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Pip FLOO~c <br />Z~fl~~ 29 <br />a o <br />o ~~J) o <br />'G yebnyy. 1!!~\ay5 <br />Board of Directors <br />I Executive Committee: <br />Cathy Reynolds <br />Chairman <br />City/County of Denvar <br />Debra Vickrey <br />Chairman Pro-Tam <br />Arapahoe County <br />Paul Danish <br />Secretary <br />Boulder County <br />Erica Crosby <br />Division of Minerals and Geology <br />1313 Sherman Street, Room 215 <br />Apri125, 2002 <br />a <br />0 <br />m <br />S <br />0 <br />0 <br />z <br />0 <br />Gretchen Cerveny m <br />Treasurer e <br />Ciryof Wheat Aidge <br />w <br />Elaine Valente <br />Member at Large <br />Atlams County ~ <br />Members: <br />City of Broomfieltl <br />Steve Burkholtler <br />City of Lakewood <br />Ken Fellman <br />City of Arvada <br />Stephanie Foote <br />City/County of Denver <br />Nancy Heil <br />City at Westminster <br />B. H. Hotfmaster <br />Engineer <br />Michelle Lawrence <br />Jefferson County <br />City of Aurora <br />Kathleen MacKenzie <br />City/County of Denver <br />W. Mike Maxwell <br />Douglas County <br />Jim McShane <br />Town of <br />Columbine Valley <br />Deborah Ortega <br />City/County of Denver <br />Art Patton <br />Engineer <br />D <br />a <br />R <br />z <br />0 <br />x <br />RECEB~IE~ <br />APR 2 6 iis~? <br />L. SCOtt TUCker, Executive Director <br />Division of Minerals and Gevic,; <br />Subject: Review of Permit Amendment Application (AM-002) <br />Aggregate Industries, Brighton Mine, Permit No. M-1977-436 <br />Cam.vne.•r~i~ t~nc~ ~lu>n-c~a. <br />Dear Erica: <br />This letter is in response to your request for our comments concerning the <br />above-referenced application. We appreciate the opportunity to review this case only as it <br />relates to the South Platte River. We have the following comments to offer: <br />The typical grouted boulder rundown for each off-site tributary needs to show <br />more detail, including crest elevations, toe elevations, and cross sections. <br />According to the Urban Storm Drainage Criteria Manual, grouted boulder <br />structures are limited to 4:1 slopes. <br />2. The open channels from the point at which the off-site tributaries enter the mine <br />site to the grouted boulder rundowns need to be designed and constructed during <br />the mining operation. <br />3. The applicant has stated that the off-site tributary boulder rundowns into the <br />mining cells will be constructed by the future operator of the reservoir (which is <br />our understanding to be the City of Thornton). This is unacceptable to the <br />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 <br />0052 Watersheds Outfall Systems Plan Alternatives Development and <br />Evaluation Report" (OSP) dated November, 2001, it is imperative that adequate <br />drainageway stability measures (i.e. boulder rundowns) be constructed during <br />the mining phase to control upstream degradation and protect the Brantner Ditch <br />and Riverdale Road from potential damage. <br />spr/bryan/min&geo <br />