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L J <br />• <br />HYDROLOGY AND WATER pUALITY DEMONSTRATION <br />CBM-I DEGASIFICATION WELL -DRILL PAD SAE <br />SANDBORN CREEK MINE <br />In order to exhaust gas from the Sandbom Creek Mine, a degasification well was drilled into the mine <br />workings. A drill pad was constructed for [he installation of the degasification well. The drill pad general <br />location is shown on the revised Drawing 2.05-M4, Drainage and sediment Control Plan. The area <br />disturbed by the drill pad is approximately 1.64 ac. Due to the relatively small azea affected by the drill <br />pad, Oxbow believes that alternative sediment and drainage control methods can be used to control erosion <br />from the pad site. <br />Oxbow proposes to consWC[ a clean water diversion to divert runoff from the up-gadien[ watershed <br />around the drill pad. (see Drawing 2.05-M3, Facility Details) Oxbow also proposes to c ntrol and prevent <br />sediments from leaving the site by routing all runoff originating on [he drill pad to silt fence 1 cared down ~~ <br />gradient of the drill pad. The silt fence will be constructed of anchored straw bales. n addition, other than <br />the cut required to construct [he drill pad, the pad is nearly flat and in a roughened condition. Berms will <br />be constructed on either side of [he drill pad, as shown on Drawing 2.05-M3, Facility Details, to route <br />runoff to the straw bales. Any runoff which leaves the drill pad will run-on undisturbed areas, which are <br />vegetated with grass and brush, and will not enter any drainage for a minimum of 600 fee[. The <br />unpdisturbed area should be more thaan adequate to treat any runoff that discharges from the pad azea. ~-- <br />Howevc-R 7'NG ccE~N-wnrc~2 OrvC,QJrei+, ~.tRn. AND 5°TRAw (3ALC5 <br />writ ,C6MnrN r13 iPE~~rkG-D SAE STR~R~QES, <br />A berm (1' high) will be placed around rite topsoil stockpiles [o prevent any loss of soil. <br />The silt fence efficiency was modeled using the SEDCAD4 silt fence utility. A flow rate of 5.6gpm/sq.ft. <br />was input [o the model to represent straw bales in lieu of a silt fence. The flow rate was obtained from <br />Barfield (1978). The berms and clean water diversion were designed using the SEDCAD4 channel utility. <br />The following is submitted to demonstrate that the straw bales can effectively treat the runoff from the 10- <br />year, 24-hour storm event. <br />ASSUMPTIONS: <br />1. The location and dimensions of the drill pad are as shown on the attached Drawing prepared by <br />Oxbow. <br />2. Hydrology and sedimentology inputs are similar to parameters used on other SAE submittals a[ <br />Oxbow. <br />3. In the post-closure condition of the drill pad, the mud pits will be filled and the entire disturbed area <br />will be seeded and mulched. Therefore the hydrology analysis presented in this SAE is worst case. <br />The clean-water diversion will not be reclaimed until vegetation is established on the drill pad. <br />HYDROLOGY AND SEDIMENTOLOGY INPUTS <br />CLEAN WATER DIVERSION <br />Undisturbed Watershed (Figure t) <br />Watershed Area <br />Soil type <br />CN <br />29.5 <br />C <br />63 (undisturbed land) <br />'"., <br />;`S' <br />I1 <br />1.-I <br />DegasDrilPadSAERev I .msword <br />