Section 319
NONPOINT SOORGE PROGRAM ACCESS STORY
Removing Legacy Pollutants Restores Fish Consumption Use
\A/ t h H I H The Texas Department of State Health Services (DSHS) banned people
V VdlGrDOOy I mprOVGO from possessing fish taken from Lake Como because the tissues of these
fish contained high concentrations of potentially harmful chemicals. The
fish possession ban prompted the Texas Commission on Environmental Quality (TCEQ) to include Lake Como
on the state's 1996 Clean Water Act section 303(d) list of impaired waters. In response to the water quality
problem, local, state and federal agencies implemented a range of best management practices (BMPs) in the
city of Fort Worth. Recent risk analyses by the DSHS have shown that fish tissue pollutant levels have dimin-
ished sufficiently to rescind the fish possession ban. The TCEQ determined that Lake Como is fully support-
ing its fish consumption use and removed the lake from the 2008 303(d) impaired waters list.
Problem
Lake Como is a 10-acre impoundment of an
unnamed tributary to the Clear Fork Trinity River
in Fort Worth (Figure 1). The lake drains a 743-
acre watershed that is 65 percent residential.
DSHS issued a ban on the possession of all
fish species from Lake Como in 1995 because
of elevated levels of several legacy pollutants
including polychlorinated biphenyls (PCBs) and
the pesticides chlordane, DDT and dieldrin. In
1996, TCEQ added the lake to the state's 303(d)
list of impaired waters due to impairment of its
designated fish consumption use.
Legacy pollutants are those pollutants that
have been banned or had their uses restricted,
yet remain in the environment. These materials
were widely used in the past in products such
as pesticides, coolants and lubricants. Area
soils were contaminated through direct appli-
cation, leaks and spills. Extensive urban devel-
opment in the watershed caused contaminated
soils to erode and accumulate in Lake Como.
The pollutants then entered the food chain and
became concentrated in fish tissue.
In 2001 TCEQ and EPA approved a total
maximum daily load (TMDL) for Lake Como for
legacy pollutants in fish tissue. The endpoint
of the TMDL was to restore the fish consump-
tion use by meeting the DSHS' criteria for con-
taminant levels. The DSHS procedures specify
that the additive risk of all contaminants
cannot exceed either the cancer risk level or a
non-carcinogenic hazard index.
Figure 1. Lake
Como in Fort
Worth, Texas.
Project Highlights
Fort Worth's Environmental Management
Department (FWEMD) operates the
Environmental Collection Center (ECC), a perma-
nent, year-round facility that accepts household
hazardous waste from residents of Fort Worth
and other areas. The ECC modified its record
keeping to track the amounts of legacy pollut-
ants collected. The city used the information as
a measure for evaluating its pollution prevention
program and targeting its educational efforts.
Fort Worth educates residents about local
watersheds and the inherent problems associ-
ated with the use of pesticides. The city holds
Lake Festivals and cleanup events. In 2004,
the event included more than 30 information
booths and educational activities. The city also
installed a message board at the lake to provide
water quality information. FWEMD produced a
stormwater pollution prevention public service
advertisement shown at local movie theaters.
To reach a wider audience, FWEMD staff made
presentations about water quality issues to
numerous groups in the Fort Worth area.
The U.S. Geological Survey (USGS) conducted
sediment and runoff sampling and analysis to
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evaluate loading of legacy pollutants, trends
and sources of pollutants. The DSHS collected
fish tissue samples for developing a quantita-
tive risk characterization that was the basis of
a revised health risk assessment that DSHS
adopted in 2008.
Results
Sampling of sediments in the reservoir detect-
ed all four legacy pollutants responsible for
the fish consumption bans. However, con-
centrations of DDE, PCBs and chlordane have
declined in Lake Como sediment since the
1960s. Results of core samples taken in the
lake show a decrease over time in the pollut-
ants of concern, with the exception of dieldrin.
Sampling of residential stormwater outfalls
showed that legacy pollutants were present
and being transported in urban runoff.
Pollution prevention and source control prac-
tices helped reduce legacy pollutant levels.
Fort Worth's educational program led to a
21 percent increase in the number of citizens
using its permanent household hazardous
waste facility. As of 2006, ECC collected and
logged more than 8,000 pounds of materials
containing legacy pollutants.
Mean TMDL Contaminant Concentrations in Fish Tissue
Lake Como, TX
(n=4) 1997 (n = 5j
n - number of samples
nd - all samples less than detection limit
na - samples not analyzed for contaminant.
Raw data obtained from the Texas Department of State Health Services
• Chlordane
• Dieldrin
ODDE
npCBs
Figure 2. Trends of chlorinated hydrocarbons in Lake Como core
sediment and Lake Como inflow suspended sediment. Kendall's
tau rank correlation test was used to indicate whether there was
a statistically significant relation between concentration and time,
from 1965 to top of the core.
The combination of these investigations, man-
agement activities and the natural attenuation
of the pollutants proved to be effective for Lake
Como. Recent fish tissue monitoring shows that
concentrations of legacy pollutants comply with
the endpoint target in the TMDL (Figure 2). For
example, chlordane fish tissue data collected
in 1994 show a mean value of 1.78 milligrams
per kilogram (mg/kg) and a range of values from
1.00 to 2.90 mg/kg. By 2008, data showed that
chlordane concentrations in fish tissue had
declined to mean of 0.036 mg/kg, with a range
of values from 0.013 to 0.086 mg/kg.
The final risk assessment by DSHS found that
"no single contaminant in fish from Lake Como
increased the likelihood of systemic or carci-
nogenic health outcomes in people who eat
fish from this lake." Additionally, DSHS risk
assessors found no increase in the lifetime
excess cancer risk with simultaneous exposure
to more than one contaminant. This exposure
scenario also does not increase the risk of sys-
temic adverse health outcomes in those who
would regularly consume fish from Lake Como.
These findings demonstrate that historical
contamination has attenuated, resulting in
reduced fish tissue concentrations. Because
of the actions taken to restore Lake Como, and
since PCBs and the pesticides bioaccumulat-
ing in fish tissue are all banned, TCEQ believes
levels in fish tissue will continue to decline. On
the basis of the DSHS findings, TCEQ deter-
mined that Lake Como is fully supporting its
fish consumption use and removed the lake
from the state's 2008 303(d) impaired waters
list. Periodic monitoring of fish tissue in the
future will serve to confirm that concentrations
remain below levels of concern.
Partners and Funding
Fort Worth contributed to the project by
educating the public and collecting hazardous
household waste. USGS investigated legacy
pollutants in sediments. TCEQ and USGS each
contributed $39,000 for the joint investigation.
TCEQ contributed approximately $25,000 in
EPA section 319 funds to cover the DSHS's
analytical expenses. DSHS matched the grant
with salaries and in-kind services to collect the
samples and develop the risk characterizations.
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-08-001BB
September 2008
For additional information contact:
Roger Miranda
Texas Commission on Environmental Quality
Water Quality Planning Division, TMDL Team
512-239-6278 • RMiranda@tceq.state.tx.us
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