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• • <br />STATE OF <br />iiiiuiiiiiiiiuiii <br />999 <br />COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Deparlmeni of Natural Resources <br />7373 Sherman 8t., Room 275 <br />Denver, Colorado 80203 <br />Phone: 13031 866-3567 <br />FA%:1303)832-8106 <br />October 29, 1997 <br />Stevan O'Brian <br />Environment, Inc. <br />7985 Vance Dr., Suite 205A <br />Arvada, Colorado 80003 <br />®E-vvE~ ®~FICE <br />~'uELIC FILE ~ppY <br />FILE: -~~-020 <br />~1TE: f ~ <br />~~ <br />~~~~~ <br />DEPARTMEI~IT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames 5. Lothhead <br />Execmrve Duenor <br />Michael 9. Long <br />Division Dnecror <br />RE: Pit No. 1 , Permit No. M-77-020, Amendment Application (AM-O1) Second Adequacy Review <br />Dear Mr. O'Brian: <br />The Division reviewed your responses to the preliminary adequacy review of the amendment application <br />for Delta Sand and Gravel Company's Pit No. 1 . Original comment numbering, and the Division's <br />responses to your replies are listed below. Please respond to the remaining concerns, to the Durango <br />Field Office (address below), prior to the decision due date set for November 5, 1997. If you are unable <br />to respond by that date, please request an extension of the decision due date. If neither an adequate <br />response or a request for extension are received by the decision due date, the Division will have no <br />choice but to deny the application. <br />MINING PLAN <br />1. The commitment to conduct soil tests and amend the soil accordingly is acceptable under these <br />conditions. <br />2. Response acceptable, except that the rate of seed planting should be 3.0 pounds pls/200 s.f., not <br />3.0 pls/200 s.f. <br />3. Because Russian knapweed has allelopathic properties that are thought to sterilize the soil where the <br />dead plant material falls, it is recommended that the mowing process be conducted with machinery that <br />collects the cuttings so they can be disposed of properly. Chemical weed control will probably be <br />necessary, in addition to mechanical controls, to control the Russian knapweed infestation on site. <br />Again, I highly recommend that the pond embankments be seeded with perennial grasses to help in <br />preventing infestation of these slopes with Russian knapweed. I have included a report on one of the <br />most recent studies conducted on control of Russian knapweed. I encourage you to read it and adjust <br />the weed control plan accordingly. The report indicates that mowing has negligible effect on Russian <br />knapweed. Additionally, plots that were seeded with perennial grasses after chemical treatment were <br />most successful at controlling Russian knapweed. <br />4. If 7.78 acres of the East Parcel will be excavated before reclamation begins, it appears that the <br />maximum area of disturbance for calculating reclamation costs would be when the 7.78 acres has been <br />excavated but reclamation, including regrading of the East Lake exterior slopes, has not been initiated. <br />Additionally, the West Lake map contours indicate the west side of the West Lake would also require <br />regrading at this point in the life of the operation. Please revise the mining plan map, reclamation plan, <br />and reclamation cost estimate to account for the steeper grade on these slopes. Please clarify, if these <br />observations are not correct. <br />