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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman St, Room 215 <br />Denver, Colorado 80203 <br />Phone: f303) 866-3567 <br />FAX: 1303) 832-8706 <br />May 22, 2002 <br />Ms. Connie Nickle Davis <br />Aggregate Industries <br />P.O. Box 337231 <br />Greeley, CO 80633 <br />RE: Aggregate Industries, Brighton Mine, Permit No. M-1977-436 <br />Petmit Amendment (AM-02); Adequacy Questions <br />Dear Ms. Davis, <br />~~ <br />olvlsloN aF <br />MINERALS <br />GEOLOGY <br />RECLAMATION <br />MINING•SAFETY <br />Bill Owens <br />Governor <br />Greg E. Walther <br />Executive Director <br />Michael B. Long <br />Division Director <br />The Division of Minerals & Geology ("Division") has conducted an adequacy review for Permit Amendment 02 (AM- <br />02) for the Brighton Mine, Permit No. M-1977-436. The Division is required to make an approval or denial decision <br />no later than June 20, 2002, therefore, your response to the following adequacy review concerns should be <br />submitted to the Division as soon as possible. <br />The Division received numerous letters from vazious government agencies regarding the Amendment <br />Application. These letters were sent to Aggregate Industries via fax on Apri130, 2002. Specifically, please <br />address the following issues; <br />1. Letter from Bryan W. Kohlenberg of the Urban Drainage and Flood Control District dated Apri125, 2002. <br />a) The typical grouted boulder rundown for each off-site tributary needs to show more detail, including crest <br />elevations, toe elevations, and cross sections. According to the Urban Storm Drainage Criteria Manual, <br />grouted boulder structures aze limited to 4:1 slopes. <br />b) The open channels from the point at which the off-site tributaries enter the mine site to [he grouted boulder <br />rundowns need to be designed and constructed during the mining operation. <br />c) The applicant has stated that the off-site tributazy boulder mndowns into the mining cells will be <br />constructed by the future operator of the reservoir (which is our understanding to be the City of Thornton). <br />This is unacceptable to the District. Since the applicant has chosen to intercept these tributaries rather than <br />channelize them to the South Platte River, as per the "Todd Creek and DFA 0052 Watersheds Outfall <br />Systems Plan Alternatives Development and Evaluation Report" (OSP) dated November, 2001, it is <br />imperative that adequate drainageway stability measures (i.e. boulder mndowns) be constructed during the <br />mining phase to control upstream degradation and protect the Brariter Ditch and Riverdale Road from <br />potential damage. <br />2. Letter from Norman J. Wells, Jr. of the Natural Resources Conservation Service (NRCS) dated Apri] 8, 2002. <br />a) One concern may be filling of the entire pit during storm events and the elevation of the spillways no[ <br />allowing the wetlands to reestablish due to long term, deep depth of water. Some wetland plants can not <br />withstand and maintain themselves when they are subjected to more than a certain depth of water. Since <br />no elevations were shown on the map, it is hard to tell if this could happen. <br />