Ballard was sole-sourced by the City of Renton under a deceleration of emergency, issued by the mayor, to provide marine support services to clean approximately one mile of eight-inch sewer piping along the shores of Lake Washington.
Scope of Work
The line had experienced a thirty percent reduction in flow and needed to be inspected and cleaned. Ballard worked with Bravo Environmental to perform the Closed-Circuit Television (CCTV) and cleaning scope of work, due to their expertise and previous experience with the system.
Barges and equipment were mobilized in the Duwamish Waterway and pushed by tugboat through Ballard Locks to the project site located in Lake Washington. Temporary manholes were cut into the live line in two locations and then reassembled using modern materials. For the three existing manholes located in the lake, prefabricated fiberglass temporary manholes were provided so access could be gained. CCTV and cleaning activities continued at those locations until complete. In addition, a separate contract was issued to Ballard to perform a life expectancy assessment of the sewer line. Ultrasonic testing and coupons were taken from six different locations for analysis. Lower than projected lake levels existed during the project, so a bypass piping system had to be designed and installed by Ballard so the excavation barge could be closer to the work sites. PVC piping with flanged connections was used to build the temporary piping runs so it could be reused in different locations if necessary.
Late in the project, it was discovered that the Ballard Lock was closing early for its annual maintenance, so strategies had to be changed to ensure timely completion of the project, as well as getting back through the lock before the closure. The project was completed safely, ahead of schedule, and under budget, despite the challenges faced throughout the project.
Client: City of Renton
Location: Renton, WA
Diver Depth: 15ft