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iii iiiiiiiiiiiu iii STAB DIVISION OF MINERALS AND GEOLOGY Department of Natural Resources 131 J Sherman St., Room 215 Denver, CO 80203 Phone:1303) 866-3567 FAX:(30J)832-8106 T0: Jim McArdle FROM: Bob Kirkham %f'ro~ DATE: July 27, 1995 RE: Subsidence features COLORADO JUL J t i'~~J OF ~O[o ~`~ = *.~ ~'vicio~ ~ u. ~~~u,erais is Geology . Ne •`18 ]6 s• Roy Romer Governor Michael 8. Long Division Direuor reported by Janet Binns near New Pryor mine Pursuant to your request I conducted afield investigation of the hazardous subsidence features immediately west of the New Pryor coal mine near Aguilar that were recently reported by Janet Binns. This mine was reclaimed a couple of years ago during a coal bond revocation project by Kessler Reclamation that was supervised by Randy Streufert. Both features reported by Janet are beyond the limits of the previous coal bond revocation project. They are near (within a couple of hundred yards), but do not coincide with any earlier AML closures that we installed during past projects. Neither feature currently poses a significant hazard that would warrant inclusion in a future AML project. One feature is about 10' X 10' X 5' deep, wh ile the other is about 10' X 18" X 4' deep. Both occur in surficial deposits; bedrock was not observed in either. The floor of both pits is vegetated, the walls are not vertical, and neither appears to allow access to underground workings. The features probably partially filled with soil eroded from their walls during the heavy rainstorms of the past spring and early summer. The features should be checked again next year, but unless they become mare hazardous I would not encourage reclaiming them using AML funding. Another subsidence feature located in a swats drainage about 250 feet east of those reported by Janet does pose a physical hazard and should be safeguarded by the AML program. This feature appears to be immediately west of the area reclaimed during the bond revocation project, based on grading patterns and vegetation distribution. It appears that fill placed during the bond revocation project was slightly higher than the floor of the drainage, and water may have ponded up in a shallow depression behind the fill. This feature is about 6' X 7' X 9' deep and is developed entirely in soil. The floor of the feature contains a pile of collapsed soil debris, and underground voids extend laterally east and west from the collapsed area. One void is about 3' H X 6' W and extends about 10 feet off to the west before it disappears out of sight. The other is about 2' H X 2' W and runs a few feet to the east until disappearing. This feature should be addressed by a future AML project. Should this feature and a few others associated with coal mines near Walsenburg and Trinidad should be included in the next construction grant? cc: Janet Binns