This article appeared in the February 2019 issue of the Georgia's Cities newspaper.
The piano-key weir spillway design used in Peachtree City
n 2018, the city of Peachtree City completed its largest infrastructure project since the city’s existence— a new spillway for the 240-acre Lake Peachtree.
Lake Peachtree sits in the heart of the community, visible from Georgia Highway 54, and serves as both a recreation amenity for Peachtree City residents and as part of the Fayette County water system.
Four years earlier, in March 2014, significant voids were discovered under the almost 50-year-old spillway while the lake was lowered for shoreline maintenance.
“Failure of the 50-year-old Lake Peachtree Dam would jeopardize the safety of homes and businesses downstream, along with a major thoroughfare across the southern half of the city,” said Betsy Tyler, Peachtree City public information officer. “Failure to bring the dam and spillway up to modern standards could have threatened the existence of the lake.”
Lake Peachtree remained lowered through a dredging project in 2015 while temporary repairs were made to the spillway, but the city immediately moved forward with the design for a replacement built to Category 1 Dam standards.
Peachtree City chose a piano-key weir (PK weir) designed by Schnabel Engineering, one of the first in North America. The crenelated design allowed the city to meet the modern outflow requirements for significant storm events while avoiding the costs of relocating a nearby roadway bridge just south of the lake and dam that limited the space in which to work. The design also provides the discharge capacity needed to pass the runoff associated with the state-required design storm event. The PK weir will also provide aesthetic value.
Integrated Science and Engineering (ISE) served as the project manager for construction, which was performed by North Georgia Concrete between September 2017 and August 2018. The $4 million spillway is capable of passing 100,000 gallons of water per second. The entire structure weighs an estimated 15 million pounds, and the project required 22,000 cubic yards of earthwork, 3,840 cubic yards of concrete, and 420 tons of steel to build.
At the October 2018 dedication for the new spillway, Peachtree City Mayor Vanessa Fleisch expressed her appreciation to the Fayette County Board of Commissioners, which invested $2 million in the project. She also thanked the citizens of Peachtree City for their patience with a lowered lake during the process.
Then in November of 2018, the U.S. Environmental Protection Agency recognized the Lake Peachtree Dam Spillway project as one of 30 clean water infrastructure projects for excellence and innovation within the Clean Water State Revolving Fund (CWSRF) program. The CWSRF financed $3.2 million of the spillway project.
In addition to the EPA recognition, Schnabel Engineering was recognized for their Lake Peachtree Spillway design by the American Council of Engineering Companies of Georgia with the 2019 Engineering Excellence State Award in the Water Resource /Wastewater and Stormwater category.
“It isn’t often you undertake infrastructure repairs and end up with a landmark, but the design of the spillway and the adjacent bridge have become that for Peachtree City,” said Fleisch.