The Maine Senate has passed a bipartisan metal mining bill that would ban open pit mines and wastewater impoundments, although some environmental advocates fear it does not go far enough.

LD 820, An Act To Protect Maine’s Clean Water and Taxpayers from Mining Pollution, passed in the Senate Tuesday morning by a vote of 34-0.

The bill, sponsored by Sen. Everett Carson, D-Cumberland, and backed by the group he used to lead, the Natural Resources Council of Maine, emerged earlier this year after five years of debate over large-scale metal mining and proposed regulations that would have been created under the 2012 Maine Metallic Mineral Mining Act.

LD 820, which now heads to the Maine House, would amend the controversial 2012 law with provisions banning open pit mines, large wastewater impoundments and mining on public lands, along with a host of other limits and requirements that backers say would make it the strongest metal mining law in the country.

“The bill was designed thoughtfully and carefully … to take the long view,” said Carson in remarks before the vote.

Carson noted that the bill would ban open pit mining, “the most polluting form of mining in our country,” and the kinds of wastewater impoundments that have failed and led to environmental disasters in others parts of North America and around the world.

The bill would prohibit the use of wet mine waste, a source of acid mine drainage and other naturally occurring contaminants, and instead require “dry waste management” where waste rock is stored in lined structures that prevent water buildup and runoff.

Carson also emphasized the bill’s requirements for mining companies to have enough funds to cover the costs of a mining failure.

“Perhaps most importantly, it sends a message to mining companies with its provision in what we call financial assurance,” he said.

A company that wants to apply to develop a metal mine in Maine would have to post sufficient cash “to cover the cost in the event of an accident or spill of a worst-case accident or spill,” as determined by an independent third party, Carson said.

LD 820 came together this legislative session at the same time that the Department of Environmental Protection was in its third attempt at drafting regulations to implement the 2012 law.

Two other versions of the agency’s proposed mining regulations were voted down by lawmakers amid concerns that the original law and its provisions were not strong enough to protect the state from mine failures and the costs of cleanup. The 2012 law was originally sponsored by Rep. John Martin, D-Eagle Lake, and was prompted in part by J.D. Irving Ltd.’s interest in potentially developing a mine for copper and other metals at Bald Mountain in Aroostook County.

Sen. Tom Saviello, R-Wilton, also praised LD 820 before the vote.

“Sometimes it takes a long time to bring closure, but I believe we have done it,” he said, alluding to the years of deliberation over the proposed regulations from the 2012 law.

Saviello said that the bill put up strong protections, while also creating a potential pathway for some mining, which he argued Mainers should be open to accepting if they also use smartphones and other products that contain metals that may come from poorer countries with less-stringent labor and environmental standards.

“A mining company can come here, but they will have to be extremely responsible and have a huge hurdle to jump over,” Saviello said.

While the bill has received bipartisan support, it also has divided Maine environmental advocates, splitting those such as the NRCM, which helped develop the bill, and the group Association for the Protection of Aroostook Waters, whose members are calling for an outright ban on mining.

Shelly Mountain of Mapleton, a member of the Aroostook group, said she and others opposed the bill because they believe mining for metals in the water-rich state cannot be done safely. Mountain said they also object to a provision of the bill that allows a certain amount of groundwater contamination within the immediate mine shaft.

“There has not been a mine anywhere that has not contaminated the surrounding groundwater,” Mountain said in an interview earlier this month.

In a Facebook post following the vote, Sen. Shenna Bellows, D-Manchester, called the vote on LD 820 the “hardest vote I’ve had to take this legislative session.”

Bellows said that she supports a complete ban on mining in Maine, but voted for the bill because it does have some “significant and impressive environmental protections.”