PORTLAND — Engineers opened the floodgates Monday on a 162-year-old stone dam on the Stroudwater River so it could be inspected for damage that city officials believe occurred several years ago when debris struck the upstream wall.

The dam, located near the Westbrook Street bridge, was built in 1850 for floating logs down the Stroudwater River to the Fore River, and was expanded in the 1900s for ice harvesting, according to city records.

Additional Photos

Water is released from a dam during the drawdown of the water level on the Stroudwater River in Portland. At one time the dam was used in logging and grist mill operations. Maine has more than 600 dams listed on the National Inventory of Dams maintained by the U.S. Army Corps of Engineers. The actual number of dams and impoundments is believed to exceed 1,000, however, because the Army Corps' list excludes structures smaller than 4 feet. John Patriquin/Staff Photographer

William Peterlein of Summit Geoengineering Services talks to city workers along the Stroudwater River after the water was lowered so the dam could be inspected. The upstream water level has been dropping, leading officials to suspect there is a leaky sluice gate. Derek Davis/Staff Photographer

Last inspected in 1998, city officials believe the dam was damaged several years ago when heavy rains washed debris down the river and it struck the dam, said Jon Emerson, the city’s utilities coordinator. Damage likely occurred to the upstream sluice gate, which allows the city to control upstream water levels, he said.

“Something came down and really hit the framework of that sluice gate quite hard and bent it,” Emerson said.

The city was planning to repair the sluice gate, but noticed an apparent leak on the downstream wall, prompting the city to conduct a full dam inspection, he said.

“We wanted to make sure before we did any of that repair work that the structural integrity of the dam was sound,” Emerson said.

There are 647 dams in Maine, according to a 2010 inventory conducted by the U.S. Army Corps of Engineers. Only 29 of those were built before 1900.

Records indicate the 150-foot-long Portland dam varies in height from 10 to 16 feet and is part of the Stroudwater National Historic District. In 1944, dam owner Ralph Leavitt of Portland deeded the dam over to the city, provided it “repair said dam in a proper and workmanlike manner to prevent leakage.”

The dam has a history of being used in logging and grist mill operations, but today it has no functional use, Emerson said. “Really, there is no purpose other than aesthetics,” he said.

On Monday morning, crews from Maine-based Summit Geoengineering Services Inc., which is being paid $5,000 by the city to inspect the dam, opened the sluice gate and drained the river to view both sides of the dam.

The dam can store a maximum of 221,940 cubic meters of water, and its normal reservoir storage is 187,416 cubic meters, according to city records. On a typical day, waters cascade over the top of the dam.

On Monday, the upstream shoreline retreated by 20 to 30 feet when the river was drained, said William Peterlein, co-owner and president of Summit Geoengineering Services.

The inspection, originally scheduled to take place over three days, was complete by Monday afternoon. Peterlein said he would have a report prepared for the city within three weeks outlining recommended repairs.

“It’s in pretty decent shape for the age,” said Peterlein, who noted the sluice gate seemed to be in decent working order. “We’ll probably recommend some basic maintenance.”

The city will use the inspection results to plan for future repairs of the dam, said city spokeswoman Nicole Clegg.

Staff Writer Randy Billings can be contacted at 791-6346 or at:

rbillings@mainetoday.com

Twitter: @randybillings