Phelps Dodge Sierrita Mine Monitor Wells in Mill Area

Well No.  BW-1, 2, 3

Although the facilities in the mill and leach areas are supposed to be closed circuits, the levels in the wells monitoring groundwater show high levels of sulfates, TDS and other heavy metals. Part of this contamination may be from the spills, also it can be from cracks or leaks in the liners. These levels cannot be regulated because the are on the site. What's do keep them from seeping off the site and contaminating all the water in the area, not just the water downhill from the tailings impoundment.

Radiochems in Monitor Well No. BW-3
On-site: South of milling area near Duval Canal

Unfortunately, although sulfates and TDS are not regulated since they are not carcinogens, the reports are more often tests of Sulfates and TDS. Strangely, the data is quite sparse for the regulated metals!

However, a bit of data from the early 1990's was found in the ADEQ files:

In 1990 tests some of the toxic heavy metals were extremely high. The regulated level is in parenthesis after the results.

Copper = 12,920 ug/l [10 ug/l], Iron = 3,720 ug/l [50 ug/l], Managese = 16,620 ug/l [10 ug/l], Zinc 26,030 ug/l [10 ug/l]

Others toxic metals, including Cadmium, Cobalt, Selenium, are above the allowed level, but not as off the charts.

Date	Hardness	Calcium mg/l	Magnesium mg/l	Sulfate	Arsenic mc/l	TDS	Alkalinity	pH
#1 9/27/90		600	320	2,960		5,060	129	7.6
10/8/90		630	268	2,817		4,762		6.66
7/9/91		590		2,632		5,349
#2 9/27/90		681	351	2,600		5,010	171	5.8
10/10/90		640	350	2,320	<.01	4,800	43.5	5.6
8/19/92		590	310	2,323		3,975		6.6
9/16/93		575	350	2,176		4,680		7.07
7/30/97		752	416	2,270		6,610		7.8
#3 10/8/90		430	113	1,584		3,106		7.05
12/17/93		495	117	1,557		3350		7.64
7/30/97		498	127	1,710		3,530		7.7