KENNEBUNK — A Kennebunk firefighter and member of the York County Hazardous Materials Response Team was shaken up Monday after being thrown off a ladder and onto a concrete floor by an explosion inside a building at the Kennebunk sewage treatment plant.

Kennebunk Fire Chief Stephen Nichols, who was outside the building, said it sounded “like a bomb going off” inside the plant.

The firefighter, whose name is not being released due to health care privacy laws, was transported to Southern Maine Health Care in Biddeford as a precautionary measure. The firefighter, who was wearing a suit and airpack at the time of the explosion, was released after being checked out by doctors.

“He is probably going to be a little sore in the morning,” Nichols said.

Nichols said employees at the treatment plant at 71 Water St. called him Monday morning around 10:40 a.m. to report that a worker might have inadvertently mixed two chemicals in a holding tank at the plant.

Nichols, who established the county’s hazardous materials team, called in the county team as well as a hazardous materials team from the Portsmouth Naval Shipyard in Kittery. Nichols is planning to retire at the end of this month.

It took a couple of hours for the teams to get organized and in position before the York County team entered the sewage treatment plant. The Kennebunk firefighter climbed a ladder on the storage tank and dropped a stick of litmus paper into the tank to measure acidity levels.

Nichols said the litmus paper triggered a chemical explosion that blew the firefighter off the ladder. He fell backwards and landed on the plant’s concrete floor – a drop of about 10 feet.

The explosion, which bent some interior piping, took place around 2:30 and set off the building’s sprinkler system.

The explosion created a gas cloud. After it dissipated, another hazardous materials team entered the building to make sure it was safe. Nichols said that by Monday night the plant had returned to normal operations.

Customers of the sewer district were not affected by the incident, Nichols said.

Dennis Hoey can be contacted at 791-6365 or at:

dhoey@pressherald.com