KILLINGLY — Almost five years after residents approved funding the project, workers are poised to begin a massive, multi-million upgrade of the Killingly waste water treatment plant.

Local leaders and state legislators, as well as design and construction crews, are expected to attend a ground-breaking ceremony on May 30 at the Wauregan Road Water Pollution Control complex to mark the formal start of the work at the facility.

The two-year refurbishment project at the 48-year-old main facility will focus on replacing original parts too outdated to meet state and federal guidelines for the removal of nitrogen and phosphorous.

Town Engineer Dave Capacchione said crews will also demotion unused structures and add in new components aimed at increasing the plant’s efficiency.

“They’ll be new equipment to automatically remove all the baby wipes people flush and end up tangling up the system, decreasing the life span of some parts,” he said. “But we still don’t want people disposing of those wipes though their toilets.”

Capacchione said an incinerator building that has sat unused since 1974 will be razed and the plant will be reconfigured to allow workers better access to equipment.

In September 2014 — less than a month after a referendum on the issue failed — residents approved spending $25.8 million for work at the main Wauregan Road plant and the Rogers pump station.

The pump station work, which included replacing outdated electrical components, was completed last year for $2.5 million.

A state funding package will cover 20 percent — or $5.1 million — of the overall cost, with the rest being paid through a 2 percent loan from the state Department of Energy and Environmental Protection’s Clean Water Fund.

That loan will be paid back over 20 years with a sewer user fee increase that took effect in July 2017. The increase is an 11 percent jump per year for four years, increasing the average sewer use bill for a single-family home from $316 to $524 by the fourth year.

One planned job at the site — the demolition of the 76-year-old former treatment plant — was taken off the project list after Hutchinson Precision Sealing Inc agreed to raze the structure in exchange for the town selling it 1.4 acres for $1 in 2017.

But Town Manager Mary Calorio said that agreement is in limbo.

“We’re in a holding pattern right now,” she said. “I need to re-examine the documents related to the issue as I’m not sure any agreement was actually finalized.”

Massachusetts-based RH White Construction was awarded the contract for the main plant work with its bid of $18.1 million.

Capacchione said sewer users in town should not expect any interruption of service during the upgrade work.

“Workers are out doing road-widening work now,” he said. “This plant is like a 1974 Chevy Nova that’s been driven coast-to-coast and needs repairs.”