ALCOSAN Flow Control Project

Approximately every ten years, the sewage inceptor line in the middle of the Monongahela River in Pittsburgh, PA must be cleaned to allow proper flow. In early 2013, Brayman was contracted to install precast concrete coffer boxes around the pipe to allow for easier access to the pipe for cleaning operations. The design, developed by Brayman and The Lewis Consulting Group, consists of a permanent base unit with watertight lid and temporary riser units.

The base unit contained a “doghouse” to fit around the pipe. Tremie concrete was poured around the pipe and base unit, essentially joining the two with a water-tight seal. Once the tremie concrete achieved the proper strength, riser sections that projected above the water surface were eventually stacked onto the base unit. The entire assembly was stressed together using four all-thread rods. Neoprene seals in each of the joints created water-tight installation once stressing was complete.  Pipe cleaning then commenced and once the work was completed the base unit remained in place for future cleanings.