A company lobbying lawmakers to unearth in Southside Virginia what is thought to be the nation’s largest uranium deposit needs to overcome significant health and environmental obstacles before the site is mined, according to a long-awaited study released Monday.

The 22-month review by the National Academy of Sciences and National Academy of Engineering said that “steep hurdles” need to be surmounted before Virginia’s longtime ban on uranium mining could be lifted.

The 302-page report says uranium could be mined, but the company would have to protect workers, the public and the environment in Virginia, which has no experience unearthing radioactive element.

Many in Richmond expected the study to provide conclusions supportive of lawmakers seeking to lift the ban, but the report instead struck more of a cautionary tone. It also outlined ways mining could be conducted in the state.

“Internationally accepted best practices, which include timely and meaningful public participation, are available to mitigate some of the risks involved,” said Paul Locke, associate professor at Johns Hopkins Bloomberg School of Public Health and chairman of the committee that wrote the report. “However, there are still many unknowns.”

The state’s Coal and Energy Commission, which ordered the study, will review the findings and recommend to the General Assembly in the next few weeks whether Virginia should lift the ban.

The study failed to address the site — a largely rural 200-acre swath in south-central Virginia — or recommend whether it should be mined. Critics argue that the study is tainted because the company, Virginia Uranium, picked up the $1.42 million cost.

Virginia Uranium executives say the study provides a path for the state to repeal a three-decade moratorium next year — making it one of the most controversial and unpredictable issues expected in the 60-day session that starts next month.

“The study shows that major technological and regulatory advances over the past 30 years have dramatically improved the environmental and public health performance of the uranium mining and milling industry,” said Patrick Wales, a geologist and the company’s project manager.

The company has aggressively lobbied lawmakers. It has spoken to 100 of 140 legislators and flew more than a dozen of them to France and Canada to visit uranium mines. It has donated more than $150,000 to candidates in Virginia and retained five of Richmond’s most influential lobbying and public relations firms, according to the Virginia Public Access Project, a nonpartisan tracker of money in politics.

“What concerns me is we are rushing to put legislation forward in some ways before we fully understand what’s before us,” said Sen. William M. Stanley Jr. (R-Franklin), who represents the area. “We deal with thousands of bills . . . and what I want is for [legislators] to take careful consideration of this. This is our home.”

Two uranium deposits were found three decades ago in Coles Hill, near Chatham, a small town in Pittsylvania. They begin at the ground’s surface, under land used for cattle, and run about 1,500 feet deep.

Virginia Uranium said tests indicate that about 119 million pounds of uranium — worth as much as $10 billion — are below the surface. It is the world’s seventh-largest known deposit — or enough to supply all U.S. nuclear power plants for about two years or Virginia’s demands for 75 years.

The 20-member Coal and Energy Commission asked the National Academy of Sciences in 2008 to conduct the study, despite objections from the General Assembly.

Several studies have been released, but Del. Terry G. Kilgore (R-Scott), the commission chairman, said his panel, made up of legislative and gubernatorial appointees, will rely on the national academies’ report as well as a second state-ordered study released this month on mining’s economic impact.

Environmental groups seized on the report as proof that their concerns about mining in Virginia’s relatively rainy climate could contaminate natural resources, cause cancer or other illnesses and have long-term effects on plants and animals.

The Coles Hill area supplies drinking water locally and to parts of Hampton Roads and North Carolina. Thirty-two governmental organizations in Virginia and North Carolina have passed resolutions to keep the ban.

“This is a huge validation for many of the core concerns that we have been raising,” said Cale Jaffe, senior attorney with the Southern Environmental Law Center. 

Gov. Robert F. McDonnell (R), who wants to make Virginia the “energy capital of the East Coast,’’ said he could not comment until after the new year when he expects that his staff will review the study.

Company officials say safeguards have been put in place since mining at Coles Hill was first considered and that the federal government regulates mines and mills with regard to safety and homeland security.

Uranium would be mined underground. The result, a sandy substance called “yellow cake” uranium, would be packed into drums and shipped while the remaining crushed rock would be kept on site, underground or in a pit.