A bill that critics say opens the door to the storage of depleted uranium in Utah is now state law after the deadline passed for Gov. Gary Herbert to veto or formally endorse the proposal.

Herbert confirmed to The Salt Lake Tribune that he allowed HB220 to take effect without his signature. The measure passed the Legislature last month on a 50-20 vote in the House and a 23-6 vote in the Senate.

“Why I let it become law was because it’s going to put protections in place for Clive,” Herbert said, referring to EnergySolutions’ disposal facility in Tooele County.

HB220 does not explicitly permit EnergySolutions to accept and store depleted uranium — which increases in radioactivity over time — but it alters the state’s long-standing ban on Class B and C radioactive wastes. The bill language could allow depleted uranium to be accepted into the state as a Class A material, despite it eventually growing in radioactivity to exceed Class C standards.

EnergySolutions is among the top donors to state lawmakers. Only two of the 38 legislators taking campaign contributions from the company voted against this bill.

Herbert, who has been critical in the past of storing higher-classification waste in the state and does not accept campaign donations from it, said that some of his concerns were addressed by HB220 requiring the federal government to eventually assume responsibility for the EnergySolutions disposal site.

“The important provision in there, which may make it harder to bring these other [waste classifications] in, is the federal government has to take on ownership and long-term care and maintenance of the facility out there,” Herbert said. “That’s something that I’ve been working on for years.”

Last month, activists with several environmental groups urged Herbert to veto the legislation. Among those groups was HEAL Utah, which on Monday objected to Herbert’s decision to let HB220 take effect without his signature.

Scott Williams, HEAL executive director, said his organization acknowledges the need for appropriate storage and disposal of radioactive waste. But the plan by EnergySolutions, he said, does not go far enough to address risks.

“This is the kind of waste that future generations need to be protected from,” he said. “A shallow burial in an area that is likely to flood in the future is just inappropriate for this waste.”

Williams said there are a lot of things in HB220 he doesn’t like, but he added that the language in the bill related to federal maintenance could function as a potential stopgap.

Because depleted uranium grows more radioactive over time, Williams said, the need to manage a disposal site and its environmental impacts will almost certainly outlast EnergySolutions as a private operator.

“The stuff stays radioactive, or increases in radioactivity, for thousands and thousands of years if not millions of years,” Williams said. “The company will shut down. At some point, they’ll exhaust the disposal capacity of that site, and they’ll want to shut it down.”

On Monday, Herbert sent a letter to leaders of the House and Senate informing them of his decision to allow HB220 to become law. In the letter, Herbert says he had reservations about how the bill came forward, but that he recognizes the need for Utah to have a “robust site-based performance assessment standard.”

“Public safety is my primary concern with the issue of radioactive waste,” Herbert wrote. “With the modifications that have been made to this bill, I believe public safety is protected and it will be more difficult for depleted uranium to come into Utah than under current law.”