HOLYOKE — For decades, millions of gallons of the city’s sewage have flowed into the Connecticut River on a regular basis during periods of heavy rain.

On Monday, the city began a lengthy, $30 million plan to fix the problem that will involve updating thousands of feet of sewer line, storm drains, and manholes over the course of the next 12 years.

“At my office, we receive constituent calls on every subject under the sun, believe it or not,” said Mayor Joshua Garcia, speaking to the public from the corner of George and Vadnais streets where work will commence. “From kittens and trees, to potholes on our streets. But the calls that concern people the most are the discharge of untreated wastewater into the Connecticut River.”

The forthcoming work is designed to bring the city into compliance with clean water standards by the time its complete in 2037, the mayor said.

In a 2023 settlement with the U.S. Department of Justice, the city agreed to take steps to reduce its discharge of sewage into the river, which is a violation of federal and state regulations.

Holyoke owns and operates a sewer collection system that serves about 70% of the city, with two-thirds of the system carrying both sewage and stormwater. During periods of heavy rain, the wastewater volume can exceed the capacity of the sewer system or the treatment facility, causing the excess wastewater to discharge into the Connecticut River before it is treated. Such combined sewer overflows, or CSO discharges, contain raw sewage and are a major water pollution concern.

Garcia decried this century-old, single-pipe system as “primitive,” since heavy rains or melting snow frequently overtake the city’s water management capacity.

The project to alleviate these conditions, referred to as the River Terrace CSO Separation project, will bid adieu to the single pipe that carries waste from all these different sources. Instead, drainage separation infrastructure will be installed — a move expected to reduce 85% of waste in water and bring the city into compliance with the Clean Water Act, the national law governing the country’s waterways.

The city kicked off Phase A on Monday, a $10.5 million project overseen by Ludlow Construction and funded by a 0% interest loan from the state.

Two more phases are planned, and the city is searching for funding help to complete this work. Some funds are coming from the Commonwealth Clean Water Fund and the Environmental Protection Agency, and Garcia thanked U.S. Sens. Elizabeth Warren and Ed Markey for earmarking $2 million in federal funds that will be used in the second phase of work.

Garcia also thanked Councilman Mike Sullivan, “who never let’s me forget how important it is to invest in things that we don’t see — and that’s the infrastructure underneath our feet.”

“In the end, the result will be a huge leap forward in environmental stewardship by the City of Holyoke,” Garcia said.

Victoria Houle, the city’s assistant engineer, said that while roads are ripped up to make way for new piping, residents can expect periods of sewer and water outages.

Updates will be made to Holyoke’s Facebook page, and notices will be posted on doors outside of where work is taking place.

Work is beginning at the corner of George and Vadnais streets where the mayor held his press conference. Other streets that will be impacted during Phase A include Hampton Knolls Road, Jefferson Street, Liberty Street, Woodbine Lane, Bemis Road, Meadowview Road, Hillview Road, and Northampton Street.

Designs for Phase B, a $12 million phase that is scheduled to be completed by September of 2029, are still being completed. The third and final phase will replace the pipes in the Springdale area of Holyoke, with exact costs still unclear.

Mary Monahan, interim director for the city’s Department of Public Works, said the Board of Public Works will enter into negotiations for a new contract with Veolia North America, to operate, maintain, repair, and improve wastewater and flood control systems in the city.

The city has had a long-term arrangement with Veolia, but in past months bids were put out for other companies to oversee the city’s water. However, it seems likely that Veolia, which was among bidders for the spot, will be the company selected out of a pool of three after negotiations, Monahan said.

Issues with CSO runoffs are not unique to Holyoke. Both Chicopee and Springfield as well as other towns throughout western Massachusetts also experience runoffs.

The mayor gave a brief history lesson explaining how this situation in Holyoke arose in the first place.

“As you all know, Holyoke was once the first planned industrial city in the United States,” he said. “Infrastructure back in the day was primitive and included combined source systems that collect rainwater, domestic sewage, and industrial wastewater into one pipe.”

The mayor said this design worked OK under normal circumstances, with the wastewater being directed to the city’s wastewater treatment plant, where contaminants were removed and water quality improved before being discharged into the river.

“But that’s under normal circumstances. Heavy rains or extraordinary snow melt would occasionally overwhelm the capacity of the system and result in untreated discharge,” said Garcia.

Samuel Gelinas can be reached at sgelinas@gazettenet.com.