WASHINGTON SUBURBAN SANITARY COMMISSION

The autumn of 2007 brought a challenging project to Walker Diving. The Washington Suburban Sanitary Commission contracted Johnston Construction Corp. (prime) of York, PA and Walker Diving (sub) to perform the intake repairs to the Howard T. Duckett Dam in Laurel, MD. The scope of the work for Walker Diving consisted of replacing the two sluice gates that were below the water level and replacing the entire trash rack guide in front of the tower structure. The project commenced with the trash racks. After the original racks were removed, the crews spent some time cleaning debris from the bottom of the tower structure. After the bottom was clean they started to install the new stainless steel track rack guides. This was achieved by anchoring into the concrete structure through pre-drilled holes in the guides with mechanical anchors. Drilling for the anchors was made difficult by the presence of steel reinforcing rods at almost every location. Two lower sections of racks were then lowered into place to prevent debris from re-entering the intake structure. The removal of the old gate and installation of the new gate required the cooperation of Walker Diving and Johnston Construction for the heavy lifting involved. One of the tasks to be performed before the new sluice gates could be installed was to rethread the existing studs to comply with the new gate thickness. The crews also had to shorten and rethread many of the studs due to a conflict with the new gates. When both of the gates were in place the prime contractor was able to perform their work behind them, now in the dry.