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Mr. Michael S. Savage Page Two June 28, 1985 It is our understanding that the Division is somewhat concerned about the potential for low pH discharge from the sediment pond, given the inflow from the old Victory No. 1 mine portals. If monitoring indicates a pH below 6 at the sediment pond outlet, Peerless will add lime to the sediment pond in order to increase the pH to an acceptable level (6 to 9). An acidity test will be used in order to determine the quantity of lime which should be added to the pond. No water will be released from the pond until the appropriate amount of lime has been added and the pH has stabilized within acceptable limits. The Division feels that subsidence will occur upon abandonment of the Coal Gulch Mine. This subsidence will affect the Cliff House Sandstone, which is probab y contributing water to the Arness/McGriffin Mine. A discussion re ardin robable ortal, discharge quantity and quality is necessary. Response: The source of the present discharge from underground workings is the abandoned Victory No. 1 Mine. Discharge was occurring from the old mine portal prior to any disturbance by the Arness/McGriffin Coal Company. The proposed Coal Gulch mining plan has been designed to minimize potential subsidence effects and it is anticipated that any subsidence which may occur will be negligible. If, as the Division indicates, significant subsidence does occur, effecting the Cliff House Sandstone, potential increases in the inflow rate to the old workings will be limited by local geologic structures and the relatively small areal extent of the old workings. The vertical continuity of fracture patterns typically associated with subsidence is generally limited. Since the Cliff House Sandstone is separated from the coal seam to be mined by a relatively thick interval of siltstones and shales, the probability of significant increases in vertical permeability is small. In addition, the general area is a recharge zone for the Cliff House Sandstone which exists in an unconfined condition. Under these conditions, the hydraulic pressure within the Cliff House Sandstone is low even though the hydraulic gradient is relatively steep. Because of the low hydraulic pressure, groundwater movement would still be governed by the hydraulic gradient even if significant subsidence and fracturing were to occur. Present discharge from the old workings has been observed to vary between approximately 5 and 15 gallons per minute. It is anticipated that minor increases in inflow wou result in a discharge of no more than 20 gallons per minute with no significant change in water quality. d"® ? ~~~y NNE' ~~~~