Design and build project to discontinue Hurst Impounding Reservoir, a Category A Reservoir and decommission it from the scope of the Reservoirs Act.
The Reservoir is bordered by a golf course and residential properties and situated on the western margins of the Peak District National Park above Glossop in Derbyshire.
Temporary works were undertaken to divert flows around the reservoir and protect the work area flooding up to a 1:100 year storm event.
Manmade structures were demolished on site including a 500m long bywash channel and cascade, syphon house, gate valve building and inlet gates.
50,000m3 of sediment was excavated from the reservoir basin and re-engineered into suitable class 2 fill for placement within the new valley sides.
50,000m3 of material was excavated from the earth dam and placed in layers within the new valley profile.
The design also included construction of a new flood plain to prevent flooding downstream. This flood plain included two hibernacula for breeding birds and 10 scrapes and ponds for wildlife.
A new gravel trap area was constructed to collect silt and cobbles deposited during storm events. This consisted of a 55m long precast wall made up of 1t blocks, two 300mm thick boulder slabs with site won boulders set in the concrete slab and the installation of 2nr bed check weirs.
A FOG (Fire operations group) pond was constructed, which will provide a water collection point for helicopters, should there be a moorland fire within a two minute flying time of the local area. This is made up of granular material, GCL lining and erosion matting internally and externally. An existing spring had to be diverted to create the inlet and supply for the FOG pond while the outlet was filled with sub armour and armour and channelled into the main river.
50m of gabion baskets were also installed to retain a newly constructed access road and retain the existing golf club track.
Other works included the installation of 2760m of stock proof fencing and associated field gates, 10nr bat boxes along with bird boxes and temporary seeding of the entire area.
Stringent water quality had to be maintained throughout the works with daily records and monitoring including turbidity, PH, scour protection and noise levels. The maximum turbidity requirement of the water was 20FTU and CHC had a target of 95% compliance, which was successfully achieved.
Image courtesy of SUAVE Aerial Photographers - www.SuaveAirPhotos.co.uk