The man who oversaw Wisconsin's frac sand boom for the past two years is stepping down, saying on his way out that the state needs more field inspectors to ensure regulatory compliance but that state laws are adequate to keep the industry in check even as it grows beyond expectations.

Tom Woletz, a senior manager for the Department of Natural Resources, told the Star Tribune he is leaving for semiretirement in Montana, where his family owns a 1930s-era cabin near Yellowstone National Park. He said he is quietly submitting his resignation this week and is not being hired away by the industry.

"I would have left a long time ago, but I was in my dream job," said Woletz, who turns 60 this month.

"I'd say he'll be sorely missed," said Mike Parsen of the Wisconsin Geological and Natural History Survey. Parsen, who heads a study of surface water in a heavily mined area of Chippewa County, said Woletz has been an important, nonpolitical resource for a wide range of groups. "He's the lone state contact for the public side of this."

In August 2011, at the cusp of Wisconsin's frac sand boom, Woletz became the agency's go-to expert on mining and processing of silica sand. He joined the agency in 1975 and described his final assignment as: "Anything frac goes to Tom."

In the past three years, Woletz said, Wisconsin frac sand mining and processing have exploded from a handful of pioneering facilities to a nation-leading industry of 105 mines and 65 processing sites. By comparison, Minnesota has eight or nine commercially producing frac sand mines.

Woletz said he and his colleagues have been expecting growth to level off, but there's been no lag in new applications. "We've talked about peak sand, but … it doesn't seem to have slowed," he said.

Woletz, who lives in Eau Claire, coordinates permits, conducts training, handles media questions and consults with legislators, county administrators, township officials, civic groups and others on frac sand issues.

Wisconsin's pro-business climate under Gov. Scott Walker has triggered allegations that the state is cozy with the sand industry — a charge Woletz rejects. Earlier this month, the nonprofit Wisconsin Democracy Campaign reported staggering growth in campaign contributions to Wisconsin politicians from natural gas and sand mining interests. The sum mushroomed from $18,762 in 2007 to $413,642 in 2012.

Woletz said it's true that Wisconsin has yet to fine or prosecute any frac sand company for violating regulations. A few major cases have been pending for months at the Wisconsin Department of Justice, but long waits are not unusual, he said.

Woletz said he's never been discouraged from taking enforcement actions against violators. While state sand mining regulations are good, he added, "it would be nice" to boost field staff to ensure compliance. For instance, the DNR wanted 10 new air quality inspectors but settled for two in this year's budget process.

Tony Kennedy • 612-673-4213