Feature: Sound Evidence
Professional Surveyor Magazine - August 2010
By Brendan Burke
During the dark hours of an early summer night thieves worked quickly on the shipwreck site, blowing a large hole in the sea floor with their propwash deflector. After exposing a pile of cannon, anchors, and other wreckage, they laid their target open like a wound, ready for looting.
Divers used hand-held sledges to pound on the cannon to see if any were made of bronze, and after ascertaining that they were all iron, they selected two for removal. They used lift bags or a derrick cable to break the guns away from their 235-year-old resting place and loaded them onto a boat. Only weeks later, divers from the Lighthouse Maritime Archaeological Program
(LAMP) in St. Augustine, Florida encountered the looted site and reported the theft to local and state authorities.
Looting shipwreck sites in many countries is illegal, and strict legislation is in place to protect the publicly owned, submerged resources. In Florida, shipwreck looting can be a felony with heavy fines and prison sentencing. Moreover, after being looted, shipwreck sites lose their integrity as intact sites of cultural value.
To monitor these sites, LAMP, the archaeological and historical research division of the St. Augustine Lighthouse and Museum, purchased a Klein
3900 Search and Recovery sidescan sonar as part of our ongoing First Coast Maritime Archaeology Project, funded by Florida’s Division of Historical Resources
. It has been used to monitor sites in northeast Florida as well as several other locations along Florida’s coast. The sonar unit can generate an image of known wreck sites on a regular basis to ensure their integrity and security.
Since its founding in 1565, St. Augustine has been continuously operated as a port city and thus is the nation’s oldest port. Ships have been wrecking in and near its waters for almost 450 years. The cannon mentioned above came from the oldest identified wreck in the area, a British sloop called the Industry, lost in 1764. Carrying a cargo of seven cannon, several single-fluke mooring anchors, and axe bits and other tools, the Industry had been commissioned by British authorities in New York to transport supplies to the newly acquired East Florida following the Seven Years War.
After sailing down the coast, the Industry was blown aground on the St. Augustine bar and soon came to grief. Hull remains have never been found, and it is possible that the cargo was essentially ”dumped” from a broken hull with the ship coming to pieces. Period records indicate that debris was strewn along the shore, perhaps indicating that the ship broke up after the initial wreck.
In 1997 archaeologists in St. Augustine discovered the wreck when a magnetometer survey conducted two years prior identified diving targets. Most of the wreck was buried, but tentative investigations had revealed its nature as a historic wreck. Excavations were planned to carefully document and retrieve artifacts for study. However, the propwash-created hole and subsequent cannon theft dashed these plans because the site was no longer undisturbed.
Instead, archaeologists had to rely on salvage archaeology to recover what they could from the exposed and delicate site. Once the protective layer of sand had been removed, artifacts could not survive the ravages of the sea. Fortunately many of the exposed artifacts were documented and removed for conservation and are now on display in our museum.
Our sonar’s two principal duties are to survey the sea floor for shipwrecks as well as to monitor known wrecks for damage, looting, or newly emerged artifacts. In response to the 1999 looting of the Industry site, LAMP ramped-up its approach to protecting submerged cultural resources around the nation’s oldest port. Known sites have had their coordinates entered into the Florida Fish and Wildlife Conservation Commission
’s (FWS) chart plotters and are prioritized as protected cultural locations. The FWS boats can monitor local sites from as much as 15 miles away, even while motoring in the opposite direction.
However, monitoring does not solely focus around illegal site disturbance. Heavy seas, sediment migration, erosion patterns, and a host of other energy sources can have detrimental effects on archaeological sites. Given the long period of historic occupation within the region, there are many unrecorded sites located at the water’s edge.
Recent History Saved through Sonar Research
A special research project undertaken by LAMP is a study of St. Augustine’s working waterfront, primarily the San Sebastian River. For almost 500 years boats have been built on this narrow and muddy ribbon of water. Until the early 20th century it was an active, but not bustling, fishing port as well as boatbuilding center for the region.
The 1940s changed all of that, and at least nine boatyards were responsible for building well over 3,000 trawler hulls, mostly for commercial shrimping. Oral histories, documentary evidence, and old aerial photographs were the primary means of preserving this past prior to our acquisition of sidescan sonar. Imagery of the river bottom has contributed greatly by filling in the gaps where other research avenues dead end.
By finding areas of automobile tire concentrations (the tires were used for fenders) where docks no longer exist, we are able to pinpoint places where shrimp boats formerly docked and were repaired. Also important is the relocation of abandoned marine railways, where the trawlers were initially launched and then hauled out for repair. Most of these old marine ways still exist below the waterline and can help us identify where historic building yards once existed. LAMP is currently reconstructing a composite image of this historic waterfront.
In June 1869, the steamer Cricket left Key West bound for New York. Her captain, A. E. Lozier, ran her north up the coast until she ran low on fuel just south of Cape Canaveral. By the time Cricket approached St. Augustine on the night of the 15th she was, as an article in The New York Times stated, “on her last stick of fuel and forced to burn bacon.” Low on steam, she came to grief between the outer and inner buoy, working in the heavy surf for three hours on a sandbar. When her keel broke, she was declared a total loss and abandoned.
In 1996, archaeologists began to work with a wreck identified during a 1995 survey that had an exposed boiler, steam engine, propeller shaft, propeller, and anchor. On and off for the next several years divers took measurements and recorded the wreck in place. During the summer of 2007, LAMP divers noticed that the wreckage was out of its original alignment as built into the ship.
Not long after acquiring the Klein 3900 sidescan sonar a monitoring trip to the steamship was undertaken to verify the site’s curvature. The initial trip and numerous recent monitoring scans all reveal that, indeed, the wreck had been distorted by the original wrecking sequence or subsequent storms.
Software provided by Chesapeake Technology, Inc.
has been used to generate image mosaics of the wreck, which, when exported to GIS software or Google Earth, can be made partially transparent to visualize wreck changes. The noticed curvature existed along the centerline of the wreck. Without physically excavating the keel structure of the vessel, it is plausible to say that the hull may be broken between the boiler and the engine. Because heavy equipment like this is usually placed amidships and low in the hull to maximize stability, it is likely that the Cricket’s keel broke where the most weight was present to work the wood to breaking point. Thus, it is possible that this steamship wreck may be the Cricket. Without the ability to mosaic the wreck site and analyze sonar imagery from different directions, identifying the wreck’s curvature would have been difficult at best, considering the very poor visibility facing divers on the site.
Before and after the Storm
While Northeast Florida has been relatively lucky in the past few years to have seen few hurricanes, we still have had our share of destructive northeasters and tropical weather. Tropical Storm Fay, which stalled over St. Augustine for almost three days during August 2008, caused substantial sediment migration around the inlet, along our beaches, and on the seafloor. Even distant storms that bring great surfing swell can create high-energy surge along shallow bottoms and can dynamically change wreck environments. Hurricane Bill, which veered out to sea during the summer of 2009, set up great onshore rollers measuring up to ten feet, which covered ongoing excavations with more than two feet of sand in as many days.
As weather continues to affect the coastline, LAMP will continue to develop site formation modeling based on weather-induced change. Sonography is the most time- and dollar-efficient way to do this.
Not only has sidescan sonar made the archaeologist’s job easier, but software that creates sonar image mosaics, such as Chesapeake Technology’s SonarWiz, enriches the data to make it easier to understand and present in meaningful ways. Mosaics of large areas in wreck-prone environments can also have the added advantage of using bottom classification to locate areas where barely exposed wreckage is magnified by its sediment plume. We see the ability to export sonar imagery to GIS, Google Earth, and other similar systems as a direct path to make sonography more relevant, useful, and a client-friendly product for cultural resource managers worldwide.
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Brendan Burke works as a staff archaeologist for the Lighthouse Archaeological Maritime Program in St. Augustine, Florida and is involved with maritime survey around Florida’s First Coast. He is currently working on an anthropological study of shrimp boat building in St.
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