Dams are subject to seepage through their foundations and abutments. Seepage may result in excess fluid pressures or uplift pressures beneath elements of the dam, thereby becoming a safety concern with respect to the stability of the dam. Pressure-relief wells are an integral part of a dam's seepage control system. These wells are generally designed to be free flowing and placed to intercept zones in dam foundation materials that are sensitive to elevated fluid pressures. Pressure-relief wells reduce excess fluid pressures by allowing water to be safely discharged from the zone affected by the excess fluid pressure (U.S. Army Corps of Engineers [USACE], 1992). Upon completion of review of historic pressure-relief well discharge rates and down-hole video camera observations for a pressure-relief well network (Figure 1) at Garrison Dam, ND, it was determined rehabilitation efforts were required. Rehabilitation methodology and results for this pressure-relief well network are presented in this paper. Figure 1. Location of the pressure-relief well network and associated piezometers at Garrison Dam, ND (1 ft = 0.3048 m). Garrison Dam and reservoir (Lake Sakakawea) comprise a multiple-purpose project consisting of a rolled earth-filled dam, an emergency spillway, and a hydroelectric-generating plant. The reservoir stretches 178 mi (286 km) and has a capacity of 2.3 million acre-ft (2.8 billion m3) for flood control, conservation, navigation, power development, irrigation, recreation, and other uses. The dam is 11,300 ft (3,440 m) long; 210 ft (64 m) high; 60 ft (18 m) wide at the top; and 2,600 ft (790 m) wide at the base. Construction on the dam began in 1947 and lasted 7 years. Reservoir filling began in 1953, and the minimum operating pool was reached in 2 years and 5 months. The pressure-relief well network consists of eight pressure-relief wells, each 6 in. (15 cm) in diameter, …