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Field-Testing the New USGS Portable Auger Drilling System (PADS) in Louisiana and South Carolina
The inaugural trip for the PADS was to Cocodrie and Port Fourchon, LA, over September 16-23. Phil McCarty and Mike Brown (University of New Orleans) assisted Jack Kindinger (principal investigator), Jim Flocks, Chris Reich, Nick Ferina, and Chandra Dreher (all of USGS) in testing the coring capability of the system. In Cocodrie, the first day was spent working out some of the kinks. On the second day, the PADS reached a depth of 50 ft and obtained near-continuous cores of typical deltaic sediment. The system was moved to Port Fourchon, where only 1 day of coring was conducted before having to pack up and leave because of the approach of Hurricane Isidore. All work in Louisiana was conducted from an aluminum barge in 2- to 3-ft water depth. From October 8 to 17, Chris Reich, Nick Ferina, and Jason Greenwood (USGS) conducted drilling with the PADS at North Island, SC, a heavily wooded sand spit approximately 10 mi long by 1 mi wide, bordered by Winyah Bay to the west and the Atlantic Ocean to the east. We worked in cooperation with Eric Wright (assistant professor of marine science at Coastal Carolina University, Conway, SC) and were assisted in the field by Eric, Scott Harris (also an assistant professor at Coastal Carolina University), and five undergraduate students. Because the only access to North Island is by boat, the PADS and a four-wheel ATV were transported to the island on an aluminum barge that was driven partly up onto the beach, where the equipment and ATV were unloaded. Site 1 was located along the axis of the island. A depth of approximately 40 ft was reached with the auger; however, no core was recovered, owing to running or flowing sands, which tend to plague most other drilling systems, as well as the PADS. Running sands occur when drilling reaches the water table and fluidized sand flows upward into the core barrel. Standard core catchers located at the base of the inner barrel cannot retain these sands. The water table was less than 5 ft deep at site 1. Because we were unable to take a core, we decided to drill to bedrock (approximately 40 ft down) and sample the sediment on the auger flights as they were withdrawn from the ground. This plan worked well. Sediment texture ranged from green-gray fine sand at the top of the hole to light-cream-colored lime mud with coarse quartz grains at the base. The lime mud is probably a residual product from weathering of the limestone bedrock.
Site 2 on North Island was on the foredune set. It took 1 day to break down the PADS at site 1 and move it over a series of large dunes with the ATV to site 2. Drilling at site 2 proved to be more difficult because the auger pipe stopped at a depth of approximately 25 ft for unknown reasons. Again, running sands kept us from obtaining any sediment cores. The auger pipe was eventually retrieved, and the PADS was dismantled and hauled back across the island to be loaded on the barge for the long boat ride back to the dock. Overall, this system has a strong potential for work in many environments. The problem with running sands is being addressed, and solutions will be tried and tested. At present, at least five potential projects have a need for the PADS.
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in this issue:
Adriatic Sea Sediment-Transport Cruise Assateague Island Vegetation Mapping Field-Testing New Portable Drilling System Woods Hole Field Center Open House St. Petersburg Field Center Open House Fourth-Graders Tour St. Petersburg Field Center
Planning Gas-Hydrates Research Science and Politics in Ecosystem Decisions Louisiana Coastal-Restoration Advisory Board Air Medical Transport Center Tour |
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U. S. Department of the Interior | U.S. Geological Survey
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