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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. 2 Copies of the 303(d) lists can be found at http://www.scdhec.net/water/html/tmdl.html. 3 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. 1 1 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 2 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. 4 3 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 5 3 4 2 1 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. 5 4 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). 6 5 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. 7 6 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. 7 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]