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~ ~ItiN6NTYM166 <br />~ COAI. COMPANY <br />A Cyprus Ama: Company <br />iiiiiiiiiiiiiiuiu <br />999 <br />Twentymile Coal Corporation <br />29515 Routt County Road k 27 <br />Oak Creek, Colorado 60467 <br />970-879-3800 <br />June 21, 1996 <br />Mr. Kent Gorham <br />Environmental Protection Specialist <br />Division of Minerals and Geology <br />1313 Sherman Street, Roont 215 <br />Denver. Colorado 80203 <br />Re: Application of Cutrine Plus Algaecide at Pond A <br />Dear Mr. Gorham: <br />Q~r~IVFD <br />JUN 2 5 ~gy6 <br />Division of nninerdis a l+eu,09Y <br />As per our conversation this morning, Twentymile Coal is planning [o treat Pond A with Cutrine Plus to <br />control algae. Filamen[a[ious algae is causing problems with the filter system for mine water collection <br />from Pond A. <br />In order for this chemical to be effective in controlling [he algal growth, the concentration of copper must <br />be maintained at 0.2 ppm for a minimum of 3 hours. This concentration is above our daily maximum <br />efFluent limitation of 0.13 ppm. We plan to temporarily plug [he riser orifices [o allow for dilution of the <br />copper to within our efFluent standards. The water surface elevation is currently at approximately 6935.5 <br />and the top of the riser is a[ an elevation of 6938. Based on [he latest stage-storage surve}', approximately <br />49.4 acre-feet of additional water can be held between the current water surface elevation and the top of the <br />riser. Assuming that inflow equals outflow, it will take approximately 108 hours to raise the water level in <br />the pond to the top of the riser. The plan for application of Cutrine Plus at Pond A is as follows: <br />• Plug the orifices on Friday, June 21, 1996 at I:00 p.m. <br />• Apply 70 gallons of Cutrine Plus on Saturday, June 22, 1996 at 5:00 ant using aerial spraying. <br />• Monitor the water level in Pond A on a daily basis. Based on estimated inlow, assuming no <br />significant rainfall, the water level should overtop the riser around 1:00 am on Wednesday, June <br />26, 1996. <br />• Remove the riser plugs on Tuesday, June 25, 1996, unless [he water overtops the riser earlier <br />due to rainfall contribution. <br />• Collect sample for potentially dissolved copper immediately after flow resumes. <br />I have included a copy of the manufacturer's product usage information, MSDS, and calculations for your <br />review. Please contact me if you have any questions or require any further information concerning this <br />matter. <br />TWENTYMILE/COjA~L COMPANY, <br />Environmenml Specialist <br />/tdr <br />enclosures <br />fir: r. Idon.rnenrlkenlculr. doe <br />