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USGS Assists in Recovery of the Civil War Submarine H.L. Hunley
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Recovered: The H.L. Hunley in the lifting sling.
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The Confederate submarine H.L. Hunley carved its name in history 136 years ago by being the first submarine
to sink a ship. The Hunley sank for unknown reasons on February 17, 1864, after successfully ramming a spar
containing a 90-lb black powder charge into the wooden hull of the Federal Union blockade ship USS Housatonic.
The Housatonic was destroyed. Submarine engineer Horace L. Hunley built the sub, which was only 4 ft in diameter,
40 ft long, with 16-inch-wide conning towers and was powered by a hand-turned crank operated by the crew.
The Hunley had sunk twice before. The first time, five men died and four escaped. The second time, eight
crewmembers perished, including the inventor. The third and last time, the Hunley went to the bottom with
a crew of nine aboard. Novelist Clive Cussler had located the submarine in 1995 near the tip of the north
jetty at Charleston Harbor about 4 miles off Sullivans Island, SC.
Members of the St. Petersburg Field Center (SPFC) staff assisted the National Park Service, South Carolina
Institute of Archeology and Anthropology, and U.S. Naval Historical Center in their quest to raise the sub
for historical and archaeological preservation (Fig. 1). The SPFC staff involved were Mark Hansen, Nancy Dewitt,
Dana Wiese, Bo Suthard, and Dave Bennett. Archeologists were also interested in the submarine's fateful victim
but the Housatonic was too fragmented for recovery.
Artist rendering of the sub (courtesy of
Friends of the H. L. Hunley). Note conning towers at top and rudder end at right.
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The USGS provided geological expertise to archeologists to help reveal the structure of the sediment layers
around the Hunley and the Housatonic and to understand the submarine burial sequence. This information was crucial
for planning purposes that would ultimately lead to successful resurrection and preservation of the historic submarine.
In May 1999, the USGS scientists collected chirp (high-resolution) seismic and 500-kHz sidescan data adjacent
to and over the Hunley and Housatonic wreck sites from aboard the SPFC's R/V G.K. Gilbert. Five 20-ft-long sediment
cores were collected within a distance of 25 ft from the Hunley and three cores were taken near the Housatonic site.
The cores were used for groundtruthing seismic data, and a local engineering firm analyzed the sediments for
geotechnical properties. Geotechnical properties were needed to assess the bearing capacity of the underlying
sediments during the excavation and raising process.
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Left to right: Bo Suthard, Mark Hansen, Nancy Dewitt,
Clive Cussler, and Dana Wiese.
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Mark Hansen theorizes that the historical morphologic changes of the Charleston Harbor ebb-tidal delta are
important for explanation of the Hunley's burial sequence. Tidal-flow patterns and shape of the ebb-tidal
delta were radically altered when 19,000-ft-long jetties were constructed at the mouth of Charleston Harbor
in 1890. Prior to jetty construction, the majority of Charleston Harbor's 2.2 billion ft³ tidal prism flowed
through an S-shaped main ebb-tidal channel that runs from Fort Sumter south along Morris Island, then directly
eastward at Lighthouse Inlet. During this time, tidal currents near the Hunley site were estimated to be low,
~1-2 knots. Jetty construction dramatically changed tidal-flow patterns by diverting the main ebb-tidal
channel and tidal flow directly east, to a location 300 ft from the Hunley site. Measured current flows
on the Hunley site now are 4-5 knots.
The Hunley went down on the eastern flank of the then existing ebb-tidal delta, which consisted of fine to medium
sands. Tidal currents were relatively low, consequently minimal scouring and subsequent settling occurred,
resulting in the submarine being fully exposed on the seafloor. Twenty-five years after the sinking, the jetties
induced strong tidal currents over the ship, resulting in rapid scouring and settling. The scouring/settling
process continued until contact was made with a firm Pleistocene clay layer, at which point settling ceased.
This sequence and time frame are confirmed by biofouling studies that indicate the submarine was exposed on
the seafloor surface for only 15-20 years. We suggest that the ship's rather rapid burial into anoxic deltaic
sediments helped preserve the sub by slowing the oxidation rate.
After two years of intensive geotechnical analyses, engineering, and planning, recovery efforts began in March 2000.
The Hunley was successfully raised from the ocean floor on August 8th and was returned to Charleston for
preservation. The USGS scientists were invited to witness the raising, partake in the celebration,
and meet with Clive Cussler. It will take months just to figure out how to access the interior of the sub
without damage. It will take 5-10 years to excavate the sediment-filled interior, remove the crew's remains and any
associated artifacts, and preserve the vessel. After restoration, the submarine will be on display at the
Charleston Museum in Charleston, SC. The journey of the H.L. Hunley is now complete.
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September 2000
in this issue:
cover story:
Recovery of Confederate Submarine H.L. Hunley
Crater Lake Mapping
Lake Erie Nearshore Habitat
Channel Islands
Pinnacles Area—Gulf of Mexico
Gulf of Maine
Seafloor Mapping Seminar
Ocean Science Forums
Blacks in Government
SF Bay Oil-Spill Hazards
Gas Hydrates
Presentations
Arrivals
Visitors
September Publications List
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U. S. Department of the Interior | U.S. Geological Survey
