A dam that supports one of metro Birmingham, Ala.'s major drinking water sources will undergo an $85 million overhaul after years of leaking millions of gallons of water each day.

The Birmingham Water Works Board (BWW) in mid-September approved construction contracts for work on the more than 100-year-old Lake Purdy Dam in Shelby County.

The board voted 7-1 to grant a $78.7 million contract to Thalle Construction Co., located in Hillsborough, N.C., and $6.8 million in management fees for Arcadis, an engineering firm with an office in Birmingham; Schnabel Engineering in Glen Allen, Va.; and Birmingham's A.G Gaston Construction.

"Our end goal is to always make sure we are providing safe, affordable, quality water to our customers," Tereshia Huffman, chair of the BWW board told AL.com. "This dam is old, and it was time for us to put in an intentional effort to make sure we got the funding."

She added that the project will improve the dam's structural stability and address water leaks at its foundation.

The Lake Purdy Dam was built in 1909, and its impoundment of the Little Cahaba River created the reservoir in 1923. Six years later, the dam was raised by 20 ft. to bring the lake to its current 990 acres just above the confluence of the Little Cahaba and Cahaba rivers.

The structure is accessed from Lake Purdy Dam Road with gated entrances on Sicard Hollow Road and Cahaba Valley Road. Water released from the reservoir's spillway proceeds into the Cahaba where it is taken up by BWW's Cahaba Pumping Station.

For years, though, the water department has discussed the need for repairs at Lake Purdy Dam.

In 1980, the structure leaked about 1.5 million gal. per day, according to old BWW board meeting minutes obtained by AL.com. The discharge rapidly accelerated between 2018 and 2019, eventually reaching about 7.6 million gal. daily, the agency's records revealed.

At the time, engineers estimated it would cost between $75 million and $100 million to rebuild the entire structure.

A failure of the dam would prevent BWW from delivering water to the south end of the city's system, engineers told the board in 2019.

Repair Project Likely to Last Almost Four Years

Plans call for the massive rehabilitation and repair project to begin in November and continue until April 2028. It will involve removing trees and diverting water at the dam.

Crews also are slated to make 2 mi. of road improvements from Alabama Highway 119 near the Brook Highland neighborhood to the dam's site to support construction traffic.

Funding for the project comes via a $171 million federal loan from the U.S. Environmental Protection Agency (EPA) and was authorized by the Water Infrastructure Finance and Innovation Act (WIFIA), part of the Water Resources Reform and Development Act of 2014.

BWW also will use some of the money to replace lead service lines that connect homes and businesses to water mains. Doing so is a major step in reducing the risk of lead exposure to residents and businesses, the agency said.

Paired with Inland Lake in Blount County, Lake Purdy is a key drinking water source for the Birmingham area's 600,000 customers.

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