Maine state's House of Representatives in the US has rejected a proposal to overhaul mining rules that would allow large-scale operations.
The bill LD 750 includes some site restrictions on mines, as well as various requirements for mining companies to monitor, close and cleanup their sites.
The proposal mandates mining companies to provide financial assurance to cover potential environmental problems, and states that treatment of contamination is also compulsory for at least 20 years once a mine closes.
The measure emerged three years ago, following interest expressed by Canada-based JD Irving to mine metals valued at around $1.7bn at Bald Mountain in Aroostook County, Maine.
JD Irving's subsidiary Aroostook Resources is believed to have spent nearly $70,000 for a regulatory change that may lead to the mining of metal-rich Bald Mountain, a remote spot located 35 miles west of Presque Isle in Aroostook County.
At that time, the legislature was asked to revise the state's mining regulations.
Opponents it the house said that the new rules leave taxpayers with the cleanup costs and would not be enough to protect against pollution in lakes and rivers.
According to critics, the measure would potentially expose Maine to high costs, with tailings materials left from the ore separation process expected to damage to water quality.
The bill further faces votes in the House, as well as the Republican-controlled Senate.
In response to the vote Natural Resources Council of Maine Scientist Nick Bennett said: "This vote reflects Maine people's strong concern about weak mining rules.
"This is a victory for clean water and all the Mainers who depend on it for their livelihoods. It's also a victory for Maine taxpayers, who should never again have to spend their hard-earned money cleaning up a mining disaster."