Development of the Rosemont mine will dramatically alter these scenic views along Hwy. 83 leading to Sonoita. Photograph by Marion Vendituoli

In a controversial decision on March 8, 2019, the South Pacific Division of the U.S. Army Corps of Engineers in San Francisco, California issued the last required permit to construct the Rosemont Mine in the Santa Rita Mountains southeast of Tucson. 

This permit is the latest blow to environmental groups, including Save the Santa Ritas, and various indigenous tribes who have actively opposed the proposed open pit copper mine. Hudbay Minerals, the parent company of Rosemont, owns 900 acres of private land. In addition, the mine will use 3328 acres in the Coronado National Forest. 

The recent Record Of Decision (ROD) is in contrast to the previous public notice given in July 2016 by the District Corps of Los Angeles which denied the Clean Water Act Sec 404 permit to the Rosemont mine. The ROD, written by the Federal branch of the Corps, overturns the district decision for the following reasons: lack of jurisdiction of the Corps to assess groundwater impact; the updated mitigation plan submitted by Hudson Bay; and the anticipated economic benefit at the state and national level of the proposed mine.

Save the Santa Ritas wrote, “The permit authorizes Hudbay to dump millions of tons of potentially toxic mine wastes on more the 2,500 acres of Coronado National Forest. The waste rock and mine tailings will obliterate desert washes and streams that provide significant recharge to the ground water supplies relied upon by residents of the Tucson metropolitan area.”

However, the ROD states, “the effects of the proposed operations of the mine, including full excavation of the mine pit, are not within the Corps’ purview…The Corps’ scope…extends only to those direct, secondary, and cumulative effects associated with the discharge of fill material into waters of the U.S., including direct, secondary, and cumulative effects to surface water quantity and quality. Any effects related to the excavation of the mine pit, including those related to groundwater quantity or quality, are outside of the Corps’ scope.” “The Corps declines to exercise jurisdiction where none exists, including the operation of the mine and its associated impacts on groundwater. This will disappoint many.”

The Corps recognized that there will be both temporary and permanent detrimental effects because of mining activity. However, the ROD repeatedly iterates that many of these concerns are outside the purview of the Corps. They acknowledge that there will be “temporary detrimental effects to conservation, general environmental concerns and safety; permanent detrimental effects to aesthetics, historic properties, and recreation.” It also states that the mining will beneficially impact economics, wetlands, flood hazards, and floodplain values. 

Compensatory Mitigation Plan

Historically both the EPA and the previous Corps decision discredited the mitigation plans offered by Hudbay. Now the Corps seems satisfied with the updated (2017) Hudbay plan which includes compensatory mitigation “activities on the Sonoita Creek Ranch and Rail X Ranch sites and the removal of four stock tanks near the proposed mine site.” (Corps ROD) 

The proposed compensatory mitigation is within the floodplain of Sonoita Creek and Hudbay is required to receive local approval for their activities. The Corps decided to provide compensatory mitigation credit to Hudbay for Sonoita Creek because it has been defined by the Arizona Game and Fish Department (AGFD) as a valuable wildlife corridor. 

The Corps requires Hudbay to do the following at Sonoita Creek to “compensate for the loss of waters of the U.S.” because of the proposed mine: “Rehabilitation of 61.54 acres of Sonoita Creek and its tributaries; Enhancement of 6.0 acres of Sonoita Creek Ranch ponds; Re-establishment of 34.58 acres of Sonoita Creek channel buffer; Rehabilitation of 6.22 acres of Sonoita Creek channel buffer; Enhancement and preservation of 66.30 acres of Sonoita Creek ephemeral tributaries buffer; Enhancement and preservation of 4.41 acres of Sonoita Creek ephemeral tributaries; and enhancement and preservation of 19.28 acres of ephemeral channels including avoided portions of Sonoita Creek, Corral Canyon, and other unnamed ephemeral tributaries to Sonoita Creek. Overall, the Sonoita Creek mitigation would create approximately 1,590 acres of new conservation area.” 

Impact for Native American Tribes

The Corps decision has received condemnation from the Native American tribes Tohono O’odham, Pascua Yaqui and Hopi. The tribes oppose the mine because it will destroy historical and cultural sites of importance. The Corps outlines mitigation measures in their ROD, but Stu Gillespie, the attorney for indigenous tribes, said that these measures are “totally inadequate.”(The Daily Star, March 19 2019)

Impact on Recreational Activities

The ROD discusses the temporary detrimental impact on recreational activities, including the relocation of the Arizona Trail. In addition, night sky viewing will be impacted because “the cloudless night skies, minimal atmospheric pollution, and low humidity of the southwestern United States provide ideal conditions for this activity. The Kitt Peak National Observatory and the Smithsonian Institution’s Fred Lawrence Whipple Observatory…in the Coronado…rely on the area’s naturally dark, unpolluted skies for optical and infrared astronomy research.” The Corps admits that the mining activities will cause temporary detrimental effects to the dark skies and astronomy, traffic, air quality, and noise and permanent detrimental effects on recreation. 

The ROD concludes that “overall, the proposed action would result in both detrimental and beneficial effects to the needs and welfare of the public.” 

Opposition groups to the mine have stated that they will fight this decision in court with lawsuits. Wade Bunting, a Sonoita resident said, “We remain hopeful that planned litigation will prevent the development of the Rosemont mine. If the project is allowed to proceed it will seriously affect our quality of life in the Mountain Empire. Travel to and from Tucson will be hazardous, tourism traffic will decrease, affecting local businesses and area attractions, and, most significantly, our ground water will be affected.”