History of mining in Green Valley area

Twin Buttes was the first mining area in what is now the “copper mining district” southwest of Tucson. In the late 1870’s, it was the nostalgic get-rich scene of picking copper and silver from outcroppings and shallow deposits. This burro and pick axe reality lasted for some 25 years. After 1900, the mining continued on sporadic basis as heavier equipment was developed to probe the earth where known deposits existed. Around 1928, a railroad line was constructed from the mine to Tucson. A small smelter for alleviating the ore of unwanted metals was constructed near the Santa Cruz River. [No regard for the environment in those days.] The principal production was from small mines about one mile west of Twin Buttes.

In 1950, Banner Mining Company acquired the mining claims in the area and used more scientific methods of digging probing wells to determine the richest deposits of ore. After some twelve years, Anaconda Company obtained a long-term lease from Banner Mining. In 1963, Anaconda, a corporation with its office on Broadway in New York City, took a long term lease with Banner and did extensive exploration for several years. They then began development of the Twin Buttes site by stripping of 400 to 600 feet of “over burden” to expose the bedrock that contained the ore. This earth-moving feat took four years, so the first authentic copper concentrate was produced in 1969.

In 1973, Amax Mining Company became the owner by acquiring Banner Mining and formed a 50-50 partnership with Anaconda, naming the company, Anamax. Using heavy equipment, between 1973 and 1983, 1.3 billion tons of ore was removed. The ore was copper oxide, instead of copper sulfide (as in the Duval/Sierrita mine), which has a richer percentage of copper, and evidently can also contain uranium also. The pit was 1 mile wide, 1 ½ miles long and 200 feet deep. The ratio of copper was 14 pounds per 170 million tons of ore, so nearly 1.3 billion tons of bedrock and sediments remain on site in piles and impoundments.

Its neighbor the Duval/Sierrita mine was developed by the Duval Corporation, originally, the Duval Texas Sulfur Company. The company diversified into copper in 1959, when it purchased the Esperanza orebody, which had been explored, but considered too poor to develop by Kennecott Copper Company, a few years earlier. Taking advantage of Vietnam War-era need for copper, Duval received an $83 million loan from the General Services Administration to develop the low-grade (0.28 percent copper) Sierrita deposit, located near the Esperanza mine. When it opened in 1970, Sierrita had an annual capacity of 80,000 tons of metallic copper. Pennzoil Company bought a controlling interest in Duval in 1968, then sold its copper properties to Cyrus Minerals in 1986.

In the early 1970’s there were two law suits over water rights and water quality in the Green Valley area. Data collected in the early 1970’s by the United States Geological Survey showed increased concentrations of sulfate and total dissolved solids in down gradient well monitored over time, suggesting tailings pond recharge at one mine. Information from the water rights case suggested significant groundwater recharge was occurring through tailings ponds. (Thuss, 1978)

As a result, in the early 1980’s, there was a study with recommendations for the three mines in the area: Sierrita, Twin Buttes and Mission mines. The report, “Ground-water Monitoring in the Tucson Copper Mining District” was developed by a Mines Task Force and Environmental Planning and Advisory Committee of the Region and was prepared and published in 1983 by Pima Association of Governments (PAG) with approval of Water Quality Control Council. They summarized their conclusions as follows:

  1. Recharge from the tailings ponds at the ASARCO Mission, Anamax Twin Buttes, and Duval mines has locally degraded the quality of downgradient groundwater. High contents of sulfate and hardness are indicative of the recharge.
  2. Migration of recharged water from the ASARCO Mission tailings ponds appears to be limited at present by pumpage of the ASARCO mine supply wells.
  3. Recharged water from the Anamax Twin Buttes pond no. 2 appears to be moving toward at least one public-supply well. Pumpage of an interceptor well or wells may be desirable.
  4. Pumpage of the interceptor wells near the Duval Sierrita pond is not adequately controlling the movement of recharged pond water. At least two downgradient public-supply wells appear to be threatened. A substantial increase in the volume of pumpage from interceptor wells appears to be necessary.
  5. Enhanced monitoring programs appear to be necessary at each of the three study areas. These include additional characterization of the [tailings] pond water and determination of water recharge. Also, contents of cyanide, molybdenum, selenium and selected trace organic chemical constituents should be determined in water from wells affected by tailings pond recharge.

Despite the thorough analysis, there was no long-term follow-up. Originally, the Arizona Health Dept. mandated a “Groundwater Quality Protection Permit” from the various mines. All the mines were sent a notice in 1985 that they would have to show that their operations did not pollute water supplies beyond a certain limit.

Soon afterwards, in 1985, the Cyprus Minerals Company [ For much of the 1990s, Cyprus Minerals Company was the largest single funder of the anti-environmental movement in the western part of the U.S.] purchased Twin Buttes from Anamax Company and the Esperanza-Sierrita complex from Duval.

In 1985 Green Valley Coordinating Counsel had a strong environmental chairman, Charles Bates. At that time Environmental Protection Agency was conducting hearings around the country concerning environmental problems caused by tailings ponds. Green Valley constituents were disappointed in that the hearing was held at a hotel in east Tucson, away from Green Valley and away from the tailing pond sites.

In 1987, the Arizona Department of Environmental Quality (ADEQ) was formed and it took over the monitoring of pollution. The interest of Pima Association of Governments waned to such an extent that when PAG published their final report 20 years later in 2002, they did not include any figures from the Duval/Sierrita mine. When PAG requested data, the representative from Phelps Dodge Corporation wrote PAG that PD had filed all the data with ADEQ; therefore, all the data they needed was available there. [A true statement.]

In 1987 and again in 1992, the Sierrita mining operations were cited by the Environmental Protection Agency for acid mine drainage, a traditional problem of hard rock mining. Oxidation of exposed sulfide minerals in mine tailings and waste piles releases toxic heavy metal ions and acidic hydrogen into surface and groundwater. The water pollution problems that result from acid mine drainage are very difficult to clean up.  Because of the continued violations, they were fined over $175,000 in 1996.

Traditionally, the biggest environmental problem with mining is with the smelting process. By the late 1970s, Phelps Dodge’s smelters in Ajo, Douglas and Morenci were not meeting federal standards for air quality. The Environmental Protection Agency gave PD until January, 1985 to comply with standards. By 1987, all three smelters had closed as it was not economically feasible to meet air quality standards.

However, there remains a smelter for molybdenum at the Duval/Sierrita Complex. Smelters are required to have complicated pollution reducing fittings on the smokestacks. While operators were cleaning the smokestack, instead of closing down the smelting temporarily, the operators used a bypassed the smokestack—some 361 times between 1994 and 1999. Green Valley residents complained to the Department of Environmental Quality, who simply called the mine and were told, everything is fine up here; we aren’t polluting. Incensed at the disregard for the situation, several Green Valley residents flew to San Francisco to complain personally about the nuisance. The EPA investigated, suits were filed, and finally in 2004, Phelps Dodge paid $1.4 million for the air-quality violations. Of course, they used the excuse that they did not own the mine at the time of the violations.

Phelps Dodge and Cyrus Amax Minerals merged in 1999. According to their letter, signed by the CEO, Steven Whisler, they were one and the same company, using the name of Phelps Dodge.

All mining companies are required to have a permit that sets the limits of pollution in any given body of water, surface or underground. The Department of Environmental Quality had been dogging the owners of Duval/Sierrita mine since 1988 that they had to produce proof of their compliance with certain standards. Although Twin Buttes mine did show its ability to comply and did receive a permit in 1988, Duval/Sierrita mine never qualified. The process got so bogged down that in 1995, they started the whole process over again. The permit was set to go into place in 1997, but somehow the mining operations never met the criteria. Then in 2003, Governor Janet Napolitano mandated that all mines have their Aquifer Protection Permits in place by January, 2006.

This provided an opportunity for the residents of Green Valley to enter into the debate as a “stakeholder” since the residents had been using the slurry from the mining operations in their homes for washing and cleaning (but everyone drank bottled water) for over ten years. Department of Environmental Quality is holding a public hearing in Green Valley, August 17, 2005.

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