Cape Cod’s Wastewater Management Challenge and 208 Plan Update

Cape Cod is challenged to clean up impaired coastal water quality resulting from excess nitrogen loading from septic systems. There are 57 separate watersheds to coastal embayments that are defined by groundwater flow. Wastewater from only 3% of the developed 133,000 parcels on Cape Cod presently receives advanced treatment. The estimated volume of untreated wastewater from on-site septic systems is 9.5 billion gallons per year, of which residential use accounts for 82%. Total maximum daily loads established to restore coastal water quality indicate that an average of 54% of the septic nitrogen load will need to be reduced from watersheds to impaired waters. The wastewater flow required to be collected from the impaired watersheds is estimated at 3.2 billion gallons per year. The cost of conventional infrastructure to achieve that goal is estimated to be $4 billion to $8 billion dollars. The magnitude of the projected costs has challenged Cape Cod’s regional and municipal governments to investigate and implement innovative wastewater solutions that are affordable and sustainable over immediate and long-term time scales. The Cape Cod Commission has recently been designated as the 208 planning agency to lead the development of an appropriate response to the regional wastewater challenge. Therefore the commission will be conducting a watershed-based planning approach that includes the development of a wastewater management planning tool called the Watershed/Multi-Variant Planner. Watershed MVP combines interactive mapping, land-use and water-use data, and general cost information in a flexible application that enables the user to develop wastewater management scenarios to evaluate their cost-effectiveness in achieving water-quality objectives. Watershed MVP is a web-based scenario planning application that will allow technical experts and the general public to generate and compare wastewater management alternatives at neighborhood, watershed, and subregional scales.