KINGSTON, R.I. – November 1, 2021 – The town of Charlestown is collaborating with University of Rhode Island wastewater management experts in a pilot project to develop a comprehensive approach to reducing the amount of nitrogen from septic systems that enters the groundwater and finds its way into drinking water and the nearby salt ponds.
The collaborators were awarded a $750,000 five-year grant from the U.S. Environmental Protection Agency’s Southeast New England Program to install, test and monitor a new nitrogen-reducing septic technology, install stormwater mitigation measures, develop a community education and engagement plan, and prepare a summary document that will enable other communities to follow suit.
“The town of Charlestown has been very proactive in its wastewater management and watershed management, and this grant builds on the successful approaches that they’ve tried in the past,” said Alissa Cox, director of the New England Onsite Wastewater Training Program at URI, who will lead the project with Charlestown’s Onsite Wastewater Management Program Director Matthew Dowling.
According to Cox, septic systems in coastal communities like Charlestown can have a negative impact on groundwater, drinking water and public health. When nitrogen makes its way into groundwater, it can impair drinking water quality and create algal blooms in salt ponds that can lead to low oxygen levels and fish and shellfish kills.
“Many communities like Charlestown throughout coastal New England rely on local groundwater for drinking water and onsite septic systems for wastewater management,” said Dowling. “Unmanaged systems and comingled septic plumes can impact not only drinking water quality but also the coastal ecosystems that these communities depend on as a major component of their economies. So, investing in septic system management becomes a priority.”
The new septic technology will be tested at up to 10 homes near the western end of Green Hill Pond and the eastern end of Ninigret Pond. It is called a nitrogen-reducing layered soil treatment area system, in which a septic system’s drain field consists of a layer of sand over a layer of sand mixed with sawdust. When septic effluent moves through the layers, the sand layer converts the ammonium into nitrate-nitrogen and the sand-and-sawdust layer converts the nitrate-nitrogen into a gas that dissipates into the atmosphere instead of making its way into the groundwater.
Cox said this technology is far less expensive than the proprietary technologies many companies are seeking to install in similar places, some of which can cost up to $40,000.
“We’ve seen this layered soil treatment system working in other parts of North America, especially Canada, Florida and Cape Cod, and we’re trying to bring it to Rhode Island and other parts of New England,” Cox said. “Instead of using one of the expensive proprietary systems, you can use this non-proprietary drain field to reduce nitrogen. It’s another option homeowners can consider.”
URI’s role in the project is to assist with the design, installation and monitoring of the new layered soil treatment area systems and compare them to the performance of the more expensive, proprietary systems installed elsewhere. Other partners are Save The Bay, which will install stormwater mitigation measures to reduce the impact of stormwater runoff on the salt ponds, and the Salt Ponds Coalition, which will conduct water quality monitoring to assess the impacts of the installations.
Cox and her colleagues will work with all of the partners on the public education and engagement component of the project.
“My vision is to create watershed celebration days where we have a series of tours of the new layered systems and stormwater management measures so people can see and learn more about them,” Cox said. “It might be like a combined block party and tour to engage the community. We’ll reach out to cultural and historical representatives of the watershed to provide cultural perspective and community engagement, along with other community groups, to make it more of a celebration and to give folks an understanding of these new tools for protecting the watershed.”
By the end of the five-year project, Cox expects to have prepared a blueprint in collaboration with the town of Charlestown for how other coastal communities with a large number of septic systems can improve their watershed management while meeting regulatory requirements.
“Our final report will be a case study of our successes and the lessons we’ve learned so it can be used to train other communities,” Cox said.