|
||||||
|
|
|||||||
|
||||||||
|
Drilling for Submarine Ground Water at Cape Cod National Seashore
An interdisciplinary U.S. Geological Survey (USGS) and National Park Service (NPS) science team conducted submarine drilling operations at Cape Cod National Seashore from August 22 to 26. 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 (ATV)-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 in 2004. 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 ft 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 ft thick as far offshore as measured (about 1,300 ft).
Ground-water sampling was conducted by John Bratton, John Crusius, and Dirk Koopmans (USGS, Woods Hole Science Center, Woods Hole, MA). Andy Massey (USGS Massachusetts-Rhode Island Water Science Center, Northborough, MA) operated the drill rig, and Tim McCobb (also USGS, Northborough) operated the resistivity probe, a Geoprobe Systems Direct Image tool modified for marine work. Contractors Mark Avakian and Len Perry (TG&B, Inc.) operated the barge and secured anchors and spuds. Divers Michael Casso and Sandy Baldwin (USGS, Woods Hole) helped remove drill pipe left in the pond after drilling was complete. Evan Gwilliam and Kelly Chapman (NPS, Cape Cod National Seashore) provided a continuous tide-stage record. John Colman and Denis LeBlanc (USGS, Northborough) provided helpful input during the design and implementation stages of the field effort. The work was supported by the USGS Coastal and Marine Geology Program, the USGS Massachusetts-Rhode Island Water Science Center, and Cape Cod National Seashore.
|
 |
in this issue:
Sonar Survey of Sea-Floor Habitats Drilling for Submarine Ground Water
USGS and Elementary School Receive Mayor's Top Apple Award
Chinese Delegation Visits USGS to Discuss Gas-Hydrate Studies
|
||||||||||||||||||||||||||||||||||
U. S. Department of the Interior | U.S. Geological Survey
previous story
