Hoopes Dam: Reservoir Raising in the Absence of Dam Safety Regulations

Hoopes Dam is a 110-foot high concrete gravity dam owned and operated by the City of Wilmington, DE. The dam impounds a pumped storage reservoir that is fed by a combination of adjacent reservoirs and pumping stations, ultimately from the Brandywine Creek. In response to water supply concerns generated by drought conditions in the early 2000’s, the City retained O’Brien & Gere to investigate the feasibility of raising the normal pool elevation of the reservoir while addressing any dam safety issues that may exist at the site. The resulting dam raising/improvements program consists of a phased construction approach to accommodate the City’s budgetary constraints; focusing on dam safety issues and a modest spillway crest raising in the first phase, with possible additional reservoir raising and operational and aesthetic improvements in the second phase. The design of the first phase of the program was completed as the Delaware dam safety program was just becoming established, so the improvement features were based on a combination of standard dam safety practices in other states and practical engineering.