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© TerraMatri>tc <br />MONTGOMERY WATSON <br />Natural Resource Group <br />~~GEIVED <br />October 30, 1997 N~~ Q 3 991 <br />Mr. Tom Kaldenhach Division w .vuuelals & Geology <br />Colorado Division of Minerals and Geology <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />Re: Hayden Gulch Terminal, Inc., Permit No. C-91-081 <br />Rail Loop Pond -Storage Capacity Demonstration <br />Dear Mr. Kaldenbach: <br />ii~iii~ljriii~<<iii <br />On behalf of Mr. Thomas Perrosky of Hayden Gulch Terminal, Inc. (HGTn, attached, <br />please find three copies of a Technical Revision (TR) request for HGTI's, Hayden Gulch <br />Loadout (Loadout). The purpose of the TR is to demonstrate that the Rail Loop Pond's <br />existing configuration has adequate capacity to treat stormwater runoff from the 10-year, 24- <br />hour storm event and meets the intentions of Colorado Mine Land Reclamation Board Coal <br />Regulations, Rule 4.05.5 and 4.05.6. <br />The demonstration consists of runoff modeling utilizing the SEDCAD+ computer model. <br />The results of the demonstration indicate that the existing configuration of [he pond is <br />capable of treating runoff from the 10-year, 24-hour stortn event, and prevents, to the extent <br />possible, the additional contribution of suspended solids to receiving waters. <br />In addition to the capacity demonstration, this TR request also addresses embankment <br />freeboard requirements. Observations by HGTI personnel and a review of the existing Rail <br />Loop Pond as-built drawing suggest that there is insufficient freeboard between the top of <br />the embankment and the water level in the combination spillway flowing at design depth. <br />To meet the intentions of Rule 4.05.6 (11)(e), HGTI proposes to raise the top of the <br />embankment to meet the 1.0 foot freeboard requirement. <br />1.0 INTRODUCTION <br />The purpose of this TR Application is to demonstrate chat the Rail Loop Pond's existing <br />configuration has sufficient capacity to treat stormwater runoff form the 10-year, 24-hour <br />storm event and meets the intentions of Colorado Mine Land Reclamation Board Coal <br />Regulations, Rule 4.05.5 and 4.05.6. <br />The location of the Rail Loop Pond and the contributing watershed area are shown on <br />Exhibit 12-2, Surface Water Control Plan Map, of the existing, valid HGT[ Permit. <br />In reviewing the existing, valid Permit during preparation of the Permit Renewal <br />Application it was determined that the existing storage capacity of the Rail Loop Pond was <br />slightly less than the original design capacity as presented in the original Permir Application. <br />PO Box 174018 Te1:910 879 fi2fifi Serving the 1Norld's Env~ranmenral Needs <br />1475 Pine Grove Road Fax 9709]9 9048 <br />Sreamhaat Spnngs. Colorado <br />80477 <br />