Dams are an important part of our infrastructure, creating water supply reservoirs, serving as storm water and flood control structures, hydroelectric generating facilities and creating recreation lakes. Many dams in existence today were constructed in the first half of the 20th century and are showing their age. These structures require rehabilitation to bring them into compliance with current dam safety standards and keep them safe for public use. McMahon & Mann’s services include characterizing the geology and hydrogeology of the dam embankment foundation and surrounding valley, evaluating the stability of the embankment and spillway and the capacity of the spillway to pass the design storm. We have also designed earth and rock anchorages to improve the stability of slopes and embankments. In addition to remedial work on dams, the principals at McMahon & Mann recently served as expert witnesses for three dam failures in New York State. McMahon & Mann has also pioneered the development of non-destructive test methods to evaluate the condition of dam tiedowns including an assessment of whether they have corroded and lost tensile capacity. We have successfully applied these test methods to two dams in New Brunswick, Canada. Currently, these condition assessments are carried out by Earth Reinforcement Testing, Inc., now a division of McMahon & Mann.