GENERAL43367 - Laserfiche WebLink

Home Browse Search

lies too deep to be mined by surface methods and the Lennox is relatively thin and discontinuous within the permit area. The Wadge coal is the only seam to be mined as par[ of this operation. The surficial geology of the area is composed chiefly of sedimentary rocks, of marine and non-marine origin. These sedimentary rocks were formed through the transgression and regression of an epicontinental sea. Alluvial deposits are locally present in stream valleys, particularly along the larger streams. Colluvial slides and slumps are also present in canyons and gullies throughout the area. Slide bodies which could potentially affect the stability of mining related structures in the northern portion of the permit area have been identified, and mitigation measures are addressed in Section VII., "Backfilling and Grading" of this document. Geologic baseline information including: local and regional structure; stratigraphy; and information on interburden, overburden and coal geochemistry is provided in Volume 2, Tab 6, of the permit application. Ground Water Bedrock ground water aquifers have been identified as the Wolf Creek coal seam, the Wadge coal seam, the Wadge overburden including the discontinuous Lennox coal seam and the Trout Creek sandstone. Recharge to these and other aquifers in the area is a function of infiltration ofsnow melt and rainfall at outcrops along the anticline. All aquifers exhibit water table conditions near the outcrop. However, observation wells installed downdip indicate the aquifers are all under artesian conditions with increased pressure related to increased depth. Quality in all aquifers is poor and undesirable for use as either a drinking or irrigation supply. The Seneca II-W Mine permit area lies on the western flank of the Sage Creek Anticline, a local structure located within the more regional Sand Wash Basin. The Sage Creek Anticline is thought to control local ground water flow, as artesian head increases with distance from the anticlinal axis. Ground water occurs in the alluvium associated with Hubberson Gulch within and adjacent to the permit boundary. Quality of this water prohibits its use for drinking and severely limits its use for irrigation. Drinking water and irrigation standards were exceeded for TDS, Conductivity and Manganese. Surface Water The mine permit boundary encompasses two surface watersheds. Most of the mine site and the major portion of the disturbed area will drain into Hubberson Gulch and an unnamed tributary to Dry Creek. A small area on the eastern edge of the permit boundary drains to Sage Creek. Seneca 1[-W Findings Document 6 June 15, 2001 Permit Renewal No. 3