1996-09-16_HYDROLOGY - M1977378 - Laserfiche WebLink

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1111111111111111111 999 STATE OF COLOMDO DIVISION OF MINERALS AND GEOLOGI / Department of Natural Resources Post-It®Fax Note 7671 Dal Pages Z P F r,7, 1313 Sherman St., Room 215 To From / Denver,Colorado 80203 Y i c t ^ Phone:(303)866-3567 Co./Dept. Co FAX-(30 3)832-8106 Phone# Phone# DEPARTMENT OF Fax# �Ja•-z�f 7 (� Fax# NATURAL ff l RESOURCES Romer DATE: "eptember 16, 1996 Governor James S Lochhead TO: Wallace Erickson / Executive Director Michael B.Long FROM: Allen Sorenson - 77 -3 7� Division Director RE: Bulkhead Designs, Gold Prince Mine Sunnyside Gold Corp. , CDPS No. CO-0044768 Wally, I received your voice mail from last week, and received SGC' s bulkhead designs today. I have reviewed the designs for a 5 foot long concrete bulkhead to be placed in competent rock approximately 150 feet inby of the Gold Prince portal, and for a 2. 5 foot long concrete bulkhead to be placed just inby of the portal. Assuming that SGC will employ the same bulkhead location preparation methods as were used for the Sunnyside Mine bulkheads, and further assuming that a concrete mix approved for the Sunnyside bulkheads will be used for the Gold Prince bulkheads, and that a 28 day concrete strength of 3000 psi will be achieved, these designs are adequate. Since the inby bulkhead has been designed to withstand the maximum topography limited hydrostatic head, a pressure monitoring device is not necessary. Also, I don't see how the outby bulkhead will result in any water quality improvements, since any water impounded by this bulkhead will simply be re-routed through the near surface fracture system. However, installation of the outby bulkhead may provide information that could be valuable if shallow bulkheads are eventually considered for the American Tunnel. I would recommend that, if you have time, the inby bulkhead location be inspected prior to the concrete pour. During such an inspection, you would want to observe: 1. The effectiveness of cleaning and scaling operations, e.g. , there should be no loose rock in the bulkhead location, and the location should be clean and dry. 2. The competence of the rock at the bulkhead location. There should be a low fracture frequency, and no open fractures. 3 . There should be a minimum of a five foot span between bulkhead forms.