More than 10,000 gallons of sewage spilled out of a manhole and into Flat Creek Tuesday, and the city’s environmental services administrator says construction debris could be to blame.

Shortly after the city workday began Tuesday, a public utilities employee discovered sewage flowing out of the top of a manhole located at the end of Murphy Boulevard.

The sewage had come out of the manhole at the cul-de-sac on the road and made its way about 100 feet to the waters of Flat Creek. The spill came after 15 to 20 large chunks of asphalt and concrete blocked the sewer line just off Browns Bridge Road, said Horace Gee, Gainesville’s Environmental Services Administrator.

Gee said some of the chunks were as large as a gallon jug, and could not have made it down the sewer lines on their own.

"I’m not accusing nobody, but pieces of debris that large, they can’t be flushed down a toilet or anything like that," Gee said.

"We were sort of astonished once we got down to the source and started pulling it out."

"The shape of (the chunks of asphalt) indicated that it was from construction debris," said Gee. "It’s unfortunate that we have to take the blame, because we own and operate the sewer system, but this was definitely nothing we could have prevented."

The department estimates that more than 10,000 gallons of sewage spilled from the line, categorizing it a significant spill by the state’s Environmental Protection Division. It is the second "significant" sewage spill in the last month and a half after the department went more than a year without any significant spills.

"When you don’t know it’s just a guess," Gee said. "It’s better to err on the high side than the low so that ... if the state finds anything out of order at least you’ve erred on the high side."

Gee said when the line was repaired, sewage was flowing through it at 60 to 80 gallons per minute. The sewage flow in that area — a road lined with local industries such as KipperTool and Harris Electric — depends on the time of day, Gee said.

"We knew that it ran for an hour and a half before we got it restored and we don’t know how long prior to that, so we just took the high side and that way we covered all of our bases," Gee said.

Since the department reported a spill of more than 10,000 gallons, utilities employees will have to take samples of the water above and below the site where the sewage entered the creek for seven days and report their findings to the state Environmental Protection Division.

Follow-up samples will be required once a month to ensure that the creek is returning back to normal after the spill, Gee said.

"Generally, when you have this, after the flow’s restored, everything’s back to normal within 24 hours," Gee said.

Signs have been posted at the site of the spill, and Gee said the department cleaned the area and fixed the sewer line within an hour and a half Tuesday morning.