EWEB drains the Walterville canal for annual maintenance
By Susan Palmer
WALTERVILLE – To understand what Eugene Water & Electric Board staff biologist Lisa McLaughlin is talking about when she says “fish screen,” completely disregard the word “screen” and think instead of three tractor-trailer-size concrete funnels.
They span the Walterville canal a quarter-mile from the intake along the McKenzie River, and they have a simple purpose. They keep Juvenile salmon and resident trout from getting sucked into the two turbines generating power at the end of the canal.
They resemble screens the way a stepladder resembles an elevator.
These concrete funnels redirect juvenile fish from the canal to a large underground pipe that carries them back to the McKenzie River, where they can more safely make their way to the Willamette River and eventually out to sea.
The massive size — the fish screen is actually visible on a Google maps satellite image — keeps the water velocity slow so that delicate smolts and fry — recently hatched and juvenile salmon — are less likely to be injured as they pass through, McLaughlin said.
EWEB has mostly emptied the Walterville canal this month to do annual maintenance on the fish screen. On Tuesday morning, about 18 inches of water sat in the bottom of a system that can handle 2,500 cubic feet per second. Small trout swam about in the shallow water, crawfish scuttled among the rocks and a nutria skeleton lay exposed on a low gravel bar.
The annual investment in preventive maintenance makes sense, said operations supervisor Rich Callison, who was directing the efforts of three EWEB workers on Tuesday, one of whom had gashed a finger replacing a leaky butterfly valve.
The fish screen cost EWEB $9 million. Built in 2003, it was part of a broad range of fish-friendly improvements the federal government required in order to renew EWEB’s power generating permit on the Leaburg-Walterville system.
The Walterville turbines are capable of generating 9 megawatts. Combined with Leaburg’s turbines, they create enough power to supply nearly 11,000 homes.
The maintenance work is done about this time each year to coincide with the peak return migration of adult chinook. With no water in the canal, the adult fish heading upriver to spawn don’t waste precious energy trying to get into it, McLaughlin said.
Emptying the canal is a slow process that takes several days to keep from damaging its earthen walls, Calfison said, Conversely, filling the canal with McKenzie River water also must be done slowly so fish in the river don’t get stranded by the sudden drop in flow.
“It’s a delicate process,” McLaughlin said.
EWEB is required to make sure the system functions effectively. McLaughlin said surveys when the fish screen first went in showed that the vast majority of young salmon survive the trip through the screen, down the underground pipe and to the McKenzie.
“It’s=s really complex, but it works really well, and keeps our impact on juvenile salmon at a minimum,” she said.
EWEB expects to begin refilling the canal today, with the flow fully restored by Friday.