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r k ~ OF CO~ III III III IIII I ~~ „` ~~'g sss .. ~ /B 76 ~ Roy Romer, Governor DEPARTMENT OF NATURAL RESOURCES MINED LAND RECLAMATION DIVISION FRED R. BANTA, Director August 18, 1989 Mr. Jim Stover Permittee Liason Grand Mesa Coal Company 743 Horizon Court, #205 Grand Junction, CO 81506 RE: Tecnnical Revision IJo. 6 Adequacy Response, Red Canyon Mine, C-81-034 Dear Mr, Stover: The staff has evaluated the technical revision on the hydrologic monitoring plan modification. The rationale for the reduction in monitoring was evaluated in light of assertions made in the Kamon Tempo Hydrology Appendix, and the Mined Land Reclamation Division Findings document in the probable hydrologic consequences section. It would be useful to review the expected immediate and long-term hydrologic impacts of the Rea Canyon Mine with the proposes plan. sedimentation would occur following storm events, the Division proposes that sampling frequency oe cnanged from three times a year to twice a year - once during peak flow and again during a late Sumner storm event. Increased sedimentation below the recently revegetated disturbed area may occur for the next couple of years until a good cover is established at the site. To that end, Grand Mesa is proposing monitoring of two sites above and below the site in the Carbon Ditch for field parameters three times a year. As the recently regraded site may result in an increase in salinity, conductivity and OH are useful measurements, but the Division is also interested in any cnange in total suspended solids at the two sites. As The Kamon Tempo report suggested that operation impacts on Ward Creek might include dewatering of the stream and changes in flow. The rationale for the monitoring reauction indicates that no flow reduction was observed and that the expected depletion might not be detectable. Ward Creek was undermined in July of 1981 and pumping of mine infl ow ended in August of 1980. However, flows at the downstream Ward Creek site were recorded only twice during that period in May, 1986. Altnougn no depletion was observed, more monitoring would support Grand Mesa's assertion better. STATE, OF COLORADO 215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567