About 135 bushels of river herring died Wednesday when they were able to swim beyond a device designed to keep debris out of the Stillwater Dam and were chewed up by the turbines.
Andy Davis, the director of communications for Brookfield Renewable, which owns the dam, said local operations staff discovered dead fish farther downstream at a dam in Orono. The fish were “out-migrating,” or heading from fresh water back to the sea after spawning.
“Our staff immediately investigated and discovered the source of the alewives was actually the Stillwater facility, where the alewives were somehow getting into turbines of powerhouse A,” Davis said in an email. “Our team immediately shut down the station and mobilized divers to inspect the situation.”
Davis said the teams found that the trash racks, which are used to keep debris out of the facility, were shifting, which produced a gap that the river herring were able to get behind.
“Our staff began repairs yesterday and are continuing today,” he wrote on Friday.
In an email to stakeholders from Brookfield compliance specialist Richard Dill of Brookfield Renewable, Dill explained the ongoing situation Thursday.
Dill said that the Stillwater A station was shut down at about 1 p.m. Wednesday, and further shoreline surveys on the west and east shores of the Stillwater Branch turned up only a couple additional fish. A much larger number of fish had been found, many without their heads and tails, at the downriver Orono facility.
Those fish — roughly 8,900 of them — were disposed of according to an established plan, Dill wrote.
“Per the standard operating procedure in the Orono Operations and Maintenance Plan- Appendix G ‘Mortality Event Plan,’ the approximately 66 bushel of river herring (~135 per bushel) were provided to the Ellsworth Alewife Harvester to be used as lobster bait,” Dill wrote.
According to the Maine Department of Marine Resources, the incoming Penobscot run of river herring for this year has nearly ended, with more than 1.9 million fish counted at the Milford Dam.