Hudbay Minerals Inc. is planning extensive additional exploration drilling at the proposed Rosemont open-pit copper mine that appears to be an effort to expand the amount of known copper reserves that could lead to greater production and extend the life of the mine beyond the now projected 20 years.
Additional production would also greatly increase the amount of waste rock and mine tailings that would be produced at the mine planned for the northeastern flank of the Santa Rita Mountains on the Coronado National Forest southeast of Tucson. More than 99 percent of the rock and ore that would be mined will end up as waste rock and tailings.
A deeper pit could also have greater negative impact on the ground water aquifer in the area, particularly on several endangered fish and frogs in Las Cienegas National Conservation Area in the valley immediately east of the mine site.
More waste rock and tailings dumped on more than 3,000 acres of Coronado National Forest could also increase negative impacts on Cienega Creek and Davidson Canyon, which are classified as Arizona Outstanding Waters and legally protected from any degradation.
The Arizona Game & Fish Department has already raised concerns about toxic metals leaching from the mine’s proposed “dry stack tailings” facility for 500 years. AGFD notes that the Final Environmental Impact Statement for the mine included “new information” from the Coronado National Forest’s environmental consultant that predicts “several heavy metals in the Rosemont stormwater waste rock runoff, including copper, selenium, arsenic, mercury, molybdenum could degrade, or significantly degrade, the existing water quality of downstream watersheds.” The pollutants, the department states, “are toxic to aquatic species, and mercury and selenium are bioaccumulative in insects, invertebrates, amphibians and fish.”
The new drilling was reported Friday on the blog of the State Geologist of Arizona. The blog reported that Rosemont Copper Company Vice President Lance Newman announced the company will be drilling 85,000 feet of new core holes, all on private land Rosemont owns within the current open pit boundaries at the proposed mine site. The drilling, the blog reported, is in conjunction with an extensive geological and technical review of Rosemont’s work to date.
The pit is projected to cover 950 acres, according to Rosemont’s Final Mine Plan of Operations. The pit includes 590 acres of private land owned by Rosemont and 360 acres of Coronado National Forest land.
Newman, according to the blog, emphasized that HudBay is committed to development of the Rosemont mine as one of their centerpiece operations. Hudbay has indicated it will seek to develop additional mines in the area.
Rosemont’s former owner, Augusta Resource Corporation, stated last winter in a Director’s Circular that the present mine site could have an additional 3 billion pounds of copper reserves. Augusta had already determined the Rosemont site has 5.9 billion pounds of “proven and probable reserves”.
The February Director’s Circular stated the “estimated additional mineral resources presently total about 1.9 billion pounds of copper and an additional 1.1 billion pounds of inferred copper resources. Augusta’s management believes that, if upgraded, these additional measured and indicated resources and additional inferred resources could significantly increase annual production and mine life.”
The U.S. Forest Service last December released its Draft Record of Decision approving Rosemont Copper’s mine plan of operations for the proposed mine based on an industrial operation “expected to produce an estimated 5.88 billion pounds of copper, 194 million pounds of molybdenum, and 80 million ounces of silver.” The current mine size would result in total surface disturbance of an estimated 5,888 acres of combined private lands, lands administered by Arizona State Land Department, and Coronado National Forest lands.
Augusta Resource had also repeatedly stated that mining operations could expand beyond the Rosemont site to at least three additional mining claims located in close proximity that are now controlled by Hudbay: Broad Top Butte, Copper World and Peach Elgin. If these claims were developed, Augusta’s copper project would sprawl over the top of the Santa Ritas and spill over on to the western slope, where the mining operations would be visible from Green Valley and other towns, something that has generated significant concern and controversy in the past.