Contractor Costain has begun work on a major scheme to replace Ambergate reservoir for Severn Trent Water.

Costain will supplement, then replace, Europe’s second-largest covered reservoir at Ambergate, north of Derby. The existing reservoir, roughly 190 x 100 metres in size and completed in 1910, is reaching the end of its lifespan.

Its 110 million-litre capacity provides water supplies for a large area of Derbyshire, Nottinghamshire and Leicestershire. It cannot simply be closed while a replacement is constructed, explains Simon Roberts, Costain’s representative on the project board.

“We have to build the largest reservoir we can – about 87 million litres – on the space available to us elsewhere on the site. Once we commission this new reservoir, we can take out the old one and build a new one in its footprint for the remainder of the capacity – 50 million litres.” The reservoir will therefore have an increased capacity of 137 million litres when it is finished.

Costain will need to move some 100,000m³ of earth to create a new ‘shoulder’ to the hill as the reservoir site slopes dramatically. A new connection will also have to be created to link it to the Derwent Valley Aqueduct.

That part of the project will be completed first. The existing reservoir will then be decommissioned, demolished down to ground level and the second new reservoir constructed in its place.

Site clearance is underway, with the earthworks due to start shortly.