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Section 319
NONPOINT SOURCE PROGRAM SUCCESS STURY
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Addressing Erosion Improves the Lower South Fork Payette River
Waterbodv Improved The presence of erodin9 access roads on National Forest
land prompted the U.S. Department of Agriculture's Forest
Service to identify Idaho's South Fork Payette River as not meeting the desired future
condition goals (physical and biological) outlined by the Boise National Forest Plan. As a
result, the 24-mile-long lower South Fork Payette assessment unit was added to Idaho's
1994 Clean Water Act (CWA) section 303(d) list of impaired waters for sediment. In an effort
to reduce sediment loading into the river, the Forest Service closed some erosion-prone
roads and fixed eroding areas on other roads. Recent data show that sediment levels have
dropped, but until biological data are collected, the Idaho Department of Environmental
Quality (DEQ) will be unable to conclusively say that this segment is supporting its
beneficial uses. As resources permit, DEQ will collect biological data to confirm that the
assessment unit has been restored.
Problem
The 813-square-mile South Fork Payette River sub-
basin begins in the Sawtooth Mountains and joins
the Middle Fork Payette River near Garden Valley,
Idaho (Figure 1). Most of the subbasin is in Boise
County. The primary land use is forest; the subbasin
is owned and managed almost entirely by the Forest
Service (Boise and Sawtooth national forests).
Over the years, numerous roads were constructed
for resource extraction and used for backcountry
access and recreation. As they eroded, many of
these roads contributed excess sediment to the
South Fork Payette River (Figure 2). In 1990 the
Forest Service developed the Boise National Forest
Plan. At that time, a segment of the main stem of
the South Fork Payette River was determined to be
water quality-limited on the basis of exceedances of
the Boise National Forest Plan standards and guide-
lines, as well as best professional judgment. As a
result, South Fork Payette River assessment unit
ID17050120SW001 _ 05 (a 23.98-mile-long, fifth-
order river segment stretching from the Deadwood
River to the Middle Fork Payette River) was added
to the 1994 CWA section 303(d) list for not fully
supporting its cold water aquatic life beneficial use
because of the presence of excess fine-grained
sediment.
South Fork Payette
River Subbasin
Figure 1. The South Fork Payette River
subbasin is in west-central Idaho.
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Project Highlights
The Forest Service outlined water quality improve-
ment goals in its 1990 Boise National Forest Plan.
(The plan has since been updated; a 2010 version is
available.) To help achieve those goals, the Forest
Service has implemented numerous projects in
South Fork Payette River subwatersheds to reduce
sediment loads entering the South Fork Payette
River. Work in the South Fork Payette headwaters
(upstream of the impaired assessment unit) has
included closing 18 miles of road (2004, 2006
and 2009), performing road maintenance on 70 to
100 miles of road annually (2005-2013), closing six
dispersed campsites to minimize impacts on ripar-
ian areas (2006 and 2008), stabilizing a 0.10-mile-
long road cut (2007), replacing one stream crossing
(2008), stabilizing one eroding streambank (2008),
capping and revegetating 5 acres of fine-grained
mine tailings (2007 and 2009), and replacing one
culvert to improve fish passage (2011). Work occur-
ring directly along the South Fork Payette River
fifth-order assessment unit has included replacing
four culverts to improve fish passage and to reduce
erosion from the streambanks and roads.
Results
Recent monitoring results indicate that sediment
levels in the South Fork Payette River have declined.
Data collected in 2008 by the U.S. Geological Survey
(USGS) showed that turbidity levels were low, rang-
ing from 1 to 25 nephelometric turbidity units (NTU).
Idaho's turbidity standard requires that turbidity
levels not exceed background levels by more than
50 NTU instantaneously or more than 25 NTU for
more than 10 consecutive days. South Fork Payette
River data showed that the highest measurement
of 25 NTU (on May 22, 2008) occurred at high flows
of 3,940 cubic feet per second. This is far below the
instantaneous standard and would also comply with
the 10-consecutive-day standard.
In addition, in 2009 DEQ measured 14.8 percent
depth fines in pool tailouts (the areas just above or
below rapids) in the fifth-order assessment unit. This
meets the monitoring target of a 5-year depth fines
mean of 27 percent or less with no individual year
being greater than 29 percent (a target adapted from
the South Fork Salmon River Subbasin Assessment,
which was developed in 2005 and updated in 2009).
Figure 2. An eroding road cut in the South
Fork Payette subbasin (photo by USDA
Forest Service).
Collectively, these data indicate that assessment
unit ID17050120SW001 _ 05 has improved. To
confirm beneficial use support, DEQ will collect
biological data in the near future. The assessment
unit will remain in Category 5 (on the state's CWA
section 303(d) list) until monitoring is completed.
Partners and Funding
Key watershed partners include the Boise and
Sawtooth national forests, the Federal Highway
Administration and the Idaho Department of
Transportation. DEQ and USGS collected moni-
toring data. Partners have invested more than
$1.2 million on restoration and fish passage projects
along the fifth-order assessment unit, including
funds from the Forest Service (maintenance and
Legacy Road funding) and the Federal Highway
Administration (Highway Transportation for
Aquatic Organism Passage [HTAP] program funds).
Between 2011 and 2013, partners spent more
than $1.5 million within the upstream fourth-order
assessment unit, using funds from HTAP, the Idaho
Transportation Department and the Forest Service.
UJ
O
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-14-001HHH
September 2014
For additional information contact:
Marti Bridges
Idaho Department of Environmental Quality
208-373-0382
Marti.Bridges@deq.idaho.gov
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