Rock Island Dam Pier 1 Spillway Repairs

Project Summary

This project included major concrete structural repairs to the spillway at the Rock Island Dam. Work included demolition of the existing conduit raceways along the downstream face of the spillway deck, demolition of existing lighting conduits, installation of new lighting conduits and electrical boxes, installation of new LED lights and new lighting circuit wiring, rehabilitation of the existing expansion joints at spillway piers, and concrete repairs. The project furnished and installed new conduit raceways between the powerhouse electrical bay and the middle fish ladder.

Structural repairs to the dam included the installation of post tensioned anchors and epoxy injection grouting. IMCO developed detailed work plans and partnered with subcontracts for the post tension anchors and injection grouting. The drilling work that helped stabilize the dam had to be performed over the side of the spillway. The epoxy injection for the crack repair scope was under tight scheduling requirements in order for the PUD to regain spillway access for their fish spill habitat conservation program.



Rock Island, Washington


Chelan County PUD

Contract Amount

$5 million


October 2020 – November 2021

Project Highlights

Working over an active spillway, performing an incredibly high-risk task, required careful safety planning and daily coordination with dam operations.