Ellsworth’s costs for public fire protection are about to go up, but not just because of upgrades to the city’s fire hydrants or to its fleet of fire trucks.

They are increasing — in part at least — because the city is building a new $20 million water treatment plant on Branch Lake.

It’s one example of why property taxes in Ellsworth have been going up — which was a central issue in the local City Council election earlier this month — even as Ellsworth has encouraged development to try to dilute the tax burden among a growing number of residents and property owners.

The city, through its property taxpayers, is required to pay 30 percent of its water department operating costs, according to rules set by the state Public Utilities Commission. The rest of those costs are covered by rate payers whose properties are connected directly to the water distribution system.

In exchange for the city paying 30% of those costs, the city’s fire department gets unlimited use of water at fire hydrants, which are owned and maintained by the water department, to fight fires. This year, the city’s share of those operating costs is $465,000.

But that amount covers less than the required 30% — it’s more like 26% — because of development in recent years that has added new metered properties to the water system, according to Nick Henry, a consultant hired by the city to help shepherd the expected rate hikes through the PUC approval process. As the share covered by metered customers has increased, the city’s share for public fire protection has decreased, he said.

So even without a new treatment plant, the city would need to raise more money to cover the 30% requirement set by the PUC. And though the cost of building the new $20 million plant is being covered by grants and low-interest loans, the increased city share will help pay the debt service on the plant and distribution upgrades water department plans to make once the larger and more modern facility is brought online.

“The age of that building and system shows pretty significantly,” Charlie Pearce, Ellsworth’s city manager, said of the current intake treatment plant on Branch Lake. “There’s some months this year where we’re toggling at pretty much max capacity.”

To meet the PUC requirement, the city’s share of the water department’s operating expenses is expected to increase to $610,000 by the summer of 2027, 31% higher than it is now. A small increase of 1.5% for both the city and rate payers is planned for this coming March, with higher hikes in each of the city’s next two budgets, which will go into effect on July 1 each of the next two years, Henry said.

Upgrades the city already has been making this summer to hydrants that have been out of commission are funded in this year’s budget, city officials have said.

Construction on the new intake treatment plant, which will be built next to the existing one on Clearwater Way, is expected to begin in the fall of 2026, city officials have said.