Offshore Vibracore Investigation of Potential Beach Sand Borrow Areas


As part of its responsibility to maintain the beaches throughout New Jersey and Delaware, the U.S. Army Corps of Engineers (USACE) uses offshore borrow areas to hydraulically dredge and pump sand back to the beaches, thus replacing the sand lost from rising sea levels and storms. Typically, suitable borrow areas are identified by collecting sand samples via the process of vibracoring.


Montrose team members were tasked by the USACE to manage and oversee the vibracoring investigation and identify suitable borrow areas needed to replenish the sand across New Jersey and Delaware. The operation would take place on a live-aboard boat roughly two to three miles offshore. Aside from the potential adverse weather conditions the team would encounter throughout the project’s duration, they would also have to contend with the possibility of accidentally bringing aboard unexploded ordinance.


Living aboard a boat provided by the USACE, Montrose experts collected core barrels of beach sand. To do so, the team used an advanced vibracore drilling method that vibrates the core barrel at a high enough frequency to make the barrel sink under its own weight. When the core barrel was extracted, the core was placed on a specially constructed plexiglass trough that hung off the side of the boat. The plexiglass trough served as a blast shield that enabled the team to screen the core for unexploded ordinance. Once the core was deemed safe and brought aboard the vessel, sand samples were then collected for laboratory classification. Additionally, the Montrose team also used underwater photography and a clamshell sampler to assess a contractor’s claims of extra costs associated with working a particular borrow area. At the completion of the vibracore investigation, the areas were found to be viable borrow areas for sand replenishment

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