WATERVILLE — The cause of a frozen pipe that burst last weekend at Waterville Public Library — damaging the building and hundreds of books — was the fact that insulation had become dislodged from around an air-handling grill in a wall, allowing cold air to enter the wall.

City Engineer Greg Brown said Thursday that the grill allows outside air to enter a building or exhausts building air to the outside. When workers tore the library wall apart, they discovered the problem, Brown said.

“We’ll have Houle’s Plumbing Heating & Air Conditioning come in and relocate the lines and insulate properly so this never happens again,” Brown said.

Library employees discovered when they arrived at work Saturday morning that a copper pipe in the ceiling of the staff work room on the ground floor had burst, sending a jet of water through an open doorway to the room containing the children’s nonfiction stacks and covering the carpeted floor of that room and the staff room with about 2 inches of water. The water seeped from the nonfiction room down a ramp and into the lobby of the library, the main entrance of which is off Appleton Street.

The wall where the air-handling grill was located is on The Concourse side of the building and just feet from the pipe that burst.

Walls and ceiling tiles were damaged and at least 500 nonfiction children’s books about animals, natural history, wildlife, science, geography and other topics were destroyed, as were three staff computers, a color copier and furniture. Officials are assessing whether other books are salvageable.

The library was closed over the weekend and Monday and re-opened Tuesday.

Brown said a quick response by the city’s Fire Department and Advance 1 Cleaning Services, of Waterville, made a big difference in the amount of damage that occurred.

He said Advance 1 employees worked diligently to open up walls, remove water and dehumidify the library.

“I do think we dodged a bullet,” Brown said Thursday. “This could have been a lot worse. The Fire Department was there with an excellent response. My understanding is, they went above and beyond the call of duty to make sure it was contained. Advance 1 did an incredible job — very knowledgeable, very professional.”

Officials understand what the issues are, what caused the flood and what repairs are needed and will spend the next few days working to put the library back together, according to Brown.

The amount of monetary damage had not been assessed as of Thursday, but an insurance adjuster from the Maine Municipal Association, which insures city property, was expected to visit the library.

“We won’t know until a week or so what the full extent of damages are,” Brown said.

Brown said a roof leaked at the library early in December, and that was a separate problem. That leak caused damage in a fire alarm panel and the problem is being solved, he said.

He said he is not sure if carpeting that became wet in Saturday’s flood will have to be replaced. He said Advanced 1 might be able to clean and dry it.

Library Director Sarah Sugden was unavailable Thursday for comment, but she said Monday that Advance 1 workers had placed stacks of books inside a trailer parked outside the library to freeze them, and they were expected to be free-dried to help prevent mold.

She said that on Dec. 16, the day before the flood was discovered, a 40-year-old copper pipe in the ceiling of the staff work room burst, but the staff discovered it quickly. Houle’s responded and fixed that pipe, Mechanical Services of Augusta also responded, and the water was contained to the staff work room and nothing was damaged, according to Sugden.

Amy Calder — 861-9247

[email protected]

Twitter: @AmyCalder17