Mar. 19—A project to boost water levels at Lake Thunderbird will cost millions to implement, a recent pilot project and preliminary estimate finds.

The city completed a pilot project in the fall to treat wastewater and then discharge the highly treated water into the lake to augment water levels.

The practice is known as indirect potable reuse and was identified as a preferred method to increase water supply in the city's 2060 Strategic Water Supply plan.

Utilities Director Chris Mattingly said preliminary reports on the city's pilot project indicated capital costs could reach about $135 million.

"Since we are just getting the costs, we have not determined a revenue source," Mattingly told The Transcript.

The City Council on Tuesday approved a $196,190 contract with Garver Engineering to study the economic feasibility of the project, which could conclude the cost will be less, Mattingly said.

The engineering study will show the city "how to optimize" the technology to avoid augmenting the lake only when it's necessary.

"This might have an optimum effect on the pricing too, and possibly, we can trim the estimate," he said.

Garver's contract is for a year-long look at the program, according to Mattingly. An engineering report will also be required by the Oklahoma Department of Environmental Quality before the city could move forward.

If voters approve a water rate increase in June, the funds will have to go to water line replacements and other capital projects — not indirect potable reuse, Mattingly said.

In addition to the cost hurdle, the project faces some challenges before it can be implemented. The Central Oklahoma Master Conservancy District (COMCD) operates the lake through an agreement with the U.S. Bureau of Reclamation.

Amanda Nairn, the conservancy district's board president, said it could eventually assist the city in looking for grants to offset the projects costs, but the two other cities which use the lake for drinking water and the board would have to approve the project before it can move forward.

"In order for us to pursue any funding or assistance to Norman for pursuing Indirect Potable Reuse, the board and the other member cities would need to agree on IPR (indirect potable reuse) as a future goal," she said. "We are currently letting Norman do their due diligence on vetting the possibility and, it is my understanding, they have included Midwest City and Del City throughout their current work in order to keep them up to date on the newest information."

The closer the project gets to reality, the more seriously a probe for funds would be for the COMCD board, Nairn said.

"It is not currently an imminent agenda item in the near future," she said. "So, we have not researched funding opportunities, but municipalities are eligible for BOR grants as well."

A request for comment on the project from Midwest City and Del City officials was not returned Friday.

Council member Stephen T. Holman, who represents Ward 7, said officials from those cities have warmed up to the idea of indirect potable reuse. Holman served on the city's 2060 Strategic Water Supply committee in 2013-2014.

"City staff has been working with Midwest City and Del City on this idea for over a decade," he said.

When discussion on the technology began, those city officials were skeptical, but based on more recent conversations, they've "warmed up to the idea," Holman said.

"So, they haven't really seen a demand for more water resources and you're talking reusing wastewater," he said. "I think it was maybe an 'ick' factor and why would they (approve it) if they don't need more.

"But I think over the years as other cities have done it, and with resources becoming more scarce in parts of the county, the more discussions we've been able to have and the more we've been able to show the science behind it ... they've definitely warmed up to the idea for sure."

Holman said the funding is an issue, and it would likely mean "a series of rate increases" in the future.