1993-07-27_INSPECTION - M1977378

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(Page 2) MINE ID # OR PROSPECTING ID # Mom ;-378 INSPECTION DATE 7-27-93 INSPECTOR'S INITIALS ACS OBSERVATIONS This inspection was conducted primarily in relation to TR-14, the proposal to install bulkhead seals within the underground workings of the Sunnyside Mine to eliminate discharge from the Terry Tunnel, and limit discharge from the American Tunnel to those inflows that occur outby of the Sunnyside Gold property line. To that end, the four proposed bulkhead locations within the workings were visited, as well as the location of an existing water-door that is tied into the ribs with concrete. American Tunnel Bulkhead Location The approximate location of the proposed American Tunnel bulkhead has been marked with spray paint, but the precise upstream and downstream ends of the bulkhead have not been determined. The ribs in the American tunnel are heavily coated with diesel exhaust residue. There is very little inflow in the form of seeps, etc. for a considerable distance in either direction from the proposed bulkhead. The observed hydrologic conditions in the American Tunnel corroborate the conditions detailed in the Simon Hydro-Search report submitted with TR-14, i.e. once you are approximately .5 miles inby of the portal, overburden pressure is sufficient to essentially close off the joints and fractures within the rock mass to any flow of water. Almost all flows entering the American Tunnel inby of the approximately .5 mile point are from discrete veins or shear zones with enhanced permeability. The following observations apply not only to the American Tunnel bulkhead location, but to the other three locations as well: 1. The tunnel walls at the bulkhead locations are dry. 2. The only geologic structures observed at the bulkhead locations are joints. At least three sets of very tight extension joints were observed at each location. Thorough scaling at the bulkhead locations will be necessary to remove any (observed to be few) loose rocks that have resulted from near surface intersection of the joint sets. 3. The ribs at each bulkhead location are irregular, as would be expected, and appear to easily exceed the criteria for irregularity required to cause the concrete shear strength to be the controlling shear parameter for bulkhead performance, however, it was agreed that the operator would prepare two orthogonally opposed long-sections depicting tunnel irregularity at each bulkhead site once the locations are cleaned and scaled. In addition, the bulkheads will be sited in such a way that the downstream ends will coincide with inward tapering tunnel dimensions. 4. The intermediate composition volcanic rock that occurs at all bulkhead locations is extremely competent as evidenced by a ringing sound emitted when struck with a hammer. This observation is born out by the uniaxial compression test results submitted with TR-14. I-level Water Door This location was visited because it offers an opportunity to examine a concrete structure installed within the mine over 50 years ago. The concrete water-door frame was submerged for about 25 of those years, and, obviously, was not constructed with a concrete mix with the level of sophistication of that proposed for the impounding bulkheads. The old concrete was observed to be in good condition, and could probably serve the purpose for which it was installed even today. There is some degradation of the concrete at its edges, but the seal between the concrete and the ribs is still quite good. B and F-level Brenneman-Sunnyside Connection Bulkhead Locations The operator has requested partial approval of TR-14 to permit installation of these bulkheads prior to resolution of certain obstacles to approval of the American and Terry Tunnel bulkheads. Mucking out of the floor has been initiated at the F-level site, and the same observations regarding rock competency, geologic structure, etc. mentioned previously,