Council approves 5% budget increase for The Dalles Wastewater Treatment Plant

Over 12 months, the plant cleans nearly 920 million gallons, enough to fill roughly 1,400 Olympic-sized swimming pools. This number will continue to grow with Google’s two new data center buildings requiring ‘round the clock cooling, and the city is gearing up more spending to accommodate that capacity.

City councilors have signed off on a $1.49 million amendment to the operations contract for the wastewater treatment plant, locking in funding for the next 12 months while highlighting how the more than 70-year-old facility and 100-plus miles of sewer lines quietly underpin daily life in The Dalles.

At a regular city council meeting on June 23, Public Works Director Dale McCabe announced the annual budget adjustment for the plant management contract, which is in year three of a 15-year pact with engineering giant Jacobs (OMI). He added that this money was already set aside in the 2025-26 budget.

Before putting the amendment to a vote, Councilor Timothy McLaughlin said, “Our city remains fortunate to have such an outstanding company serving the wastewater needs of our community.”

Behind the fences: how the plant actually works

When wastewater arrives, machines separate liquids from solids. The liquid stream is filtered, aerated and sanitized, then returns to the river.

The concentrated solids are pumped into two 210,000-gallon anaerobic digesters: giant, hot vats where bacteria break down organics, kill pathogens and produce a methane-rich biogas that was slated for collection by an award-winning green energy design intended to produce power to offset the plant’s expenses.

Plant Manager Oscar Ferris said this methane-powered micro-turbine is not currently generating electricity, due to equipment issues.

“We are trying to analyze how much biogas we actually produce, what we can do to capture that and use it beneficially, and then what we can do to potentially increase that and get more power to the grid,” he said.

After at least 15 days in the digester tanks, the material is no longer called “sewage sludge.” Federal rules say it can be classified as biosolids, a nutrient-rich soil amendment that can legally be land-applied on farms, forests or mine-reclamation sites once it meets strict metal and pathogen limits.

Broken digester lid added critical expenses

This past year, a valve connecting the two digesters became clogged, leading to pressurization that damaged one of the digester lids. The plant repurposed an aeration basin to hold biosolids while conducting repairs to the digester lid.

“While we did have to do some unorthodox operations, we were able to maintain compliance with Class B biosolid regulations throughout the year that we were down,” Ferris said, crediting regional Jacobs teams who located spare parts and loaner pumps.

The digester mishap triggered a nearly $700,000 insurance claim that is still being paid, City Attorney Jonathan Kara pointed out.

The plant added an 8-inch emergency pop-off hatch in case of future debris-related backups like this so pressure won’t damage the structure. Jacobs’ report noted that if this hatch were to pop open, “The result would require biosolids cleaning from the tank and surrounding areas, but would not cause any damage to the structure itself.”

Plant in search of another mechanic

Jacobs touts a company-wide goal of 80% planned maintenance; the local crew hit 96%, according to the report. Ferris noted that 2023 brought a recordable injury.

“We championed a positive attitude and just reinforced our safety culture, and we now sit at over 700 days without a recordable incident,” Ferris said.

Staffing remains tight. “We have been down a mechanic for, gosh, probably about eight months now,” he said, noting that qualified applicants are scarce and often have rapid turnover.

Touching on the company’s commitment to promoting sustainability in the community, Ferris listed several local initiatives, including a partnership with Oregon State University.

“One of those is the renewable energy study that we have going on to find a better way to utilize that for the future of the wastewater treatment plant for more sustainability,” he said.

Limits to adding hot water to the Columbia River

The federal Clean Water Act sets out temperature maximums for fluids dumped in the Columbia River, specifying that the water needs to stay below 20 degrees Celcius, or 68 degrees Fahrenheit, in order to protect salmon and steelhead populations.

From June 1 through Oct 31, the plant’s Environment Protection Agency permit limits it to adding no more than about four billion kilocalories of heat to the river each day, averaged over the month. Because that limit is the product of temperature and flow, hotter flows means the plant must either discharge less water or cool it down to stay within its fixed “heat budget.”

Outside the warm weather window the numeric cap is off, but the facility still has to measure and report its discharge temperature to regulators.

In January, the council authorized a “thermal impacts analysis” to study the causes and impacts of warm water discharge.

The analysis would also develop a “thermal trading plan,” a water-quality trading program overseen by Oregon’s Department of Environmental Quality that lets wastewater plants balance out the heat or pollutants they release by buying credits that pay for cleanup projects elsewhere — or by tackling their own river-health efforts, such as planting shade trees along streambanks.

Environmental advocates, however, have questioned the scheme’s effectiveness. In a 2024 interview with Columbia Insight, DEQ conceded that the state does not take water-temperature readings to verify that these “traded” fixes actually make rivers cooler.