THE DALLES, Ore. — Residents of The Dalles have detected smoky notes in their drinking water during recent wildfires, but the water is safe, city officials said. And thanks to round-the-clock work, crews protected the city water plant from flames that turned the soil black right down to a nearby creek.
But fire has created a longer-term threat to the water supply for the city of more than 14,000 at the east end of the Columbia Gorge: the potential for fall and winter rains to wash rivers of silt from the bare earth into the water headed for the treatment plant.
It wouldn’t be the first time. A fire in 1967 ripped through the watershed where surface water is collected behind a dam and then treated for consumption.
That was followed by heavy rains and so much ash, silt and sediment flowing into the treatment plant that it had to shut down “for an extended period of time,” said Dave Anderson, the city’s public works director.
The city planted grass to stabilize the ground, Anderson told The Dalles Chronicle, but “we were still seeing water quality impacts during heavy rain events 20 years later.”
The watershed collects rainwater and snowmelt — averaging about 16 inches a year. It covers about 22,000 acres.
Nearly 25 percent of it has burned in this year’s Government Flats fires, which were considered about two-thirds contained Wednesday.
In some areas, Anderson said, the fire may have burned so hot the root systems of grasses are dead, and the plants won’t green up come springtime.
Another storm like the Aug. 16 lightning barrage that started the Government Flats fires worries him: “A really heavy rain like that is going to be a problem for us. It caused flooding in town and fires in the watershed, from the same storm cell.”
The city can switch to well water, its supplemental source in the summer, for a few days.
He’s looking at grass and grain varieties to see what the city can get in the ground quickly.
“We’re looking for seed varieties with the goal of getting some fall grain up,” he said.
Next would come tree-planting, Anderson said, which would be “kind of like Phase Two and that will be done when we think we have the best conditions to be successful. It may be spring, it may be fall. It depends on how much rain and when we get it this fall.”
Other options include putting down a woodchip product or bales of hay, and installing a silt fence like the fencing around construction projects.
“We’re kind of looking at everything that might be available to us, with the sense of doing something sooner rather than later,” he said.