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!~ . 51A1 t, OF COLORADO Roy Romer, Gove DEPARTMENT OF NATURAL RESOURCES MINED LAND RECLAMATION DIVISION DAVID C. SHELTON, Dlreetor DATE: March 6, 1987 T0: Peter O'Connor FROM: Steve Renner RE: King Coal Subsidence Monitoring - (C-81-035) As you know, there has recently been considerable discussion regarding the subsidence monitoring requirements at the King Coal Mine near Hesperus. I have researched the permit, Public Files and permit history, and have conducted informal discussions with Division personnel involved in permitting the operation in 1981 and 1982. During the permitting process, the Division determined that a potentially impacted structure (The Huntington Ditch) existed above the King Coal Mine. The regulations (2.05.6(6) and 4.20) require that certain measures be undertaken by the permittee to (1) ascertain the effect of subsidence upon potentially impacted structures, and (2) undertake appropriate mitigation. The permittee elected to meet the requirements of the regulations by committing to visually monitoring the ditch for cracks and fractures, and by committing to affect necessary repairs to the ditch in the event of subsidence related damage. Inter-office correspondence date October 30, 1981, stated that the proposed observation and repair plan was acceptable and met the requirements of the regulations. The memorandum also stated that it would be prudent for the operator to perform survey observations, which would more accurately determine if the ditch was subsiding. Upon resolving the Huntington Ditch issue, the Division became concerned that the King Coal operation would undermine Pine Gulch, one drainage south of Hay Gulch. Again, the Division was concerned that subsidence processes would cause the gulch to de-water into the mine. This concern was alleviated by way of correspondence dated December 23, 1981, from a consultant for National King Coal, Inc. to the Division. This correspondence specifically stated that no mining would take place beneath Pine Gulch. In compliance with the approved permit, National King Coal, Inc., has, on a regular basis, submitted ditch inspection and subsidence monitoring reports to the Division. These reports generally consist of a statement by the operators' consultant which summarizes field observations made during the inspection. A number of these reports state that actual field surveys have been, or will be, conducted for the operator. No data from any of these surveys could be found on file (public or specialist) with the Division. Many 423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. (303) 866-3567