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American Tunnel Bulkhead No.3 Construction Certification Report Page 2 The construction stages for certification aze listed below. Bulkhead Buffer -Lime Placement Two tons of hydrated lime were placed at the downstream face of Bulkhead Not and two tons were placed between the cofferdam and upstream face of Bulkhead No.3. In addition, an additional two tons were placed at the downstream face of Bulkhead No.3. Bulkhead location preparation (scaling and washing) The bulkhead site was scaled clean of loose material and sandblasted to remove any surface coating that may have been present. It was then washed down and vacuumed clean of water, sand and rock residue. This stage of site preparation was adequate to maximize the potential for bonding between the rock and the concrete and was also inspected by the design engineer, John F. Abel, Jr., and DMG during their respective pre- pourinspections. • The final excavation was within the dimensions used for design, 12' wide x 15'high. By-crass or diversion oiae The diversion pipe through the bulkhead is a 6" Schedule 40 -stainless steel pipe fitted with one thrust collar (3/8" thick - 2" larger in diameter than the pipe) and two light gauge seep collars. The thrust collar was placed at a distance of greater than 5' from the downstream face to allow any loads to be distributed to the tunnel walls. Two seep collars were placed downstream of the thrust collar, to minimize the ability of impounded water to travel along the outside of the pipe. Bars were welded inside the pipe (upstream side) to provide a stop for the grout pig to simplify grouting the pipe full upon completion of the bulkhead. The pipe entrance was extended upstream to a temporary cofferdam, placed to keep the bulkhead area dry during construction. The pipe system was adequate to keep the azea dry until after the concrete had sufficient time to cure. The original TR submittal anticipated that a 4" Schedule 40 -stainless steel pipe would be adequate to transport the flow through the bulkhead area during construction but because the flow was larger than anticipated at the time of submittal, the size was increased to 6" in order to assure adequate capacity for the flow during construction without increasing the depth of the cofferdam. This change would have no material effect on the constructed bulkhead.