1985-05-29_REVISION - C1981012 - Laserfiche WebLink

Home Browse Search

• Ms. Candace Thompson May 29, 1985 Page Two When planned preparation plant design modi#ications are completed, the plant should be a true "closed system" with zero discharges. However, it is prudent to anticipate an occasional discharge resulting from equipment malfunction, power failure, etc. These discharges would normally be small and infrequent, but it is likely that larger discharges from the thickener will occur when it is drained occassionaly (2-3 times per year) for repair or routine maintenance. Under this technical revision, these discharges will be directed to Pond 006. The attached calculations indicate that draining the thickener will discharge approximately 2.0 acre-ft of water, .2 acre-ft discharge sediment, 7.0 gallons of cationic flocculant and .7 gallons of anionic flocculant. The sediment is composed of coal and rock that are too fine for capture by the preparation plant (less than about 60 mesh). Flocculants are Nalco brands 8872, an anionic high molecular weight settling agent, and 8852,a moderate molecular weight liquid cationic coagulant. Pond 006, as it presently exists (including losses on west end resulting from thickener construction and sediment build-up), has a capacity of 3.2 acre-ft to the 7388 ft spillway elevation. Therefore, it has the necessary capacity to accomodate occasional thickener and other discharges, but in order to handle 3 discharges per year for 3_y_ear o • (i.e. 3-yr sediment load), a capacity of 3.8 acre ft is required with clean-out at 3.l acre-ft 7 (60% sed. load). - -~ WFC has made application to the Colorado Department of Health to modify the NPDES discharge permit for this pond under this proposed revision. However, discharges from this pond are anticipated to be few because water will be recycled through the plant whenever practical. ,~ WFC does not anticipate that use of Pond 006 as a containment structure will ~ - adversely impact either the surface or underground hydrologic regimes. As shown above, ~ "y the pond should never have more than 1.1 acre-ft of sediment before clean-out. Previous studies by Water, Waste and Land, Inc in WFC's Revision to the New Elk Mine Permit Application for the New Elk Coal Preparation Plant and Refuse Disposal Area (Exhibits 111.4-1 and III.4-2) have indicated that hydrologic impacts from refuse material are minimal. Exhibit II[ .4-1 (Leaching Characteristics of Coal Refuse) suggests that hydrologic impacts resulting from relocation of the river and filling the old channel with refuse would be negligible. Because the affected area and volume of sediment material in Pond 006 are both small, hydrologic impacts should also be negligible. u