2011-03-17_REPORT - M2007044 (2)

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Erb F t&, Resources RECEIVED RECEIVED March 14, 2011 MAR 21 2011 MAR 17 2011 Ms. Deborah Lebow Aal I?iyision of ReciamaUon, GRAND JUNC:I iON MELD OFFICE USEPA Region 8, Indoor Air Program Mining & Safety DIVISION OF 1595 Wynkoop St. RECLAMATION MINING & SAFETY Denver, CO 80202-1129 Re: 2010 Radon Emissions Modeling for the Whirlwind Mine o. _ v y C? M- 02 Dear Ms. Lebow Aal: The Whirlwind Mine is an underground uranium and vanadium mine located at 30100 5110 Road in Gateway, Colorado. No ore has been produced from the mine to date. The Whirlwind Mine has been on stand-by since November 2008 with only maintenance activities being performed since that time. In December 2009, Energy Fuels discontinued dewatering operations and allowed the lower portion of the mine, which contains the ore zone, to flood. At the same time ventilation tubing was disconnected in the decline, so as to ventilate only above the flooded area. Energy Fuels also discontinued monitoring of radon levels in the exhaust portal at the end of 2009 given that the ore zone was no longer being ventilated. Ventilation of the mine has occurred only as needed in 2010 for underground maintenance and environmental compliance activities, averaging 5.6 hours per month. Active ventilation is limited to the decline and non-mineralized drifts above the flooded ore zone. Energy Fuels was recently informed by U.S. EPA staff that they interpret mining to include any time the mine is being actively ventilated and that an annual radon emissions report would still be required for a mine that is ventilated on an intermittent basis. Given that radon emissions were not measured in 2010, Energy Fuels conservatively estimated radon levels to be equal to the highest recorded quarterly average concentration during 2008 and 2009. These measurements were collected using Landauer Radtrak Environmental Monitors placed in the mine decline, near the portal. Calculation of the effective annual dose equivalent of radon exposure to the nearest resident, school or office resulting from an underground uranium mine ventilation system is required under 40 CFR 61 Subpart B. The radon effective dose equivalent was calculated using the COMPLY-R program with the following input parameters. • The exhaust flow rate at the portal was determined by measurements conducted throughout 2010. • The nearest public receptor is a part-time resident, located approximately 600 meters northwest of the mine portal. Full-time residency was assumed for the COMPLY-R modeling. • The average wind speed was assumed to be 2.0 m/s (COMPLY-R default value). S;11' 1 1: 44 R;-vd,