The hazardous material that closed the Atherton Avenue overpass over U.S. Highway 101 in Novato on Tuesday morning was muriatic acid commonly used as a pool cleaner, the Novato Fire Protection District said.
A passerby saw several containers spilled on the on-ramp around 7:35 a.m. When fire crews arrived, the chemical was emitting gas, and the Marin County Hazardous Materials Team responded.
The hazmat team neutralized the chemical from four one-gallon plastic containers with sodium bicarbonate to lower the ph level to the same level as water. Traffic was diverted away from the spill, and all roads in the area were open by 10:45 a.m., the fire protection district said.
When undiluted, muriatic acid, also known as hydrochloric acid, can lead to skin tissue burns and irritation, and inhaling the fumes can cause respiratory issues, according to the Novato Fire Protection District.
The spill caused the asphalt to bubble and release what appeared to be smoke, the California Highway Patrol said. The CHP closed Atherton Avenue between Redwood Boulevard and Armstrong Avenue.
Traffic on both sides of Highway 101 was not affected by the spill, the CHP said.
Investigators believe the four gallons of acid were not properly secured in a vehicle and slid off when the vehicle made a left turn onto the on-ramp of northbound 101, the CHP said.