A Minnesota frac sand company has volunteered to conduct a full environmental review of its controversial mining project proposed near Winona — a step that reflects pressure from state regulators and could set a precedent in the fast-growing industry.

Commissioner John Linc Stine of the Minnesota Pollution Control Agency said the sudden commitment on Thursday by Minnesota Sands LLC to prepare an environmental-impact statement,is a positive step. The company previously maintained that a less stringent review completed last year was adequate to gain permit approval by Winona County as early as next month.

“We’re offering to do this,” said Jennifer Dessner, a spokeswoman for Minnesota Sands. “We want to continue to put our best foot forward.”

Some environmentalists cheered the development, which could set an example for other multiple-phase projects as well as delaying any near-term digging and hauling of frac sand from a pair of proposed strip mines in rural Saratoga Township, south of Whitewater State Park. Full environmental impact reviews can take a year or more because they include detailed descriptions of a project and its anticipated effects on air quality, drinking water, surface water, soils, wildlife, roads, traffic safety, agriculture and people.

While the review is in process, all permitting decisions are on hold.

“It’s good news,” said Jim Gurley of Winona Area Citizens Concerned About Silica Mining. “It’s no exaggeration to say that the health, welfare, and safety of Winona County citizens is at stake.”

Frac sand mining, an industry that has grown explosively in Wisconsin since 2009 and is spreading in Minnesota, is chiefly regulated by the counties, townships and cities where the facilities want to locate. But in the case of Minnesota Sands, the Pollution Control Agency and Minnesota Department of Health weighed in two weeks ago with strong recommendations for the most comprehensive review allowed under state rules. Winona County was to have the final say, and a commissioners’ meeting was set for the first week of March to consider the state recommendations.

Stine and Health Commissioner Dr. Edward Ehlinger strongly urged that the county study not just the proposed Dabelstein and Yoder mines southwest of Winona, but also related sand mines in nearby Fillmore County and a proposed $70 million frac sand processing facility and rail-loading site near St. Charles.

Minnesota Sands has said the proposed St. Charles operation — which has yet to win local approval — would be the largest frac sand processing facility in the United States.

Stine and Ehlinger said the projects should be studied as one big hub-and-spoke operation, including a review of possible cumulative effects. It would be the first such review for a Minnesota frac sand project, Stine said. Other industrial sand companies in Minnesota have been required to conduct comprehensive environmental reviews to obtain operating permits, but none of those involved a network of facilities spread over parts of several counties.

“Overall it’s positive when a company steps forward like this,” Stine said. “The questions lie in the details now.”

Dessner said Minnesota Sands’ decision was influenced by the desires of the MPCA and Health Department.

The Land Stewardship Project, an environmental group with an office in nearby Lewiston, said it will watch the process closely because of the company’s previous reluctance to engage in a thorough environmental review.

“These projects are not appropriate for the community, given the strain they would put on the environment, human health and the infrastructure,” said Johanna Rupprecht, a spokeswoman for the organization.

Jason Gilman, Winona County’s planning and environmental services director, said state law will now govern the process, including setting the scope of the review. If the scope is multicounty, Gilman said, there’s a chance the state will take charge.