December 12, 2010 - Bend Bulletin - Muddy mix prompts water system scrutiny
Dec 15, 2010
Muddy mix prompts water system scrutiny
Oregon DEQ is working with the city of Bend to solve a glitch that can send a silty plume into Tumalo CreekBy Nick Grube / The Bulletin
Published: December 12. 2010 4:00AM PST
On one of his regular jogs through Shevlin Park last month, Bill Buchanan noticed something strange about Tumalo Creek.
As the Bend attorney ran along one of the trails, he saw that the water had begun to change color, trading in its crisp, clear complexion for a reddish brown that left the stream milky and opaque with sediment.
There was even a short section where the different hues ran parallel with each other, almost like merging lanes of traffic, before eventually mingling together and traveling downstream toward Tumalo Creek’s confluence with the middle portion of the Deschutes River.
“It looked like the chocolate river in the Willy Wonka movie,” Buchanan said. “If you go two miles upstream, Tumalo Creek is as clear as can be.”
While Buchanan had seen this sort of turbidity event happen on Tumalo Creek before, he always assumed it was natural runoff caused by rain or snow melt.
It wasn’t until he undertook efforts to convince the city to change directions on its proposed $73 million overhaul of its Bridge Creek water system that he realized that the sedimentation was man-made, and in fact was caused by a design flaw in the city’s current surface water infrastructure.
The Oregon Department of Environmental Quality is now looking for a way to solve this problem, and as a result of receiving photos of the creek from Buchanan, visited with city officials last week to try to find a solution.
“It really was a severe case of turbidity in the water,” said Eric Nigg, the DEQ water quality manager for Central Oregon. “We’re not looking at enforcement right now. We want to solve the problem, and at this point are just trying to work with the city to make sure it doesn’t happen again.”
The turbidity Buchanan saw during his run was coming from a series of pipes and ditches the city of Bend uses to put excess water it takes from Bridge Creek back into Tumalo Creek. Most days this water is clear when it reaches the creek from this diversion channel, but a clog at the top of the ditch caused it to overflow, resulting in a significant amount of erosion that sent dirt and other debris into the stream.
Nigg said this sedimentation can have major impacts on fish and fish habitat by muddying up spawning grounds and making it difficult for the fish to breathe. It can also affect insect and other invertebrate species that live in the creek that can be a food source for the fish.
“Sediment in any creek is a pollutant,” Nigg said.
‘This isn’t a new thing’
The city’s current surface water system has a long history of discharging silt and other debris into Tumalo Creek.
When the city first designed its Bridge Creek water system in the 1920s, it didn’t include any mechanism that allowed it to limit how much water came through its infrastructure. This means that every day the same amount of water is diverted through a nearly 10-mile-long pipeline as it makes its way to Bend, regardless of whether there is enough demand to use it all. City officials have also said that if this water wasn’t constantly rushing through this pipeline, it would likely collapse.
To handle the excess water, the city installed an overflow apparatus at its Outback Treatment Facility located about two miles up Skyliners Road. Outback is designed to collect and treat all the water from Bridge Creek before distributing it to town.
For decades, this overflow system would dump the excess water that came into Outback over a hillside next to the site that led down to Tumalo Creek. This water would then cascade over a steep embankment, causing a significant amount of erosion as it made its way back into the stream, which is where it would have naturally flowed if the city hadn’t diverted it from Bridge Creek in the first place.
About 14 years ago, however, the city added some new infrastructure to its system to prevent this erosion from happening. This included putting in some culverts to take the excess water from the Outback Facility and convey it around the steep embankment. The water would then go through a piece of equipment that essentially slowed it down before making its way to Tumalo Creek.
While this worked to prevent turbidity in the creek, Heidi Lansdowne, the project manager for Bend’s Water Division, said it wasn’t fail-safe. At least a couple of times a year, she said, the culverts would become blocked with debris or, in some cases, beaver dams, resulting in overflows.
She said there were also instances where Bridge Creek water combined with excess well water that was being pumped at the Outback Facility to overwhelm the culverts, which were only designed to handle surface water.
“This isn’t a new thing,” Lansdowne said. “This has been going on for years.”
Lost in the shuffle
Finding a fix to the overflow problem used to be at the top of her priority list, Lansdowne said, but with the upcoming surface water project and cuts in engineering staff, the momentum just sort of dissipated.
City employees were also supposed to check the overflow culvert as part of their daily rounds to make sure there weren’t any clogs in the system. Lansdowne said the problem was that this monitoring was never formalized, and it sometimes was “overlooked.”
With the recent turbidity event and subsequent visit from the DEQ, she said the city will try to bolster its monitoring of the overflow infrastructure. This means city employees will check the Outback overflow system as part of their daily routine to make sure there isn’t anything clogging up the culverts or ditches.
“It’s back on the radar,” Lansdowne said. “We’re very on top of it, and we’re doing everything we can to mitigate the situation.”
In the Bend City Council’s approved $73 million upgrade to the city’s surface water system, which includes adding a new pipeline, a state-of-the-art treatment facility and a possible hydropower plant, Lansdowne said overflows should be rare. The city must overhaul its system to meet federal clean water mandates and replace its aging pipelines.
When this work is completed, Lansdowne said the new Bridge Creek intake infrastructure will have a valve at the top of the pipeline that will allow the city to only take as much water as it needs at any one time.
For instance, if the city only needs 5 million gallons a day, it will only take that 5 million gallons versus what happens today where the city takes about 11 million gallons, diverts it for about 10 miles, and then dumps an excess 6 million gallons out when it reaches the Outback Facility.
“When that new project gets up and operational, that overflow will be dry 99 percent of the time,” Lansdowne said. “But we still have to have it in case of an emergency bypass.”
She added that as a part of the upcoming overhaul, the overflow system will also be improved in an effort to prevent future erosion and turbidity events.
Nigg said that after last week’s DEQ inspection he feels confident the city can solve its overflow problem in the near term with some simple operational changes. If not, he said, the DEQ will have to take another look at the issue.
Should overflows continue to increase sedimentation in Tumalo Creek, he said the DEQ might force the city to get a discharge permit through the U.S. Environmental Protection Agency’s National Pollutant Discharge Elimination System program.
The program is meant to regulate discharges of pollutants into surface water. Municipalities along with other industries are required to get this permit if they are discharging anything into a body of water.
Nigg said a common example of a municipal project that would need a discharge permit is a wastewater treatment plant that dumps its treated effluent into a river.
The city likely wasn’t required to get a discharge permit for its surface water diversion project, he said, because it was simply taking clean water from one source, Bridge Creek, and depositing it into another source, Tumalo Creek.
“It isn’t one of those things that rises to that level of concern because it’s clean water,” he said.
Even if the city doesn’t need to get a discharge permit for its current overflow problem, Nigg said his agency might require one for the new Bridge Creek project. In the meantime, he said, the priority for the DEQ is to prevent the city from depositing any more sediment into Tumalo Creek.
“Our chief concern is trying to eliminate this discharge of turbid water,” Nigg said. “And we’re going to try to work closely with the city to do that.”
Nick Grube can be reached at 541-633-2160 or at email@example.com.
Published Daily in Bend Oregon by Western Communications, Inc. © 2010