PEARCE, ARIZONA – In 2011, Toronto-based exploratory mining company Commonwealth Minerals (focused on exploring and developing properties in Arizona) began re-exploring the old Pearce Commonwealth mine. The mine, according to Commonwealth exploration Vice President Hall Stewart, was Arizona’s second-largest historical producer of gold and silver with a heyday as an underground mine between 1895 and 1926.
Commonwealth, like earlier exploration companies in the 1990s, seeks to determine the potential of the property to be a proven resource; the company proposes a 100 meter deep open-pit cyanide-leach silver-gold operation.
The mine would be located right on the Pearce-Gleeson-Courtland Road and “everything eastward would be part. Pearce Hill would be moved eastward. The old collapsed stopes now honeycombing the entire hill would be mined and waste rock would be moved east with a leach pad south of the hill. We do not intend to put waste back into the pit. Ore would be crushed, stacked on the leach pad and leached with cyanide and then the solution would be pumped through a precipitation plant. After that the metal would go to a small “Dore” silver-gold refinery on site,” said Stewart. “The mine will not produce any tailings, as tailings are the residue from milling and we do not currently plan to construct a mill.”
All mining would be done on either patented/private land or on state leases. The company has 133 un-patented BLM and Homestead Act lode claims but Stewart said that no mining was planned for these claims, rather they would serve as a buffer. The mining of federal un-patented claims would require the Federal National Environmental Protection Act (NEPA) to be implemented, as it has at the Rosemont mine, and would call for a comprehensive environmental analysis, generally an Environmental Impact Statement. Currently Commonwealth is exploring on some claims but has no stated intent to mine. However as it stands, the mine would need to comply with the Endangered Species Act, any discharge permits, and other Federal environmental laws, as well as all Arizona state permits. Stewart believes the process is advancing to the point where they can soon begin an application to Arizona Department of Environmental Quality (ADEQ) for an Aquifer Protection Permit (APP) that would ultimately allow them to pump 3,000 gallons per minute of water for eight and a half years and hopefully more. The process plant will circulate 3.000 gallons per minute, but groundwater pumping will only be 15 to 20 percent of this volume to make up for the water lost to evaporation (450 to 600 gallons per minute).
The current plan will consume a total of between 750 and 970
acre-feet per year. This is about the same consumption as 200 acres
of alfalfa, Stewart said.
“Roughly 50% of that water would get recycled,” said Stewart.
The APP would prohibit groundwater pollution from leaving the site; a large challenge for Arizona mines thus far.
The water consumption is slightly more than a 2012 estimate for the AEPCO power plant; the city of Willcox pumped 987 acre feet in 2007 and the state estimated 167,400 acre feet for the Willcox basin in 2008. Hydrological studies have not yet been completed that would indicate what groundwater depletion or water quality impacts could be on the water table or whether the mine would likely leave behind a pit lake.
Stewart added that, from looking at well logs and from climbing down into the old underground workings of the mine, that, “I’m estimating that the water table in this region has dropped about 100 feet in the last 100 years. The water level within the mine has dropped substantially below the area worked in the past, rather than rising after pumping out of the stopes was halted.”
“From meetings we held in Pearce during 2011 and 2012, I know that people are worried about water consumption issues around here, especially farmers and ranchers, but the current problems in groundwater decline wasn’t a result of mining but agriculture. The bad metals market meant that we had very little money to work with during 2013 and did almost nothing,” Stewart said.
Local property owner Lynn Haber, who describes herself as having lived “on and off in Pearce since 1997,” talked about her observations over the years.
“I have watched the water tables decline. I spent many days horseback riding up in the Cochise Stronghold. I have witnessed the Stronghold tanks going dry and not refilling. The Cochise Spring has gone dry for good. I have watched the huge oak trees wither and die over time because their roots can no longer reach the deepening water table.”
“The many farm fields in our valley have sucked much of the life from our land already. The Commonwealth Mine will destroy our town,” she told the Range News.
“I cannot fathom how they will use 3,000 gallons of water per minute. That’s an entire swimming pool every minute! Where are they getting that from?”
Haber went on to say, “Do they know we are in the desert? I believe they do not care about our town and this valley’s water supply. They will take their silver and gold, deplete our water supply, pollute our land with their toxic processing chemicals and then pack up and leave.”
At this time, Commonwealth is not yet able to present a picture of current water quality in the area surrounding the mine nor establish whether the older underground workings polluted groundwater. They will be completing a hydro-geological study in order to do so.
Stewart said, “Right now we have well records to measure quantity, but as we begin discussions with ADEQ we will need to measure water quality (to determine baseline before the mine begins operation.)
“We are hoping that because we have one well at Pearce School that has been monitored for water quality for a long time that we can gather water quality data for only 4-6 quarters instead of the 8 quarters that ADEQ normally requires from an APP applicant. The water quality at the school is normally potable but it has exceeded the drinking water standard for arsenic. How we can address the issue of the school being so close to the mine is a concern. The school well is slightly ‘up-gradient’ of the mine site although frankly I think that the lens of water lying below Pearce is pretty level”
Stewart estimated that the mine would process about 36 million tons of ore in the above mentioned period and produce about the same amount of waste (tailings from the leach pad and overburden). Company figures have estimated that boreholes to date had measured 6.36 million metal ounces of silver with another 25.95 million “indicated” silver, and 74,800 measured ounces of gold plus 314, 500 “indicated” ounces.
He went on, “These figures can be used in Canadian reports but are not acceptable in the U.S. However we have a new technical report, a prefeasibility study that will be released soon that we think will establish that these resources we’ve discussed are actually reserves.”
Stewart added that the company would “be providing 100 long-term good-paying jobs and that our preference is to hire local.
Sunsites-Pearce Fire District Administrator Tom Schelling said there would be a positive impact on the District if the mine does begin full operations.
“The increased value of the mine would increase the assessed property value of the entire fire district and increase tax revenue from the mine property into the district. Added jobs would bring additional homes sales in the area, which again would help to increase the assessed property value of the district,” he told the Range News. What? Increase assessed property….at what cost? Human lives?
“With current property values on the decline these last few years, seeing them increase would help to keep future tax rates down while allowing the district to maintain its high level of service to the community,” Schelling said.
Murray McClelland, president of the Pearce-Sunsites Chamber of Commerce, said, “As far as the town of Sunsites and what an operating/profitable mining concern would do for us economically is beyond our wildest dreams.”
“Sunsites population has been in a steady decline for the last few years. So in reality, if Commonwealth and/or future partners eventually start the mine up, Sunsites could easily see its population double,” he told the Range News.
“We do not have enough rental housing, products and services to support a massive increase in our population. The balancing act that real estate investors are currently doing is attempting to look into our crystal balls and determine how much risk we’re willing to take and when,” McClelland said.
“If we wait too long however, I’m afraid the wave could roll right on past us, to a certain extent, if we’re not prepared to act as soon as the mine operation looks like a real deal. Stay tuned….”
For her part, however, Haber is not so sure about these economic benefits. Pointing out that Commonwealth Minerals is a Canadian corporation, she said, “It only cares about making money. I do not believe it will bring in jobs. I believe they will bring in their own qualified staff.”
She noted that in the company’s technical data report “shows on their included map that the nearest town is Willcox. It does not even show us – Pearce – on the map. It pretends we do not exist.”
“It states in the report that the surrounding valley is ‘barren’ and is ‘low in plant diversity,’ implying that the mine’s destruction would make no difference here. Have they not seen our beautiful (Cochise) Stronghold? Have they not seen our fields of spring poppies and large diversity of trees, shrubs and cacti?,” Haber said.
“I believe they will damage this area until it is, as they say – ‘barren.’”