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Watershed Management Efforts Help Reduce Sediment Loading in Credit River
\A/ato hnH I	Qr| Runoff from urban and agricultural areas led to excess sediment arid
BY 1 '• ~ 60 suspended solids loading into the Credit River. As a result, in 2002 the
Minnesota Pollution Control Agency (MPCA) added the entire Credit River to the state's Clean Water Act
(CWA) section 303(d) list of impaired waters for failing to support the aquatic life beneficial use because
of turbidity impairment. Watershed partners worked with private landowners to stabilize streambanks
and ravines, thereby reducing erosion and sediment runoff into the river. Several cities in the watershed
also implemented nonpoint source pollution control projects to reduce urban runoff. Monitoring data
from 2008-2009 showed that excess turbidity was no longer present, prompting the state to remove the
Credit River from Minnesota's list of impaired waters in 2012.
Problem
The Credit River watershed is in Scott County,
Minnesota, and it covers a drainage area of approxi-
mately 59 square miles. The river originates in
New Market Township and flows north through
Credit River Township before discharging into the
Minnesota River in the city of Savage (Figure 1),
The primary land uses in the watershed are urban
(30 percent), agriculture (27 percent) and forest
(22 percent). Other land uses include wetland,
pasture, water and sand mining. The watershed
includes large amounts of highly erodible land,
especially in the headwaters area.
Excess sediment and suspended solids in a water-
body can block light penetration and inhibit healthy
plant growth, increasing turbidity. (Turbidity is a
measurement of the degree to which light traveling
through a water column is scattered by suspended
organic particles, including algae, and inorganic
particles. It is measured in nephelometric turbidity
units, or NTLJ.) Elevated turbidity can also inhibit
aquatic organisms' ability to feed, affect gill func-
tion and cause spawning beds to be covered in
sediment Data from the Metropolitan Council
Environmental Services (MCES) collected in the late
1990s showed that 24 percent of samples exceeded
25 NTU. A waterbody is considered impaired by
turbidity if 10 percent or more of water samples
exceed 25 NTU.
On the basis of these data, Minnesota added the
entire length of the Credit River (22 miles, from the
headwaters to the Minnesota River) to the 2002
CWA section 303(d) list for failing to support the	„ „ Tl „„	.
river's aquatic Iffe beneficial use because of turbid-	figure 1 I he 22-mile-long Credit River empties into the Minnesota
...	, un.A . , .... ,	River. Multiple partners collaborated to install a variety of
ity impairment. MPCA identified the primary source	++¦¦+¦ +u u ¦ / u ^	\
' x , . ,.x .	A I. x i xx x	restoration projects in the basin numbered on map.
of the turbidity impairment as polluted runoff from
urban and agricultural land uses.
Minnesota River
Credit River
Watershed
Credit
-River
Watershed
Prior Lake.
^ '
Legend	*
o Monitoring Site
A Lake Monitoring Site
• Preliminary Monitoring Sites *
Impaired Reach
—	County Ditch
—	Stream
—	Major Road
County Boundary
~~ Lake
nil Credit River Watershed
~ Scott WMO
B Blackdog WMO
Lower Minnesota River WD
ESS Prior Lake-Spring Lake WD
~~ Vermillion RiverWMO
O City of Savage Pervious Pavement, Rain
Gardens and Green Roof
© City of Savage Grade Stabilization
© City of Savage Stream Stabilization (2)
and Cedar Tree Revetment (2)
® City of Prior Lake Rain Gardens (9)
© Grassed Waterway
Scott County
Lakeville

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In 2007 the Scott County Watershed Management
Organization .(Scott WMO) hired a consultant to
conduct a comprehensive geomorphic assessment
of the river to identify potential project locations at
which to improve water quality. Water quality was
restored before a total maximum daily load (TMDL)
for turbidity was finalized.
Project Highlights
Through a number of nonpoint source pollution
control efforts, sediment loading in the Credit River
watershed has been reduced. Mechanisms such as
the National Pollutant Discharge Elimination System
(NPDES) regulation of stormwater discharge from
municipal separate storm sewer systems were
instrumental in controlling sediment loadings, as
were locally led erosion control programs involving
many watershed partners.
Figure 3. After
restoration (right),
Utica Ravine has
gently sloping
streambanks that are
vegetated and stable.
Figure 2, Before
restoration (left),
the rapidly eroding
streambanks of
Utica Ravine were
contributing large
amounts of sediment
downstream.
Between 1999 and 2010, the City of Savage, Credit
River Township, Scott WMO and other watershed
partners led a number of management efforts to
improve water quality in the Credit River. Through
its technical assistance and cost share program,
the Scott WMO has supported several watershed
projects, including streambank stabilizations with
private landowners, as well as several innovative
low impact development (LID) projects, such as rain
gardens, with the cities of Savage and Prior Lake.
Over the past several years, partners have also
installed grassed waterways (vegetated channels
used to direct water flow and reduce soil erosion
from croplands) and added cedar tree revetments
(anchoring trees along a streambank to decrease
erosion).
The local cities and Scott WMO have also targeted
projects and capital improvement programs to
reduce sediment loading into the Credit River. In
2010 the City of Savage, Scott WMO and other local
partners used Minnesota Clean Water Legacy Act
(MCWL) funding and a Scott WMO grant to recon-
struct and stabilize the 2,600-foot Utica Ravine,
which had contributed significant sediment loads
to the Credit River (Figures 2 and 3). This project
reduced sediment loading by an estimated 50 tons
per year.
Results
Credit River turbidity data continuously collected
from 2008 through 2009 showed that only 1.2 per-
cent of samples exceeded 25 NTU, indicating that
the river now meets the turbidity criterion to support
its aquatic life beneficial use. On the basis of these
data, the MPCA recommended that the river be
removed from the 2012 list of impaired waters. The
state attributes the water quality improvement, in
part, to installing nonpoint source pollution control
projects, adopting better construction erosion con-
trol practices, and implementing more permanent
vegetative coverage throughout the watershed.
In 2011 the MPCA approved the Scott WMO's Credit
River Protection Plan, which assessed the efficacy
of current management efforts and provided an
outline for future protection strategies in the Credit
River watershed to ensure that the river remains
unimpaired.
Partners and Funding
Project partners included the Black Dog WMO,
Minnesota Board of Water and Soil Resources
(which provided $130,000 for the Utica Ravine
project), cities of Lakevilie. Prior Lake and Savage,
townships of Credit River and Spring Lake, Lower
Minnesota Watershed District, MPCA, MCES, Scott
County, Scott Soil and Water Conservation District,
Scott WMO (which provided $20,000 for the Utica
Ravine project), and Three Rivers Park District. MPCA
provided $84,575 in MCWL funding to the Scott
WMO to support the development of the Credit River
Protection Plan Other major partners involved with
developing the Credit River Protection Plan included
the MCES, the Black Dog WMO and the cities of
Savage and Prior Lake. State funds (serving as match
for the CWA section 319 grant) supported the MPCA
staff project manager responsible for overseeing
development of the protection plan.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
E PA 841 - F -13 -00 TB
January 2013
For additional information contact:
Brooke Asleson, Project Manager
Minnesota Pollution Control Agency
612-757-2205 • Brooke,Asleson@state.mn.us
Paul Nelson, Natural Resource Program Manager
Melissa Bokman, Sr. Water Resources Planner
Scott County Natural Resources • 952-496-8475

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