Lessons Learned - Artesian Head at Earth Dams in Glacial Country

Management of seepage to mitigate artesian head is a critical factor to assess and maintain the stability of earthen embankment dams. This is particularly important at dams that are constructed on glacial soils. Too often there is a fundamental lack of a thorough understanding of the glacial geology and a lack of vision about the possible variation of subsurface conditions from that depicted in a limited number of test borings, and how that variance could require a shift in design approach to contend with the presence of artesian head. A discussion of practical Lessons Learned will be presented that are based on several past dam rehabilitation projects that were completed. The discussion will focus on both what was done during the initial site characterization, followed by the development of mitigation details and design strategy, and measures taken to adapt implementation based on actual conditions encountered during construction. One of the example projects will highlight lessons learned to address dam rehabilitation at an earthen embankment where an artesian head was encountered that rose above the dam crest elevation at a test boring that was drilled and sampled near one of the dam abutments.The goal of the presentation is to equip the audience with Lessons Learned to address situations where an artesian head is encountered to rehabilitate earthen dam embankments.