Section 319
NONPOINT SOURCE PROGRAM SUCCESS STORY
Removing Pyritic Rock Fill and Installing Limestone Buffers Restores
Sweetwater Lake Tributaries
\A7atPrhnrliP9 ImnrnvpH Rock material containing pyrite was used to upgrade a
waterooaies improved forest rogd on A|gskg,s Pnnce of Wg|es |s|gnd Acidic
runoff from the pyrite had caused heavy metals to dissolve out of surrounding native rock,
creating high metal levels in portions of five streams draining into Sweetwater Lake. As a
result, the Alaska Department of Environmental Conservation (ADEC) added the streams to
the state's 2010 Clean Water Act (CWA) section 303(d) list of impaired waters for metals.
Project partners excavated the pyritic rock and installed limestone buffers. All five streams
now meet water quality standards (WQS). Alaska plans to propose removal of these
waterbodies from the state's 2014 list of impaired waters.
Problem
The Sweetwater Lake watershed is in the largely
undeveloped Tongass National Forest on Prince of
Wales Island in southeast Alaska (Figure 1). While
upgrading Forest Service road 3030 (FS 3030) in
2006, the U.S. Department of Transportation's
Federal Highway Administration, Western Federal
Lands Highway Division (WFLHD), inadvertently used
rock fill that contained pyrite. The rock was crushed
and used as roadbed and in stream crossings along
more than 3 miles of FS 3030. When exposed to
air and water, the pyrite oxidized to sulfuric acid,
which in turn dissolved heavy metals present in the
surrounding native rock material. Surface runoff
and groundwater carried the metals into numerous
streams, polluting a portion of each stream directly
downstream from the road. The streams empty into
Sweetwater Lake, which was not affected.
In June 2007 WFLHD identified culvert corrosion
occurring at a stream crossing, identified the road
fill as a likely source of acidity, and began monitor-
ing water quality. Data showed that five streams
crossing FS 3030 were affected. The levels of sul-
fate and metals (including aluminum [Al], cadmium
[Cd], copper [Cu], iron [Fe], manganese [Mn], nickel
[Ni], and zinc [Zi]) exceeded the natural background
conditions as defined by Alaska's WQS. A biologi-
cal survey revealed no fish or macroinvertebrates
present in affected areas downstream of FS 3030,
indicating that these portions of the streams were
not supporting their "growth and propagation of
fish, shellfish, and other aquatic life" designated
use. As a result, ADEC placed five streams on the
state's CWA section 303(d) list in 2010 (Table 1).
Sweetwater
Lake
Tributaries
'rince of Wales
• Island 1"
US 0 18Mite
Southeast Alaska
Figure 1. Sweetwater Lake is in southeastern Alaska.
Table 1. Unnamed Sweetwater Lake Tributaries Listed
as Impaired in 2010
Waterbody"
Stream 3
Stream 6
Stream 7
Stream 8
Stream 9
WaterbodylD
AK-10103-010
AK-10103-012
AK-10103-013
AK-10103-014
AK-10103-015
Impaired Length
(miles)
0.4
1.14
0.3
0.3
0.8
Listed
Parameters
Al, Cd.Cu, Fe
Al, Cd.Cu,
Fe, Mn, and
sulfate
Al, Cd, Cu,
Fe, Mn
Cd, Cu, Fe,
Mn, Ni, Zn
Al, Cd.Cu,
Fe, Mn,
Ni, Zn, and
sulfate
' The waterbodies are unnamed tributaries and are referred to by number.
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In this watershed, background levels of metals are
elevated because of naturally acidic conditions.
(The upland areas include acidic peat and sedge
bogs.) Therefore, when ADEC established cleanup
goals, the elevated background concentrations of
metals in unaffected stream reaches were consid-
ered representative of the natural water quality con-
ditions (i.e., the conditions that support aquatic life
in this area). To monitor stream condition, samples
were collected during each monitoring event at a
reference site in each stream (a site along the same
stream but above the influence of the pyritic rock)
and analyzed for the same parameters as those at
the test sites. The concentration at each reference
site was used to establish the natural-condition,
background-based WQS for each monitoring event.
Table 2. Metal Levels Found in Stream 3
(in Micrograms per Liter)
Project Highlights
Under federal law the pyritic rock met the defini-
tion of a release of a hazardous substance subject
to site cleanup rules under the Comprehensive
Environmental Response, Compensation, and
Liability Act (CERCLA). WFLHD cooperated
with state and federal partners to stop the acid
rock drainage and restore the affected streams.
Between 2008 and 2010, partners implemented
numerous time-critical removal actions (TCRAs)
under CERCLA, including excavating approximately
100,000 cubic yards of pyritic rock and replacing
it with limestone. In areas where rock could not
be removed, partners installed limestone buffer
trenches to neutralize the acid drainage.
Results
Removing pyritic rock and adding limestone buf-
fers has increased pH levels and decreased metal
concentrations. For the post-TCRA monitoring
periods in 2011, 2012, and 2013, samples from all
five CWA section 303(d)-listed streams were below
or approximately at WQS. Table 2 presents sample
results for Stream 3. (The data for other streams
show similar results, but they are not presented
here because of space constraints.)
Biological monitoring conducted in 2011 showed that
the streams now support their aquatic life designated
use: 12 out of 14 surveyed reaches received a very
good rating, and two received a good rating based on
the Alaska Stream Condition Index for benthic macroin-
vertebrates. Sampling teams also noted the presence
of juvenile fish in all 14 stream reaches. On the basis
of these data, ADEC plans to propose removing all five
tributaries from the 2014 impaired waters list.
Date
9/9/2008
12/13/2008
5/2/2009
9/11/2010
8/21/2011
8/14/2012
8/10/2013
Aluminum
4,150
(410)
210
(87)
90
(140)
240
(270)
260
(360)
230
(300)
70
(250)
Cadmium
2.7
(0.37)
<0.2a
(0.24)
<0.2a
(0.2)
<0.2a
(0.21)
<0.1a
(0.2)
<0.1a
(0.1)
<0.1a
(0.34)
Copper
460
(14.8)
<5.0a
(8.57)
<5.0a
(1.57)
2.0
(7.22)
3.4
(7.32)
1.2
(5.51)
6.4
(13.4)
Iron
39,000
(2,000)
480
(1,000)
<200a
(200)
1,210
(1,500)
680
(1,000)
1,060
(1,490)
460
(5,560)
a Analyte concentrations were below the detection limits.
Notes:
' The water quality standard established for each parameter for each
monitoring event is shown in parentheses. These standards are based on
levels identified at a reference site upstream of the project area.
' Results exceeding WQS are in bold.
The TCRA for this site along Stream 3 was completed on 10/31/2008.
Monitoring was conducted for 5 years to document recovery.
Partners and Funding
Partners on the cleanup project included the
WFLHD, the U.S. Department of Agriculture's
Forest Service, the U.S. Environmental Protection
Agency, and ADEC's Contaminated Sites Program.
Other local, state, and federal agencies that pro-
vided technical assistance or cleanup plan review
included the Alaska Department of Transportation,
the Alaska Department of Natural Resources, the
Alaska Department of Fish and Game, the National
Oceanic and Atmospheric Administration's National
Marine Fisheries Service, the U.S. Army Corps of
Engineers, and the city of Coffman Cove.
WFLHD funded the TCRAs through the Alaska
Forest Highway Program under the SAFETEA-LU
(Safe Accountable Flexible Efficient Transportation
Equity Act: A Legacy for Users). Restoration costs
included $4.3 million to cover engineering, manage-
ment, and sampling costs and another $6.7 million
to excavate hazardous rock fill, install new rock and
limestone buffers, and rebuild the road. WFLHD also
helped develop a rock fill identification protocol now
being used nationwide by the U.S. Department of
Transportation.
s
30
S
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-15-001P
February 2015
For additional information contact:
Gretchen Pikul
Alaska Department of Environmental Conservation,
Division of Water, Nonpoint Source Section
907-465-5023 • gretchen.pikul@alaska.gov
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