Lewiston is getting set to enter uncharted waters.

For nearly a century, the city has drawn the majority of its drinking water from the Clearwater River and treated it at the plant on Railroad Avenue in East Lewiston. That supply is supplemented by a network of wells.

But much of the historic plant will meet the wrecking ball in October to make way for $42 million in improvements to the treatment and distribution system that voters overwhelmingly approved in 2019. Several mobile microfiltration water treatment trailers will be temporarily brought to the site next March to help meet summer water demands for as long as seven months. But during the winter, the city will have to rely on groundwater pumped out of its wells for its entire water supply.

And even though several city wells have been plagued by mechanical problems over the last several years, water projects supervising engineer Alannah Bailey said the plan devised by the city and project contractor IMCO General Construction should ensure that water rationing won’t become an issue during peak irrigation season in 2022.

It all revolves around what those in the water supply business call “firm capacity.”

“Which is being able to supply water with your largest asset not available,” Bailey said. “We’ve essentially designed it to have our largest well and another high-producing well out of service, and still supply that peak demand.”

The largest well is called Well 6, and it sits adjacent to Bryden Canyon Golf Course. It has suffered several breakdowns over the past decade, but has a new pump and motor. The city also has staged a backup pump and motor at the well site so repairs can be made quickly if any new problems arise. Public Works is taking that approach with all the remaining wells with thorough assessments and by prepurchasing backup parts.

In addition, Well 3, that is primarily used to irrigate Normal Hill Cemetery, has been approved for drinking water supply so it can be called on in the event of an emergency. Finally, part of the $42 million bond is for the construction of Well 7 on Nez Perce Grade. It has been drilled, and production tests will take place next month. If all goes as planned, it will be finished and approved for public use early next year, adding even more to the city’s groundwater supplies.

Having Well 7 available also means the portable treatment trailers probably won’t need to be at the treatment plant site as long, reducing the overall cost of the project.

“We’ll have a ton of extra supply out there,” Bailey said.

Funding boosts/stumbling block

Passage of the water bond by 90 percent of voters means funding for the new plant is secure. But its overall financial picture got a big boost when the city was able to gain the assistance of the Idaho Department of Environmental Quality and its revolving loan fund. That resource gave the city a low, 1.625 percent interest rate over 30 years, far better than it would have received on the open bond market. The funding package also includes about $926,000 in loan forgiveness.

The project got another fiscal boost from the Army Corps of Engineers, which awarded $673,000 to help design a new water intake for the plant. The intake is upstream from the Clearwater Paper mill, and was built by the Corps along with the levee system to serve the existing water treatment plant. But it never worked as intended, and was used only for a couple of months.

That intake represents one stumbling block because of its rapidly inflating cost. Bailey said the city planned to build upon the existing infrastructure, but closer inspection revealed extensive problems, like substandard concrete and rebar.

“We’re finding that we can’t use a lot, so that (initial estimate of) $3.2 million is turning into closer to $7 million,” she said.

There are several funding options, including planned applications for more Corps funding, other grants and the city’s allotment of American Rescue Act funds. Congress also is considering a massive round of new infrastructure funding that could trickle down to Lewiston. And some of the state loan money also could be applied, she added.

Out with the old

The historic status of the original, red-brick portion of the existing treatment facility that dates to 1924 was another issue. But the Idaho State Historic Preservation Office approved its demolition and a remediation effort that requires the city to fund a citywide historic preservation plan. Bailey said a cultural resources firm will do that work for about $15,000, which will come from the state loan funding.

Conditions at the old plant have been deteriorating for generations, with corrosion of pipes and disintegration of concrete as the major issues. The state of the plant has threatened its reliability, and its ability to meet environmental regulations, according to the city. But the new plant will feature a state-of-the-art filtration system that uses porous membranes to remove particles and microbes.

“It essentially restricts anything of a certain size from getting through,” Bailey said. “So you can’t produce poor-quality water. It’s impossible.”

Final purification will be done with chlorine and ultraviolet light. The project’s consultant hasn’t made a recommendation on whether the city should add fluoride to the water as it currently does, however.

Design for the new plant is approaching 60 percent completion, and will be finished by the end of the year. Public Works will go to the city council on June 28 to ask for approval of an “early-works” package to buy components that require a long lead time before they can be delivered. Once design is at least 90 percent complete, another request for final funding will come to the council, probably in September.

“We want to have that final design and council approval to spend before we start tearing down infrastructure,” Bailey said.

According to the city, IMCO’s design and construction plan will help meet objectives that include keeping the project on budget at its existing location, allow for future expansion, implement integrated controls for the entire water system and — most importantly — keep the taps flowing for residents and businesses until the new plant comes online in late 2022 or early 2023.

Once complete, it will join the city’s wastewater treatment plant in North Lewiston as fully updated facilities ready to serve residents for decades to come. Wastewater projects supervising engineer Joe Kaufman said the rebuild of the wastewater plant is about two-thirds complete and on schedule for final completion by the end of next April.

Mills may be contacted at jmills@lmtribune.com or (208) 848-2266.