Ben Hill Reservoir Dam Stability Evaluation
The City of East Point, Georgia retained United Consulting to perform a Dam Visual Seepage Assessment, Limited Geotechnical Exploration, and Dam Slope Stability Evaluation of the Ben Hill Reservoir Dam, which is approximately 55 feet high, with a crest elevation of approximately 933 feet Mean Sea Level (MSL). It has a crest 12 to 15 feet wide and an impoundment storage capacity of 350 to 500 acre-feet. The dam is classified as a Category I Dam per the Georgia Safe Dams Program Classification System.
United Consulting conducted a site visit to assess the current conditions of the dam, focusing on seepage, wetness, and soft areas on the downstream slope. The area was mapped using a probing rod to define the limits of wet/soft zones, while collecting and recording piezometer water and lake levels. Additionally, a limited geotechnical exploration program included two Standard Penetration Test (SPT) soil borings, drilled on the dam’s crest and middle bench of the dam to auger refusal depths of 98 feet and 48 feet, respectively.
The laboratory testing included soil classification tests (grain size/hydrometer, and Atterberg limits), Consolidated Undrained (CU) Triaxial Shear Strength tests, and permeability tests. Slope stability and seepage analyses were conducted to evaluate dam stability under various conditions, including steady seepage (long-term), rapid drawdown (short-term), and steady seepage (short-term) seismic conditions. These analyses assessed the current conditions and the impact of constructing a stabilization berm, which was required to increase stability factors of safety to meet the Georgia Safe Dams Program’s minimum requirements for a Category I Dam.
