How Models Matter in the Three Bays Estuary and Watershed The map to the right shows a portion of the Town’s three phase, 30-year sewer plan which is designed to address the state mandate to lower the nitrogen load in our watershed to improve the health of the Three Bays estuary. The Massachusetts Estuary Project (MEP) model has been the critical arbiter of the forecast success of the sewer expansion plan. While we applaud the sewer plan and all the work our town has put into the effort, we question some of the “absolutist” conclusions of the MEP model. We are told that the area in yellow, Phase 3, which is not scheduled to be completed for over two decades, must be 100% sewered for the model to indicate successful nitrogen load reduction. We have several real-world problems with this conclusion. Are we looking at the problem myopically? A new approach or new model may help us solve the problem differently. If other interventions including stormwater management and fertilizer reductions are implemented, this would reduce the required wastewater reductions. How can that be? Some of these new technologies remove 95% or One of our main issues with the more of the nitrogen load from individual homes. Wouldn’t an expanded MEP model is that incorporating treatment area accomplish the same thing as 100% in a smaller area? new Enhanced Innovative Additionally, the EIA approach treats wastewater in situ, whereas Alternative (EIA) technology municipal treatment simply moves the treated effluent to another location appears to fall short of solving with all the associated pumping costs and long-term energy commitments. the problem when compared This removal also creates recharge considerations for the aquifer. to sewer expansion. It is important to remember that the watershed ignores town boundaries, so some treatment should include Sandwich. 4 | Barnstable Clean Water Coalition | Fall/Winter 2025 BCleanWater.org