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Mogul Mine Bulkhead <br />Certification Report <br />Page 2 <br />The construction stages for certification are listed below. <br />Bulkhead Buffer -Lime Placement <br />One ton of hydrated lime was placed between the cofferdam and upstream face of the <br />Bulkhead. <br />Bulkhead Location preparation (scaling and washing) <br />The bulkhead site was scaled clean of loose material and sandblasted to remove any <br />surface coating that may have been present. It was then washed down and vacuumed <br />clean of water, sand and rock residue. This stage of site preparation was adequate to <br />maximize the potential for bonding between the rock and the concrete bulkhead and was <br />also inspected by the design engineer, John F. Abel, Jr., and DMG during their respective <br />pre-pour inspections. <br />Removal of fractured rock resulted in a height and width that exceeded the original <br />design assumption. In order to check the validity of the design, John Abel Jr., the design <br />engineer, was asked to check the design using actual dimensions. His report, attached, <br />modified the original design with the substitution of #8 rebar on 12 inch centers in place <br />of #6 rebar for the downstream side of the bulkhead. His report verifies the original <br />selection of #6 rebar at 12" spacing for the upstream side. <br />BV-pass or diversion pipe <br />The diversion pipe through the bulkhead is a 6" Schedule 40 -stainless steel pipe fitted <br />with one thrust collar (3/8" thick - 2" lazger in diameter than the pipe) and two light <br />gauge seep collars. The thrust collar was placed at a distance of greater than 5' from the <br />downstream face to allow any loads to be distributed to the tunnel walls. Two seep collars <br />were placed, upstream and downstream of the thrust collar, to minimize the ability of <br />impounded water to travel along the outside of the pipe. The pipe entrance was extended <br />upstream to a temporary cofferdam, placed to keep the bulkhead area dry during <br />construction. The pipe system was adequate to keep the area dry until after the concrete <br />had sufficient time to cure. <br />The outlet end of the by-pass pipe was equipped with a stainless steel gate valve and <br />blind flange, drilled to accommodate a pressure monitoring gauge. At the owners <br />stipulation, the pipe was sized lazger than the minimum 4" diameter specified in the <br />design to accommodate drain-down of the mine pool at a future date in the event the <br />owner desires to re-open the Mogul mine. <br />