Plan 5 – The “Preferred Plan” Advanced Innovative and Alternative (I/A) septic systems – 189 parcels would be required to convert their existing septic systems to an Advanced I/A in the first phase of the plan. If this first phase did not remove enough nitrogen to the needed level to return the pond to a healthy ecosystem, then an additional 44 units would be required to upgrade to an Advanced I/A in 2039. This is the Preferred Plan chosen by the Town, because they want to explore the possibility of using these advanced septic systems across a watershed for wastewater treatment. If the Town had picked the sewering option as its preferred option, then the DEP would not allow the Town to investigate using I/As.
Plan 5, the Advanced I/A plan, will be implemented in two phases. Phase 1 is the green colored area and the start date would be in 2025. If needed, Phase 2, which includes the yellow colored parcels, would start in 2040.
What a conversion to an I/A will involve depends on the homeowner’s current system. A cesspool would need substantial replacement, while a Title V septic might only need an additional component. There are three or four different types of I/A systems the Town is looking at to remove the necessary amount of nitrogen (Title Vs emit 40 mg/L while these advanced systems will need to emit less than 10mg/L). The Town would purchase the units and give them to the homeowner. The owner will be responsible for landscaping and installation costs. The Town will also need to set up a management entity to periodically test all the I/As to make sure they are working properly. Homeowners will pay the semi-annual fee for the testing and monitoring of the systems.
Unknowns –Using just Advanced I/As to lower the nitrogen pollution levels in an estuary has never been done before. Will the Mass Department of Environmental Protection (DEP) agree to this? Will they believe the Town’s Monitoring Plan is robust enough to achieve the needed levels? The Advanced I/As that can meet the very low nitrogen levels have still not been certified by the state for “General Use”. In addition, the costs for monitoring, reporting, and making any necessary adjustments to the I/As are still preliminary.