Laserfiche WebLink
(Page 2) <br /> MINE ID # OR PROSPECTING ID # M-77-378 <br /> INSPECTION DATE 6/28/95 INSPECTOR'S INITIALS ACS <br /> OBSERVATIONS <br /> A pre-pour inspection was conducted of the American Tunnel bulkhead location. Final <br /> preparations for pouring the reinforced concrete bulkhead were underway at the time of this <br /> inspection. <br /> A concrete coffer dam had been constructed inby of the bulkhead locations. Mine water <br /> collected behind the coffer dam is routed into the American Tunnel bulkhead bypass pipe that <br /> penetrates the concrete dam, and is flush mounted at the upstream face of the coffer dam. <br /> Construction of the coffer dam provided an opportunity to test the efficacy of the procedures <br /> that will be used for the American Tunnel bulkhead pour. The water-side bulkhead form <br /> prevented access to the coffer dam for inspection, but it was observed that no water was <br /> infiltrating the bulkhead area from the upstream side. <br /> The bulkhead forms are constructed from 2x6 and 2x12 lagging with 3/4" plywood sheathing on <br /> the interior of the forms. The forms are braced by angle iron pinned into the sill, back, <br /> and ribs. The forms are further braced at the sides and base with heavy duty pipes bolted <br /> to the forms and to the interior of the tunnel. The form to form bulkhead length was <br /> measured to be 25'3" at the stainless steel observation pipe. <br /> Several measurements were taken at the air-side rebar cage. This cage is constructed of #10 <br /> bars. No spliced bars were observed. Spacing of the bars was 7 inches at all locations <br /> measured. The rebar cage was 3.5" from the form at all locations measured. Ends of all bars <br /> were no more than 6 inches from the tunnel perimeter. The cage was not wired or otherwise <br /> connected to the form. <br /> Several measurements were taken at the water-side rebar cage. This cage is constructed of <br /> #6 bars. No spliced bars were observed. Spacing of the bars was 12 inches at all locations <br /> measured. The rebar cage was 3" from the form at all locations measured. It was observed <br /> that one of the vertical bars was more than 6 inches from the back, however, this bar was <br /> butted to the sill and could be slid upward into the proper position. This correction was <br /> implemented while I was still on site. The cage was not wired or connected to the form. The <br /> design call for 5' long #6 bars to surround by-pass pipe inlet and outlets at a 45 degree <br /> angle. It was observed that one of the water side angled bars was only 42" long. This is <br /> because of the proximity of the of the by-pass pipe to the rib and sill. It was agreed that <br /> a 5' bar would be installed, but would be bent as necessary to facilitate its installation. <br /> Thrust rings on the bypass pipe were measured and found to meet the design criteria of .5" <br /> thick, outside diameter 6" greater than that of the pipe, and at least 6.5' from the <br /> downstream bulkhead face. There are two such rings on the bypass pipe; in addition two <br /> connecting flanges will provide additional resistance to thrust, and to seepage along the <br /> pipe/concrete interface. <br /> There are 3 thrust rings on the observation pipe. They are 3/8" thick and extend 2" beyond <br /> the outside of the pipe. <br /> Mechanisms to extend and retract three slick lines along the back were in place and were <br /> inspected. <br /> The approved design calls for the bypass pipe to be supported every 5' through the bulkhead. <br /> The bypass pipe is supported by poured concrete footings and wired securely to metal rings <br /> in the sill. The poured footings exceed the cinder block supports recommended in the design. <br /> However, the spacing as measured was greater than 5' between footings, and were generally <br /> about 7' . The reason for the 5' spacing specification, is to conservatively protect the pipe <br /> from damage under the full weight of the poured concrete assuming that no concrete had filled <br /> in below the pipe to provide support. Larry Perino agreed to photograph, videotape, and <br /> certify that the concrete will fill in below the pipe prior to pouring any significant <br /> quantity that would apply a load to the pipe. With this commitment, there is no need to <br /> provide additional pre-pour support. <br /> Sunnyside Gold has provided, and the Division has accepted, the required demonstration that <br /> sufficient perimeter area irregularity exists at the American Tunnel bulkhead site to prevent <br />