This project involved the complete removal and replacement of a trash rack system and supporting structure, at the headworks of an operational hydro-electric facility in Powell River BC. The structural members had become compromised due to the effects of corrosion over the years, and were at risk of failing.
The main challenge the crew faced was the narrow work window allowed by the utility. The requirement was to complete the entire project within a 30 day complete outage.
Dominion Divers teamed up with Nanaimo Foundry and Engineering Works of Chemainus BC, who fabricated all the new components. One of our experienced underwater construction dive teams visited the site after the award, to obtain detailed measurements and geometry of the intake structure. Our team then got together with N.F’s project team to develop a plan that would allow the work to be done in the safest manner, meet the specification and minimize downtime to the client, noise and inconvenience to the community and harm to the environment.
The first task was to remove the existing structure. It was decided that in order to keep diver involvement to a minimum, and meet the schedule, the structure should be removed in as few lifts as possible. To accomplish this, a 160 ton crane was brought in as this was the largest crane the work area would accommodate. The divers used exothermic cutting equipment to cut the structure into sections and carefully rigged them so that they could be safely lifted.
To expedite installation the new structure was pre assembled in modules that would later be positioned, aligned, connected and anchored to the the dam by divers using a variety of hydraulic and pneumatic tools. This was made somewhat easier by building- in a degree of adjustability in some of the connectors.
After 28 days of 2 shifts per day the job was successfully completed to everyone’s satisfaction.