2019-04-25_REVISION - C1981019 (2)

Home Browse Search

RULE 4 PERFORMANCE STANDARDS Rule 4 Performance Standards 4-15 Revision Date: 4/25/19 Revision No.: MR-200 In accordance with Rule 4.05.9(13), the permittee may retain impoundments to be permanent to support the post-mine land use. The Gulch A Pond has been requested by the surface landowner (please see Volume 2B, Exhibit 1B) to remain as a permanent impoundment. Inlcuded with this request and part of the Gulch A watershed the surface landowner also requested that the East Side Collection Ditch remain as permanent structures. The Gulch A Pond in it’s current configuration (which will also be the post-mine condition) meets the requirments of Rules 4.05.9(13)(a) – (f). The Gulch A Pond has not exhibited any water quality issues with any discharges from the pond. The normal water level in the pond is typically well below the primary discharge elevation. The surface landowner has adequate access via a road from State Highway 13 to the pond, and the size of the Gulch A Pond is adequate for livestock watering which is the intended post-mine use. 4.05.10 Underground Mine Entry and Access Discharges Colowyo currently conducts surface coal mining exclusively. 4.05.11 Ground Water Protection There are no aquifers or continuous sources of ground water within the stratigraphic section from which the Colowyo Mine mines coal using surface mining techniques. This is also noted in Section 2.04.7. In addition, there are no continuous aquifers of regional extent within the entire Williams Fork Formation in the location of the Colowyo Mine. Occasionally, a minimal amount of water is found under perched conditions in noncontiguous lenticular sandstones and in fractured coal under the sandstones. No toxic concentrations of acid forming materials have been found in the overburden, reclaimed slopes or surface and ground water system associated with the Colowyo Mine. No adverse effects on groundwater quality are expected to occur due to mine excavations or backfilling. 4.05.12 Protection of Groundwater Recharge Capacity The reclamation plan as described in 2.05.4 will return the disturbed lands to approximately the pre-mining condition; therefore, ground water recharge capacity is expected to approximate the premining condition. Also, because of the minimal existence of ground water in the mining area, the mining operation and subsequent reclamation should have no adverse effect on the existing ground water recharge capacities. The history of the ground water monitoring plan is further documented in 4.05.13. The mine has not established Point of Compliance locations for ground water monitoring because of a lack of ground water. The following discussion is provided to document this: The aspect of monitoring ground water is dependent on whether or not there is a continuous, non-perched ground water layer/zone to monitor. Since active mining at Colowyo Mine began 30 years ago, the mining zone in both the East and West Pits have not encountered any significant ground water, except for perched ground water. Therefore, the following is presented to clarify the ground water conditions at the Colowyo Mine.