Action Water-3.2: Onsite Wastewater Systems
Full Action Statement
Support cesspool phaseouts and onsite system maintenance region-wide, and advanced septic system upgrades or extension of central sewer service in priority areas.
Action Description and Statement of Need
About 38 percent of the Narragansett Bay Watershed’s residents are served by septic systems and cesspools (Chapter 7 in Narragansett Bay Estuary Program (2017)). Cesspools are outdated, low-performing onsite wastewater treatment and disposal systems (OWTDS) that are already being phased out in Rhode Island and Massachusetts, although thousands still remain in the Narragansett Bay region. Septic systems can threaten ecosystem and public health when they underperform or fail due to improper use, maintenance, location, or saturated leachfield soils. Residential septic systems have been linked to nitrogen loading (Valiela et al. 1992; Cole et al. 2006; Reay 2004), micropollutant pollution (Phillips et al. 2015), and organic wastewater contaminant pollution (Swartz et al. 2006) in coastal bays via transport through groundwater. Further, areas with high septic system density have been shown to contribute more to pathogen loading in waterways compared to areas with low septic density (Sowah et al. 2017). Within the Narragansett Bay region, the Coastal Salt Ponds watersheds have been the focus of significant management action to address OWTDS given the known contribution of onsite systems to water quality degradation in this area.
For priority water quality hotspots, OWTDS may be converted to central sewer service or, where sewer service is unavailable, cost prohibitive, or otherwise undesired, traditional systems may be upgraded to advanced treatment systems that deliver enhanced nitrogen removal. Wastewater treatment facility plans should be updated on a regular basis to reflect changing conditions and actual population growth.
Region-wide, efforts are needed to encourage regular inspection, maintenance, and pumping of septic systems. In Rhode Island, municipalities can establish local management programs to encourage or require OWTDS maintenance and Onsite Wastewater Management Plans to meet local needs. As of 2024, 21 towns in Rhode Island have adopted Onsite Wastewater Plans. Approved Plans make towns eligible to apply to the Community Septic System Loan Program for funding to provide interest-free loans for homeowners to fund septic system repairs and upgrades. Over the past 20 years (Spring 2024), 65 loans have been issued to 19 towns totaling 23 million dollars (Rhode Island Department of Environmental Management, Office of Water Resources 2024). RIDEM establishes minimum standards for alternative or experimental OWTDS and requires advanced nitrogen-removing treatment for new and repaired systems in targeted areas, including the Coastal Salt Pond and Narrow River watersheds. There were 8,537 alternative or experimental treatment components installed in the state as of July 2024. RIDEM cautions that these systems require a greater level of oversight to ensure they operate and perform according to design and desired level of treatment (Rhode Island Department of Environmental Management, Office of Water Resources 2024).
Massachusetts requires new construction in nitrogen-sensitive Natural Resource Areas to install nitrogen-reducing septic system technologies. Others in Natural Resource Areas must upgrade their systems by 2030, unless their town applies for a Watershed Permit to provide other nitrogen-reduction solutions. Currently, there are no Natural Resource Areas in the Narragansett Bay region. Massachusetts offers an OWTDS repair tax credit and the state’s Housing Financing Agency offers septic repair loans.
NBEP will fund OWTDS assessments, plans, public outreach, and other projects that build local capacity for improvements.
Potential Projects
Fund studies to assess the contribution of OWTDS to water pollution where there are gaps in understanding.
Support efforts to encourage property owners to properly maintain OWTDS, including those operating with advanced treatment technologies.
Outputs
White papers or other research products that document OWTDS performance in areas that currently lack information
Cesspool removals
Advanced treatment systems installed in priority areas
Outcomes
More OWTDS meet high standards of performance
More waterways previously impaired by OWTDS pollution meet designated uses
Indicators
Wastewater Infrastructure, Nutrient Loading, Dissolved Oxygen, Chlorophyll, Water Clarity, Water Quality Conditions for Aquatic Life, and Water Quality Conditions for Recreation, Marine Beaches, Shellfishing
NBEP role
Fund capacity and projects, Synthesize and communicate science
Implementing Partners
EPA Region 1, RIDEM, MA EOEEA, MassDEP, NEIWPCC, Save The Bay, URI Cooperative Extension, RI Division of Statewide Planning
Location
Narragansett Bay region
Timeline for initiation
2033-2036
Estimated costs/potential funding sources
$10M+
NBEP 320/SNEP, EPA SNEP, RI and MA Clean Water State Revolving Funds