A Watershed-Based Plan in Action
by Andrew Crance
Andrew Crance is a master's student in Coastal Marine and Wetland Studies at Coastal Carolina University, and interns with CCU’s Environmental Quality Lab where he performs field and analytical water quality work. As part of his internship, Andrew also develops scientific outreach products, like this article, for the Coastal Waccamaw Stormwater Education Consortium.
Murrells Inlet is a small town nestled in the low country of South Carolina along the Murrells Inlet estuary. The Murrells Inlet estuary watershed covers approximately 9,313 acres, with 3,108 acres being suitable for shellfishing. The productive waters and strong sea-faring culture within Murrells Inlet have led to it be dubbed “The Seafood Capital of South Carolina.”
Since the 1970’s, South Carolina Department of Environmental Control (SC DHEC), has performed routine water quality testing and found high levels of fecal bacteria throughout the Murrells Inlet watershed. These fecal bacteria pollutants serve as an indicator for the likely presence of other harmful pathogens. With public health and safety in mind, 736 acres (24%) of oyster beds previously used for shellfishing have been indefinitely closed. Oysters have been recognized as an important economic commodity for the region. They are also a keystone species that indicate the overall health of the ecosystem. Therefore, maintaining water quality standards that meet shellfish regulations is of the utmost importance.
In 2004 SC DHEC began an analysis of 24 of their monitoring sites to determine a Total Maximum Daily Load or TMDL. A TMDL calculates the maximum amount of a pollutant that can enter a water body and still have the water quality meet government regulations. The TMDL identified 8 of the 24 sites to be exceeding shellfish water quality standards. It didn’t, however, identify where in the watershed the pollution was originating from.
To investigate potential sources of the fecal bacteria, Murrells Inlet 2020 and CCU’s Waccamaw Watershed Academy in conjunction with Horry County and Georgetown County Stormwater Departments formed a volunteer water quality monitoring program. They recruited volunteers from the community to perform routine sampling. These volunteers have helped foster a stewardship ethic within the community. The data collected by the volunteers were used to put together a watershed-based plan, which was approved by the SC DHEC in 2014. The priority goals of the plan are:
- To identify the source of the fecal bacteria pollution;
- To improve the water quality by reducing fecal bacteria pollution by 80% over a 20-year period;
- To continue to highlight the history and importance of oyster fishing in Murrells Inlet;
- To increase public awareness about the sensitivity of the oyster beds and promote ways to protect this resource.
The plan is being implemented by a steering committee whose membership includes some of the water quality volunteer monitors.
To reduce the fecal bacteria pollution, several best management practices (BMPs) have been identified and implemented throughout the watershed. The structural BMPs implemented so far include floating wetlands, filter socks, and a constructed wetland. The floating wetland is an artificial island populated with native wetland plants. These plants help reduce nutrient loading and lower turbidity. The filter sock is a filter device that intercepts flowing water in a ditch or creek and filters sediments to which bacteria tend to adsorb. A constructed wetland is a wetland built by altering an upland landscape. These wetlands accept stormwater runoff which can then undergo natural filtration by the plants and soil. All of these BMP’s act to remove fecal bacteria by harboring protozoans that feed on microbes.
During 2017-2018, the volunteers sampled upstream and downstream of each BMP twice a month to monitor the effectiveness of some of these BMPs. The data show variability in the degree of bacteria removal. In the case of the constructed wetland, which was installed in 2018, more time is needed for the wetland plants to mature and thereby reach its maximum pollutant removal effectiveness.
Although the BMPs are still new and as yet few in number, there is already good news. In SC DHEC’s 2018 Shellfish Management Annual Report, three shellfishing sites have been upgraded and now meet the Approved Classification in the Murrells Inlet estuary. This means that the shellfishing area within the estuary will be expanded beginning in 2019. The data shows, however, fecal bacteria loading is significant following rain events of 4” or greater. This means that SC DHEC issues a precautionary closure at selected sites for a 24-hour period after such a rain event.
Moving forward, there is still a lot of work to be done. The Coastal Waccamaw Stormwater Education Consortium will host public outreach events to publicize what is being done and what individuals can do to be better stewards of Murrells Inlet. Stormwater managers will deploy more BMPs and try different types of BMPs. Coastal Carolina University’s Environmental Quality Lab will continue to support the efforts of the volunteer monitors who measurements at the sites downstream of the BMPs will continue to serve as an assessment of their effectiveness. This collaboration between state officials, local stormwater managers, scientists, public educators, and local citizens will help sustain the history and culture of Murrells Inlet and protect its beautiful estuary.
To read the Watershed-Based Plan visit: http://murrellsinletsc.com/environment/
To read the 2018 Shellfish Report visit: https://www.scdhec.gov/food-safety/shellfish-monitoring-program-overview/monitoring-station-reports