Keeping cool: Trees along Bear Creek could solve city's effluent problem

The city of Ashland could save millions of dollars by planting trees.

Ashland is facing a requirement from the Oregon Department of Environmental Quality to do something about the overly warm, treated sewage effluent that it dumps into Ashland Creek, which then flows into Bear Creek. Warm water can be harmful to fish.

But building a cooling tower and a chiller to cool the effluent would cost $6.1 million to $8.1 million, plus another $200,000 annually for operations, according to research done by Idaho-based Keller Associates, a firm hired by the city to create a sewage master plan.

Over 20 years, that mechanical cooling option would cost $10.1 million to $12.1 million — putting a heavy burden on Ashland sewer customers who already pay the highest sewer rates in the Rogue Valley.

In contrast, planting and maintaining trees along eight miles of Bear Creek to cool its waters would cost $3.4 million spread out over 20 years, Keller Associates found.

The savings compared to the mechanical cooling option would be $6.7 million to $8.7 million over two decades.

Keller Associates looked at an option to sprinkle treated sewage effluent on hundreds of acres of city-owned land north of Interstate 5, but that would cost $5.3 million to $10.8 million for construction. Treated effluent also makes up a significant share of Ashland and Bear Creek water flows that are important to fish. Creek levels would drop if the effluent were sprinkled on the hillside.

Communities all across Oregon are dealing with the potentially costly mandate to stop emptying warm effluent into creeks and rivers.

Dick Pedersen, statewide director for DEQ, paid a personal visit to city officials on Monday to tell them that while the tree-planting strategy is relatively new, DEQ would support Ashland's decision to take that route. He said Medford also is interested in tree planting to mitigate the effects of its warm effluent.

"We believe it's an option for the future," he said.

Pedersen said the beauty of the tree-planting strategy is that it costs less than other options, while also improving the health of the watershed in multiple ways. He said many calculations have been done about the cooling effects of tree shade on water.

He said the tree planting does have to be planned and carried out carefully.

"Well-planned riparian work works. You want your investment to hold. It's not just sticking a few willow twigs in the ground and calling it good. We've seen that fail," Pedersen said.

The tree planting strategy has been tested on a large scale in the Tualatin River watershed in the Portland area. Cities along the river and CleanWater Services, a public utility, have planted more than a half-million native trees and shrubs since 2005. The project's "Tree for All" Community Tree Planting Challenge has involved volunteers and school, nonprofit and community groups.

Participants are ahead of their goal to plant 2 million trees over 20 years to improve water quality and habitat in the Tualatin watershed, according to

Trees have been planted along 36 miles of that river, said David Primozich, director of ecosystem services for Portland-based Freshwater Trust.

Representatives of Freshwater Trust met with city officials on Monday to offer their nonprofit group's services in spearheading the tree planting effort along Bear Creek. They would work with local groups and residents on the project. Rather than buying land along the creek, they would negotiate with property owners to get long-standing agreements that tree planting and maintenance could take place.

The Freshwater Trust Managing Director Alan Horton said his group would submit annual tree planting project monitoring reports to the city to prove the project's effectiveness, along with annual bills over a 20- to 25-year period.

With the idea so new, councilors have yet to make a decision whether to pursue the tree planting approach. But several said the approach seems promising if calculations are right that tree shade can effectively cool Bear Creek.

"I think you had me initially at 'lower cost,'" said Councilor Greg Lemhouse. "I appreciate the significance of the DEQ director saying he believes in the potential of the project."

Staff reporter Vickie Aldous can be reached at 541-479-8199 or

Correction: The subhead has been corrected to accurately reflect this story.

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