The Colorado State Patrol is investigating a single-vehicle semitrailer rollover on U.S. Highway 550 at milepost 69.8 that has closed the highway between milepost 50 at the bottom of Coal Bank Pass and milepost 70 at Silverton.

Highway 550 will likely not open until Thursday evening because of a delay in a tanker that can receive the product, Jeff Chmielewski, of the Colorado State Patrol, said in a news release.

About 7:30 p.m. Wednesday, a red Peterbilt truck-tractor hauling a tank trailer lost control while northbound on Highway 550 at milepost 69.8, just south of Silverton. The semi drove across the oncoming (southbound) lane up a small embankment and overturned onto its right side. The tank trailer separated from the tractor and rolled an additional ½ time coming to rest on its left side, near the road.

The semi, operated by Miller Transporters of Jackson, Mississippi, was hauling stabilized methyl methacrylate monomer, a highly flammable liquid used in a variety of plastics. The tank did not rupture, but an undetermined amount leaked from a valve. The tank continued to leak Thursday morning, and a tanker was on the way from Salt Lake City to offload the chemical.

The driver, Micah Rodgers, 45, of Pineville, Louisiana, was transported to Montrose Memorial Hospital for evaluation.

Colorado State Patrol Hazardous Materials technicians and cleanup and remediation crews were on scene.

There are no health hazards at this time, Chmielewski said. Motorists and pedestrians will be required to keep a safe distance, behind the road closure.

Highway 550 will remain closed until the chemical is offloaded.

Silverton San Juan Fire and Rescue Authority, Silverton San Juan County Ambulance Association, San Juan County Sheriff’s Office, Durango Fire Rescue, and the Colorado Department of Transportation are assisting with this incident.