Dams & Hydro

The project involved a 3.5 m raising of the FSL of Midmar Dam using a reinforced concrete labyrinth spilling. No raising of the flank embankments was required and the work was limited to demolishing the spillway bridge and piers, a modification of the spillway crest and the construction of 3.5 m high reinforced concrete labyrinths.

Midmar Dam was originally constructed in 1965 and was designed for the full supply level to be raised by the simple addition of radial gates. When this solution was designed by the owner, the local water board, who were paying for the proposed raising, commissioned ARQ to evaluate the design proposals. ARQ reviewed the postulated design and various alternatives and came to the conclusion that a fixed reinforced concrete labyrinth was the most cost-effective option and could be implemented at a cost of approximately 30% of the radial gate raising option.

The associated solution was considered too complicated for the dam owner to design and ARQ was consequently appointed to complete the raising design and assist with construction supervision.

The project was successfully implemented within a very tight programme and inside the allocated budget.

The raised spillway has now been successfully operating since 2003.

ARQ completed the conceptual design and the detailed construction design for the raising. In addition, ARQ commissioned and supervised the hydraulic model testing and provided assistance during construction.

Project details