Mirror Lake Dam is located in the Town of Herkimer, New York, and is classified by the NYSDEC as a High hazard Class C dam. Mirror Lake is an oxbow lake created by a former meander of West Canada Creek. Mirror Lake Dam consists of a gated structure at the south end of Mirror Lake, two earthen embankments on either side of the lake, and a hydraulic canal that connects the northern end of the lake to West Canada Creek through another gated structure. The gate structures and other features were added to improve the dam in the 1960s and 1970s for the Herkimer Flood Control Project.

McMahon & Mann teamed with Bergmann to complete an engineering assessment for the dam. This included a subsurface exploration program of soil and rock borings, installation of standpipe piezometers, and laboratory testing. The embankment fill primarily consists of sands and top of bedrock was variable across the site. These conditions were incorporated into the seepage and stability assessment of the embankments that was included as part of the engineering assessment report.