Cleanup is underway in Saugatuck after a large spill of polystyrene plastic pellets, known as “nurdles,” along I-196, some of which entered the Kalamazoo River and nearby wetlands.

State officials say the spill occurred January 27 when a northbound semi-trailer left the roadway near the south end of the I-196 bridge during snowy, icy conditions. EGLE says snow had largely hidden the extent of the spill until last week’s thaw.

The pellets, used in manufacturing, stretch along the freeway shoulder for at least four miles. Some sank in the river while others floated. MDOT plans to close a section of northbound I-196 Thursday night to remove the largest pile and repair a damaged guardrail.

The Michigan Department of Environment, Great Lakes, and Energy is overseeing cleanup efforts alongside MDOT.

Nurdles are considered microplastics, which can accumulate in the environment for decades and pose risks to wildlife.