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A'urrorh,~r 1'/97 CICC-,\',;cLmcni 1'r~ld l.)ruunryr nriurr-AJinc i .7 • According to Division of ~4inerals and Geoloey (DMG) Regulation 3.03.1(3)(6), no more than 60 percent oFthe bond can be released until the applicant demonstrates that exishng conditions will result in equivalent or lesser sediment contributions [o surface runoff when compared with pre-disturbance conditions or rmdisturbed areas. The following information is provided to meet the requirements of the specified demonstration. The post-mining land use for Mine 3, Blocks North and Soudt has been defined/as pastureland. Slopes average appmximately 6%° in the Mine 3 North Block and approximately 2~° in the Mir1e-~ SouthBloch. ~ ~ ~ / 1 ~v /~o / Three approved reference areas are located in Block South for Mine 3 including cropland, pastureland, ~and low sage. The cropland referenc/area is approximately 3.4 acres with an ave ar ge slope of approximately ?P/v and is located adjacent to Middle/Creek. The pastureland reference area is approximately 3.9 acres with an average slope of approximately 18% and is located on the hillside east of th~mined area. The low sage reference area is approximately 3 acres- with an average slope of approximately 16% and is located on the west side of the mined area. v 7 '_ '_ Due to the ~i>;tiifican[ variability__dt topography between [he reference areas and [he reclaimed parcels, it is inappropnate to develop a direct sediment vield comparison behveen [he areas [o satisfy DMG Regulation 3.03.1(3)(6). In [he alternative, a SEDCAD + model has been developed by CYCC to demonstrate that runoff from Blocks North and South results in equivalent or lesser sediment contributions to surface runoff when compared wilt adjacent undisturbed conditions. SEDCAD+ is a computer software program developed [o assist - in the evaluation of stonnwater runoff, erosion, and sediment control management techniques. ~" The 1995 and 1996 Block North vegetation surveys and 1996 and 1997 Block South vegetation. un~ C ^r ' conducted by CYCC and available soil information from the existing permit document were utilized~as input to • the SEDCAD+ program. To develop a comparative model for unmined adjacent areas, ~CYCC utilized vegetation information derived from the 1995, 1996, and 1997 Cropland, Low Sage, and Pastureland Reference Area vegetation surveys conducted coincident with [he Block North and South surveys! These reference area ` Dave been established as being representative of [he vegetation found in adjacent, unmined lands. - ~ . ~ _ -- - - - - -- ~ M^1 ry . {~ The reclaimed blocks and associated reference area boundaries do not coincide with watershed boundaries ~~4v' ~ n therefore, representative portions of the areas are modeled on a small scale with model inputs selected as 2,-r appropriate to distinguish those characteristics unique to the reclaimed sites. Grading practices which enhance surface roughness,-reduce the length of overland flow, rand increase infiltration are the primary modeled attributes which strengthen the reclaimed area's ability to reduce suspended solids concentrationsly~ Jd-~ °tsr~"O pt- t.'`` ' I o model areas with similar topography and soil types, CYCC combined the vegetation survey information for r,- .I './ ~~, the Cropland, Low Sage, and Pastureland Reference Areas_with information on the topography and soil types rte, ,r I determined for Blocks North and South.r The soil types and topography found in Blocks North and South are' X~ ,similar [o [he soils and topography found in adjacent unmined areas. f The Combined Reference Area soil t}'pe and vegetation data were modeled with the topography of the reclaimed areas [o develop a representative small watershed for comparison with the reclaimed areas. By modeling comparable adjacent areas in this manner, the sediment yield demonstration provides a reasonable comparison of the success of the revegetation efforts and [heir effects on surface runoff and sediment loads. fn~o w '~ ~.~ 1<r~~ ~Y~ [- Saxxrwl~a ~ is\bo n d rel \m ina)\sed\sed m ine3.duc