Three people reported “pins and needles” sensations while in the water at Menemsha’s Crab Corner on July 15, according to harbormaster Ryan Rossi, who believes stray voltage was at play. Chilmark selectmen have voted to shut Crab Corner as a result. After consultation with Cole Powers, Rossi has formed a theory as to where that voltage came from and why. Through his company, Powers Electric, Powers, previously Chilmark’s inspector of wires and now the town’s assistant inspector of wires, made electrical infrastructure upgrades in Menemsha topping $350,000, which were meant to stop a previous stray voltage problem and safeguard against new ones, among other things.
Rossi said Powers told him he did not believe those upgrades or any other harbor electrical infrastructure caused the sensations people felt, but that a visiting boat was to blame. Just-installed electrical pedestals along the bulkhead between Crab Corner and the Menemsha Texaco are, Rossi said, adherent to the latest codes, and therefore will shut off electricity to any vessel receiving shore power if an electrical fault occurs. Shutoffs have already happened to boats using these pedestals several times this season, he said. However, the electrical pedestals on the transient dock don’t possess this technology, though they are still up to code based on when they were installed, he noted. When a vessel with a faulty electrical system takes a slip at the transient dock and taps shore power, the pedestals cannot detect electric faults, and don’t cut power as a result. Therefore the voltage that has seeped into the water seeks to ground itself, he said.
The suspicion, Rossi said, is that the voltage from such a vessel travels to the steel bulkhead along the rim of the harbor. The electric field this boat-to-bulkhead phenomenon makes is believed to be what the folks in the water may have experienced. Rossi described it as a “battery” effect, and said he was told by Powers that the closer an electrically problematic vessel is berthed to the bulkhead, the stronger the field becomes. Rossi said it was impressed upon him such a field could fatally electrocute someone in the water in some instances. Upon hearing that, Rossi said, he moved to close Crab Corner.
Asked if the pedestals on the transient dock could be upgraded with a ground-fault system, Rossi said probably not at this time, because far too many vessels are ill-suited to plug into them, and would immediately trigger a ground-fault shutoff. Rossi estimates 50 percent of vessels that visit the transient dock would trigger a ground-fault system. Moreover, since four vessels can plug into one pedestal on the transient dock, one bad-apple boat could knock out shore power to three other boats if it triggered the pedestal’s ground -fault system.
The problem, he said, lies with vessel electrical codes, which have not kept pace with marina electrical codes. Rossi said he is looking into devices that will analyze the safety of a vessel’s electrical output as an interim remedy. Rossi said his department’s goal is to reach out to the boating public and inform them of the need to upgrade their vessel’s electric systems.
“We’re not the only marina that’s having this problem,” Rossi said.
Chilmark inspector of wires Rob Young declined to comment about Crab Corner. Powers could not be reached for comment.
