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• • iii iiiiiiiiiiiiiiii <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmern of Nalu rat Resources <br />1313 Sherman SI., Room 215 <br />Denver, Colorado 80203 <br />Phone: (3071 866-3567 <br />FAX:13031832-8106 <br />DATE: July 7, 1994 <br />To: Steve Shuey // <br />FROM: Christine Johnston//~~ <br />RE: Technical Revision No. 22; Somerset Mine; <br />Permit No. C-81-022 <br />~~ <br />n <br />~~~~~ . is <br />DEPARTMEM" OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames 5 Lochhead <br />E~eculive Director <br />Michael 8. Long <br />Division Director <br />Pursuant to your request I have reviewed the application for a <br />technical revision received from the Somerset Mine. My review <br />included the bond estimate and hydrology. The following is my <br />comments regarding those topics: <br />Hvdrologv <br />The assumptions provided in the model are acceptable. I calculated <br />the peak flow for Diversion Ditch A and B, the Collection Ditch, <br />and Emergency Spillway to be higher than Somerset's calculations. <br />However, the ditches and spillway proposed in the application are <br />still adequately sized. When I was reviewing the pond sizing using <br />SEDCAD, a caution message was given. It cautioned that the stage <br />of the principle spillway may cause bed scour and may not meet <br />effluent limitations. It recommended that the stage of the <br />principal spillway be increased. However, the peak settleable <br />concentration is 0.06 ml/1, which is just over the limit of 0.05 <br />ml/1. In addition to raising the principle spillway, Somerset <br />could install some sort of protective lining or armor the area <br />around the inlet to the spillway. The pond is adequately sized and <br />the emergency spillway does not require riprap. I have enclosed <br />all the SEDCAD print-outs for your information and for the file. <br />Reclamation Estimate <br />The reclamation estimate for this project totals $8,327.00. I have <br />updated the Cost Summary Form and added or revised the following <br />tasks: <br />Task 47A (revised) $ 641.00 <br />Task 50A 3981.00 <br />Task 60 616.00 <br />Task 61 634.00 <br />Task 62 136.00 <br />