u. <br />Oil & Grease, mg/l <br />Settleable Solids, m1/l <br />30-Day Avg. Daily Max. <br />0.61 <br />35 70 <br />6.5-9 <br />10 <br />0.50 <br />'rA y