Summary Information for Field Activity 2005-035-FA

Area of Operations: Salt Pond, Salt Pond Channel, Salt Pond Bay, Cape Cod National Seashore, Massachusetts, United States, North America, North Atlantic

Dates: August 22, 2005 to August 26, 2005

Chief scientist: John Bratton

   John Colman, USGS-WRD-MA/RI

Objectives: Drilling from barge using ATV-mounted rig (supplied by USGS-WRD-Northborough, MA) to collect groundwater samples from beneath Salt Pond, Salt Pond Bay, and connecting channel.

Type of Activity: Sampling;

Information to be derived: Subsurface electrical resistivity profiles

Summary: Article for Soundwaves by John Bratton, September 9, 2005: Drilling for Submarine Ground Water in Old Cape Cod. In order to test some hypotheses about groundwater flow under and into an estuary at Cape Cod National Seashore, and to constrain results of previous modeling efforts, an interdisciplinary USGS science team conducted a drilling operation in late August (22-26). National Park Service managers are concerned about nutrients that are entering the estuary via submarine groundwater discharge that are leading to eutrophication and harmful algal blooms. The team used a USGS ATV-mounted drilling rig secured to a barge (Fig. 1) to advance an electrical resistivity probe or collect submarine groundwater samples at seven sites in Salt Pond, Salt Pond Channel, and Salt Pond Bay (Fig. 2). 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 sediments to a depth of about 45 feet below the sediment surface. The channel connecting the pond to the bay has nearly fresh water at shallow depths (10 feet below sediment surface or less). Most surprisingly, Salt Pond Bay is underlain by a layer of fresh ground water over 50 feet thick as far offshore as measured (about 1300 ft). Groundwater sampling was conducted by John Bratton, John Crusius, and Dirk Koopmans (USGS-GD-Woods Hole). Andy Massey (USGS-WRD-MA/RI) operated the drill rig and Tim McCobb (USGS-WRD-MA/RI) operated the resistivity probe. Contractors Mark Avakian and Len Perry (TG&B, Inc.) operated the barge and secured anchors and spuds. Divers Michael Casso and Sandy Baldwin (USGS-GD-Woods Hole) helped remove drill pipe left in the pond after drilling was complete (Fig. 3). John Colman and Denis LeBlanc (USGS-WRD-MA/RI) provided helpful input during the design and implementation stages of the field effort. The work was supported by the Coastal and Marine Geology Program, and the MA-RI Water Science Center. Captions: Fig. 1 Andy Massey (USGS-WRD-MA/RI) operates a drilling barge that is temporarily stranded during low tide on a mudflat at Cape Cod National Seashore. Fig. 2 Approximate drilling locations in Salt Pond, Salt Pond Channel, and Cape Cod Bay. Fig. 3 Divers Michael Casso and Sandy Baldwin (USGS-GD-Woods Hole) prepare to enter Salt Pond to remove submerged drill pipe near the center of the pond.

Contact: John Bratton (jbratton@usgs.gov)

InfoBank: uses the identifier B-1-05-CD. Visit this site for more information.

Related Links: http://soundwaves.usgs.gov/2005/10/fieldwork3.html