Vatnsafl

Blönduvirkjun

Norðurland

Verkís services was feasibility study, project planning, economic study, tender documents, civil work design, mechanical systems design, environmental impact assessment and electrical systems design.

 Stærðir: installed capacity 150 MW, rated discharge 39 m3/s, head 287 m
 Verktími: 1997 - 2011

Almennt um verkefnið:
The Blanda hydroelectric project is located in the Blanda river in northern Iceland. The main reservoir is 40 km north-west of the glacier Hofsjökull. The underground powerhouse and appurtenant structures are located 25 km further downstream, approximately 40 km south from the town Blönduós. The river Blanda is retained at Reftjarnarbunga, a dam is in the Kolkukvísl tributary of the river Vatnsdalsá and the river Gilsá at Eiðsstaðabunga.

The Blanda rock-earthfill dam and Kolka dam create the main storage reservoir Blöndulón. The main features of the appurtenant structures in the Blöndulón reservoir are an overflow spillway, a bottom outlet and a diversion gate structure. The diversion waterways from the main reservoir to the intake pond are through 25 km of canals and lakes. The intake pond Gilsárlón is made by a dam in Gilsá river downstream of Gilsvatn lake. The main features of the appurtenant structures in the intake pond are an overflow spillway and a bottom outlet. A headrace canal leads from the Gilsárlón pond to the intake structure, which has trash racks, bulkhead and a radial gate.

A steel pressure pipe 4,0 m in diameter leads from the intake to a vertical steel-lined pressure shaft, down to the distribution to three Francis turbines in the underground powerhouse.

The draft tubes of the turbines open into a tailrace tunnel that leads to a canal in the riverbed of Blanda. An access tunnel leads to the powerhouse cavern. A vertical cable, ventilation and emergency exit shaft leads from the power­house to the transformers and the control- and switchgear house located at ground surface. From the generators the energy is conveyed via 250 m long 11 kV cables to the step-up unit transformers and from there to the HV switchgear. The station is equipped with modern control- and protection systems for remote monitoring and operation.