Q
A
NONPOINT SOURCE SUCCESS STURY
Arizona
Private Landowner Helps Control Mine Waste, Restoring Mule Gulch
Waterbodies Improved
Polluted runoff from historic mining introduced metals and acidic
water into Mule Gulch, causing metal concentrations and pH levels
to fail state water quality standards. As a result, two segments of Mule Gulch were added to the state's
impaired waters list for pH and metal impairment in 1998. Remediation efforts conducted in the early
2000s reduced acid mine drainage (AMD) and improved pH and metal levels. Due to this improvement,
Arizona removed four pollutants along two segments of Mule Gulch from the impaired waters list in 2014.
Problem
Mule Gulch is in Bisbee, Arizona, in southeastern
Arizona. Mule Gulch flows east from the Mule
Mountains towards Whitewater Draw (Figure 1).
Mine tailing waste plies, tainted road surfaces, stream
sediment and smeiter fallout caused increased metal
concentrations and iow pH levels in Muie Gulch.
Mule Gulch first appeared on Arizona's 1998 List of
Water Quality Limited Waters as having specific water
quality violations due to dissolved copper, cadmium,
dissolved zinc and pH (low). Arizona Department of
Environmental Quality's Totai Maximum Daily Load
Unit sampled the stream during 1998 and 1999,
and the data obtained supported this assessment of
impaired water quality in Muie Gulch.
Because of rapid changes in water quality and flow
observed during a July 1999 precipitation event, an
intensive sampling and monitoring system (e.g., stream
gages, data loggers, probes) was established in late
1999 and early 2000 (Figure 2).
In 2002 Reach 090A (headwaters to Bisbee WWTP)
was added to the 303(d)-list for dissolved copper
and zinc. Dissolved copper was as high as 12,000
micrograms per liter (|ig/L) (185 times the aquatic and
wildlife standard) and exceeded standards in 20 of 36
samples (55 percent) in Mule Gulch. Dissolved zinc was
as high as 3760 (ig/L (10 times the aquatic and wildlife
standard) and exceeded standards in 14 of 36 samples
(about 40 percent). Water quality standards for cad-
mium, zinc and copper are hardness dependant, while
standards for pH require values between 6.5 and 9. In
2004 the existing segments were further separated
into Reach 90A (headwaters to above Lavender Pit),
Reach 90B (Lavender Pit to Bisbee WWTP), and Reach
90C (Bisbee WWTP to l-lwy 80 Bridge).
Figure 1. Mule Gulch is near Arizona's southern border.
Project Highlights
The following restoration projects were implemented
by Freeport McMoRan Corporation (FMC), a private
mining company:
lj Lower Mule Gulch (2003). Activities included remov-
ing sulfidic materials from drainage, capping sulfidic
slopes with inert fill, and constructing riprap and
grouted riprap channels for erosion control.
2.	Upper Mule Gulch (2004). Activities included cap-
ping of sulfidic fill with inert cover and placement of
low flow interceptor on north side of channel.
3.	"C" Canyon (2006). Mine stockpiles were removed
and the footprint was covered with inert capping.
4.	Mission Canyon (2007). A center dividing wall was
constructed in a concrete culvert to divert mine-
contacted water from Mule Gulch flows. The mine-
contacted waters are confined to the north side of
the channel and are then diverted to the Lavender
Pit by a 60-inch diameter pipe under Highway 80.

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Mule Gulch Watershed
I I Mule Gulch Watershed
* Surgace Water Sites
1.5 Miles
0.75
	 AZ 150803D1-337
Figure 2. Seven water monitoring sites were
established to assess water quality in Mule Gulch.
5.	Mule Gulch at NW #7 (2009). Activities included
removal of stained sediments in channel, removal
of sulfidic stormwater management berms and
replacement with inert fill, and placement of riprap
and grouted riprap for erosion control.
6.	Dubacher Canyon (2012). Activities included removal
of sulfidic stockpile from Dubacher Canyon, and
channeling of stormwater flows from Dubacher
Canyon to the Lavender Pit.
7.	Soils VRP (2014). Activities included removal of
smelter fallout and other mine-related waste from
the soils of privately held properties, and the place-
ment of clean backfill.
FMC actions have included removing contaminated
material, adding erosion control measures, capping
waste, and rerouting stormwater. All have had a net
effect of improving water quality in Mule Gulch as
discussed below.
Results
FMC has implemented several projects within the last
decade that have improved conditions in Mule Gulch
(Table 1). Through this work, zinc, cadmium and pH
are now meeting water quality standards in two Mule
Gulch segments, 15080301-090B and 15080301-090C,
prompting Arizona to remove them from its impaired
waters list in 2014.
The Upper and Lower Mule Gulch and Mission Canyon
projects described above had the most impact by
keeping stormwater runoff from mineralized areas
from entering Mule Gulch. Although significant
reductions in dissolved copper concentrations have
occurred, the copper impairments will remain for
three Mule Gulch reaches in the watershed.
Partners and Funding
The restoration of Mule Gulch was funded by FMC;
these actions have had a net effect of improving
water quality in Mule Gulch. Arizona Department of
Environmental Quality supported water quality moni-
toring and reporting.
Table 1. Post-restoration dataa b on reaches 90B and 90C
sampling sites SPMLG012.79 and SPMLG07.81, respectively).
Date
Reach 90B pH
Reach 90C pH
Reach 90C
Dissolved
Cadmium
(mg/L)
Reach 90C
Dissolved
Zinc (jLig/L)
9/7/16
7.95
8.23
0.072
6
8/9/07
8.13 (8.2)
No data
1.88
120
7/31/07
8.00
8.00
ND (ND)
ND (ND)
7/20/07
7.08 (6.8)
7.17 (6.9)
ND
ND
3/23/07
7.16
No data
ND
ND
a ND = nondetect; below method reporting limit
b Data in parentheses indicate duplicate samples
^EDSrX
PRO^°
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-16-00100
December 2016
For additional information contact:
Jason Sutter
Arizona Department of Environmental Quality
602-771-4468 • js9@adeq.gov

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