Operations Manager Schnabel Foundation Company Cary, IL
Abstract Description: Panbowl Lake was formed in the 1960’s as a by-product of mountain-side cuts and earthen dam embankments to allow State Route 15 to be constructed. In 2021, the largest flood in recorded history of the North Fork of the Kentucky River occurred, bringing the river level to within inches of the topping the dam and allowing water to seep through, causing the town of Jackson, KY to be evacuated. A similar event occurred again in the Summer of 2022.
In the Fall of 2022, Schnabel Foundation Company was awarded a contract to construct a cutoff wall for the Kentucky Transportation Cabinet. Construction began in the Winter and lasted until Spring of 2023. Originally designed as sheet piles, Schnabel proposed a Value-Engineering credit to install overlapping drilled secant piles to ensure that the wall was continuous, was able to penetrate uncontrolled rockfill and be socketed into bedrock. Installed a maximum of 55 feet deep, the secant piles were drilled with full depth temporary casing, filled with unreinforced concrete and overlapped up to 6.5 inches.
Since an alternate approach was being used, numerous quality control measures were taken to confirm the watertightness of the secant pile wall. Individual pile verticality measurements confirmed the overlap at depth. Crosshole Sonic Logging and full-depth cores confirmed the integrity of the concrete throughout the pile. Core-holes were also used to run in-situ permeability tests on the secant piles. Lastly, piezometers were installed on either side of the wall to measure fluctuations in the water level during flood events.
Learning Objectives:
Secant piles can effectively cutoff water flow through an earth dam.
A Value-Engineering approach saved money and offered a higher quality product.
Continued flooding events require constant re-evaluation of existing infrastructure.
