From PFMs to PZ Readings: Considerations for a Dam Seepage Modification

Wet areas have historically been observed along the downstream toe of the Clear Fork Reservoir Dam. The reservoir and dam are operated and maintained by the City of Mansfield, Ohio for water supply. To supplement the water supply, the City also relies on a network of groundwater wells, including one well screened directly below the dam embankment. To address the wet areas, identified risk-driving potential failure modes (PFMs), and the deficiencies indicated by engineering analyses, a graded filter toe berm was designed and constructed. The toe berm design considered the seepage PFMs and the impact of the groundwater well network. The project is an example of how risk assessment of dams can be scaled to focus on specific, targeted issues that have been observed. It also shows the importance of considering nearby infrastructure (groundwater wells) to design and construct an appropriate dam safety solution.