The Board of Directors of Central Alabama Water received an update on the Lake Purdy Dam rehabilitation project.
For Immediate Release: Tuesday, October 21, 2025
Note to media: Central Alabama Water has broadcast quality, HD video of the Lake Purdy Dam construction site from October 14, 2025. You may access the video on YouTube at https://www.youtube.com/watch?v=CEc2IR6pvZU.
The Board of Directors of Central Alabama Water (CAW) Monday night received an update on the Lake Purdy Dam rehabilitation project. Construction is currently underway on Phase 1 of the project which involves installing roller compacted concrete as structural support to strengthen the dam. The cost of Phase 1 is $28 million.
As part of the update, the board authorized three additions related to the project:
- a dye test to check for seepage pathways;
- exploration drilling on the left side of the dam; and
- installing a deep foundation on the right side of the dam.
“Lake Purdy Dam is a historic structure, and this project presents a generational opportunity to ensure the dam serves our customers for decades to come,” said Phillip Wiedmeyer, Vice-Chairman of the CAW board and a retired engineer. “We are committed to comprehensively addressing infrastructure projects that are critical to our ability to provide high quality water to our customers.”
Current Condition and Safety of Lake Purdy Dam
Central Alabama Water has been assured that Lake Purdy Dam is safe and there is no imminent danger to the public. The reservoir was nine feet below its full capacity as of Friday, October 17. This is due to the dry weather usually experienced during late summer and early fall. Because of these conditions, it would take more than seven inches of rainfall in 24 hours for the water level to reach the crest of the dam. That is the equivalent of a 25-year storm. Therefore, there is little risk that water could overflow the top of the dam.
Dye testing to check for seepage
Schnabel Engineering, part of the engineering team for the overall project, will perform a reservoir dye test as soon as next week. Dye will be released in two locations upstream of the dam. Engineers will then take photos of the downstream area at regular intervals for three hours and provide a report on the results of the test. The testing is estimated to cost approximately $10,000.
Two colors of dye will be used. The dye is non-toxic, biodegradable and NSF approved. Passersby may notice some of the dye in the Little Cahaba River and possibly the Cahaba River for a brief period. There is no risk to the river or to drinking water because water from the Cahaba River is filtered and treated at the Shades Mountain Filter Plant before it is distributed to customers.
Exploration drilling on the left side of the dam
Schnabel Engineering will oversee the drilling of exploration holes on the left, downstream side of the dam. This project is designed to confirm geological conditions. The exploration drilling is expected to take one or two days to complete. The exploration drilling is estimated to cost approximately $25,000 and the Schnabel oversight effort will be covered by the firm’s existing contract.
“While we’re at this point in the project, it makes good business sense to conduct additional exploration before the area is covered with concrete,” Wiedmeyer said. “We can do this exploration at minimal expense and receive data to help inform future decisions.”
Installing a deep foundation on the right side of the dam
Engineers will oversee installation of a deep foundation of micro piles on the right side of the dam by drilling a series of holes, installing steel pipes filled with rebar and concrete and then pouring a concrete slab on top. This will further strengthen the dam’s foundation and prepare it to receive the roller compacted concrete that will be installed in front of the existing dam. Design of this project is expected to take two weeks, and construction should be complete by the end of December. Cost estimates for the deep foundation will be available once design is complete. However, the costs will be covered by contingency funds budgeted into the overall project.
About Lake Purdy Dam and Reservoir
Lake Purdy Dam and Reservoir are located in northern Shelby County. The original construction of the dam was completed in 1910. A project completed in 1929 raised the dam to its current height of 73 feet and length of 445 feet. The reservoir has a capacity of 5.6 billion gallons. It is a major drinking water source for a large portion of the CAW’s service area including Birmingham, Homewood, Hoover, Mountain Brook, Vestavia Hills and surrounding areas. Visit https://www.bwwb.org/lakepurdy for more information.
About Central Alabama Water
Central Alabama Water (CAW) serves customers in Jefferson, Shelby, St. Clair, Blount and Walker counties. The CAW operates four filtration plants, a certified testing laboratory and has more than 4,100 miles of water main in its distribution network. Visit www.bwwb.org for more information.
