The Dalles Nestled near the woods along Mill Creek, the city’s water treatment plant escaped unscathed from the Government Complex Fire, thanks to around-the-clock fire protection.
But another potential threat is yet to come. If heavy rains hit this fall and winter, runoff from the thousands of barren, burned acres in the watershed could send rivers of silt into the plant.
“That’s going to be the time that we could have some real adverse impacts from this fire,” said Dave Anderson, The Dalles public works director.
The root systems from trees, brush and grasses all help keep soil in place during rains and snowmelt, and they serve as a barrier to erosion. When they’re gone, erosion can run unchecked.
This lesson of nature was made clear in 1967, when the Schoolmarm Fire ripped through the watershed. After the fire was out, heavy fall rains came, and so much ash, silt and sediment flowed into the treatment plant that it had to shut down “for an extended period of time,” Anderson said.
Even though the city planted grass seed to stabilize the ground after that 1967 fire, “We were still seeing water quality impacts during heavy rain events 20 years later,” Anderson said.
With that historical lesson in mind, Anderson, who spent a full week concentrating on protecting the plant, has now turned his attention to preparing for fall and
The city’s watershed covers some 22,000 acres. Nearly 25 percent of it, or 5,400 acres, burned in the fire.
“It’s in the area of the watershed closest to the water treatment plant so there isn’t really any chance for natural settling [of sediment] or dilution to help us out,” he said.
As for the future risks presented by the burned ground, Anderson said, “the areas in which the fire burned hotter and the hillsides are steeper are going to be the areas of highest concern.”
In some cases, the fire may have burned so hot the root systems of grasses are dead, and won’t be able to green up come springtime.
He’s looking at a variety of solutions — and ways to fund them. He’s developing a restoration plan “to rehabilitate the watershed as quickly as we can.”
As part of that effort, he’s talking to the U.S. Forest Service, the Natural Resource and Conservation Service, Wasco County Soil and Water Conservation District, the Oregon Department of Forestry, the Oregon Department of Fish and Wildlife and private landowners in the area.
“We’re in that mode of planning for the worst and hoping for the best, but also trying to actively do what we can do,” he said.
If the water treatment plant does get overwhelmed with silt and sediment, the city can switch to its well water to supply city residents. The 45 water connections between the city and the plant have a three-day supply of clean water.
Possible options for preparing for fall rains include seeding the area — including hand seeding — with an ultimate goal to plant trees when the time is appropriate.
“We need to get some moisture first, we need to get some water in the ground so those seedlings can survive,” he said. “The tree planting is kind of like Phase Two and that will be done when we think we have the best conditions to be successful,” he said. “It may be spring, it may be fall. It depends on how much rain and when we get it this fall.”
The area that burned gets an average of 16 inches of precipitation a year, he said. As for potential problems from silt runoff, Anderson said it’s purely a matter of how bad a storm is.
If it’s anything like the Aug. 16 lightning storm that started the fire, “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.”
Meanwhile, he’s studying various types of grass and grain seed.
“We’re looking for seed varieties with the goal of getting some fall grain up.”
Other options include putting down a woodchip product or even bales of hay.
Other mechanical options including installing a silt fence — like the type of fencing put around construction projects — to contain silt runoff.
“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.
He said the city back in 1967 did not do any aerial mulching.
“In fact, they did very little if any replanting of trees. They got it stabilized and let the rest of the replanting happen naturally.”
One potential hazard that is being corrected already is the network of firefighting trails and firebreaks that were created to fight the fire.
“Those end up being pathways of bare dirt that go straight up and down the hillside, and are sources of sediment from erosion.
“But part of the fire suppression is putting those things to bed. They’re already correcting those things,” he said.
As for how close the fire came to the treatment plant, Anderson said, “It burned right up to it. I mean – right up to it. It’s black right down to the creek beside the plant. We had structural protection crews and fire engine screws stationed at the treatment plant basically 24 hours a day during the worst part of the fire.
“Helicopters were dipping right out of our backwash water lagoons to the control the fire around the hills around the plant.”
While houses around the plant were evacuated, the plant manager, who lives on site, was allowed to stay.
The city some years ago did move the treeline back from the buildings at the water plant. But some vegetation had grown in close to the buildings, so firefighters did some tree trimming and brush removal and sprayed foam on buildings, away from the water, to protect them from fire, Anderson said.
The city also got complaints from residents that the water tasted and smelled smoky. “We did some sampling, we also detected a smoky aroma to some of the samples that we took. We’re evaluating different options to try to mitigate that. We’re doing some different things with treatment right now,” he said. One option may be to dilute the water with well water. “We certainly believe it’s a temporary situation and a direct result of having a fire in the place our water comes from. It’s only an issue of aesthetics. The water is safe to drink,” he said.