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III Ilillliilllll III <br />999 <br />~ ~~ _ ~ <br />October 27, 1993 <br />Mr. ]ouph Dudash <br />Colorado Division o! Minerals and Geology <br />1313 Sherman, Room 215 <br />Denver, CO 80203 <br />Subject: Technical Revision No. 31, Response to 10/13N3 Adequacy Revinv, Golden Eagle Mine. Permit No. C-81-012, Basin <br />Resources, Inc. <br />Dear Mr. Dudash, <br />Greystone has reviewed the Technial Revision No. 31 Adequacy Review datcd October 13, 1993. Please review the attached SEDCAD+ <br />documentation, and responses to the adequacy letter. Rcsponses to the questions are fisted in the order in which they were requested. <br />SEDCAD+ projections o[ Bow Crom the 25-year 24•hour storm event suggest Char there will be no Bow ovcr the emergency spilhvay <br />during a 25-year 24-hour storm event when the pond is full to the level o[ the primary spillway. (See Ble C:\scadWt\byron~ivpond). <br />Three punched Copies of this pond run are provided [or insertion into Exhibi[ 18 of the permit application. Basin rs submitting <br />additional, optiooa~ documentation that the emergency spillway mold handle the 25-year 24-hour storm event from the contributing <br />drainage, should the primary spillway be blocked. (See Ble C:lxadtdt\byron\spill). 71tis model assumes that all of the wafer which <br />Bows into the pond (12.4 c[s) will Bow out of the pond. Flows over the crest and outslope arc non-erosive as they have velotitie <br />less [hart 5 Cps. The design indicates tha[ there h 1-(oot of freeboard betwcen the heigh[ of Bow in the spillway and the cta[ of <br />the embankment. <br />2. Water rights documentation have been unt under separate cover. <br />3. An As-Built drawing was prepared 6R4ry3 documenting the current configuration of the river ponds. The SEDCAD+ runs <br />provided in this submittal show chat the pond will meet regulatory performance standards [or impoundments. <br />4. The river ponds were established as a diversion of the Purgatoire to provide watcr for mine usc. They have been in place sintt 1976 <br />and have not shave evidence of instability in sevrnteen (17) years. Basin acknowledges that the side slopes of the embankment <br />do not meet the requirement o[ S:1(H:~ for both slopes, but would like the Division to consider [he long-term, historipl integrity <br />as adequate evidence of stability. <br />5. Basin acknowledges their requirements o[ recertification o[ modified engineered structures. <br />Sinttrety, <br />~~ ~~ ~~ <br />Catherine W. Begej <br />Project Manager <br />Greystone <br />co Mr. Ralph Lopez, Basin Resources <br />Enclosures <br />5990 Greenwood Plaza Blvd. Suite 250 Englewood, CO BO111 <br />(303) 850-0930 Fax (303) 721-9298 <br />