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Mysterious plastic strands on Cape Cod beaches lead to a shocking discovery

Laura Ludwig, manager of the Center for Coastal Studies Marine Debris and Plastics Program, noticed a bloom of a new and mysterious yellow plastic tubing along the beaches of Cape Cod during a beach cleanup in in September 2021.


The yellow tubing has a thin rope-like appearance, and continues to wash up on Cape Cod beaches in varying lengths from 1 millimeter to an astounding 90 feet. The beach clean-up teams have pulled more than 2,000 ft of the plastic off of several beaches from Provincetown all the way to Newport, Rhode Island. 

After speculation that it looked similar to a material used in blasting rocks in quarries, Ludwig reached out to the U.S. Army Corps of Engineers, to see if similar tubing had been used in projects in the region. As it turns out, the tubing on the beaches was indeed explosive shock tubing that came from a Boston Harbor dredging project concluded in January 2022. The yellow plastic strand is used to transmit a signal to underwater explosives, placed to break up rocks as the harbor channel was deepened.

So, why did they let all of this material pollute the water?

The contractor involved with the project did apparently have a strategy for containment, with vessels on the surface picking up the tubing as it floated to the surface. However, much of the debris escaped, likely mixed in with rocky debris. 

As for the safety of the material, "the shock tube is made out of low‚Äźdensity polyethylene (the same plastic used to make grocery bags) and is considered safe for humans to touch. But many of the pieces are small enough for birds or other animals to eat and can create health problems if ingested" (Center for Coastal Studies).

According to Ludwig, both the U.S. Army Corps of Engineers and the contractor in charge are seeking ways to improve containment on future projects.