Employee Error Led to Vapor Cloud

An employee error at Dana Transport at 88 Westborough Road led to the vapor cloud that promoted safety officials to evacuate the immediate area, officials said.

The vapor cloud, which appeared to have a reddish tint, resulted when an employee mistakenly mixed four gallons of nitric acid with 20 gallons of wastewater in a 200-gallon container, Fire Chief Michael Gauthier said.

There was no leak or spill as was previously reported, officials said.

Nitric acid reacts violently when mixed with water, the chief said.

The incident occurred at about 11:15 a.m. 

No residents were in any danger, Gauthier said, but to be exceedingly cautious, officials ordered the area within a tenth-mile of the site to be evacuated.

Although North Grafton Elementary School falls outside this radius, officials decided to use "an abundance of caution'' and ordered students at the school to be bussed to Grafton Elementary School. 

Weather conditions worked in officials' favor, he said. The "perfect'' conditions, with no high winds or humidity and winds out of the north-northwest at 5 miles per hour, helped the cloud dissipate safely, he said.

The cloud headed into an unoccupied wooded area, which was also beneficial, he said.

The employee who made the error was "very lucky'' he was not injured, said Dana Transport regional representative Mike Polscelli, a Grafton native. 

He immediately recognized his error and alerted company personnel. The building was then evacuated and police were notified, as per company protocol.

Considering that trailer tractors can transport as much as 4,000 to 5,000 gallons of nitric acid, the 4 gallons involved in today's incident represented a relatively "minor incident,'' he said.

But as a town native and company resident, he said he agreed with the town's cautious approach.

Westborough Road was re-opened to traffic at about 2:15 p.m.