United States
Environmental Protection
Agency
Office Of Water
(WH-553)
EPA841-F-93-006
June 1993
Number 8
&EPA TMDL Case Study
Boulder Creek, Colorado
Key Feature:
Project Name:
Location:
Scope/Size:
Land Type:
Type of Activity:
PoIIutant(s):
Program Integration:
TMDL Development:
Data Sources:
Data Mechanisms:
Monitoring Plan:
Control Measures:
Combines habitat restoration and
PS and NPS controls to meet water
quality standards
Boulder Creek Enhancement
USEPA Region VIII/Boulder,
Colorado/South Platte River
Basin/Southern Rockies
River segment, 4.6 miles
High mountains, tablelands with
high relief
Urban/agricultural/grazing
Un-ionized ammonia (NH3)/nutrients
Region/state/local
No
State/local/academic
Modeling/full-scale testing
Yes
WWTP. upgrade/habitat
restoration/BMPs
Watershed Containing the Study Area
FIGURE 1. Location of the project site in Colorado
Summary: The Boulder Creek Enhancement Project, near Denver, Colorado (Figure 1) demonstrates a holistic approach
to water quality improvement and encompasses several aspects of the TMDL process. Although not formally submitted as
a TMDL, the enhancement project closely parallels the phased TMDL approach outlined in the TMDL guidance (USEPA,
1991). Following identification of water quality impairment, all possible causes were examined and the location and
extent of controls necessary to correct the impairment were identified. An adaptive management plan was developed to
implement the proposed controls in phases, a few at a time, to permit monitoring and evaluation of their effectiveness.
The implementation plan was modified between phases based on the evaluations.
A use attainability study, one of the first conducted in Colorado, showed that aquatic life in Boulder Creek was impaired.
Traditional monitoring indicated that instream concentrations of un-ionized ammonia were exceeded downstream of the
city's wastewater treatment plant (WWTP). Pollution contributions from each point source (the WWTP and other
dischargers) and nonpoint source (agriculture, cattle grazing, surface mining, and water diversion) along the 15.5-mile
stream section below the WWTP were evaluated to determine the most effective strategy for reducing the instream un-
ionized ammonia concentrations and improving stream conditions. This required monitoring. Data collected at the
WWTP showed it was meeting its effluent limits for ammonia, indicating either that (1) the effluent limits were not strict
enough or (2) other factors-were responsible for the impaired water quality of Boulder Creek.
Further investigation showed that high water temperature and pH were the primary causes of the un-ionized ammonia
excursions. These were linked, in part, to physical degradation of the creek's riparian zone; species diversity and density
were low even in reaches with good water quality. Therefore, more stringent effluent limits and plant upgrades alone
would not solve the problem. A combination of plant upgrades, best management practices (BMPs), and habitat
restoration was needed to improve water quality in Boulder Creek.
Contact: Bruce Zander, U.S. EPA Region VIII, Water Division, 999 18th St., Ste. 500, Denver, CO 80202-2466, phone
(303)293-1580 •,-.:••
Printed on Recycled Paper
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BACKGROUND
The majority of water quality-based permits for toxics in
Region VIII are written because of concerns related to
un-ionized ammonia and chlorine toxicity. Of particular
concern Is Ihe exposure of aquatic communities to
ammonia discharged from wastewater treatment plants
(WWTPs). In 1985, the City of Boulder Department of
Public Works needed to renew the NPDES permit for its
75* Street WWTP, a 17-year-old facility operating at
nearly 80 percent capacity. A TMDL was developed to
determine a wasteload allocation for un-ionized
ammonia. The TMDL indicatedthe need to tighten the
plant's un-ionized ammonia discharge limits, because
monitoring showed Boulder Creek was exceeding water
quality standards for un-ionized ammonia 5.6 and 8.5
miles downstream of the plant's outfall, even though
the WWTP was not violating its current discharge limits
(Windell et al., 1991). ".'.'. • "'•",
,-•.,'. --.. •' -. . ., ..'?f '.-."I
Subsequent studies, which looked at the watershed in
more detail, indicated that WWTP upgrades alone would
not solve the problem because the ammonia toxicity was
caused largely by the degraded condition of Boulder
Creek itself. Below the WWTP, the creek is
channelized, its banks are exposed and unstable, there is
little or no streamside vegetation to provide shade, and
there is a lush growth of instream aquatic vegetation.
The resulting high temperature and pH favor the
conversion of ammonia to its toxic, un-ionized state.
The City of Boulder proposed the Boulder Creek
Enhancement Project to alleviate the un-ionized ammonia
problem and defer expensive modifications at the
treatment facility. The first step would improve the
quality of the effluent at the WWTP using partial
nitrification; the second would restore the riparian zone
along the river; and the third would restore instream
habitats. The second and third steps would be
implemented in phases.
This approach to improving instream water quality by
using restorative techniques in the riparian zone in
conjunction with traditional treatment methods was
appealing for several reasons. The estimated cost was
far less than the cost of relying on WWTP upgrades
alone, and improving the physical condition of the
stream and its riparian zone would enhance the aesthetics
of the creek, making it more appealing and useful to
property owners. Also, if part of the enhanced area
could be acquired by the city for use as a public park or
greenway, it would add a valuable asset to the
community.
Both the State of Colorado and the U.S. Environmental
Protection Agency (USEPA) Region VIII believed that
the Boulder Creek Enhancement project had merit and
agreed to work cooperatively with the local community
iciijnplement it. USEPA Region VIII has provided
guidance and financial aid to Boulder to support the
city's instream monitoring efforts, the development of a
water quality model to project diel variations of instream
wafer quality, and construction costs for the plant
upgrade. The city of Longmont has also received
Support for their instream monitoring efforts which
provided data used in this project. Volunteers from the
community are providing labor and materials to aid in
the restoration of this important community resource.
Upon completion of the restoration effort, it is intended
that a new TMDL that is based on a healthy ecosystem
will be developed and permit requirements for the
WWTP will be revised.
A CHARACTERIZATION OF BOULDER
CREEK ' "
The St. Vrain subbasin (Figure 2) has a drainage area of
978 square miles (USEPA, 1992a). Boulder Creek,
from its headwaters in the Southern Rockies to the St.
Vrain, drains approximately one-third of this basin. The
region is typically mountainous tablelands with high
relief. Land in thejieadwaters is predominantly
forested, .with some agricultural activity. Western
spruce, Douglas fir, pine, southwestern spruce,
bentgrass, sedge, fescue, and bluegrass make up the
native vegetation. The dominant soil types, boralfs, are
hjoderately lerodible. In'the Southern Rockies, B"6ulder
Creek flows rapidly through narrow, relatively deep
.channels; the mountainous terrain aerates and cools the
water, providing ideal habitat for native aquatic
communities. These reaches of Boulder Creek are
considered healthy arid functional.
As.Bpulder Creek flows west toward Boulder, Colorado,
it,leayes_the Southern Rpckies and enters the Western
High Plains, In their natural state, the plains are
tcimracterizecl' by "smoothto irregular topography; d*ry
rnojlisoil soils, which are moderately erodible; and a
natural vegetation that includes grama and buffalo grass
.XQmernik, 1987). Rainfall in the vicinity of Boulder
averages about 20 inches per year (USGS, 1985).
. JSTatural soil.loss ranges from 5 to 14 tons per acre per
,year, but is reduced in payed or urbanized areas. Most
of the land^along these stream reaches is urbanized.
..The city of Boulder is located adjacent to Colorado's
front, range in the north-central part of the state. The
city has a population of more than 95,000. Wastewater
,. .treatment for the city is provided by the 75* Street plant,
?.which~discharges an average of 17 million gallons per
day into Boulder Creek (Figure 3). Base flow in
Boulder Creek at the point of discharge ranges from 10
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FIGURE 2. The St. Vrain Watershed
to 30 cubic feet per second over 9 months of the year
(Rudkin and Wheeler, 1989). Boulder Creek is
governed by water rights, however, and during periods
of high withdrawals the creek is wastewater-dominated.
Much of the area along Boulder Creek, within and to the
east of the city, has been urbanized, but grazing lands
and agriculture still constitute a significant percentage of
the area's land use. Because the land is less
mountainous, the creek assumes a shallow, meandering
character as it flows northeast from the city. Boulder
Creek is highly channelized along these reaches, which
reduces instream reaeration. Ideally, a stream should
contain about 50 percent riffle and 50 percent pool to
support aquatic life uses, but channelization in Boulder
Creek has shifted this ratio to 97 percent riffle and
3 percent pool. Channelization has also shortened the
length of Boulder Creek below the WWTP from 30
miles to 22 miles, increasing erosion and sediment
loading (Channel 28, 1990). Gravel pits and mining
operations located along the channel also discharge
sediment loads to the creek.
Un-ionized ammonia concentrations increase as the creek
flows through these reaches and away from the city.
The critical zone, in which the un-ionized ammonia
concentration reaches a maximum, occurs approximately
8.5 miles below Boulder's 75th Street WWTP outfall
(Rudkin and Wheeler, 1989). The conditions
contributing to the degradation along this stretch include
runoff, erosion, agricultural return flows, channelization,
destruction of the riparian zone, and mining
discharge—in general, poor land use practices. The
shallow water depth and lack of cover encourage a lush
growth of photosynthesizing aquatic vegetation. This
vegetation, in turn, results in higher water temperatures
and increased pH, conditions that favor conversion of
ammonia to its toxic un-ionized form. Low alkalinity
was identified as a cause of the relatively large
fluctuations in pH.
Boulder Creek, below the WWTP, is designated to be
used as a water supply and for class 1 recreation, class 1
warmwater aquatic life, and agriculture. An inventory
of the 15.5-mile segment of river below the WWTP
found that the segment was not fully supporting aquatic
life uses (Windell and Rink, 1987a). Few of the 33
species of fish expected to inhabit this segment,
including the greenback cutthroat trout, were found.
The same study, backed by additional monitoring and
analysis, indicated that potential aquatic life uses could
not be achieved, even if discharges at the WWTP were
improved, because of the existing degraded physical
condition of the habitat. Additional measures were
needed to significantly lower the creek's temperature and
pH and, subsequently, the un-ionized ammonia
concentration. A feasibility study to evaluate the
effectiveness of BMPs and restoration measures based on
previous studies and additional field data concluded that
BMPs would enhance the effects of advanced wastewater
treatment (Windell and Rink, 1987c). It also indicated
that aquatic life uses could be attained if the aquatic and
riparian habitat was restored, nonpoint source pollution
was controlled, and poor land use practices were
corrected. The following BMPs were proposed:
concentrating stream flow in a thalweg (low-flow)
channel to lower temperature and reduce aquatic
vegetation, fencing off the riparian zone to exclude
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*»
Fourmile Creek
N
I Study.
Area
Boulder Creek
cattle, installing biological reaeration structures,
enhancing wetland areas, replanting riparian vegetation,
«nd stabilizing banks. After reviewing the study, the
City of Boulder authorized support for an aquatic and
riparian habitat demonstration project.
ASSESSMENT METHODS
Monitoring
Ongoing monitoring of mid-day grab samples 5.6 and
8.5 miles downstream from the WWTP indicated that
un-ionized ammonia concentrations at times exceed the
state's standard of 0.06 mg/L for warm-water streams.
WWTP effluent data, collected monthly from January
1982 through March 1985, indicated that there were no
Violations of the total ammonia limit during winter
"jftionths (November-May) and only three violations
during summer months (June-October). The effluent
data also showed no exceedance of pH effluent limits
that would contribute to the ammonia problem. Because
effluent concentrations are well''within prescribed limits,
Snstream monitoring data were needed to indicate the
source of the problem. Unfortunately, the available data
were not sufficient to indicate whether the exceedance
Was a result of the WWTP discharge or nonpoint source
inputs. More detailed data were needed to document the
effects of, and relationship between, land use, point
source pollution, nonpoint "source* pollution, and aquatic
life potential. Existing data did indicate that nonpoint
source* pollution contributed about 60 percent of the
biological oxygen demand (BOD), 83 percent of total
dissolved solids, 82 percent of the nitrate, 30 of the
FIGURES. Boulder Creek Enhancement Project
'"Vhospha'teVand i? percent of the* ammonia loadings
(Windelletal., 1991).
To assist in characterizing the problem, a use
attainability study was completed. The study included an
it inventory of macroinvertebrates^fish, riparian
« vJgetationVaq^aWc vegetation, land use, and nonpoint
" source pollution inputs over a 15.5-mile reach
downstream from the facility (Windell and Rink, 1987a).
.' .lie results sSowef that halJfaf Degradation", as "well as
high levels of un-ionized ammonia, was impairing
:" "" " '' ....... "'"*""
Biweekly, 24-hour water quality sampling was conducted
over a year to help identify the extent and possible
causes" of the problem (Windell and Rink, 1987b). The
results showed that un-ionized ammonia varies on a diel
basisi reaching highest levels not when ammonia'
concentrations are highest, but when temperature and pH
conditions favor conversion of ammonia to its un-ionized
form. Data collected by the Colorado Department of
Health, Water Quality Control Division (1986), indicated
that high temperatures and pH values occurred
frequently. Temperatures were observed to range from
32°C in November to 80°C in May; at times, pH values
in excess of 9.0 were recorded. Another water quality
report consisted of spring and fall synoptic studies
(WindelTand Rink, 1988); This study revealed that
when pH and temperature were high, excursions of the
water quality standard occurred daily during these
seasons. Numerous other studies have provided data for
the Boulder Creek Enhancement Project (Windell and
Rink, 1992), and the conditions in Boulder Creek will
continue to be inventoried, monitored, and reported in
i
jT
Ir<
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order to assess and quantify existing and changing
conditions in the creek.
Modeling
The flow and pH data from these monitoring studies, as
well as information assembled for the 1985 TMDL,
including nitrification rates, background water quality,
and point and nonpoint source contributions to Boulder
Creek and its tributaries, were essential for developing a
mathematical model to simulate the diel variations of
instream water quality (Chapra, 1989). A model was
completed and reviewed, but results of the verification
indicated that the conditions in Boulder Creek,
particularly the pH, were too sensitive and variable to be
accurately calibrated. The highly variable sediment
loads hydraulics, weather, and algal growth left a full-
scale demonstration project as the only practical means
of testing the effectiveness of selected BMPs for
reducing un-ionized ammonia concentrations in the
creek.
POLLUTION CONTROL AND
RESTORATION EFFORTS
Point Sources
The first step of the Boulder Creek Enhancement Project
was to improve the quality of effluent at the WWTP. In
1991, the city of Boulder upgraded and expanded the
75* Street WWTP to meet the stricter discharge limits
required by Colorado's Water Quality Control Division
in its 1986 NPDES permit (permit number CO-
0024147). Both solid and liquid waste treatment were
improved. The most extensive effort involved addition
of a nitrification trickling filter (NTF) to increase
removal of ammonia from the liquid waste stream. The
new facilities have also reduced total suspended solids
and BOD to levels significantly below permit
requirements. Sludge processing and removal also have
been improved. Although the plant is expected to
continue to meet applicable water quality standards
through the year 2010, the city is continuing to refine its
new trickling filter/solids contact system. This system
provides high-quality secondary effluent to the NTF.
The city submitted a request to the Water Quality
Control Division to consider retaining current NPDES
limits for un-ionized ammonia over the upcoming permit
period (1991-1996). This would allow time to evaluate
the results of the creek enhancement project on the
instream concentrations of un-ionized ammonia. It is
hoped that the instream water quality conditions can be
met after completion of the enhancement project because
placing still-higher restrictions on plant effluent would
require very expensive modifications and yield limited
results.
Nonpoint Sources
Initial Phases
The second and third steps of the Boulder Creek
Enhancement Project were to improve the riparian zone
along the river and restore instream habitats. The goal
of Phase I was to provide cost-effective water quality
improvement, control nonpoint source pollution, and
achieve aquatic life uses by reducing un-ionized
ammonia concentrations, pH levels, and temperature in
the creek. Phase I involved the design and construction
of six BMPs over a 1.3-mile reach that passes through
the center of a heavily grazed cattle ranch. These BMPs
included constructing high-tensile, wildlife-compatible
fencing to exclude cattle from the riparian habitat;
stabilizing streambanks using log revetments; planting
crack willow and cottonwood in the riparian zone;
replacing channelized berms with sculpted or terraced
streambanks; excavating 0.5 mile of thalweg channels on
concave meander bends; and creating three boulder
aeration structures (USEPA, 1992b).
Critical zones were established for each BMP so that, in
addition to evaluating the combined effect of the
measures, the impact of each BMP could be evaluated
separately. Baseline data were collected prior to BMP
construction, and data was also collected during
construction and after implementation. Instream
monitoring included monthly sampling for water quality,
flow and temperature, as well as fish inventories and
evaluation of canopy density, ground water levels, and
physical habitat. To date, there has been little
monitoring of BMP effectiveness.
Fencing off the riparian zone was critical to the success
of Phase I. Unless cattle were successfully excluded
from the riparian zone, the impact of all other BMPs
would have been minimal. The landowner granted a
protective easement that covered more than 40 acres.
This area was fenced in to provide a 120-foot-wide
buffer between grazing land and the stream. Stretched
steel wire on hammered posts provided inexpensive and
durable fencing. Cattle crossings were designed as
rigid, hinged double gates that could exclude cattle
entirely, or could be opened to provide a temporary
corridor across the creek. Because this was a
nontraditional use of fencing, many of the design
elements needed to be tested by observing field operating
conditions. Sections of the fencing had to be rebuilt and
redesigned. Cattle crossings were particularly
challenging because it was necessary to fence across the
creek, subjecting the structure to water-borne debris and
runoff. Both the original gate design and permanent
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crossing corridors constructed of PVC mesh suspended
from cables are now used, depending on the conditions
at each site. The permanent crossings allow passage of
debris and boaters under the fence while providing a
Visible barrier to the cattle.
Phase 1, which was completed in the spring of 1990,
yielded positive results. Not only did instream
conditions improve, but community cooperation and
interest in the demonstration project were very high.
This success spurred approval of Phase II, which
extended restoration efforts over another 1.1 miles of the.
creek. Phase II reduced the impact of return flow from
an irrigation ditch by rerouting it through existing and
constructed wetlands (USEPA, 1992b). Although cattle
grazing along the Phase n reach did not pose a serious
problem, streambank revegetation was badly needed.
The individual plantings used to reyegetate during Phase
I were only moderately successful; therefore, Phase II
Jested "wattles1'and "brush layering." Wattles are
horizontal.bundles of willow cuttings buried at or near
the creek bank. Brush layering is the backfilling of
willows into the streambank parallel to the water
surface, with the growing tips projecting into the stream
(Rudldn, 1992). Construction of rock/willow jetties to
break up erosive currents was also tested. This method
Was less expensive and less time consuming than using
riprap or other traditional construction methods.
Adaptive Strategies
Communication and availability of the project team to
deal with rapidly changing conditions proved to be an
important consideration in the design and construction
process. Atypical runoff, rapid erosion, and hydraulic
modifications as a result of the project necessitated field
modification of the original design. Team members had
to respond quickly with methods to protect previously
completed work and new designs to fit the continuously
changing system.
Phase III added an additional 0.5 mile to the project.
J^o cattle were trampling the creek and its banks in this
Section, and the channel was not as severely eroded, but
the adverse .effects of surface gravel mining posed a new
challenge. Planning called for biotechnical streambank
Stabilization, revegetation, and creation of wetlands. A
chief aspect of this phase was to reduce channel abrasion
by creating low-flow channel over approximately 0.25
miles of the project area.
; ' * '"':"'-. ¥ ,i . ' . ^'
Although conditions were less severe along the Phase III
teach, the project was complicated by the need to
raevaluate planting methods and plant species use in the
bioengineering design. The crack willow used in Phases
I and 0, though prevalent along many front-range
streams, is not an indigenous species. Peachleaf willow
was used instead to be consistent with Boulder's policy
.••-.'','••'" ^•-¥s^lii•^sd;itf8^I!5^:::"•ni'^:';^rSfe:«J; rf?4l'J-4"Ssi?;Jtil.':Sif;|ll
of encouraging native plant species. The brush-layered
vegetation demonstrated effectiveness in resisting
erosion, even during high flow conditions.
Changes in the planting method used for the cottonwood
induided. replacing the whip plantings with pole
plantings. The larger, 10- to 12:fpot poles showed more
success, and this technique was recommended for
replanting the less successful areas from previous
phases. It was also determined that spring plantings had
a, better survival rate than the faH plantings done in
^irtter,mQisture,was rnore. predictable, but
uncertaintiesJnjrpring weather conditions seemed to be
outweighed by good growth conditions immediately after
planting.
Boulder provided a site within the Phase III project area,
consjructjorijupjgort, and equipment for a graduate
research project investigating the establishment of
cottpnwoods from seed along riparian corridors. A
separate research project to investigate growth of the
peachleaf willowjwas initiated at the same time. These
are multiyear projects that may provide valuable
information on the propagation of the two species. The
first.project hasjdready reported that critical soil and
mpistur|Conditions can be determinedand can haye_r ^^
significant impact on seedling survival. Future_study
will provide information on the most cost-effective
i Jjn&IJaJ^i.p^ providing proper seed growth conditions as a
component of the BMP.
!". • '5-:f|l!fTiflJpl'S*^;!!;':;
As it is designed, Phase IV of the demonstration project
will involve a LJj-rnile reach, bringing the total number
of restored creekjniles: to 4.6. Phase IV includes „.,„.,
aspects of the first three phases and incorporates the
design_ changes made after evaluating the effectiveness of
previous methods. Results from the first three phases
support expanded use of riparian plantings combined
with the use of rock buttresses placed to protect
vegetation in the earlier stages of development. A
unique aspect of_Phase IV is the proposed use of
abandoned gravel mines to remove solids from runoff
basins disarge to wetlands
polis the runoff water a bit more before it enters the
stream.
Costs
Overall project cost has included the costs of gathering
planning and evaluating results, construction,
?«"£.^y."3 vs3j"_-:<-, - *• '.--=• >" ,'i-^"-V ™ - -• ^-- ,- •-•• . « ~ .•"Y^'f-- WT»
labor, and time. Funding for these activities
• has come from federal, state, city, local, and private
. organizations. The value of the project has also been
augmented by the donation of labor, time, and materials.
. Monitoring is being conducted by a variety of agencies.
. USEPA Region VIII is assisting the cities of Boulder and
t
IK-^~"
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Longmont with the cost of instream monitoring. City
officials authorized funding for two long-range planning
studies, a use attainability study, two water quality
studies, and a feasibility study. Aquatic and Wetland
Consultants, Inc. performed all of these. Two
monitoring studies were funded by the University of
Colorado Undergraduate Research Opportunities
Participation Program (Windell and Rink, 1992). The
first was a study on the interaction of riparian vegetation
and water temperature, funded for $700. The second
study, funded for $2,500, covered follow-up monitoring
of nonpoint source pollution controls after
implementation. One study on the interaction of riparian
vegetation, temperature, and fish population in Boulder
Creek was funded for $2,500 by the W.L. Sussman
Foundation (Windell and Rink, 1992). Monitoring data
are also provided by the U.S. Geological Survey and the
Colorado Water Quality Control Division. The WWTP
monitors and reports effluent flows and concentrations as
part of the permitting process. A portion of the funding
for modeling was provided by USEPA.
The 1991 upgrade of Boulder's 75th Street WWTP was
the largest capital project in the city's history, costing a
total of $23 million. Seventy-six percent of the total
improvement cost ($17.5 million) was expended to
remove additional ammonia; the remainder was spent on
sludge processing and disposal. Costs of the treatment
plant upgrade were covered by the city of Boulder, with
some assistance from the USEPA Construction Grants
program.
The total funding for Phase I of the demonstration
project was $125,000. Colorado provided 60 percent of
this under the state's nonpoint source control program;
the remaining 40 percent was provided by the city of
Boulder. With donated time, labor, and materials, the
total worth of Phase I is estimated at $426,000 (Windell
et al., 1991). Phase II funding, at $125,000, was
similar to that of Phase I (Windell and Rink, 1992).
Phase III of the project was funded for $75,000 (Windell
and Rink, 1992), and Phase IV is estimated as having an
on-the-ground budget of $225,000. The total cost of the
completed enhancement project is currently estimated at
$1.3 to $1.4 million (R.E. Williams, Assistant Director
of Public Works for Utilities, City of Boulder, personal
communication, March 28, 1991).
CONCLUSION
Short-term results are most readily available for cost,
constructability, and durability. Each phase of the
restoration has included a post-project review to evaluate
the success of design, materials, and construction
methods. Results of these evaluations have been put to
use in subsequent phases, as was discussed earlier. The
channel may take some time to recover and stabilize
after construction of instream modifications. Because of
this, the effects of newly created thalweg channels and
streambank revetments may not be measurable for a
year or more. Improvements of the natural system
caused by plantings will take even longer to assess.
Cottonwood shading may require 5 to 10 years to show
measurable results.
Follow-up monitoring, which is often expected to
provide rapid answers following construction, will be a
long-term undertaking requiring accumulation of data as
the project matures. So far, monitoring has shown that
vegetative plantings are much more stable and effective
than predicted. Revegetation may prove even more
effective for stabilizing streambanks than revetment or
riprap. Altering planting and harvesting techniques for
Phases I and II showed that these were critical factors in
ensuring the survival of riparian plantings. Regardless
of which methods were used, however, plantings grew
extremely well when the site was prepared properly and
the plants were adequately watered and protected from
grazing and erosion.
The Boulder Creek Enhancement Project is now well
established as a full-scale laboratory to test the feasibility
and effectiveness of combining off-site nonpoint source
control measures with traditional point source treatment
to achieve water quality goals. Both the State of
Colorado and USEPA have praised the project for its use
of alternative technology. In 1992, USEPA awarded the
project a Regional Pollution Prevention award. USEPA
has also used the project as a model for a national
pollutant loading training course. Riparian restoration
has provided multiple rewards, improving wildlife
habitats and water quality as well as removing some of
the burden of meeting water quality goals from point
source dischargers.
REFERENCES
Channel 28. 1990. Boulder creek enhancement.
Prepared by Channel 28, the City of Boulder Municipal
Channel. August 1990. Running time 18:30. Boulder,
CO.
Chapra, S.C. 1989. A simple model to assess ammonia
toxicity controls for Boulder Creek. Prepared for the
City of Boulder, CO, and EPA Region VIE. March.
Colorado Department of Health. 1986. Rationale, City
of Boulder 75th Street plant, Permit Number CO-
0024147, Boulder County. Water Quality Control
Division, Boulder, CO.
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. Omerjaik, J.M, 1987;, Ecoregions of the conterminous
United States. Annals of the Association of American
Geographers 77(1): 118-125.
Rudkin, C. 1992. Combining point and nonpoint
source controls, a case study of Boulder Creek,
Colorado, Paper presented at the Symposium on
Nonpoint Source Pollution: Causes, Consequences, and
Cures, National Center for Agricultural Law, Research,
and Information, October 30-31, 1992, University of
Arkansas, Fayetteville, AR.
Rudkin, C., and R.L. Wheeler. 1989. Stream
restoration as a water quality management tool. Paper
presented at the National Conference of Water Pollution
Control Federation, October 1989, San Francisco, CA.
USEPA. 1991. Guidance for water quality-based
decisions: The TMDL process. U.S. Environmental
Protection Agency, Office of Water, Washington, DC.
USEPA. 1992a. Water quality information system
(STORET). Retrieved December 1992, U.S. ,
Environmental Protection Agency, Office of Water,
Monitoring and Data Support Division, Washington,
DC, ,...;,,
USEPA. 1992b. Boulder Creek, CO: Nonpoint source
meets point source. NFS News-Notes No. 18 (Jan.-
Feb.):5-9. U.S. Environmental Protection Agency,
Office of Water, Washington, DC.
USGS. 1985,, National water summary, 1985. U.S.
Geological Survey Water-Supply Paper 2300.
Windell, J.T., and L.P. Rink, 1987a, A use
attainability analysis of lower Boulder Creek segments 9
and 10. Prepared for the City of Boulder Department of
Public Works, Boulder, CO.
Windell, J.T., and L.P. Rink. 1987b. A one year,
biweekly, 24-hour sampling study of Boulder Creek
vw|fr quality.^ Prepared for the City of Boulder
Department of Public Works, Boulder, CO.
Windell, J,T., and L.P, Rink. 1987c. The feasibility of
reducing unionized ammonia excursions by riparian and
aquatic habitat enhancement. Prepared for the City of
Boulder Department of Public Works, Boulder, CO.
.T., and i L.RRink. ^3%^£2
synoptic water quality study of Boulder Creek between
the 75th. Street wasfewater treatment plant and Coal
Creek. Prepared for the City of Boulder Department of
Public Works, Boulder, CO.
.T:, LR Rink, and C.' Rudkin.' 1991."
Compatibility of stream habitat reclamation with point
and nonpoint source controls. Journal of the Water
Pollution Control Federation- 3 (1 >: 9- 1 2.
: : '
Windell, J.T., and L.P. Rink. 1992. A bibliography of
reports, proposals, publications, videos, presentations,
preliminary data/draft monitoring reports, and abstracts.
Aquatic and Wetland Consultants, Inc, Boulder, CO.
This case study was prepared by Tetra Tech, Inc., Fairfax,
Virginia, in conjunction with EPA's Office of Wetlands,
Oceans and Watersheds, Watershed Management Section.
To obtain copies, contact your EPA Regional 303(d)/TMDL
Coordinator.
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