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Restoring Horse Creek and West Creek for Aquatic Life by Implementing
Best Management Practices
Waterbodies Improved
Following the large Hayman fire in 2002, Horse Creek and West
Creek in the Upper South Platte River basin were significantly
impacted by nonpoint source pollutants such as sediment and debris from storm runoff. A water
quality assessment that used a Multimetric Index (MMI) showed that these creeks failed to support
aquatic life use for macroinvertebrates. The Water Quality Control Commission (WQCC) added
Horse Creek and its tributaries, as well as West Creek, to the Clean Water Act (CWA) section 303(d)
list of impaired waters in 2012 and 2016, respectively. Numerous innovative best management
practices (BMPs) were implemented in collaboration with many partners through the Hayman
Restoration Project. After BMP installation, monitoring data confirmed that water quality was
successfully restored in these watersheds. In 2020, the WQCC removed these waterbodies from the
303(d) list for aquatic life.
Problem
Horse Creek and West Creek are in the Upper South
Platte River basin, a major source of drinking water for
Colorado's Front Range (Figure 1). In 2002, the Hayman
fire burned over 137,000 acres within the Upper South
Platte River watershed, with 50%-70% of the burn
classified as moderate to high severity.
Post-fire flooding and erosion from the Hayman fire
impaired aquatic habitat and resulted in the 303(d) list-
ings in 2012 and 2016 for Aquatic Life for Horse Creek
(COSPUS03_E) and West Creek (COSPUS03_F), respec-
tively. Excessive sediment in runoff was exacerbated
by highly erosive soils (decomposed granite). These
loads heavily impacted Strontia Springs Reservoir,
which provides 80% of Denver Water's raw water
supply and 90% of Aurora Water's supply. Sediment
in runoff also affected transportation infrastructure,
closing State Highway 67 for three months. Sediment
affected watershed health, reservoir storage capacity,
cost of water supply to Colorado's Front Range, and
fish and wildlife habitat—including habitat for Preble's
Mouse, a threatened and endangered species.
A Watershed Analysis for River Stability and Sediment
Supply (WARSSS) assessment for Trail Creek, a West
Creek tributary, estimated that flooding events gener-
ated more than 60,000 tons of sediment per year.
Figure L Horse and West creeks are in central Colorado.
In 2010, 8 years after the fire, a WARSSS assessment
Indicated that over 57,000 tons of sediment was stili
being delivered downstream to Horse Creek during
high precipitation periods. Given the severity of the
situation, collaboration with many partners was neces-
sary to Improve and protect waterbodies.

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Story Highlights
The Hayman Restoration Partnership was formed
between the National Park Service, the Coalition
for the Upper South Platte, the National Forest
Foundation, and many corporate partners and
community groups in response to the Hayman fire.
WARSSS assessments identified hot spots of sedi-
ment loading to help prioritize subwatersheds for
restoration based on water quality impacts and flood
risks. Due to the size of the watershed, a holistic
watershed restoration approach was implemented
to achieve water quality improvements through
projects funded by various sources. These included
six CWA section 319 grants (2006-2016) across
the affected subwatersheds. This watershed-based
approach focused on erosion control, revegetation,
and stream channel reconstruction and restoration.
BMPs included installing 21 sediment retention basins,
rebuilding log erosion barriers, and reestablishing nine
alluvial fans. Ponderosa pines were planted, willow
cuttings were established along the riparian areas,
and fencing was installed to reduce impacts from
recreational use. Four miles of stream were restored
by reestablishing a defined channel, armoring stream
edges, and creating instream structures that included
"rock and roll" log vanes, J-hook vanes, cross vanes,
boulder and/or wood drop structures, log sills, toe
wood pool features, and riparian benches. To decrease
sediment loading, over 13 miles of roads and seven
road crossings were decommissioned, and nine
culverts or crossings were repaired or improved. A
bridge was installed to improve river function.
Results
Water quality assessments were conducted after BMP
installation for Horse Creek and West Creek using
data from the Station ID 5971al (7/24/2017) and two
U.S. Forest Service (USFS) stations (10/11/2017). MMI
scores ranged from 63.5 to 71, an improvement from
the pre-BMP MMI scores of 21.9-34.9 at the sampling
sites. MMI values higher than the minimum threshold
level of 34 indicate an acceptable water quality
condition. Recent data show full attainment of aquatic
life use for macroinvertebrates (Figure 2). As a result,
Colorado removed the aquatic life use impairment for
(1) Horse Creek and its tributaries and (2) West Creek
in the 2020 Integrated Water Quality Monitoring and
Compared to Threshold
¦ Impairement Threshold ¦ MMI Scores
J J
USFS-Horsel	USFS-Horse2
Sample Stations
Figure 2. MMI scores for Horse and West creeks that
led to removal from the 2020 impaired waters list.
Assessment Report. Additionally, after completing
stream restoration work in Trail Creek, trout and
beaver returned to Trail Creek, indicating that wildlife
habitat had improved post-restoration. Lessons
learned from Colorado's first large-scale, post-wildfire
watershed restoration work were applied to other
areas of the state impacted by wildfire.
Partners and Funding
Primary partners in the Hayman Restoration
Partnership were the Coalition for the Upper South
Platte, National Forest Foundation, U.S. Department of
Agriculture Natural Resources Conservation Service,
USFS, Bureau of Land Management, Douglas County,
Aurora Water, Denver Water, Vail Resorts as well
as the Colorado Department of Public Health and
Environment's Nonpoint Source Program and Colorado
Water Conservation Board's Watershed Program.
Additionally, thousands of volunteers through the
Rocky Mountain Field Institute, Mile High Youth Corp,
and an AmeriCorps National Civilian Community
Corps crew assisted with trail and road work. In total,
an estimated 2,739 volunteers contributed 22,422
hours to accomplish the on-the-ground work. Various
entities invested more than $40 million dollars for
rehabilitation efforts in the watershed. CWA section
319 project funds supported the rehabilitation efforts
for the Hayman Restoration Partnership ($1.25 million
total with reported matching funds of over $1.3 million).
Continued commitments from all partners for monitor-
ing progress and maintenance of the BMPs is necessary
to protect water quality in the Horse Creek watershed.
5971al
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-21-001N
September 2021
For additional information contact:
Colorado Department of Public Health and Environment
Kenan Diker • 303-692-3597 • kenan.diker@state.co.us
Estella Moore • 303-692-2864 • estella.moore@state.co.us
Christa Trendle • 303-692-6343 • christa.trendle@state.co.us
Kate Macdonald • 720-263-1426 • kate.macdonald@state.co.us
Tammy Allen • 303-692-3554 • tamara.allen@state.co.us

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