Gov. Robert F. McDonnell has overhauled a bill approved unanimously by the General Assembly that would require owners of an oil storage facility in Fairfax City where spills have been common to bring their tanks up to code.

Legislators who sponsored the measure said McDonnell’s changes gut the bill and accused him of bowing to corporate interests that lobby about the issue.

They said that a representative from Citgo, one of several companies that own property at the site, registered to lobby on the issue March 22, days before McDonnell (R) submitted his amendment.

“I think it sends a very bad message that we would let those who would skirt our laws off the hook,” said Del. David L. Bulova (D-Fairfax), who sponsored the measure in the House of Delegates.

Successive spills from aboveground oil storage tanks at the site, which is in a residential neighborhood, created a massive underground oil plume in the early 1990s.

The pollution ultimately resulted in a $50 million settlement with several hundred neighbors whose properties were damaged and devalued. It also prompted new state regulations for such sites, including requirements that tanks be double-hulled to prevent leaks.

But the new rules applied only to tanks erected after 1992. The tanks along Pickett Road in Fairfax City, which sit at the end of an oil pipeline that stretches to Texas, were grandfathered into the old rules.

That would have changed under a bill adopted unanimously in February by the General Assembly. The measure said that oil storage facilities in Fairfax City had to be brought up to current regulations by 2021, even if they were built before 1992. The only site that fits that description is the Pickett Road facility.

McDonnell’s amendment would call on the state’s Water Control Board to review its regulations to see what, if any, new rules are needed for oil storage tanks to prevent oil leaks.

A spokesman for McDonnell said he was guided by legal advice from the office of Attorney General Ken Cuccinelli II (R), which had indicated that the measure could be unconstitutional because it was drawn to affect a single company.

McDonnell spokesman Jeff Caldwell said the amendments would strengthen the state’s ability to crack down on oil tank sites that cause pollution by allowing the Water Control Board to impose new regulations immediately.

“The governor reviews legislation to ensure that it passes legal and constitutional muster, does not have unintended consequences that would inadvertently harm the Commonwealth and its citizens, and is in the best interests of the citizens of Virginia,” Caldwell said in a statement. “His decisions to sign, veto or amend legislation are based upon these principles alone.”

But Sen. J. Chapman “Chap” Petersen (D-Fairfax), a lawyer who sponsored the Senate bill, said the General Assembly frequently passes bills that apply only to certain areas of the state. And, he said, the Constitution’s equal protection clause applies to individual citizens, not businesses.

“It’s the craziest thing I’ve ever heard,” Petersen said. “I didn’t know it was all corporations were created equal. I thought it was all people were created equal.”

Five companies operate tanks at the Pickett Road site. A spokesman for Citgo declined to comment, and a representative of TransMontaigne, which was fined after a spill at the site last year, did not return calls.

The bill was one of several environmental measures approved with bipartisan margins that McDonnell altered or vetoed.

He vetoed a bill to increase civil penalties that can be assessed on polluting landfills and another that would have allowed the state Water Control Board to a levy a fine on farmers and manufacturers who fail to report withdrawing a million gallons of water a month for agricultural or industrial use, as required by law. Both had passed the General Assembly with bipartisan support.

U.S. Rep. Gerald E. Connolly (D-Va.), who got his start in politics as president of the civic association for the neighborhood surrounding the Pickett Road facility when the plume was discovered in the early 1990s, said McDonnell’s actions appeared part of “his trial run for vice president.”

“There is an assault by Republicans at the national level on anything having to do with environmental protection,” he said. “Maybe he wants to get in on the act.”

Petersen and Bulova said they would urge their colleagues to reject McDonnell’s amendment when the General Assembly considers changes proposed by the governor to 134 bills on Wednesday. The Mantua Citizens’ Association and Fairfax City have written letters to McDonnell objecting to his amendment.

The General Assembly can reject his changes with a simple majority, but McDonnell could then veto the measure outright.

Staff writer Anita Kumar contributed to this report.