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Hayden Gulch Loadout <br />Rail Loop Pond -Storage Capacity Demonstration <br />2,000,000 ton/year Rail Car Unloading/TruckHoul Operation <br />Objective: Demonstrate that the Rail Loop Pond satisfies the requirements of Rule 4.05.9, <br />including Rule 4.05.9 (2)(b) which specifies that the impoundment contain runoff <br />from the 10-year, 24-hour storm event and Rule 4.05.9(2)(c)(ii) which specifies <br />that the spillway system be designed for the 25-year, 24-hour storm event. <br />Methodobgy: SEDCAD 4 (Schwab, 2004) <br />Assumptions and Inputs: <br />Watershed: No new areas of disturbance. All disturbance associated with construction of <br />the 2,000,000 ton per year unloading/haulage system will occur within the <br />existing facilities area disturbance boundary. <br />Contributing area, digitized directly from Exhibit 12-2, is 13.83 acres. <br />Water use: <br />• All vehicle washing off site at trucking contractors facility <br />• Anticipate coal stockpile watered once per day for 15 minutes using 300 <br />gpm water cannon -total daily application = 4,500 gallons. <br />• Assume all water drains to ponds, no evaporation or infiltration loss. <br />This is a conservative approach. <br />• Stockpile footprint approximately 0.49 acres; approximately 0.20 acres <br />of stockpile located within Rail Loop Pond watershed. <br />• Consequently, of total daily application, 41% or 1,845 gallons per day <br />(0.006 ac-ft) drains to Rail Loop Pond (this is a conservative value). <br />• All conveyor transfer points drain to Rail Loop Pond, there are 6 transfer <br />points <br />• Conveyor transfer point dust control by FOGJet atomizing spray systems <br />• Assume spray nozzles operate at maximum rate of 10 gph (0.17 gpm) <br />• Assume no evaporation or binding of water to coal dust particles, all <br />water drains to ponds. This is a conservative approach. <br />• Assume system operates 16 hours per day (960 minutes per day), then <br />system will generate 163 gallons per day per sprayer, which equates to <br />979 gallons per day (0.003 ac-ft) of water draining to pond (this is a <br />conservative value). <br />• Dust suppression on haul road HGLF-HR2 will utilize surfactants, <br />watering will be infrequent. <br />• The average pan evaporation rate for the northwest Colorado is <br />approximately 2.2 feet per year or 0.006 feet per day (from Evaporation <br />Atlas for the Contiguous 48 United States, U.S. Department of <br />Commerce, 1982). This rate is similar to the conservative estimate of <br />TR-06 12-1a.23 Revised OS/OS <br />