An interdisciplinary science team conducted submarine drilling operations to test hypotheses about ground water flow under and into the Nauset Marsh estuary system. The team used an ATV-mounted drilling rig secured to a barge to drive an electrical-resistivity probe into sediment and to collect submarine ground water samples at seven sites.
An interdisciplinary U.S. Geological Survey (USGS) and National Park Service (NPS) science team conducted submarine drilling operations at Cape Cod National Seashore. The team sought to test some hypotheses about ground water flow under and into the Nauset Marsh estuary system and to constrain the results of previous modeling efforts. NPS managers are concerned about nutrients that are entering the system via submarine ground water discharge, leading to eutrophication and harmful algal blooms. The team used a USGS all-terrain-vehicle-mounted drilling rig secured to a barge to drive an electrical-resistivity probe into sediment and (or) to collect submarine ground water samples at seven sites in Salt Pond, Salt Pond Channel and Salt Pond Bay, which are part of the estuary system.
Results are consistent with surface electrical-resistivity data collected previously. Sampling and geophysical measurements indicate that Salt Pond, a kettle pond that has been breached by rising sea level, is underlain by brackish ground water in sediment to a depth of about 45 feet below the sediment surface. Salt Pond Channel, which connects the pond to Salt Pond Bay, has nearly fresh water at shallow depths (10 ft. or less below the sediment surface). Most surprisingly, Salt Pond Bay is underlain by a layer of fresh ground water more than 50 feet thick as far offshore as measured – about 1,300 feet.