27/6/2016

Laxá III – A new intake and changes to the dam

Verkís has completed the design of a modification of the intake area of Laxá III hydropower plant in north of Iceland. The purpose is to facilitate the operation of the plant. 

Operation has been problematic from the beginning due to ice and sediment transport in the river. On severe occations the plant needs electricity to keep the turbines running. The reason beeing huge amount of ice slush that changes the viscosity of the water. The sediment transport causes twice the abration than is normal in Iceland. In addition, large stones, up to 40-50 cm, have been transported with ice into the machines.

Our solution is to erect a new intake in the intake pond  (we use the word pond here as it is only 0.03 Gl) with ice flushing spillway above it. As the name suggests, the ice flushing part is supposed to flush ice, floating in the water surface, away from the intake and back to the original riverbed downstream of the dam. The purpose of this arrangement is to prevent an icecover formation on the pond.

The sediment problem is addressed by constructing two sediment traps within the intake area, equiped with sediment removal systems from SediCon. These systems are designed to remove sediment with as little water use as possible in a safe and robust manner. The outer sediment trap and removal system is designed to deal with sand, gravel and stones with diameter upto half a meter. The inner sediment trap and removal system is larger, 20 m x 10 m, and is designed to flush out sand and gravel. Between the two sediment traps, trash racks will cover the lower half of the waterway in order to lower the risk of larger sediment (stones) passing the outer trap.

Construction is underway and commissioning is planned at the end of the year.