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United States
Environmental Protection
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Total Maximum Daily Loads
THSDLs
TMDL at a Glance
Fremont Lake #20
Phosphorus TMDL
(approved September 2007)
http://epa.gov/region7/water/pdf/
fremont_lake_20_tmdl_revised.pdf
Factors causing impairment
Primary recreation designated use was impaired from
toxic algal blooms caused by excessive phosphorus
loading
Sources contributing to impairment
Lake-bottom sediments rich in organic matter,
groundwater inflow, runoff from the surrounding
watershed
Restoration options
Treating the lake with aluminum sulfate
Stakeholder involvement
Nebraska Department of Environmental Quality,
Lower Platte North Natural Resource District,
Nebraska Game and Parks Commission, and the
University of Nebraska-Lincoln
Phosphorus TMDL Implementation Prevents Toxic
Algae Blooms and Restores Recreational Uses
Visitors to the Fremont Lake State Recreation Area in east central Nebraska have a choice
of 20 sandpit lakes for fishing and passive recreational activities. However, only two of
the lakes provide opportunities for swimming, and one of those, Fremont Lake #20, was
not an option from June 2004 through June 2006. Known for its two swimming beaches
and boating, Fremont Lake #20 remained closed for approximately 25 weeks during this
two-year period because of toxic, blue-green algae. Microcystin, a toxin that some types
of blue-green algae create can produce rashes, lesions, and blisters on humans, pets,
and livestock. In extreme cases, microcystin can be fatal if ingested. After detecting
microcystin in Fremont Lake #20, management agencies closed the beaches and
posted information advising the public to exercise caution when boating or
potentially coming into contact
with the water. Figure 1 shows
the signs used to inform the
public.
The Nebraska Department
of Environmental Quality
(NDEQ) included Fremont
Lake #20 on the 2006 Nebraska
Integrated Report because the
toxic algae impaired the lake's
primary contact recreation
designated use. In 2007 NDEQ
developed the Fremont Lake
phosphorus TMDL and
implemented a strategy that
included treating the lake
with aluminum sulfate (alum)
to reduce nutrient levels and
Status of waterbody
Aluminum sulfate treatment occurred in October
2007; weekly monitoring at East Beach showed no
health alerts during 2008
Benefits to stakeholders
Safer recreational water quality, aesthetic
improvements
TOXIC ALGAE
WARNING
Beach Closed
Until Further Notice
NO
SWIMMING
Figure 1. Beach closing sign used at Fremont Lake #20.
prevent excessive algal blooms.
As a result of the treatment,
the beaches of Fremont
Lake #20 remained open to
swimmers in 2008. Figure 2
shows Fremont Lake #20 after
NDEQ treated it to remove
phosphorus.
Figure 2. Fremont Lake #20 after alum treatment.
What is a total maximum daily load (TMDL)?
It is a study or analysis that calculates the maximum amount of a pollutant that a waterbody can receive and still meet
water quality standards. The TMDL establishes a pollutant budget and then allocates portions of the overall budget to
the pollutant's sources. For more information on TMDLs, visit EPA's website at www.epa.gov/owow/tmdl.
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How are TMDLs at work in Fremont Lake #20?
NDEQ initiated the phosphorus TMDL for Fremont Lake #20 because of the presence of
algal toxins in the lake and the subsequent beach closings in 2004. From June 2004 to June
2006, 28 percent of algae toxin samples collected from Fremont Lake #20 by the Lower
Platte North Natural Resource District and NDEQ exceeded the beach-closing criterion.
The TMDL process provided the planning framework for identifying the problem,
developing a restoration goal, and determining the necessary level of controls to restore
the beneficial uses of Fremont Lake #20. Implementing the TMDL began almost
immediately after the U.S. Environmental Protection Agency (EPA) Region 7 approved it.
NDEQ is partnering with the Nebraska Game and Parks Commission and the University
of Nebraska-Lincoln to conduct weekly monitoring of the swimming beaches. Weekly
monitoring data are available online to ensure that recreational users have access to
information on the lake's conditions (www.deq.state.ne.us/Beaches.nsf/LakeSampling).
Who were the participating stakeholders and key partners?
The key partners in developing the phosphorus TMDL for Fremont Lake #20 were
NDEQ, the Lower Platte North Natural Resource District, the Nebraska Game and
Parks Commission, the Nebraska Department of Health and Human Services, and the
University of Nebraska-Lincoln. From 2004 through 2006, NDEQ and the Lower Platte
North Natural Resource District collected the microcystin samples that were used
to develop the TMDL. In 2005 the University of Nebraska-Lincoln collected the total
phosphorus samples from the lake that were used to determine the lake's trophic status.
NDEQ, the Nebraska Game and Parks Commission, and the Nebraska Health and Human
Services System collaborated to identify the microcystin concentrations at which the
beaches should be considered unsafe for swimming. NDEQ, the Nebraska Game and
Parks Commission, and the University of Nebraska-Lincoln partnered to prepare and
execute the implementation plan. NDEQ coordinates ongoing monitoring and posts
results on its Web site.
How did stakeholders participate in the TMDL process?
The overall TMDL process includes the following elements: Clean Water Act (CWA) section
303(d) listing decisions, TMDL development, and TMDL implementation. Each element
of the TMDL process provided stakeholders with an opportunity to express concerns and
share information with NDEQ and other key partners about the water quality problems in
Fremont Lake. A description of each element of the TMDL process is provided below.
Section 303(d) listing decisions
If a waterbody does not meet water quality standards (i.e., numeric or narrative criteria)
for one or more pollutants, it goes on a state's section 303(d) list. Impaired waterbodies on
the list require a TMDL for each pollutant contributing to the impairment. Stakeholders
have the opportunity to provide input during the 303(d)-listing process. Determining
that a waterbody is not meeting its water quality standards is the first step in the TMDL
process. For the Fremont Lake #20 phosphorus TMDL, NDEQ, the Nebraska Game
and Parks Commission, and the Nebraska Health and Human Services System worked
together to identify an allowable microcystin concentration to protect recreational uses
at the beaches. This concentration was used as a numeric translator to address a narrative
water quality standard. In addition, the University of Nebraska-Lincoln collected total
phosphorus data that supported the state's 2008 Integrated Report.
TMDL development
NDEQ initiated the development of a TMDL for phosphorus to address the primary
contact recreation designated use impairment in Fremont Lake #20. The ultimate goal of
restoring the lake's recreational use is linked to reducing the phosphorus entering the lake
Fremont Lake-2
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from the identified sources. Reducing the phosphorus is needed to reduce the algal growth
that produces the toxic microcystins.
The TMDL identifies two numeric end targets for determining whether water quality
standards have been attained. The first numeric end target is an annual total phosphorus
concentration of 0.047 milligrams per liter (mg/L), which was set on the basis of achieving
a Carlson trophic status index of 60 or less. The second numeric target is to have fewer
than 10 percent of microcystin samples exceed 20 micrograms per liter (ug/L). Both of
these numeric targets are translators of the narrative standard.
Through the TMDL development process, NDEQ determined that no point sources
discharge to the lake and that nonpoint and natural sources are responsible for the
phosphorus load. The largest load is from the bottom of the lake and is the result of
years of accumulation and decomposition of organic matter (e.g., leaves, algae, dead fish).
Rough fish, primarily carp and white perch, also dominate the lake and can contribute to
the nutrient problem through their excrement and resuspension of nutrients bound to
bottom sediments.
NDEQ used the Canfield-Bachman model to determine the existing phosphorus loads
to the lake and the reductions needed to achieve the target concentration. The allowable
phosphorus load was allocated to nonpoint and natural sources; because there are no
permitted point sources, the wasteload allocation was zero.
NDEQ made the draft TMDL available for public review and comment. Despite the
availability of the draft, NDEQ did not receive any public comments.
TMDL implementation
In 2007 an interagency workgroup of NDEQ, the Nebraska Game and Parks Commission,
and the University of Nebraska-Lincoln received funding from EPA and the Nebraska
Environmental Trust for Blue-green Algae Control at Fremont Lake #20. In October
2007, aluminum sulfate (alum) was applied to the lake to sequester nutrients and make
them unavailable for algal growth, thus lowering algal densities and eliminating the toxin
production. Aluminum binds chemically to phosphorus, removing the phosphorus from
the water and controlling its release from sediments to limit algal growth. Phosphorus
inactivation was determined to be the best option for treating the lake because it is a
closed system that receives only limited external nutrient loading.
Fisheries renovation was also conducted with the alum treatment. Rotenone was applied
to the lake to kill the existing fish, and the lake was restocked with bluegill, largemouth
bass, and channel catfish in June 2007.
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Total funding for the project came to just over $500,000. It paid
for staff time; equipment, supplies, and laboratory costs; the fish
renovation; algaecide and alum application; and water quality
monitoring through 2009.
What is the current status of Fremont Lake #20 as a
result of the TMDL process?
Before treatment, the beaches on Fremont Lake #20 were closed, and
health alerts were issued for approximately one-third of any summer,
making it one of the most affected lakes in the state. After the alum
treatment, the lake has experienced excellent water quality with little
algae present. Figure 3 shows the improvements in phosphorus and
microcystin concentrations after alum treatment in 2007. Average
summer phosphorus concentrations decreased from 110 ug/L to 21
ug/L, chlorophyll decreased from 82 ug/L to 8 ug/L, and microcystin
concentrations decreased from an average of 21 ug/L to concentrations
below the reporting limit of 0.15 ug/L. There were no beach postings in 2008 as the
M-
05
J-
05
Alum Treatment
50 .E
O-
05
J-
07
O-
07
Figure 3. Changes in phosphorus and microcystin concentrations in Fremont Lake
#20 after alum treatment.
Fremont Lake-3
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maximum microcystin concentration reported that year was 0.23 ug/L. Fremont Lake
#20 has remained off the health alert list, and beaches have remained open, leading to
increased recreational opportunity. The lake appears on Category 4A of the Nebraska
2008 303(d) list because a TMDL has already been developed.
How did local stakeholders benefit from the TMDL process?
Management practices applied in Fremont Lake #20 to achieve the TMDL targets and
restore the lake's beneficial uses are expected to provide the following benefits to the
stakeholders:
O Improved recreation and aesthetics. Users of Fremont Lake #20 have cleaner and
safer water to engage in their recreational activities such as swimming, fishing, and
boating. Posting water quality information online also allows users to make more
informed decisions as to their recreational activities.
O Increased tourism dollars into the local economy. As many as 800,000 people visit
the Fremont Lake State Recreation Area each year. Before treatment, Fremont Lake #20
had the reputation of being the most affected lake in the state for toxic algae. As a
result, recreational enthusiasts spread the word that the lake was not open for business.
As one of the popular lakes for power boating, it is possible that its closing resulted in
a decline in annual visitors. With improved water quality, the lake will likely help to
retain or increase the number of visitors to the recreation area.
O Established effective partnerships. The treatment of Fremont Lake #20 was made
possible through funding provided by the Nebraska Environmental Trust and the
Nebraska Game and Parks Commission. Funding for water quality monitoring was
provided by the University of Nebraska-Lincoln and CWA sections 106 and 319
funds administered by NDEQ and EPA. The cooperation among NDEQ and other
stakeholders in the watershed has established strong partnerships necessary to address
other water quality problems in the Fremont Lake watershed.
Fremont Lake-4
©EPA
December 2009 • EPA841-F-09-002M
For more information on the Fremont Lake #20 phosphorus TMDL, contact
Paul Brakhage, Water Quality Assessment Section, NDEQ, paul.brakhage@nebraska.gov, (402) 471-4224
For more information on the Nebraska TMDL Program, visit www.deq.state.ne.us/SurfaceW.nsf/Pages/TMDL
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