First, I would like to thank the ADEQ staff for the tremendous job they have done and are continuing to do for the community of Green Valley in addressing the sulfate plume. Two years of study have produced several reports beneficial to the community, particularly the one on the Aquifer Characterization of the region (which had never been done before) and the final report on the Feasibility Study outlining the possible processes for cleaning up the sulfate plume itself. I was quite satisfied and pleased with the decision of Freeport-McMoran to choose a remediation method that was not the cheapest and was not the easiest. I honestly think it is the solution most beneficial to the Green Valley water users.
Freeport-McMoran chose Option Five that consisted of two parts to remediate the existing plume. The two parts are separate operations and not dependent on each other in any way I can discern. I do not understand any assertion that if one part turns out to be impossible to accomplish, then the other part will be null and void. Actually, both parts have challenges to overcome.
Part 1: Proposed well field east of tailing impoundment
I did not agree with omitting the radioactive chemicals and heavy metal data from the Mitigation Order, which only included sulfates. At that time, we took what we could get, that is, to keep sulfates at 250 mg/ltr., which is still 500% the ambient level in this region. However, the fact remains that there are radioactive chemicals, including Gross Alpha and radon, in the plume that have migrated from the tailing impoundment to the monitor wellfield on State Trust Land (see attached Radiochems in Monitor Well data). The heavy metal data monitoring has been extremely sparse, but we do have data from one well (see attached Composite Monitor Well 15 data) along the impoundment, indicating the potential danger.
I maintain that the potential of migration of these radioactive chemicals toward Green Valley’s public water supply should be considered when placing the wellfield that will be pumping water. It seems, and I have not been shown differently, that a well field along the perimeter of the west border of Green Valley will bring the potentially dangerous radioactive chemicals and heavy metals in closer proximity of public wells. I realize there are sentinel wells in place to avoid such an occurrence, but avoiding the possibility will be a superior plan and potentially a less costly one.
Considering the attached data, it is of utmost importance that the monitor wells in place are tested regularly.
Further, it does make sense that the poorer quality water is used in the mining operations. However, this avenue could cause two consequences. The tailing water will be further concentrated with contaminants, thereby, all the more necessitating a new lined impoundment away from public wells. Second, there is a concern for the miners’ health who will be working in the area where the water contaminated with radon is delivered, but apparently OSHA guidelines will take care of this concern.
This plan requires purchase of State Trust Land, which can be a tedious process. We will be imploring the state officials to cooperate with Freeport-McMoran to implement this solution, which is surely an advantage for the health and well-being of Green Valley residents.
Monitor Well MH-15
Monitor Well MH-11
Part II: Proposal of New Tailing Impoundment
Since the mining company has found that it will be able to mine copper for another 30 years, the present tailing impoundment would double in height from 300 ft. to 600 ft. The combination of potential of water and air pollution is foreboding for all concerned. We certainly welcome the possibility of a new impoundment, and again hope that the State Trust Land Dept. will cooperate to facilitate the obtaining of property necessary for this project to be accomplished in a timely manner.