Project Detail

Millstone Outfalls Fish Barriers Restoration

Waterford, CT

Scope of Work

Cianbro installed new fish barriers across the Unit 2 (west) and Unit 3 (east) outfalls of the Circulating Water System Discharge Canal located at the Millstone Nuclear Power Station. The barriers prevent marine life from populating the canal so that an ambient temperature drop during a dual-unit outage will not result in mass fish kills.

Project Details

  • Performed site work to prepare the environmentally sensitive area for construction, including widening the access road and installing erosion and sedimentation control measures 
  • Installed temporary walkways and access platforms between the structures 
  • Performed underwater construction, including demolition of the existing structures
  • Completed a concrete tremie pour of a new foundation for the west structure 
  • Installed four new concrete crane and wash pads 
  • Placed approximately 250 yards of concrete and 40 tons of rebar 
  • Demolished the existing access platforms and installed new ones
  • Performed underwater repairs on the four existing concrete abutments 
  • Fabricated over 38 tons of new structural steel 
  • Pre-assembled the new structures on-shore and installed each (weighing 50,000 pounds) as a complete unit
  • Installed new modified louvered fish screens 
  • Installed a new polyester grating and handrail system and 22 new LED lights across the abutments
  • Installed a new HDPE domestic water line
  • Installed approximately 750 linear feet of 316 SS Rigid Conduit with a mix of new cable to support the design

Lean, Innovative, and Unique Project Solutions

One of the biggest challenges was the extremely small tolerances for installing the new structures into existing abutments. Cianbro’s Construction Design team worked diligently to model the existing abutments and engineer adjustable rigging to enable the structure to be installed within these tight tolerances. The project team also worked closely with Cianbro’s in-house steel Fabrication and Coating facility to tweak dimensions during fabrication to align with the modeling. This upfront planning and teamwork resulted in the replacement of the two structures ahead of schedule.


ENR New England Best Project Award

ABC Connecticut Excellence in Construction Award