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potential hazard exists, the CDMG will be promptly notified of the potential hazard and of any appropriate emergency procedures formulated and/or implemented to protect public safety and remediate the potential hazard On completion of operations, a is anticipated that the Area 1 Basin will be reclaimed, as described under Section 2.05.4(2)(c) of the PAP. Reclamation will involve backEilling the basin area with either coal waste or spoils, placemem of a minimum of 4 feet of suitable spoil (if used for coal waste only), topsoil replacement, and revegetation. ~oil~s~tinfl Disc}rarp~e, Grotmd Water Movement, and Quality Considerations The Area 1 Basin is designated as a coal waste disposal site, has been used for coal waste disposal in the past, and maybe utilized for this propose in the future. When the coal preparation plain was constructed and commusroned, however, all coal waste previously placed in the Area 1 Pit was removed and run through the coal preparazron plant to recover the associated coal The Area 1 Pit is an open excavation with a bedrock highwafl on the north and west sides and a spoil slope on the south and east sides. The bedrock on the highwall side contains a sequence of saturated sandstone and siltstone units referred to as the "overburden aquifer". The characteristics of the overburden aquifer are fully described in the PAP text under Section 2.04.7. The permeability and storativiry of the overburden aquifer have been detemtined by conducting pump tests at several locations in the pemrit area At the EnergyNo. 1Mine, average horizontal permeability is 2.9 gallons per dayper square foot, vertical permeabiliryis 0.1 gpd/fr2, and storativiry is 1.7 x 10.4 (umt-less). The average yield of wells penetrating the overburden aquifer rs 17.6 gpm Hydraulic conductivities in the overburden aquifer are, therefore, very low, except in localized areas where the aquifer has been extensively fractured by joints and fauns. The reclaimed spoil material up-dip from the pit forms an unconfined aquifer which serves to recharge the local ground water system Water from snowmen and rainfall infiltrates into the spoils to the floor of the former mine pit and then moves down-dip along the pit floor where it tends to pool against the highwalL Based both on calculated . values and previous monitoring of this area, inflows to the Area 1 Basm from spoil spring discharge are estimated at a ma~nmum of approximate}y 35 gpm, with peak spoil spring discharge occurring dumng a brief period (a few days to a maximum of two months) during late spnng. Since the Area 1 Basin is at the final highwall, the limited volume of water resuhing from infikration through the spoils water tends to collect and accrunulate m the pit. The head of any spoil water accumulation in the pit normally exceeds the elevation of the piezometric sruface in the adjacent overburden aquifer, consequently spoil water accrurnilations infihrate itrto the highwall, providing recharge to the overburden aquifer. From this area, ground water flows to the nonh under the gradient of prezometric suuface as shown on Map 13, Twentymile Park Hydrology. Strip mitring operations at the Energy No. 1 Mine ceased in 1980. Daring the mining operations, groundwater inflow from the overburden in the highwall was minimal. Since that time, infikration of water from rainfall and snowmelt imp the reclaimed spoils has ceased leaching of the spoil materials, and this leachate has accumulated in the final pit at the bottom of the dip-slope. The chemistry of the leachate water, as well as the water level and chemistry of ground water in the overburden aquifer, were monitored on a monthly basis during afive-year period from 1979 through 1983. Monitoring records are listed in Table 50, Energy Mine No. 1 Pit Water Quality, of the PAP. As shown below, actual concentrations of TDS fluctuate, due to seasonal variations in snowmen and precipitation: Year # Samples Min D Max. TDS Ave. TDS 1979 21 2080 3850 2948.1 1980 37 700 3320 2626.8 1981 22 456 2920 2608.5 1982 17 324 3320 2863.1 1983 24 520 4400 2757.9 Incident Precivitation and Run-on -The surface area of the Area 1 Basin is only approximately 5.1 acres, so water contributions from normal incident precipitation aze negligible (0.77 ac-fr fora 10-year, Z4-hr event or 0.61 percent of pond capacity). An upgradient diversion ditch (Ditch D-3) imereepts any surface runoff from TR 05-47 Ex8 V-2 Revised -March 2005