2010-12-09_REVISION - C1982057 - Laserfiche WebLink

Home Browse Search

Seneca Coal Company strips topsoil in single lifts once the woody vegetation which would interfere with handling of the topsoil has been removed, pursuant to 4.06.2(1). As an optional approach, SCC obtained approval to use a roto-clear machine that reduces large woody vegetation to chips, so that the vegetative material could be incorporated with the topsoil during salvage operations. This technique has been successfully employed at other surface mines in the region, and was used in the aspen habitat within the Wolf Creek/Sage Creek mining block in 2004. Topsoil was redistributed immediately on regraded areas when possible or was stockpiled in designated storage areas pursuant to 4.06.1(2). The amount stockpiled depended on pit advance, season of the year, and reclamation activities taking place at the time of salvage. Stockpiled topsoil was placed in stable areas and protected from wind and water erosion by planting of a quick-growing vegetative cover. Single lift stripping mixes different soil horizons and thereby dilutes heavy clay concentrations encountered in various subsoils. Although soil survey information and soil handling plans contained in the PR-1 application were detailed and comprehensive, several issues of concern were raised during the adequacy review. The Division questioned what field characteristics would be used to define appropriate salvage depths and requested justification for complete or partial salvage variances proposed for a number of soil map units. SCC provided appropriate detail in regard to field salvage depth determinations. Generally, in shale derived soils dominated by western wheatgrass/alkali sagebrush vegetation, a 6 inch depth was salvaged. In sandstone, derived soils dominated by mixed brush vegetation, salvage was terminated at the sandstone bedrock contact or when a characteristic reddish brown clay subsoil was encountered. In response to the salvage variance concerns, various tables, exhibits and text sections were revised to indicate that all suitable topsoil would be salvaged and that no salvage variances were being requested. The proposed soil replacement depth was changed from 1. l feet to 1.3 feet. Based on disturbed area modifications, updated soil balance calculations, and reclamation plan changes made in association with PR-5, the approved average replacement thickness in the original permit area is 1.3 feet, and average replacement thickness in the South Extension area is 1.1 feet. Within designated aspen planting exclosures, approved average replacement soil thickness is 4.0 feet; within upland shrub establishment areas topsoiled in 2006, average replacement thickness is 0.6 feet. Certain statements in Tab 21 indicate that topsoil in map units 101,103 and S 103 may be of questionable suitability based on rock fragment content. Current information indicates that topsoil in the subject map units is suitable and was salvaged. Soil stabilization methods proposed by the operator consist primarily of minimal seed bed preparation (resulting in a roughened soils surface) and use of either a straw mulch or a quick growing annual grain cover crop on all topsoiled areas. Reclaimed areas will be inspected annually by the operator as required by the proposed rill and gully maintenance plan, and additional stabilization measures will be implemented if results of the annual evaluation warrant such modifications. Graded spoils with excessive clay content as Seneca II-W Findings Document 44 C1982057 Permit Renewal No. 5 December 9, 2010