The Indian Point nuclear power plant in New York, which last year leaked radioactive material into groundwater near New York City, will close by April 2021, Governor Andrew Cuomo said on Monday.

“For 15 years, I have been deeply concerned by the continuing safety violations at Indian Point, especially given its location in the largest and most densely populated metropolitan region in the country,” Cuomo said. “I am proud to have secured this agreement with Entergy [the plant’s operator] to responsibly close the facility 14 years ahead of schedule, to protect the safety of all New Yorkers.”

Location of Indian Point. Photograph: Mapbox, OpenStreetMap

The plant has had 40 “safety events”, “operational events”, and shutdowns since 2012. The shutdowns have exposed apparent fragility in the nuclear facility’s workings: in December 2015 the plant was shut down for three days after droppings from a “large bird” caused an arc between power lines and a transmission tower. In April 2016, Entergy admitted it had found that bolts holding together the interior of one of Indian Point’s reactors were damaged and, in some cases, missing.

Entergy also came under fire in 2016 after the Guardian published a safety assessment of proposed natural gas pipelines to be built by energy pipeline company Spectra on Indian Point property. The assessment, provided to the Guardian by engineer Paul Blanch and obtained through a freedom of information act (Foia), was partly hand-drawn and did not adequately account for the damage to the plant that could result from a breach of the lines.

Local environmental groups have made the plant a nemesis, though those who work at the facility in Buchanan, New York, want it to remain open. The plant employs just under 1,000 people; Entergy’s chairman and CEO, Leo Denault, thanked Indian Point’s employees in a statement on the coming closure and said the company was “committed to treating our employees fairly and will help those interested in other opportunities to relocate within the Entergy system”.

Paul Gallay, of activist group Riverkeeper, has campaigned long and hard to have the plant closed. “Given the scope of the risk Indian Point poses, this is an essential step to a safer and more secure New York,” Gallay told the Guardian.

Gallay said that although the announcement was encouraging, the project of detoxification was just beginning. “The very first priority is to get the spent fuel out of the overpacked storage pools where it’s resided for the whole 45-year length of the operation of the facility,” he said. “This agreement requires that and must be followed by prompt and full radiological decommissioning.”

But he was pleased, he said. With Indian Point closed, “necessary cleanup work can begin in earnest”.