In 2018 the ODNR selected DLZ to provide professional engineering and environmental services at Lake White State Park in Pike County. These services evaluated the indeterminate water movement, water transfer, and seepage from the Lake White reservoir and groundwater system.
Lake White Dam is a Class I (high-hazard potential) structure consisting of a 39-foot high, 4,200 feet long earthen embankment dam. It has a concrete spillway that impounds 6,015 acre-feet of water at a normal summer pool. Originally built in 1935, the Lake White Dam underwent two subsequent significant improvements completed in 2006 and 2017. Approximately one month after substantial completion of the 2017 work, seepage issues were observed downstream of the dam. Detection of significant water loss from the lake through the reservoir resulted in elevated monitoring.
DLZ’s original project scope consisted of performing water resources, geotechnical, hydrologic and hydraulic, hydrogeologic, civil, and structural engineering, and environmental review. It also included an assessment of the dam’s construction history to identify the cause/causes of the indeterminate water loss. DLZ then submitted a report of the study of summarized review and findings to ODNR. The report also suggested recommendations for controlling the water transfer problem. DLZ’s work included performing numerous soil borings upstream and downstream, including borings on the lake from a floating plant (barge). Part of the project was to install nested vibrating wire piezometers. Conducting dye testing in the lake helped identify the cause and location of the water loss.
Water Transfer Seepage Evaluation
DLZ performed a significant seepage and slope stability evaluation program of the entire earthen embankment dam. The seepage evaluation program that DLZ performed was one of the largest and most comprehensive ever for an ODNR project. Complicating the analyses were the Scioto River’s effects, located just downstream of the dam, on the tailwater and groundwater conditions. The area downstream of Lake White Dam is regularly inundated from higher pool events in the Scioto River, making calibrating the seepage models to measured piezometric readings challenging. DLZ’s seepage analyses revealed that under seepage at the dam site was a critical concern with respect to downstream sand boils, exit gradients, and uplift/heave. DLZ’s 200+ page seepage evaluation report was peer-reviewed by the U.S. Army Corps of Engineers – Huntington District for consensus.
Filter Berms Design and Construction
As a result of comprehensive seepage and slope stability evaluation, DLZ recommended designing and constructing a series of weighted filter berms and a drainage system in the dam’s downstream area. The first phase of construction completed in 2020, with subsequent phases performed as per additional analyses, and funding becomes available. DLZ is providing construction administration and testing services for the berm construction work.
During late 2018 DLZ personnel assisted ODNR with daily inspections of the dam, which included recording water flow rates from the existing dam drainage systems, measuring cracks in existing concrete structures, monitoring for signs of earthen embankment slope instability, observing existing and historic sand boil locations, and monitoring for any signs of new sand boils downstream of the dam. The project involved significant coordination with ODNR’s Engineering Division and Dam Safety Group and personnel from the U.S. ACE – Huntington District.