Repairs made to the liner in Baker City’s new wastewater lagoon last fall failed.

Joyce Bornstedt, the city’s public works director, said that when wastewater started flowing into the repaired lagoon, it became apparent that water might again be leaking through the liner.

That was the problem that prompted repairs.

The lagoon was built in 2021 on a 51-acre parcel the city bought in 2019 at the eastern edge of Baker Valley, just south of the Medical Springs Highway.

The lagoon is part of a $5.7 million project that includes a 7-mile pipeline that connects the city’s network of four smaller lagoons, which are about a mile north of Baker City and were built in the early 1960s, with the new lagoon.

The city borrowed the money for the project from the state and will repay the loan over 30 years with an interest rate of 1.36%.

When the city started filling the lagoon in the spring of 2022, workers saw what are known as “whales” in the high-density polyethylene liner, said Brandon Mahon, an engineer with Anderson Perry & Associates in La Grande and the city’s contract engineer. Those are humps in the liner visible above the water line that can potentially indicate leaks, Mahon said.

Over time, he said, it became clear that sections of the liner had failed, resulting in water leaking through.

In October 2023, Jon France, the city’s interim manager, said “poor welds” that connected sections of the liner caused the leaks.

The city’s contractor, Gyllenberg Construction, was responsible for the cost of repairs under a warranty.

Although the warranty expired Dec. 8, 2023, Bornstedt said the city’s contract with the contractor extends the warranty if the lagoon isn’t working as designed.

Mahon said Anderson Perry & Associates has worked on other lagoon projects that used the same liner material that was installed in Baker City, including in Hermiston and Nyssa, but without the problems that have plagued the Baker City project.

Bornstedt said more inspections are needed to determine whether the leaks last fall were due to some welds not being repaired, or some other factor.

She said she is concerned that some parts of the liner “have been compromised,” possibly as a result of the attempted repairs, which could require the entire liner to be replaced.

“We have concerns about the ability for it to be repaired,” Bornstedt said on Tuesday, Jan. 16.

Mahon said the liner material comes in rolls that are laid out in the lagoon. The sections are joined by heating the material to create a “double-fusion weld” that ideally results in a connection that’s stronger than the liner material itself.

When the lagoon was emptied for inspection last year, Mahon said the repairs focused on areas where the liner had leaked.

When the lagoon was partially refilled after the repairs, “whales” reappeared, Mahon said.

Bornstedt discussed the issue with the city council during a recent executive session, which was closed to the public. Oregon’s public meetings law allows councils to discuss certain items, but not to make any decisions, during executive sessions.

The purpose of the discussion was the possibility that the city would need to take legal action to ensure it doesn’t have to pay for additional work on the lagoon, Bornstedt said. The city has not taken any action so far.

She said she is planning to give the council an update on the lagoon at a future meeting.

Lagoon’s purpose

The lagoon and pipeline, which comprise the most expensive wastewater project in the city in more than two decades, was prompted by the Oregon Department of Environmental Quality (DEQ) telling city officials more than a decade ago that eventually the agency would not allow the city to pipe treated wastewater into the Powder River.

That’s how the city has disposed of treated wastewater from its four older lagoons, which are near the river, for more than half a century.

DEQ told city officials that treated wastewater could promote algae blooms and otherwise pollute the river.

The new lagoon, which is 20 feet deep compared with the existing lagoons’ depth of 6 to 8 feet, also increases the city’s capacity to store wastewater, Bornstedt said. The pipeline allows the city to move wastewater between the new and old lagoons.

Rather than piping wastewater into the river, the city plans to use water from the new lagoon to irrigate nonfood crops on private land near the lagoon.

DEQ has denied the city’s application to use wastewater for irrigation on some of that land due to a shallow groundwater table and soils that don’t readily absorb water.

Since the leaks were detected in 2022 and the new lagoon drained to facilitate repairs — the water was pumped via the new pipeline to the old lagoons — the city has been storing wastewater in the old lagoons and continuing to release treated water into the river.

The city still has a permit from DEQ to do so.

However, Bornstedt said that without the new lagoon available, the city remains close to the storage capacity of the old lagoons.

The new lagoon is “critical to our system,” she said.