The Promise and Threat of Boiling Springs: Identifying and Mitigating Risk to Sanford Dam

Sanford Dam is the largest of the dams and impounds the signature lake in the City of Boiling Spring Lakes. Following initial impoundment behind Sanford Dam in the early 1960s, local residents observed the first of multiple uncontrolled lake draining events that would occur during the dam’s nearly 60 years of service. During Hurricane Florence in September 2018, Sanford Dam breached due to overtopping. The City elected to reconstruct, which afforded an opportunity to evaluate the dam and its foundation. A review of historical records and the performance of additional subsurface investigations revealed conditions which present a risk to the dam’s safety. This paper will include a review of historical accounts of unexpected losses of the lake, a summary of the local geology and subsurface conditions revealed during subsurface investigations, an explanation of the failure mode considered most critical to the dam, and a description of the measures designed to address the threat posed by the site conditions.