Environmental activists who pushed ambitious legislation to slow the advance of frac sand mining in Minnesota have been soundly defeated on their central proposals and, with less than two weeks left in the 2013 legislative session, are clinging to a fragile game and fish amendment as their last hope for a substantial breakthrough.

The amendment, which would block excavation within a mile of any trout stream in southeastern Minnesota, is strongly backed by Gov. Mark Dayton as a way to prevent an explosion of sand mining in a region where the state has invested millions of dollars over decades to nurture a blue-ribbon fishery.

But as the session winds down, even that idea is meeting resistance in a Legislature that has been largely receptive to the industry’s message that more regulation is unnecessary and will only kill jobs and economic growth.

“It’s the only substantial [frac sand] standard left this session,’’ said John Lenczewski, executive director of Minnesota Trout Unlimited.

“Everything else is just fluff,’’ said Amy Nelson, a frac sand opponent from the Red Wing area. The trout stream language, which could face a critical vote on the Senate floor as early as Thursday, has been painted by opponents as a de-facto mining ban in southeastern Minnesota. Industry supporters also say the measure is a “slippery slope’’ that could potentially hurt taconite mining on the Iron Range and even the construction aggregate business.

“We don’t think they will get anywhere with this,’’ said Fred Corrigan, who leads the Minnesota Industrial Sand Council in a lobbying effort that is also supported by the labor union representing heavy equipment operators.

But Dayton told reporters Wednesday that he is cautiously optimistic the legislation will move forward.

“I strongly support that position and will do everything I can in conference committee to get it enacted,’’ he said.

Meanwhile, the governor scheduled a private meeting for Thursday with industry representatives, labor leaders and the commissioners of the Department of Natural Resources, Pollution Control Agency and Department of Health.

A far cry from February

Things looked different in February, when bus loads of “fractivists’’ crammed hearing rooms at the State Capitol to rally behind legislation introduced by Sen. Matt Schmit, DFL-Red Wing.

Schmit’s bill would have halted new frac sand development across the state. The proposed moratorium, which attracted national attention, was intended to last until state regulators could fully study the industry’s cumulative effects and set air and water standards to be enforced by state agencies.

Schmit’s mantra was that Minnesota needed to “get it right.’’ Western Wisconsin has been teeming with sand mining projects — with more than 100 of them approved in four years — and mining companies have been left to operate under a patchwork of regulations set by rural counties, small cities and townships. Both states hold vast deposits of ancient, crush-resistant silica sand that is suddenly in high demand as a drilling ingredient for the nation’s oil and gas “hydrofracking’’ boom.

The trout stream measure already has failed two close votes at the committee level, including one in the Senate Environment and Economic Development Committee. The committee’s chairman, Sen. David Tomassoni, DFL-Chisholm, called it government “overreach,’’ saying existing environmental controls are stringent enough.

Corrigan said the industry will continue to steadfastly oppose the trout stream amendment because state law already requires hydrogeological reviews as part of the local permitting process for individual frac sand projects. Those site-specific reviews will do more to protect trout streams than the “arbitrary’’ setbacks proposed in the amendment, including a measure that would ban digging within 25 feet of the water table, Corrigan said.

A plan not ‘out of thin air’

Schmit, the amendment’s champion, said the setback provisions were established in the context of groundwater studies embraced by the DNR. If silica sand mining becomes a pervasive new activity in southeastern Minnesota, the agency has said, widespread excavation could disrupt the flow of underground water in a way that would rob streams of cold water, the lifeblood for trout.

“The language wasn’t pulled out of thin air,’’ Schmit said.

Schmit acknowledged the defeat of his core frac sand proposals but said he remains optimistic that some fallback measures will be helpful in managing frac sand growth.

There is agreement with the industry, for example, over the creation of a state technical advisory team that could guide local units of government in drafting sand mining ordinances. Another change would give local authorities new power to extend their own moratoriums by a couple of years. In addition, the industry supports the imposition of prepermit environmental reviews on smaller frac-sand mines that have been exempt from the provision.

“Absolutely things have changed from what we introduced,’’ Schmit said. “To a certain extent we are playing defense. … I’m still optimistic we’ll leave the session with a good package.’’