2012-02-06_HYDROLOGY - C1980007 - Laserfiche WebLink

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Hernandez, Alysha From: Welt, Kathy [KWelt @archcoal.com] Sent: Monday, February 06, 2012 11:44 AM To: Stark, Jim Cc: Schiro, Robin; Hernandez, Alysha; Norris, Weston Subject: RE: 3Q11 Sediment Pond Inspection Reports Jim, Regarding your questions — the simplest answer is either the ponds are not sediment ponds (i.e. not ponds that collect mine site runoff for treatment (settling) and discharge) or they are not yet built. One is the MWTF or mine water treatment facility ponds (aka deepwell ponds) where we pump from the underground sealed water collection sump, aerate to treat for iron and then discharge through outfall 017 if needed for augmentation (it is an adjudicated water right that has not been pumped or discharged for a couple years) and the other is the polishing pond for the wastewater treatment plant (an integral part of the wastewater treatment system) that is regulated by CDPHE under our CDPS permit ( Outfall 007). Being part of our wastewater system, the pond is pumped by a licensed septic pumping contractor as need, typically once or twice a year. There are no ponds or discharges yet constructed in Minnesota Creek (i.e. Dry Fork, etc.) so there's nothing to look at or report there. As for sediment levels, it is a visual assessment that is determined based on our various experience over the past couple of decades - Having seen them be built, drained and cleaned over the years. Our environmental technicians look at each pond almost every day and can gauge how long it takes to for each pond to fill and how sediments accumulate within each pond and we (Env Engineers) keep tabs with them on how each pond is doing and then also inspect them ourselves at least weekly . As I'm sure you've noted at other facilities, the sediments do not accumulate evenly throughout these ponds and tend to gather at the inlet area, so the measurement stake or other survey methods we've used in past years have tended to be ineffective. We also schedule cleanings when we can see that sufficient sediments have accumulated at a time of year when the sediments are drier and can be readily excavated, handled and hauled (i.e. just before or well after spring runoff— the time of year when the ponds are filled and drained more often). As a result we hardly ever (if ever) allowed the ponds to even get close to a sediment level (elevation) requiring cleanout. Please let me know if you have further questions or require clarification. Cathy `Weft, Environmental Engineer III Mountain Coal Company, LLC West Elk Mine P.O. Box 591 Somerset, CO 81434 Phone (970) 929 -2238 Cell (970) 433 -1022 Fax (970) 929 -5050 From: Stark, Jim fmailto:Jim.Stark @state.co.us] Sent: Friday, February 03, 2012 12:33 PM To: Welt, Kathy Cc: Schiro, Robin; Hernandez, Alysha Subject: 3Q11 Sediment Pond Inspection Reports