Esserts reservoir

Built between 1971 and 1972, the Esserts reservoir holds water originating from Val Ferret. This water is collected and taken by the East collector to the basin.

This final reservoir covers an area of 27,000m² and can hold up to 220,000m³ of water, the equivalent of around 60 olympic-size swimming pools.

It is a riprap-type basin and the interior is covered with a layer of bituminous asphalt refurbished in 2020. The water retained at Esserts is either turbined directly at the Vallorcine power plant or pumped back into the Emosson reservoir.

During the summer, the Esserts basin allows the daily water supplies, which fluctuate significantly during this period, to be controlled. It also makes it possible to concentrate pumping when demand for electricity is low and to generate power when demand is high.

The entry valve

This valve acts as the entrance to the EAST collector. It is a 2.7 x 2.2 m flat valve and can be controlled either locally or remotely from the Bâtiaz control room. During floods or high flow rates, automated safety equipment allows this valve to operate automatically to prevent the basin from spilling over.

The head valve

The head valve is situated at the start of the reinforced shaft. When it is closed, it isolates the water retained in the Esserts basin from the downstream facilities.

The bottom valve

The Esserts basin is equipped with a bottom valve that allows quick emptying in case of danger. It is tested for good working order every year at high level with an opening of 10 centimetres.

The trap screen

The trap screen allows the intake grate to be completely cleaned by a simple vertical movement. Wood and other debris are collected through a comb and brought up to the upper part.

The reinforced shaft

The reinforced shaft, built in 1972, carries the water stored in the Esserts basin to the Vallorcine power plant. It is 508 metres long, 2.2 metres in diameter and has a gradient of 90%. Special fact: its upstream end is located in Switzerland and its downstream end in France. The painting of the interior of the shaft was redone in 2020, in parallel with the repair of the basin.

Technical file

Construction year	1971-1972
Put into operation	1975
Municipality	Trient
Volume	220,000m³
Altitude	1516m.
Type	Riprap/backfill/bituminous mix
Renovated	2020
Max. flow	27m³/dry incoming-outgoing

Esserts shaft

Construction year	1967-1974
Put into operation	1975
Municipality	Trient
Altitude	1500m.
Type	Reinforced shafts
Renovated	2020
Length	508m.
Diameter	2.2m.
Max flow	15m³/sec