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Sellards Grigg, Inc. CONSULTING ENOfNEERS /LAND SURVEYORS Mr. David Berry Coal Program Supervisor Division of Mines and Geology Department of Natural resources 1313 Sherman Street, Room 215 Denver, CO 80203 RECEIVED MAR 0 ~ 2001 Division of Minerals 8 Geoloc~/ RE: Powderhorn Coal Mine -Review of Water Plan Calculations Sellards & Grigg No. 2001014-21 Dear Mr. Berry: BACKGROUND iii iiiiiiiiiiiu iii 999 March 2, 2001 Sellards & Grigg, Inc. (S&G) has been retained by the State of Colorado Division of Minerals and Geology to review calculations by J. E. Stover 8 Associates for the discharge from the Powderhorn Mine for the discharge water plan. S&G understands that the Mine is in the process of being abandoned. The State of Colorado will accept responsibility for the Mine once it is abandoned. The abandonment requires leaving the Mine in a safe condition so that it cannot be entered by amateur spelunkers who could become lost or trapped. Ground water collects in the Mine and can build to a dangerous level capable of compromising the integrity of the entrance plug at the Northwest Portal. To relieve the water, the Powderhorn Coal Company (PCC) has installed a siphon system. Since the flow of ground water varies, the amount of discharge also varies. As a result, the siphon system can cease to operate and need repriming whenever this occurs. To keep the siphon working, personnel from the PCC use a throttling valve to keep the siphon primed. The State of Colorado prefers a system that operates automatically and does not require tinkering with the throttling valve. J. E. Stover & Associates while working for the PCC has proposed such a system to be constructed in the area of the North Decline. The North Decline is at both the north end and the low point of the existing mine. The Mine at this point is lower in elevation than the Colorado River. The purpose of this letter is to verify the calculations in order that the State may feel more confident that the proposed system will continue to operate properly in all conditions and will not require constant monitoring. THE PROPOSED SYSTEM The proposed system consists of an angled drill to the roof of the Mine, a 45° bend, and a drain pipe at a 2-percent gradient to the median of Interstate 70. Refer to the map, the profle, and the calculations by Stover shown in Figure 14-11 copies of which are attached. These calculations are essentially correct, and the proposed system should work as designed. 390 Union Boulevard, 303.966.1444 Suite 630 FAX 303.986.0994 Lakewood, Colorado 80226 E-MAIL www.sandga.com