The court ruled unanimously that regulations adopted by the state’s Water Quality Control Commission were valid under the state’s Water Quality Act.
The New Mexico attorney general and other groups, including Amigos Bravos, the Gila Resources Information Project and Turner Ranch Properties, had challenged the regulation.
The regulation dictates how mining companies are required to protect – opponents say allowed to pollute – groundwater where they operate.
“We cannot conclude that the Copper Rule violates the (Water Quality Act) because it purportedly permits rather than prevents contamination when the Cooper Rule’s plain terms contain an abundance of provisions that afford significant groundwater protection at copper mine facilities designed to prevent pollution,” said the opinion written by Chief Justice Judith K. Nakamura.
Supporters of the rule had argued that it strikes a balance and that overturning it could threaten the viability of copper mining in New Mexico.
The rule allows mining companies to exceed water quality standards at mining sites, including open pit operations and waste rock piles, as long as the concentration of contaminants found in monitoring wells around the perimeter of those areas meet water quality standards. Under the rule, pollution standards do not apply at the bottom of the pit, where water gathers in deep open pit mines.
Attorney General Hector Balderas argued that the rule would allow “widespread pollution.” He said in his petition that the case “raises the most important legal question New Mexico courts have faced with regard to protecting groundwater resources.”
The court found that the regulations “advance a comprehensive containment strategy” for acidic mining contaminants. Contaminated water in the pit is to be removed by evaporation or pumping, and groundwater monitoring wells are required outside the pit area to determine whether water quality standards are met at those locations, the court said.
The Copper Rule’s waiver of the water quality standards “reflects policy preferences and strategic choices designed to mitigate the environmental harms inherent in open pit copper mining,” the court said. “The waiver provision in no way invites industry to contaminate freely in that area.”
The justices rejected claims that the Copper Rule was invalid because it differed from past regulatory approaches for controlling water discharges at copper mines.
“To the extent the Copper Rule is a departure from past commission practice, the law makes clear that the commission is not constrained by its prior practices,” the Court said.