Chemical vapor plume at Wells Concrete in Cary causes excavation of 70 employees

All 70 Wells Concrete employees in the building Tuesday morning safely evacuated after an improper chemical mix caused a vapor plume, the Cary Fire Protection District said.

Emergency responders were dispatched at 4:47 a.m. Tuesday to Wells Concrete, formerly Spancrete, at 4012 Northwest Highway outside Cary, with first crews arriving on scene within five minutes, according to a news release.

While initial reports were for a structure fire, firefighters learned that it was no fire but instead a vapor plume in the production area of the building, the release states.

The plume occurred when Wells Concrete employees mixing chemicals in a 55-gallon drum as part of their normal work process did not mix the right concentrations, causing a chemical reaction and chemical to leak out of the drum, according to the release.

Prior to evacuating, employees dumped an absorbent over the spilled area to stop the chemical chain reaction, the release states. Several overhead doors were also left open so the plume could ventilate from the building.

The Wonder Lake Fire Protection District was asked to bring its airboat – which has a large fan – so it could be used to further ventilate the building, according to the release.

In addition to Wonder Lake, firefighters from the Algonquin-Lake in the Hills, village of Barrington, Barrington-Countryside, Fox River Grove, Nunda Rural and Wauconda fire departments through their automatic aid agreement.