1994-09-05_REVISION - M1977378 - Laserfiche WebLink

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JOHN F. ABEL,JR. MINING ENGINEER 310 LOOKOUT VIEW COURT _ GOLDEN.CO 80401 �/ 303-279-4901 FAX 27"163 •3eptember 5, 1994 Mr. Larry Perino Sunnyside Gold Corp. P.O. Box 177 Silverton, CO 81433 Dear Larry: This is the letter report you requested concerning the reparations for and filling of the Terry Tunnel Bulkhead on September 1, 1994 . I arrive at t e u ea oc a 7 : 45 a.m. Two of the water-side temperature and shrinkage rebar cage had been left out to permit access for inspection. I inspected the bulkhead for 1) the spacing and location of the bars, 2) the irregularities present on the back ribs and floor, 3) soundness of the exposed rock and cleanliness of the bulkhead form and 4) the thrust collar and water stops on the 6-inch bypass pipe .and on the 1-inch pressure monitoring and water sampling line. The rebar- cages were constructed as designed. The *10 bars had been tied into the airside cage at the minimum 3 . 5 inches from the bulkhead forms (March 10, 1993 report, page 15) and the #10 tension bars were on 7-inch centers, as: specified. The #6 temperature and shrinkage bars were tied into the waterside cage on the specified 12-inch spacing and, with the exception on the two bars that had not been tied in order for final access and inspection, the #6 bars had been tied into the waterside cage at the minimum 3 inches from the bulkhead forms, the #6 temperature and shrinkage bars were on 12-inch centers as specified, There were no splices used in either cage. The irregularities present in the roof, ribs and floor are, by themselves, more than adequate to prevent the bulkhead from being forced down the Terry Tunnel. The largest irregularity present is a joint bounded protrusion jutting about a foot down from the roof approximately 2 . 5 feet from the airside (downstream) face of the form. This irregularity proved to be difficult fill behind, but presents a significant resistance to bulkhead movement. The location chosen for the Terry Tunnel Bulkhead narrows from the waterside to the airside. The irregularity of the Terry Tunnel Bulkhead walls is excellent. and its shape is optimal for resisting movement under the design hydraulic thrust. _ The miners had done -an excellent job of removing loose rock from the tunnel roof, walls and floor. I could not find any loose rock. There was no dust. mud or alteration products present on any of the rock exposed on the tunnel. The minor quantity of water,