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American Tunnel Bulkhead <br />Construction Certification Report <br />Page 3 <br />Fittings for installation on the 1" pipe to allow sample <br />collection and pressure readings to track the height of the <br />mine pool are all Schedule 80 316L SS and the valves are rated <br />in excess of the 670 psi design pressure. The valve on the <br />12" pipe is a Class 600 316 SS Aloyco Gate Valve with spur <br />gear operator. This valve was selected after an independent <br />review and recommendation by Fearn Engineering Services <br />(letter report attached) of the final selections. <br />The 12" diameter diversion pipe was extended upstream to a <br />poured concrete coffer dam. The extension pipe (upstream of <br />the bulkhead) is 12" diameter HDPE SDR 26 pipe. The coffer <br />dam will allow approximately 10' of head on the inlet before <br />any appreciable amount of water could enter the area of the <br />bulkhead or between the bulkhead and coffer dam. A SS trash <br />box was placed at the diversion pipe inlet to prevent large <br />floating debris from entering the pipe. <br />4c) Construction of concrete forms and erection of rebar cage. <br />The forms were constructed of vertical 8" x 8" S4S posts and <br />horizontal 2" x 12" and 2" x 6" S4S lagging with a 3/4" <br />plywood lining inside the bulkhead. Bracing consisted of <br />angle iron and pipe anchored to the ribs, sill and back of the <br />drift. The form construction and bracing was adequate to <br />prevent movement during filling of the forms. <br />The rebar cages were supported by rebar dowels grouted into <br />the rib. The water side rebar cage is #6 bars on a 12" x 12" <br />grid and the air side rebar cage #10 bars on a 7" x 7" grid. <br />The respective cages were reinforced with diagonal bars where <br />the diversion pipe penetrated. As noted in the DMG inspection <br />report, one diagonal bar in the water side rebar cage had to <br />be bent in order to cross two cage horizontal bars and <br />maintain a 60" length because of the diversion pipe location <br />in relation to the rib and sill. As further noted in John <br />Abel's report, these diagonal bars in the water side rebar <br />cage were non - essential because of the basic non - structural <br />function of the temperature- shrinkage rebar. All minimum <br />clearances and spacings met design criteria prior to filling <br />of the forms. This was also confirmed by John Abel Jr., the <br />design engineer (see attached report). <br />