Here are key points of the Forest Service's draft environmental impact statement for the Rosemont Mine, and what the Environmental Protection Agency found wrong with it.
GROUND WATER QUALITY
FOREST SERVICE: Says infiltration of pollutants into the aquifer through the mine's tailings, waste rock and heap leach facility should be negligible. Water storage near the surface is expected to be sufficient to ensure that rainfall that doesn't immediately run off will be lost to evaporation or plants before seeping underground.
Heap leaching, in which a sulfuric acid solution is used to dissolve copper, will last six years. Then and for three years afterward, the mine will collect and treat seepage and reduce concentrations of contaminants below state standards. When it's closed, the leach facility will be encapsulated with waste rock to prevent liquids from infiltrating through it.
EPA: Says the Forest Service understates expected contaminant seepage levels and risks that the mine could pollute ground and surface water with contaminants such as arsenic and selenium.
Given extensive evidence of water infiltration through mines that caused pollution in Arizona and New Mexico, the EPA expects similar outcomes at Rosemont. It is skeptical that the engineered biological treatment system will work as well as the Forest Service predicts.
Also says the report doesn't adequately discuss the risks of encapsulation of waste rock, calling it an "essentially untested strategy" in the United States.
ROSEMONT: Disagrees with the statement's comment that no changes in groundwater quality are expected from mine facilities. It's also not realistic for the statement to say the mine will have "zero discharge" of contaminants. But state aquifer protection standards will be met.
FOREST SERVICE: Predicts the mine will cause large-particle pollution to increase more than three times natural background levels and come close to exceeding federal standards. Also expects regional nitrogen dioxide levels to rise 4 percent, putting the county at risk of violating federal ozone standards. Mine emissions would reduce visibility at Saguaro National Park East, 27 miles away.
EPA: Says the draft report doesn't have enough information to determine if the mine will meet national air-quality standards. Says the Forest Service uses faulty methods to calculate how much particulates are in the air at the mine site today, and how much nitrogen dioxide the mine will emit, so air pollution could be worse than expected.
The agency says the report fails to consider implications for all of Pima County if air-quality violations occur. The entire county would face stricter air-quality plans, higher costs and stiffer regulations.
ROSEMONT: Plans mitigation efforts including water sprays and wet scrubbers to control dust emissions, waste rock buttresses to break up air flow and reduce exposures of tailings to wind. Other plans include watering unpaved roads and using dust-control equipment and lower-emission vehicles .
DAVIDSON CANYON AND CIENEGA CREEK
FOREST SERVICE: Its preferred mine alternative would eliminate about 33 acres of federally regulated washes and streams due to the lowering of the water table caused by digging of the open pit. Another factor would be construction of storm drainage and other facilities that intercept water flows into Davidson Canyon and, ultimately, downstream to Cienega Creek.
The service predicts stormwater runoff from the mine would drop 33.8 percent, while flows into the Davidson Canyon watershed would drop 3.6 to 7.1 percent. The mine would cause direct and indirect loss of 1,364 acres of riparian habitat.
EPA: Says the report understates impacts on Davidson and Cienega. Is concerned that the mine will reduce water flows and degrade water quality.
The agency says the report relies too heavily on the use of annual and peak flow volumes in measuring streamflow effects, when low-flow conditions are most important because they're far more common. Cienega Creek is expected to have 1 to 3 percent less water flow 1,000 years after the mine is gone. Effects of such reductions can be much greater during late spring low-flow periods.
The project will also impact wetlands, pool complexes, and refuges and sanctuaries with special recognition under the Clean Water Act. Pool complexes support feeding, spawning and rearing for fish.
ROSEMONT: The nearly 40 acres of federally regulated washes affected by the Forest Service's preferred mining plan is the second lowest number of the five alternatives studied. The mine would affect 207 acres of total riparian area - also the second lowest total.
RECLAMATION AND CLOSURE
FOREST SERVICE: Says a reclamation and closure plan for the mine will be completed before a final environmental impact statement is published. The plan will reclaim the land as mining occurs, limit disturbance to a minimum number of washes, minimize downstream disturbances and prepare a comprehensive drainage plan.
Also, the service will require Rosemont Copper to post a reclamation bond that would provide enough money to allow the service to complete reclamation and other post-mine-closure operations needed to return the site to an acceptable condition. Since the various components of a final decision on the environmental statement aren't yet known, it is premature for the service to calculate bond amounts. Rosemont must also post financial assurances for its federal Clean Water Act and state aquifer protection permits.
EPA: Calls reclamation and closure a critical component of a draft environmental statement, and recommends that the service discuss this plan in a revised or supplemental draft environmental statement rather than a final impact statement.
That's because improper and poorly executed reclamation and closure activities have "led to severe and irretrievable environmental impacts at other mine sites, including those in the state of Arizona."
The EPA also says the draft environmental report contains no information about post-closure activities that may be needed, or their projected costs.
And it says the state aquifer protection permit for Rosemont may provide another way to raise bond money, although the numbers can be high: $120 million for the Freeport McMoRan Copper and Gold Morenci mine and about $50 million for Freeport's Baghdad mine, also in Arizona.
A revised or supplemental environmental report should summarize all post-closure activities that may be needed and how much they cost.
ROSEMONT: Has said its reclamation plan will be one of the most far-reaching ever, by starting while mining occurs rather than waiting until closure. The company has University of Arizona specialists studying the effectiveness of planting various grasses and other plans for future reclamation work.
Contact reporter Tony Davis at firstname.lastname@example.org or 806-7746.