The U.S. Environmental Protection Agency (EPA) has again issued comments critical of the proposed Rosemont Mine in Arizona.

This time, the EPA sent a letter to the Arizona Department of Environmental Quality (ADEQ) stating that the agency is not doing enough to protect neighboring streams from pollution. The Arizona Daily Star reports that it is at is at least the ninth publicly available letter or set of written comments critical of the project or of another agency’s analysis of it that the EPA has written since January 2012.

In a letter in March, the EPA said a recent state certification that the mine will meet Arizona water quality standards is unlikely to provide enough protection for Cienega Creek and its tributaries.

The ADEQ’s certification of the mine “relies on limited, voluntary (i.e., non-enforceable), post-discharge monitoring that may detect water quality degradation after it occurs,” EPA’s letter said. The ADEQ approval also calls for corrective actions at a later time, said EPA, dismissing such actions as insubstantial.

ADEQ said it disagrees with EPA’s letter, adding, “we are confident that the requirements we’ve put in place are protective of water quality in the area.”

EPA sent its April 14 letter to the U.S. Army Corps of Engineers, which must approve a crucial permit for the mine, one more sweeping and aimed at insuring the mine meets federal Clean Water Act standards. In a not-so-subtle message, EPA says it believes the water quality issues it’s raising are “directly relevant” to the Corps’ upcoming permit decision.

The numerous conditions that ADEQ imposed on the mine in its certification last February “are highly unlikely to avoid potential water quality degradation, detect anticipated or unanticipated degradation or mitigate for those impacts,” wrote Jared Blumenfeld, administrator of EPA’s San Francisco regional office that governs Arizona. “The project’s projected groundwater drawdown and flow and sediment reductions in Davidson Canyon have yet to be adequately addressed.”

EPA has a veto power over the Corps permit and wrote a letter 18 months ago to the Corps urging it not to approve the permit.

In its own statement, Rosemont Copper’s parent Canadian company defended ADEQ’s approval.

“The Arizona Department of Environmental Quality spent years participating as a cooperating agency in the EIS (Environmental Impact Statement) process and analyzing the project for possible impacts on water quality before issuing the certification,” said Patrick Merrin, vice president of the Arizona unit of Hudbay Minerals Inc.

We believe when ADEQ’s science-based decision-making is evaluated, the Corps will find that the project will not cause or contribute to a violation of state water quality standards and accord the state deference in its decision as required by the Clean Water Act,” he added.