City to expand recycled water storage capacity

Following a $1.3 million bid award to R & G Excavating in a Dec. 9 City Council meeting, Cottage Grove is moving forward with projects to add a recycled water storage pond and a pump station to the city’s wastewater treatment system.

In the same action, ahead of an expected January 2020 materials price increase, the city authorized the expenditure of an additional $259,031 for the purchase of integration materials for the project such as control panels and instruments that can “talk” to the existing components in the treatment plant.

The move brings the city closer to implementing a long-term solution to handling its daily flow of effluent.

“Essentially [the pond] will be a storage facility for treated effluent,” said Public Works and Development Director Faye Stewart. “And it’ll help us meet our DEQ (Oregon Department of Environmental Quality) discharge permit requirements.”

Effluent is wastewater, treated or untreated, which flows out of a treatment plant, sewer or industrial outfall.

The city’s effluent, which has been treated to remove contaminants, currently has no long-term storage space and must be discharged by way of irrigation or released into the Coast Fork of the Willamette River.

In 2006, the city purchased Middlefield Golf Course and began using it for irrigation purposes, easing the burden on the temperature-sensitive river. Lack of storage has been a strategic challenge for the city, however, and a large part of meeting that challenge involves managing temperature and discharge.

During high-water usage in the summer months, about 75 percent of the effluent is sent to the golf course pond to be used for irrigation.

According to DEQ standards, treated effluent released into the river must not raise the river’s temperature by a certain degree in order to reduce its impact on the ecosystem. By contrast, irrigating the plant life on the golf course requires no temperature control and saves the city the risk of violating DEQ standards.

Despite this solution, last year the DEQ issued the city a $1,575 fine when a sudden spike in temperature contributed to micro-organism growth slightly above the regulated standard.

This was the second time the city has been fined for exceeding allowed bacteria levels at the golf course. The previous year, the DEQ issued a $4,500 fine that was waived after the city agreed to plant trees and vegetation on the banks of the Coast Fork of the Willamette River.

And in September 2019, during heavy rains which increased regular water flow by nearly four-fold, the city again found itself in violation of DEQ discharge restrictions when the city was forced to release its excess storage.

Because of current effluent storage methods, this wastewater management process has been somewhat at the mercy of warm weather patterns.

Efforts to make improvements to the effluent system have been in the works since May 2017 when the city hired West Yost & Associates to perform a pre-design study of the treated effluent reuse project. 

The engineering consultant also outlined design considerations and options for the city to achieve its long-term goal of zero discharge into the Coast Fork of the Willamette River.

In light of a large cost estimate and the DEQ violations, the city decided to make the storage pond and pump station a priority.

The new pond will allow for the storage of about 12 million gallons of treated effluent. With this, the city hopes to pump the effluent to other irrigations sites such as Bohemia and Trailhead parks.

“Purple pipe,” or piping which carries recycled water which can be used for irrigation and industrial use, already exists in places like Bohemia Park.

“We’re prepared for it,” said Stewart. “We just don’t have the state approval yet.”

Ultimately, the city hopes to expand its effluent irrigation system to include multiple parks and the interchange where I-5 ramps flow into Cottage Grove.

As the bid for the pond construction came in under estimates, the city will put out another bid this month for the construction of piping to some of these destinations.

“The long-term goal is that we would not discharge during the summer months that we have a discharge limit on,” said Stewart. “Just get completely out of discharging to the river and be able to discharge solely to the golf course, parks and use it for irrigation throughout the City of Cottage Grove.”

Current irrigation methods at the parks use potable drinking water, a system which Stewart hopes to replace.

“That’s pretty exciting for me,” he said. “The other benefit of us being able to utilize the effluent is … we may be using close to 75,000 gallons of treated drinking water a day at Bohemia Park. So if we were able to use effluent, then that reduces the demand of treated drinking water, which in turn reduces the amount of water we pull out of the river, which in turn is a benefit for the environment.”

The switch is expected to reduce the cost of treating drinking water as well as extend the life of the treatment plant as about 25 percent of the city’s treated water use is put toward irrigation during summer months.

The environmental benefits, too, appear to fall in line with recent concerns raised by local citizens who have made appeals to the city to take actions which are more environmentally conscious. Stewart feels the move is congruent with such concerns.

“It’s really spot on with the kinds of things they would like to see us do,” he said. “It reduces our dependence on fertilizer, which is a petroleum product, and it helps us cool the temperature so there’s less energy being expended than if we were to build a cooling tower.”

Speaking to the safety of the method, Stewart emphasized that the effluent is being treated to DEQ standards and thus poses no risk to the population.

“Effluent is safe,” said Stewart. “In fact, we’ve been putting treated effluent on the golf course for at least 10 plus years. … There are multiple cities throughout the state that utilize it on a regular basis. The key is that our treatment plant will treat the effluent to the level that allows that type of use. The treatment that we treat to is one step below actually physically drinking the water.”

The future pond is slated to be completed by the end of next summer, but part of that timeline will depend on negotiations with stakeholders in the project.

The project will see expansion of treatment plant’s land use into the adjacent disc golf park, relocating two or three holes from the course.

“Of course, we’re going to have to work with the disc golfers and the community who helped build it,” Stewart said.


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