Construction Project for Structural Rehabilitation of River Mill Dam

摘要

The concrete buttress dam at Portland General Electric’s River Mill HydroelectricStation was constructed in 1911. More recently, investigations and detailed structuralanalyses were undertaken to re-evaluate the adequacy of the existing configuration.The hollow, concrete buttress dam is similar in some ways to a gravity dam, but is alsomuch like a conventional concrete structure subjected to hydro loads in the river. Thestructural analyses were made more complicated by detection of large variations inexisting concrete material properties.Design, construction and inspection of a structural rehabilitation project wereundertaken to adequately provide for the safety of people and structures downstream ofthe dam. The project provided a number of different structural reinforcement details,including mass concrete infill, reinforced concrete diaphragm walls, and post-tensionedbolting. Most of the heavy construction work was performed inside the dam with verylimited access and without the use of any large equipment such as cranes. Unexpectedvariations in existing foundation material properties were identified during construction.Contract management, along with much of the technical support and constructioninspection, was provided by the utility.