Download Nonpoint Source Pollution and Constructed Wetlands in the

WACCAMAW
Identification and Mitigation of
Non-Point Sources of
Fecal Coliform Bacteria
and Low Dissolved Oxygen
In Kingston Lake and
Crabtree Canal
(Waccamaw River Watershed)
The Problem
Kingston Lake and Crabtree Canal are tributary
creeks, located near the City of Conway, S.C.,
that drain into the Waccamaw River. Routine
testing performed by the South Carolina
Department of Health and Environment
Control (S.C. DHEC) has demonstrated that
these water bodies do not meet state waterquality standards1. In 1998, these waters were
found to have unacceptably high levels of fecal
coliform bacteria and low levels of dissolved
oxygen. High levels of fecal coliforms indicate
the presence of human or other animal feces in
the water. Low dissolved oxygen levels can cause
fish kills. Section 303(d) of the Federal Clean
Water Act requires states to maintain a list of
water bodies that fail to meet standards2. This
list is revised periodically with water bodies
ranked in terms of the severity of their pollution problems and impact on classified uses.
This “303(d) list of Priority Ranked
Waterbodies Targeted for Water Quality
Management Action” is used to prioritize
remediation activities. When water quality is
improved such that the state standards are
attained, the water body is removed from
the list3.
One important activity that follows 303(d) listing is the development of a Total Maximum
Daily Load (TMDL), or pollutant budget, in
which each pollution source, point and nonpoint, is allocated a maximum discharge for the
offending pollutant. The sum of the discharges
from all the sources is set so as to prevent waterquality degradation in the receiving waters.
Following implementation of the TMDL by
performing remediation or restoration activities, a site is removed from the 303(d) list if the
state water-quality standards are attained.
TMDLs require a great deal of scientific understanding to develop. Fortunately, effective
remediation and restoration activities can be
undertaken without development of a TMDL.
U.S. Environmental Protection Agency
Funds Pollution Study
Over the past three decades, pollution from
point sources has been substantially reduced
through controls achieved via the National
Pollution Discharge Elimination System
(NPDES) permit program. This leaves diffuse,
or “non-point” source, pollution as the major
cause of continuing water quality impairments.
The U.S. Environmental Protection Agency
assists states with identifying and remediating
this non-point source pollution with funds
awarded through its Section 319 Program.
Section 319 funds were awarded in 1999 to
Coastal Carolina University to determine the
source and magnitude of the bacterial contamination and low dissolved oxygen in Kingston
Lake and Crabtree Creek and to conduct a pilot
study to demonstrate techniques for reducing
the sources of these problems. This brochure
describes the results of this Section 319
Program Project which was conducted by the
Center for Marine and Wetland Studies’
Environmental Quality Lab located at Coastal
Carolina University in Conway, S.C.
The results of this project are assisting Horry
County and the City of Conway in meeting
Kingston Lake, Crabtree Canal and the Waccamaw River are classified by the state as FW* waters (freshwater). These waters are deemed suitable
for primary and secondary contact recreation and as a source of drinking water after conventional treatment. They are suitable for fishing and the
survival and propagation of a balanced indigenous aquatic community of fauna and flora. They are also suitable for industrial and agricultural
uses. See http://www.lpitr.state.sc.us/coderegs/chap61/61-68.htm for the water-quality criteria specific for Class FW* waters.
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Copies of the 303(d) lists can be found at http://www.scdhec.net/water/html/tmdl.html.
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Kingston Lake and Crabtree Canal were on the 2000 version of the 303(d) list for high levels of fecal coliforms and low dissolved oxygen. In 2003,
they were listed for high levels of fecal coliforms but not for dissolved oxygen due to standard attainment. Most of the Waccamaw River was delisted
for dissolved oxygen in 2000 following approval of a dissolved oxygen Total Maximum Daily Load (TMDL) that mandated a reduction in pointsource loading from sewage treatment plants. Controls on non-point source inputs of oxygen-demanding substances (measured as BOD5) were not
included in this dissolved oxygen TMDL. About half of the river sites covered by the TMDL have since attained the dissolved oxygen standard.
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requirements of their NPDES Phase II
stormwater permits. This new program (effective March 2003) requires the development
and implementation of a comprehensive
stormwater management program that
includes six minimum measures: (1) public
education and outreach on stormwater impacts;
(2) public involvement/participation; (3) illicit
discharge detection and elimination; (4) construction site stormwater runoff control;
(5) post-construction stormwater management
for new development and redevelopment; and
(6) pollution prevention/good housekeeping
for municipal operations.
Point versus Non-Point Source Pollution
Point-source pollution is relatively easy to
identify and control because it originates from
discrete structures such as a sewer or industrial
outfall pipe. Federal law, under the NPDES
permit program, requires all such discharges to
be regulated by permits that control the type
and quantity of pollutant discharged. Nonpoint source pollution comes from diffuse
transport pathways such as stormwater runoff
and air currents. The NPDES permit program
has recently been expanded to cover non-point
source pollution. As a result, the City of
Conway and Horry County are now required
to hold approved stormwater discharge permits.
These NPDES Phase II stormwater permits are
designed to protect water quality by controlling
the kinds and quantity of non-point source
flows entering water bodies.
Stormwater transports pollutants deposited on
land by dislodging and carrying off solid and
dissolved particles. Normal daily activities are
responsible for depositing many of these pollutants on the land. For example, cars leave
petroleum residues and metals on roadways.
Fertilizers, herbicides and pesticides accumulate
on lawns, golf courses and farmlands. Broken
sewer lines and septic tanks can cause organic
wastes (sewage) and pathogens (disease-causing
micro-organisms) to flow into surrounding
soils. Animals, including pets, livestock, and
even wildlife, are also sources of organic wastes
and pathogens. Even clearing vegetation from
the land can be a problem, as the remaining soil
is no longer anchored in place and is easily
transported by stormwater flows. In other
words, non-point source pollution problems do
not require the presence of factories or other
industrial activity. Note that some of these pollutants are natural, but their concentrations can
be greatly elevated by human activities. These
pollutants are referred to as “contaminants.”
Drainage Patterns and Kingston Lake
Subwatershed
Since water flows downhill, stormwater runoff
tends to flow towards ditches that feed into
creeks that feed into rivers. The rivers eventually discharge into the coastal ocean. If the
land has not been covered by impermeable
surfaces, like pavement, some of the water will
also penetrate into the underlying soil. Once
the soil is saturated with water, an underground or groundwater flow can occur.
Shallow groundwaters eventually discharge
through stream banks to join river flows. This
network of flows that feed into a river is
referred to as a “watershed.” These flows can
transport large quantities of pollutants leading
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to a deterioration in the quality of the receiving
water bodies.
Scientific studies have demonstrated that pollutant levels in receiving waters, such as rivers,
increase in direct proportion to the amount of
impervious surface present in a watershed.
Impervious surfaces, such as pavements and
buildings, prevent pollutant-laden stormwater
from percolating through the underlying soils.
This forces the pollutants to move with the
stormwater as it makes its way to the river.
When stormwater is allowed to percolate slowly
through soils, natural pollutant removal can
occur. Some pollutants are removed by absorption onto the soils and some are degraded via
chemical and biological processes, such as bacterial decay. Once more than 10 to 15 percent of
a watershed’s surface area has been covered by
impervious surfaces, nonpoint source pollution from storm water runoff is likely to cause
significant water quality degradation.
The Waccamaw River Watershed is located in
one of the fastest growing counties in the
United States. More than half of the surface
area of this county is covered by wetlands,
most of which are associated with the watershed. The Kingston Lake Subwatershed drains
83,446 acres through Kingston Lake Swamp
and Crabtree Canal. It is also the location of
the City of Conway which is the sole urban
center in this watershed. The Waccamaw River
is unusual in that its path lies entirely within
the coastal plain. This causes it to be relatively
slow moving and broad, with water flowing
through wide expanses of adjacent swamps.
As the waters come in contact with swamp
soils and leaf litter, organic compounds are
leached into the river water giving it a dark
brown-to-black, but clear, tint. Natural bacteria
decompose these organic compounds, leaving
the water with low dissolved oxygen levels and
high acidity. Addition of pollutants that cause
further removal of dissolved oxygen can reduce
levels to a range toxic to fish and other animals.
These oxygen-demanding compounds4 are composed of organic matter and reduced nitrogen
associated with sewage, eroded soils, decaying
vegetation and ammonium-based fertilizers.
Waters with low dissolved oxygen levels enhance
the conversion of mercury into a more toxic
form that is readily passed up the food chain.
This is part of the reason why the Waccamaw
Watershed has fish consumption advisories.
Watershed Boundary
(total Drainage Area = 18,131 sq. mi.)
The Waccamaw River lies in the Winyah Bay Watershed, the third largest in eastern U.S.A.
Oxygen-demanding compounds are measured as the “5-day biochemical oxygen demand” or “BOD5.” This is the amount of dissolved oxygen
removed from a water sample that has been incubated in a closed container in the dark for five days at 20 degrees Celsius.
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Non-Point Source Problems
in the Kingston Lake Subwatershed
Point-source dischargers, including industry
and sewage treatment plants, are unlikely to be
the major source of pollutants to the
Waccamaw Watershed because of their limited
numbers. This project demonstrates that nonpoint sources are potentially the most significant source of the observed quality impairments
in waters around the City of Conway. Given the
projected population growth for Horry County,
these non-point sources are also likely to
increase and thereby expand water-quality
problems throughout the watershed unless
measures, such as stormwater best management
practices (BMPs), are adopted.
weeks and during five storm events throughout
a two-year period (1999-2001)5. The sample
sites were located in the tributary streams
(Kingston Lake Swamp, Kingston Lake Creek
and Crabtree Canal) and immediately downstream in the Waccamaw River (Site 1 on the
map below). Kingston Lake Swamp (Site 2)
drains a rural/agricultural area that extends
almost to the North Carolina state line.
Crabtree Canal (Site 3) is a swamp that was
channelized by the U.S. Army Corps of
Engineers in the 1960’s. It drains the suburban
outskirts of Conway. Kingston Lake Creek
(Site 4) drains part of downtown Conway and
empties into Kingston Lake. Many other
stormwater runoff pipes drain other sections
of downtown Conway and empty directly into
the Waccamaw River. By sampling at these
sites, the impact of the tributary flows on the
river’s water quality was assessed.
To determine whether stormwater runoff is a
significant source of pathogenic bacteria and
oxygen-demanding substances in the Kingston
Lake Subwatershed, pollutant concentrations
and water flows were measured on alternating
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Site 1: Conway River at the City Marina
Site 2: Kingston Lake Creek Stormwater Outfall
Site 3: Crabtree Canal/Swamp at Longs Avenue
Site 4: Kingston Lake Swamp at Country Club Rd.
Site 5: Ivy Glen planned unit development
Sampling Sites in the Kingston Lake Subwatershed
Water discharge and in-situ measurements of dissolved oxygen, conductivity and temperature were conducted by the South Carolina branch of
the United States Geological Survey.
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Site 1: Waccamaw River at the City Docks
Site 3: Crabtree Canal/Swamp at Long Avenue
Site 2: Kingston Lake Creek Stormwater Outfall
Three approaches were used to determine the
source of the fecal coliform contamination.
First, the concentration of another indicator
species, Enterococcus, which is more specific
than fecal coliform bacteria for human waste,
was measured. Second, the magnitude of
potential bacterial coliform sources was estimated from existing inventories of animals
(livestock, pets, wildlife) and their average fecal
production rates. Third, multiple antibiotic
resistance (MAR) testing of E. coli (another
bacterial species associated with animal wastes)
isolated from the water samples was used to
distinguish between wildlife, livestock, pets and
human sources of bacteria6.
All the bacteria measured in this project grow
in the intestines of animals and hence are present in their feces. If they are observed in a
water sample, other more pathogenic microbes
are likely present. Thus fecal coliforms,
enteroccocci and E. coli bacteria are used as
presumptive indicators for the presence of fecal
material and associated pathogenic microbes.
Site 4: Kingston Lake Swamp at Country Club Road
Stormwater runoff caused elevations in the
levels of suspended solids, bacteria, oxygendemanding substances (BOD5), nutrients
(nitrogen and phosphorus) and chlorophyll (a
plant pigment used to measure algal abundance) at all the sampling sites. Concentrations
Funding for the Multiple Antibiotic Resistance testing was provided by S.C. Sea Grant. Training and standardized control cultures were provided
by Dr. Geoff Scott (National Oceanic and Atmospheric Administration’s Center for Coastal Environmental Health & Biomolecular Research,
Environmental Ecotoxicology Branch).
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exceeding state and federal water-quality criteria
were frequently observed. Even during periods
without rain, relatively high levels of these contaminants were observed. Pollution observed
during dry weather flows reflects slower but
chronic releases from contaminated soils, roads,
roofs, agricultural fields and livestock operations.
These observations suggest that non-point
source pollution, as transported by stormwater
flows, is a significant and persistent problem in
the Kingston Lake Subwatershed. The impact
of this pollution was not as great in the main
stem of the river located immediately below
the subwatershed (Site 1) due to dilution from
upstream river water. Nonetheless, the effect of
stormwater runoff was observable following
rain events in the form of moderately elevated
levels of pollution.
In the case of the bacteria, fecal coliform concentrations were well correlated with the two
other indicator species, E. coli and
Enterococcus. This provided abundant confirmation of chronic pollution problems at all the
sampling sites. Frequent exceedances of swimming water criteria7 were observed even in the
absence of rain. These exceedances tended to be
extremely high immediately following rain
events, with concentrations often rising over
100,000 colony forming units (CFUs) per 100
mL. Laboratory culture studies indicated that
river water is not hospitable to these bacteria as
their numbers declined below detection within
two days. While these bacteria do not appear to
survive in river water, they do appear to have
settled into the sediments and formed viable
colonies at some locations. Boat wakes have the
potential to resuspend these bacteria leading to
elevated levels in the river.
Sewage is composed of bacteria and organic
wastes, so it was not surprising that elevated levels of suspended solids and oxygen-demanding
substances (BOD5) were also observed. (Some
of the BOD5 may also have been associated with
eroded soils.) The relative abundances of the
oxygen-demanding substances were negatively
correlated with the natural organic compounds that give the river water its tint and
normally low dissolved oxygen concentrations.
This suggests that oxygen-demanding substances from non-point source pollution are
reducing dissolved oxygen levels below the
naturally low levels. Shallow groundwater
wells installed in a pristine hard wood swamp
demonstrated that groundwater seeping into
the river is a significant natural source of oxygen-demanding substances, not from organic
matter, but from reduced iron and sulfides.
Nutrient levels (nitrogen and phosphorus) were
not elevated to as great an extent as the other
contaminants but elevated chlorophyll concentrations were observed. Chlorophyll is a green
pigment produced by algae. Thus it appears that
the nutrients supplied by the decomposition of
sewage or by fertilizer runoff were rapidly consumed by algae. This sequence of events is the
beginning of a problematic syndrome called
“eutrophication.” Once algae or their consumers
die, bacterial decomposition of their organic
remains further lowers the dissolved oxygen
levels of the water. The resulting oxygen deficits
can be severe enough to cause a fish kill. This is
most common during the summer when dissolved oxygen solubility is naturally low due to
elevated water temperatures.
The results of the multiple antibiotic resistance
(MAR) testing during dry weather suggested
that humans and domesticated animals were as
important as wildlife in contributing to the
high concentrations of contaminant bacteria
observed at all the sites. The human sources
are likely associated with broken sewer lines
and leaking septic tanks. During wet weather,
the relative importance of human and domesticated animal sources increased at all of the
sites except for the rural Kingston Lake Swamp.
This suggests that rainfall drives bacteria originating from humans and domesticated animals
into the waterways (except at Kingston Lake
Swamp). As more wildlife is present in the area
The US EPA swimming water criteria for fecal coliform, E. coli and enterococci are 200, 126 and 33 colony forming units (CFU’s) per 100 mL,
respectively, based on a steady-state geometric mean of no less than five samples taken during 30 consecutive days.
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draining into Kingston Lake Swamp, it makes
sense that rainfall would drive more wildlifederived bacteria into its receiving waters.
Estimates of fecal coliform production rates
based on populations of wildlife, pets, livestock
and emissions from septic tanks and sewage
treatment plants indicated that native waterfowl are the largest producers of fecal coliform
in the watershed. Dogs and cats are secondary
in importance. Wildlife has been observed as a
significant source of contaminant bacteria in
many other communities. These findings are
particularly frustrating as the sources appear to
be “natural.” On the other hand, these results
suggest the importance of maintaining pervious surfaces in the watershed to sustain natural
soil filtration and purification processes. This
should also help preserve adequate habitat so
that wildlife densities remain close to “natural”
levels and do not overwhelm natural purification capacities.
What Can We Do?
Two general approaches, or “best management practices” (BMPs), are used to prevent, reduce and
eliminate non-point source pollution carried by stormwater runoff. One strategy relies on the
installation of structures, such as constructed wetlands, vegetated buffers, and grassy swales, that
seek to replicate the original water flow patterns, or hydrology, of the undeveloped land. This maximizes infiltration of stormwater so that natural processes can remove pollutants. The second strategy (nonstructural BMPs) relies on passive approaches, such as environmental education and preserving pervious surfaces as part of an overall regional watershed management plan.
More detail about these approaches can be found in an educational pamphlet called South
Carolina Home*A*Syst: An Environmental Risk-Assessment Guide for Protecting Water
Quality. An interactive version is available at:
http://virtual.clemson.edu/groups/waterquality/HOMASYS.HTM.
BMPs are also referred to as Low Impact Development (LID) Practices. An excellent reference
manual on this subject, Low Impact Development Design Strategies: An Integrated Design
Approach, is available at: ftp://lowimpactdevelopment.org/pub/
Demonstration of a
Constructed Wetland
Stormwater Best
Management Practice
Traditional stormwater holding ponds are
designed to contain rain runoff and control erosion. They are not particularly attractive as the
ponds typically go dry for part of the year and
are bare of vegetation. They are often reinforced
with concrete or earthen dams. Constructed
wetlands are an alternative that improve water
quality while enhancing the appearance of the
land. To demonstrate this, we retrofitted an
existing stormwater detention pond sited at Ivy
Glen, a planned unit development located in
Conway (see site 5 on the map on page 4). This
20-acre development will eventually contain
103 single-family homes and has five detention
Dry Pond prior to retrofit into multiple-pond BMP
ponds which outfall to a county ditch tied
directly into Crabtree Canal. Our retrofit converted the largest of these detention ponds
(0.65 acres) from a shallow non-vegetated dry
pond into an extended detention, multiple
pond system.
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In this system, stormwater first enters a fourfoot deep wet pond designed to promote settling
of sediment. The outfall from this pond flows
into a created wetland. Half of its surface area is
vegetated with native species that can withstand
0 to 6 inches of standing water and the other
half with species that can withstand 6 to 18
inches. The former were also used to vegetate a
shallow shelf constructed around the wet
pond. Shallow water depths ensure exposure of
fecal coliform bacteria to destructive ultraviolet
radiation and provide habitat for wetland
plants. The latter enhances sediment removal
through baffling. Microbes living in the sediment and on vegetation consume fecal coliform
bacteria and degrade oxygen-demanding substances (BOD5). Indigenous mosquito fish
provide natural pest control. Surface areas and
volumes were designed to provide a minimum
of 72 hours storage of stormwater on site for a
two-year storm.
Monitoring work conducted from 1999 to 2001,
prior to the retrofit, demonstrated significant
water quality impairments including elevated
turbidity, chlorophyll, fecal coliform, and
enteroccocal bacteria levels. The construction
work commenced in December 2001 and was
completed in January 2002. Five thousand
indigenous wetland plants of 16 different
species, provided by Mellow Marsh Farms
(Pittsboro, N.C.), were planted in February
and June 2001. Post retrofit monitoring was
conducted from May to August 2002.
After retrofitting, we observed that within a
few days following rain events, the contaminants were reduced to levels well below state
and federal water-quality limits. Permanent
educational signage was installed at the site
explaining how the system works, and is used
to educate developers, property owners and
municipal officials in how to employ BMP’s to
reduce non-point source pollution. This is
timely because the City of Conway and Horry
County are currently refining their stormwater
ordinances in response to NPDES Phase II
permit requirements.
Non-point Source Education
and Other Outreach Efforts
This brochure represents one of several activities
undertaken as part of this Section 319 Project
to provide educational information and out8
reach on non-point source pollution. Other
efforts included a volunteer water-quality monitoring program for high-school students and
civic groups. The former was funded by the
National Science Foundation and the latter by a
U.S. EPA Education grant. These monitoring
groups are called the “Waccamaw
Waterwatchers” and are an established chapter
of S.C. DHEC’s volunteer monitoring network
(http://www.scdhec.com/eqc/water/html/
wtrwatch.html). Plans are underway to expand
this program to include the entire Waccamaw
watershed through the Waccamaw Riverkeeper
program. (Contact [email protected] for further
information.) Several teacher-training sessions
have also been conducted to help establish
similar programs elsewhere.
NSF-AIRE: High-school Monitoring Program
Playcard Environmental Center High-School Teacher Training
A select group of undergraduates from Coastal
Carolina University provided invaluable assistance in the scientific work and educational outreach parts of this Section 319 Project as part of
their own independent research projects.
National Science Foundation funding under the
Rising Tide Project also enabled a teacher from
Conway High School to participate and to
develop a laboratory exercise for middle-school
students (http://kingfish.coastal.edu/marine/
risingtide/activities.htm). The lead principal
investigator served on the advisory board of the
S.C. Non-point Source Education for
Municipal
Officials
Program
(http://www.scseagrant.org/scnemo.htm),
another U.S. EPA Section 319 program project.
U.S. EPA Education Grant: Community Monitoring Group
Funding
Provided by the U.S. EPA’s 319 Program through the SC Department of Health and
Environmental Control as IDENTIFICATION AND MITIGATION OF NONPOINT
SOURCES OF FECAL COLIFORM BACTERIA AND LOW DISSOLVED OXYGEN IN
KINGSTON LAKE AND CRABTREE CREEK (WACCAMAW RIVER WATERSHED)
Project Number C 9994629-99 FY99-03
Project Cooperators
United States Geological Survey (USGS)
City of Conway - Public Works and Planning Department
Horry County - Public Works and Planning Department
SC Office of Ocean and Coastal Resource Management (OCRM)
SC DHEC - Horry County Environmental Health Services & Bureau of Water
Castle Engineering - Implementation Site Engineer
Zimmer Development Company - Implementation Site Developer
Grand Strand Water and Sewer Authority
U.S Fish and Wildlife Service - SC Coastal Ecosystems Program
Winyah Focus Area Task Force
Waccamaw Regional Planning Commission
SC Nature Conservancy - Winyah Bay Bioreserve
P.O. Box 261954 • Conway, SC 29528-6054
Contacts
For additional information regarding this project, contact
Coastal Carolina University - Center for Marine and Wetland Studies
Susan M. Libes, Ph.D., Professor of Chemistry and Marine Science
Joe Bennett, Ph.D., Environmental Quality Lab Director
Coastal Carolina University, P.O. Box 261954, Conway, SC 29528-6054
Phone: (843)349-2218, FAX: (843)349-2545, Email: [email protected]