f Use Of Time-Domain Electromagnetics (Tem) And Passive Seismic Methods To Characterize The Subsurface In East Falmouth, Massachusetts

Time-domain electromagnetic (TEM) and passive seismic methods were used to characterize the subsurface along the seacoast near Falmouth, Massachusetts. The coastline is characterized by a series of peninsulas, or necks, that extend as much as 4 km southward from mainland Cape Cod toward the ocean and are bounded laterally by shallow saltwater embayments. The necks are comprised of unconsolidated glacial deposits up to 100 m thick that overlie crystalline bedrock. The water table beneath the necks is generally about 1 to 8 m below land surface, or less than 2 m above sea level. The fresh groundwater in the glacial deposits overlies saline groundwater, although few data are available on the depth to the freshwater/saltwater interface. Most residences on the densely-populated necks are supplied by municipal water and dispose of wastewater through individual septic systems. The onsite wastewater disposal contributes to increased discharge of nitrates and other wastewater-related contaminants into the embayments, which have been degraded ecologically by excessive nutrient inputs. Actions to reduce these inputs must be based on sound scientific understanding of the hydrogeology of the necks, but the distribution of geologic materials and subsurface freshwater is largely unknown in this part of Cape Cod. This investigation provided preliminary characterization of the subsurface electrical conductivity of Davis Neck in East Falmouth.