Abstract: A dam structure for retaining water in a reservoir includes precast concrete panel assembly forming the face or upstream side. A bonded impervious liner means, such as polyvinylchloride sheet, is provided on the downstream face of the precast concrete panels assembly. The liner means includes individual membranes bonded to adjacent panels, and heat welded impervious strips are provided along the joints between the panels. A poured concrete curtain wall is provided adjacent the liner means of the precast concrete panel assembly. Roller compacted concrete (RCC) is then provided in layers on the downstream side of the poured concrete curtain wall. An elongated, substantially horizontal blocking sheet of polyvinylchloride membrane is also provided at least adjacent the base of the dam to prevent water migrating upward through the dam between the precast concrete panels and the poured concrete curtain wall.