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American Tunnel Bulkhead No.3 Construction Certification Report Page 3 Construction of concrete forms and erection of rebar cages The forms were constructed of vertical 8"x8" S4S posts and horizontal 2"x12" and 2"x6" S4S lagging. The form interior was lined with 3/0" plywood for additional strength. Bracing consisted of angle iron and pipe anchored to the ribs, sill and back of the drift. The form construction and bracing was adequate to prevent movement or failure during filling of the forms. The rebar cages were supported by dowels (rebar) grouted into the rib. The upstream rebar cage is #6 bars on a 12"x12" grid and the downstream rebar cage is #10 bars on a 6"x6" grid. The minimum clear distance from the form to the rebar is 3.5". The minimum bulkhead length was specified to be 11' and the actual length was 11'2". Trim bars (5' long) were placed at 45° to the rebar around the cutouts in the rebar cage for the pipe. All minimum clearances, dimensions and spacings met design criteria and were inspected by the design engineer prior to filling of the forms. The design report had contradictory . downstream rebar spacings between the text and calculations. The bulkhead was constructed with the more conservative spacing (ie closer spacing) which provides more strength than required by the calculations. Perimeter area irregUlarity The rock contact perimeter area irregularity required to develop the design compressive strength of the concrete when subject to the maximum design thrust was determined to be 8.8% of the area with a projection of 0.14" or more. Quantification of a minimum perimeter area irregularity was accomplished by measuring x-sections within the bulkhead length and using the generated x-sections to quantify intrusive area as a percentage of the total area between sections. A summation of the individual areas between x-sections was used for quantification of the total percentage of intrusive area within the bulkhead. This method provided an estimate of rock area irregularity of 45% which exceeds the design minimum of 8.8%. Attached to this report are the x-sections and table generated to quantify that this requirement was met.