The Coronado National Forest (CNF) is currently conducting a project to remediate the downstream effects of tailings from the 3R Mine near Patagonia. The project, which began in November 2020, is expected to be completed by April 2021.
The 3R Mine, located high on the west flank of the Patagonia. Mountains, was established in 1896 by Rollin Rice Richardson. It produced ore intermittently from 1908 to 1956, leaving behind a sizable legacy of toxic tailings. Copper was the primary metal produced by the mine. It also produced lesser amounts of silver, gold, lead, molybdenum and aluminum. It was a complex underground mine with several openings, as mine historian William Ascarza wrote: “Workings of the Three R Mine include a 1,000-foot and 3,000-foot adits, three tunnels and a 558-foot shaft, along with 20,000 feet of workings.”
Ore was first brought down the mountain’s switchbacks by burro, later replaced by a wagon road. A concentration plant was built onsite, using crushing & flotation methods. A loading dock at the New Mexico and Arizona railroad near the current Circle Z ranch allowed ore to be put on train cars destined for smelting in El Paso. The 3R operation included a camp, from which one badly damaged adobe cabin and a funky but still workable outhouse survive to this day.
The 371-acre parcel containing the mine was purchased by the Nash family shortly after they acquired the Circle Z Ranch in 1974, and has been put into permanent conservation easement, along with much of the Ranch’s 5,000 or so acres. The Ranch gets its water for both stock and humans from a shallow onsite well, so owner Diana Nash says she and husband Rick Nash are naturally supportive of the CNF cleanup & detoxification efforts.
The historical legacy of the 3R has shown exceedances (excess levels) of copper, cadmium and zinc, the three “minerals of concern” determined by Arizona Department of Environmental Quality (AZDEQ) studies in 1996 and 2003. Low pH is also of concern, and the main source of acidity AZDEQ found was acid drainage from the 3R mine, findings which led CNF to finalize design of the project.
The goal of the project is to reduce the flow of these soluble contaminants and unduly acidic water into the watershed. At this moment of continuing major drought, there’s no flow to be monitored for acidity and metal contamination, but when rain returns and water begins flowing in the tributary washes of the Sonoita Creek Watershed, future monitoring will tell if remediation projects have been successful.
The basic plan is to relocate and encapsulate approximately 9,200 cubic yards of tailings nearby. To visualize this volume, picture a football field (45,000 square feet, just over an acre) fully covered at about six feet in depth. The earthwork is being performed by the international environmental company Tetra Tech, who will be also be doing erosion control and fencing for revegetated areas.
Heading downstream, the 3R Canyon wash joins Sonoita Creek near the Circle Z Ranch buildings, flowing from there to Lake Patagonia. When water overflows the Lake’s dam, it continues into the Santa Cruz River at Rio Rico. Concern about the accumulation of possibly hazardous materials in lake-bottom sediment was reported on in a 2016 Nogales International article by Murphy Woodhouse. In that article, Woodhouse mentioned the 3R Mine as a significant source needing remediation. Also, in the article, CNF environmental engineer Eli Curiel is quoted as saying, “They built that right across the drainage bottom, so as the water comes down, it plows right through it and spreads it all around. This is going to be a tough project.”
The remediation of the 3R Mine is one of the 19,000 legacy mining sites in the State’s legacy mine remediation program, with over 120 miles of streams known to be impaired by pollutants from the sites, with associated watersheds being “home to over 150 endangered or threatened species of wildlife, fish and plants, such as the Mexican spotted owl, jaguar and leopard frog,” according to AZDEQ.