There is a lot of discussion as to whether New York City should dredge in Gravesend Bay, just south of where Aqua Survey documented the presence of a huge pile of unexploded ordnance (UXO). The UXO is right under the Brooklyn side of the Verrazano-Narrows Bridge. Dredging needs to be performed to provide access to a proposed waste transfer station in Bensonhurst, Brooklyn.
We used Side Scan Sonar to define the UXO piles near the Verrazano Bridge. Most believe the munitions came from a barge that broke loose from the aircraft carrier USS Bennington on March 4, 1954, more than five years before construction of the Verrazano-Narrows began. The barge was reported to have lost 14,470 live rounds.
It’s not the city’s only recent UXO discovery. In 2012, a large, and potentially explosive, Rodman cannonball was found by construction workers during the revitalization of the Governor’s Island ferry terminal. Aqua Survey was contracted to perform both landside and underwater surveys to lower the probability of construction activities accidentally detonating munitions. No additional cannonballs or other ordnance were found.
New York City is not alone. In 2008, dredging activities in the Miami River recovered several unexploded ordnance.
Submerged, unexploded munitions are present in most countries. Whether you are building a bridge in Cambodia, performing beach renourishment in Delaware or dredging in New York Harbor, UXO can pose a potential threat. Responsible parties are forced to decide what the proper risk mitigation measures are. With new aquatic and land survey methods available, parties are able to make more informed choices.
You want to dredge or perform construction activities. How do you know if you have a potential UXO problem? First, research the history of your work site and surrounding areas. If there is a history, or suspected history, of UXO at your site or nearby, it is advisable to perform a Side Scan Survey to look for UXO on or partially embedded in the bottom. If you can identify UXO by Side Scan, you know you have a contaminated site. However, if no UXO are identified with Side Scan, you would then use an Electromagnetic Induction Metal Detection (EM) system to identify ferrous and non-ferrous objects buried in the sediments.
Always remember, no matter how diligent you are in performing historical research and using geophysical tools, there is always the possibility UXO that are present were not detected. The purpose of performing historical research and geophysical surveying is to greatly reduce the probability of detonating ordnance or inadvertently moving it to another location.
If you feel you may have UXO issues, please contact Ken Hayes at email@example.com or call us at our main number 908-788-8700.