Earlier this week, experts provided an update to the board of Central Alabama Water on the Lake Purdy Dam and Reservoir located in northern Shelby County. The report followed media reports questioning the dam's safety, which led to inquiries about the insurance policies in effect and the new board's efforts to review the original plan, budgeted at $28 million.
Work on Phase One is progressing, with an estimated completion date of April 2026. In addition, on Monday, the Board approved three new additions to the project:
The decision to hire additional consultants to study the project was delayed for two more weeks. The issue was initially scheduled for a special called meeting last week. That meeting was canceled.
The directors were assured that Lake Purdy Dam is safe and there is no imminent danger to the public.
According to a detailed press release by the water board, 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, according to the report.
Schnabel Engineering, part of the engineering team for the overall project, will perform a reservoir dye test as soon as next week. The same team will oversee the drilling of exploration holes on the left, downstream side of the dam, to confirm geological conditions.
“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.”
Dye will be released at two locations upstream of the dam. Engineers will then take photos of the downstream area at regular intervals for three hours and prepare a report on the test results. The estimated cost of the testing is about $10,000.
Passersby might notice one of two colors being used in the Little Cahaba River and possibly the Cahaba River for a short time.
"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,” the experts said.
Finally, engineers will oversee the 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. The 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 the design is complete. However, the costs will be covered by contingency funds budgeted into the overall project.
In addition to the board voted to increase the insurance from $1 million to $10 million.
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.
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