Potential effects of reductions in wastewater return flow on the freshwater flow system in Falmouth, Massachusetts
The U.S. Geological Survey (USGS), in cooperation with the Town of Falmouth, is simulating the potential effects of proposed changes to wastewater return flow on the freshwater system in Falmouth, Massachusetts, using an existing regional groundwater flow model.
Map showing active (yellow) and inactive (grey) area of the model used to simulate wastewater return flow scenarios in Falmouth, Massachusetts.
The Town of Falmouth on Cape Cod in Massachusetts is considering changes to their wastewater disposal system to address pollution from excess nitrogen. Nitrogen is a natural part of aquatic ecosystems, but when there is too much nitrogen (typically from human activities such as wastewater disposal or fertilizer use), it can negatively affect drinking water resources and promote the growth of nuisance vegetation and algal blooms in surface waters and estuaries. A major source of nitrogen is onsite wastewater treatment systems, such as septic systems and cesspools. Currently, most developed properties in Falmouth are served by onsite wastewater treatment systems, and the remaining properties are served by a municipal sewer system. Wastewater from the municipal sewers and septage from the onsite wastewater treatment systems are treated at the Main Wastewater Treatment Facility or the smaller New Silver Beach wastewater system, and then returned to the aquifer through infiltration beds.
Falmouth is exploring the feasibility of rerouting treated wastewater from the infiltration beds at the Main Wastewater Treatment Facility to discharge at Vineyard Sound through an ocean outfall pipe to reduce the amount of nitrogen that enters the aquifer. Along with the installation of an ocean outfall pipe, the town is considering connecting additional properties in Falmouth to the municipal sewer system. These actions would reduce the amount of wastewater return flow that is discharged on land and redirect it offshore, which may have an impact on groundwater levels and streamflow in the area. To evaluate these potential impacts on the freshwater flow system, USGS New England Water Science Center and the Town of Falmouth are using a previously published regional groundwater flow model by Walter and others (2019) to simulate potential wastewater return-flow scenarios associated with the installation of an ocean outfall.
The previously published regional model, which represents long-term average conditions based on data from 2010, is first being updated with groundwater withdrawal and wastewater discharge data to represent long-term average conditions for 2019-2023. The updated model will then be used to simulate long-term average conditions in the aquifer under two wastewater disposal scenarios: (1) installing an ocean outfall that removes treated discharge at the Main Wastewater Treatment Facility and connecting properties south of Route 28 in Falmouth to the municipal sewers; and (2) installing an ocean outfall and connecting all properties in Falmouth to municipal sewers. The simulated effects of each scenario on groundwater levels and streamflow will be evaluated using contour maps and water budgets from the model. The results from the simulations can be used to aid the town of Falmouth and other stakeholders in making scientifically based decisions about their future wastewater management plans.
The U.S. Geological Survey (USGS), in cooperation with the Town of Falmouth, is simulating the potential effects of proposed changes to wastewater return flow on the freshwater system in Falmouth, Massachusetts, using an existing regional groundwater flow model.
Map showing active (yellow) and inactive (grey) area of the model used to simulate wastewater return flow scenarios in Falmouth, Massachusetts.
The Town of Falmouth on Cape Cod in Massachusetts is considering changes to their wastewater disposal system to address pollution from excess nitrogen. Nitrogen is a natural part of aquatic ecosystems, but when there is too much nitrogen (typically from human activities such as wastewater disposal or fertilizer use), it can negatively affect drinking water resources and promote the growth of nuisance vegetation and algal blooms in surface waters and estuaries. A major source of nitrogen is onsite wastewater treatment systems, such as septic systems and cesspools. Currently, most developed properties in Falmouth are served by onsite wastewater treatment systems, and the remaining properties are served by a municipal sewer system. Wastewater from the municipal sewers and septage from the onsite wastewater treatment systems are treated at the Main Wastewater Treatment Facility or the smaller New Silver Beach wastewater system, and then returned to the aquifer through infiltration beds.
Falmouth is exploring the feasibility of rerouting treated wastewater from the infiltration beds at the Main Wastewater Treatment Facility to discharge at Vineyard Sound through an ocean outfall pipe to reduce the amount of nitrogen that enters the aquifer. Along with the installation of an ocean outfall pipe, the town is considering connecting additional properties in Falmouth to the municipal sewer system. These actions would reduce the amount of wastewater return flow that is discharged on land and redirect it offshore, which may have an impact on groundwater levels and streamflow in the area. To evaluate these potential impacts on the freshwater flow system, USGS New England Water Science Center and the Town of Falmouth are using a previously published regional groundwater flow model by Walter and others (2019) to simulate potential wastewater return-flow scenarios associated with the installation of an ocean outfall.
The previously published regional model, which represents long-term average conditions based on data from 2010, is first being updated with groundwater withdrawal and wastewater discharge data to represent long-term average conditions for 2019-2023. The updated model will then be used to simulate long-term average conditions in the aquifer under two wastewater disposal scenarios: (1) installing an ocean outfall that removes treated discharge at the Main Wastewater Treatment Facility and connecting properties south of Route 28 in Falmouth to the municipal sewers; and (2) installing an ocean outfall and connecting all properties in Falmouth to municipal sewers. The simulated effects of each scenario on groundwater levels and streamflow will be evaluated using contour maps and water budgets from the model. The results from the simulations can be used to aid the town of Falmouth and other stakeholders in making scientifically based decisions about their future wastewater management plans.