Objective: Design and install new stop logs and stop-log guides to isolate pump house for long-term maintenance.


  • Successfully installed pneumatic-seal-design stop logs
  • Enabled 100-percent power plant operational throughout construction
  • Designed, fabricated, and installed one-of-a-kind stop-log guides


Because of our intimate knowledge of the facility and our exceptional design and fabrication experience, Substructure was chosen by a Massachusetts power plant to design new stop logs and new stop-log guides as part of a long-term maintenance program for the facility.  The design phase began with Substructure engineers assessing the pitfalls of the current stop logs.  After careful research and some testing, Substructure decided on a pneumatic-seal design for the new stop logs.  This design would enable the 30-foot-deep pump bays to be isolated safely and quickly, allowing complete bypass of the raw water to keep the plant 100-percent operational during construction.  The new stop-log guides were designed and built by Substructure team members before installation on site.

Substructure worked closely with plant operators and managers to ensure minimal interruptions to regular plant operations during construction.  This included coordinating crane lifts and equipment delivery, as well as planning for a regularly scheduled plant shutdown period.  During the construction phase, Substructure divers burned the old stop-log guides for removal, scarified concrete to prepare for installation of the new stop-log guides, and cleaned the traveling water screens.  The Substructure crew also installed a new upper drive assembly and new carrier links.

During the scheduled plant shutdown period, Substructure mobilized multiple crews to work around the clock to accomplish multiple tasks and maintenance operations.  Within the weeklong shutdown period, Substructure was able to complete a critical intake repair.  A diving inspection of the facility that enabled repairs of the outfall pipe and diffusers in the river were also accomplished during the shutdown.  Lastly, Substructure deployed its survey vessel, Orion, to complete a high-resolution multibeam survey of the river around the plant, including coverage of the plant’s intake and outfall structures.  This survey data was later used for permit applications by the power plant.