Massabesic Lake Dam Improvement Project, Manchester, NH
Massabesic Lake Dam in Manchester, NH is classified as a High Hazard Dam. During a 100-year breach event, approximately 70 properties would be impacted, causing devastation and likely loss of life. In addition, 10 roads would be overtopped, including portions of I-93 and I-293. SLR International Corporation was contracted by Manchester Water Works (MWW) to complete Emergency Action Plans (EAPs), Dam Conditions Assessments (including underwater inspections) and the recent final design and construction oversight for improvements to system-wide dam components. SLR Bedford, NH staff completed all inspections, evaluations, designs, and construction oversight for the project.
The complexity of, and unique and somewhat innovative approach to this project was the design of repairs and modifications to a number of dam appurtenances with phased construction occurring on the various components as part of one construction contract, with the requirement that the overall system remain operational during the improvements. These component improvements and a number of new drainage features were focused on improving overall system resiliency and sustainability. As noted in the MWW reference letter, ”The recently completed improvements represent a cost-effective and resilient design for the entire dam system.”