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Mogul Mine bulkhead inspection Page 2 August 21, 2003 <br />bulkhead tunnel section from the original 8-:ft width by 8-ft <br />height to the final maximum 10-ft 7-in width by 9-ft 6-in height. <br />Most of the increase in the bulkhead width was the result of <br />removal of loose rock on the right rib. The increased height was <br />primarily the result of removal of ballast to reach the rock floor <br />of the tunnel. The rebar was placed at 12-in centers on both the <br />waterside and airside of the bulkhead. The adequacy of the rebar <br />reinforcement was recalculated for final bulkhead dimensions. The <br />#8 (1-in) on 12-in centers deep-beam rebar tensile reinforcement <br />on the airside of the bulkhead exceeds the required tensile <br />reinforcement by 11.1$, as indicated on page 4 of the attached <br />calculation sheets. <br />A minor, less than 1-in thick dry fault cutting across the <br />tunnel axis had been grouted to resist possible acid water attack <br />on the bulkhead concrete. Scaling revealed ghat the selected <br />location did not contain the vein structure present at most other <br />tunnel locations. The vein location beyond the left rib is <br />favorable for the bulkhead and will facilitate formation grouting <br />if leakage develops along the vein during filling of the mine <br />pool. It is unlikely that the vein provides a path for leakage <br />because no drips were observed anywhere in the first approximately <br />800-ft of the previously inspected tunnel. <br />Removal of loose rock from the tunnel roof, walls and floors <br />will result in a saw-toothed bulkhead. The blocky nature of the <br />rock results in the irregularities present on the back, ribs and <br />floor extending more than 1-ft into the tunnel cross section, <br />considerably more than the specified 0.14-in. The shape of the <br />rock adjacent to the bulkhead is excellent for resisting movement <br />under the design hydraulic thrust. A few gallons of water was <br />present at low spots in the floor of the bulkhead section. The <br />pump for removing the water inside the forms was present on the <br />work platform, just outside the access opening. St-will be used <br />to remove the water on the floor immediately before starting the <br />pour. <br />Filling of the form should proceed when possible. <br />Sincerely, <br />~J ~ ' ~)~, <br />John F. Abel, Jr. <br />Colorado P,E. 5642 <br />cc. Larry Perino <br />2 <br />