Norwich ― Superlatives dominated the remarks made at Wednesday’s groundbreaking ceremony to signal the start of construction of the city’s new $200 million wastewater treatment plant.

Norwich Public Utilities General Manager Chris LaRose called the plant the largest capital project in city history while Federal Environmental Protection Agency New England regional administrator David Cash said it is the largest sewer infrastructure project in the state. And Jason Nickerson, chairman of Torrington-based general contractor CH Nickerson & Co. said it is the largest project in his company’s 84-year history.

About 40 NPU employees, city, state and federal officials gathered at the plant entrance on Falls Avenue Wednesday morning for the groundbreaking ceremony, followed by a tour of the aging plant that will be replaced piece by piece over the next five years. The project had been under design for the past 20 years resulting in multiple revisions and cost escalations.

State Rep. Derell Wilson, D-Norwich, recalled that he did his high school senior seminar project in 2009 on environmental science and the workings of the Norwich sewage treatment plant.

“To see it now come to fruition, 20 years in the making, being a regional asset, an economic driver for both Norwich and our surrounding communities is amazing,” Wilson said.

Mayor Peter Nystrom stressed the regional benefit of the plant and the critical partnership between NPU and smaller surrounding towns, with the increased Norwich plant capacity allowing Norwich to attract new businesses and surrounding towns to extend sewer service to their residents and businesses.

The plant is located on the narrow man-made island that splits the east and west branches of the Yantic River as it feeds into Norwich Harbor. The plant shares Hollyhock Island with Southeast Area Transit’s main commuter bus terminal and the Thayer’s Marine boat sales and repair facility and its related marine retail business.

Construction will be tricky, with large buses, boats on trailers and dozens of workers traveling on Falls Avenue daily.

The plant must also remain in operation throughout the construction, as aging sewage digesters, wastewater treatment buildings, large sewage pipes and outflow pipes are replaced.

“Over the next five years, the island on which we are all standing will be transformed into a modern, efficient wastewater treatment plant that will dramatically improve water quality in the Yantic, Shetucket, and Thames rivers,” LaRose said Wednesday. “Every community between Norwich and Long Island Sound along the Thames River – Preston, Montville, Ledyard, Waterford, Groton, and New London – will benefit from this project.”

The project is being funded with a combination of grants and loans, with $72 million in grant funding through the state’s Clean Water State Revolving Fund and $128 million in low-interest, 2% loans from the state Clean Water Fund, to be repaid by NPU’s 10,000 wastewater customers over the next 20 years, NPU officials said.

Graham Stevens, bureau chief at the state Department of Environmental Protection, said the project provides an environmental and economic benefit for the city and southeastern Connecticut.

“No longer will we see the overflows of untreated and partially treated sewage to our rivers,” Stevens said. “We are going to be able to handle wet weather conditions, so when we have these intense rainstorms throughout the summer, this new wastewater treatment plant and its systems will be able to handle those flows.”

c.bessette@theday.com