Grane Valley, Rossendale

Unique reservoir scheme improving the overflow and spillway facilities at two reservoirs
CLIENT
United Utilities
CLIENT'S SECTOR
Water
DATE COMPLETED
October, 2013
VALUE
£3.9m
DURATION
104 Weeks
DESIGNER
Pascoe Consulting

Overview

The main purpose of the project was to improve the overflow and spillway facilities at Ogden and Holden Wood Reservoirs, allowing PMF flows to be safely routed through the Grane Valley cascade and the reservoirs to be returned to their normal operating levels.

The sites, which are the lower two in a cascade of three impounding reservoirs, are “Pennine” type dams with clay cores  and are designated as high risk Category A. The Holden Wood embankment was constructed in 1841 and was 100m long and 18m high.

The Ogden embankment was 400m long and 15m high with a crest width of 4.5m, and is the most modern of the three reservoirs in Grane Valley, constructed between 1905 and 1910. Work at Ogden Reservoir included temporary and permanent diversion of pipelines and associated services, the construction of a new spillway formed from 1,300 individual pre cast wedge blocks, weighing 1.3 Tonnes each, the largest spillway of its kind in the UK, new overflow weir and crest bridge, CFA piled foundations, reinforced concrete stilling basin and erosion protection works.

Other works included the demolition and infilling of existing redundant tunnel sections at the toe of the embankment, new RC spillways and lining of existing spillways,   vehicular access bridges and landscaping.

Work at Holden Wood Reservoir included the construction of a new spillway complete with new weir and crest bridge, embankment slackening and new filtration systems, replacement of existing scour pipes and upgrading of associated facilities, re-use/remediation of all materials arising from site andremoval of Japanese Knotweed.

Key Challenges

EWCE completed the construction of both reservoir spillways which involved significant modifications to the overflow facilities on both embankments.

Works had to be carefully planned and agreed with the All Reservoirs Panel Engineer.

Key activities and critical temporary works included; cantilever sheet piled excavations, temporary flow diversion channels, propped excavations up to 20m in width, temporary king post retaining systems socketed into rock, temporary service diversions, temporary access bridges over spillways, temporary syphons and over-pumping facilities, temporary bunds to protect breaches in the embankment crest and large crane pads to support attendant crawler cranes amongst others.

All of these works undertaken during harsh weather conditions and within the strict timescales imposed by United Utilities.

Added Value

Re-use of all materials arising from both sites to re-profile landscaped areas and re-use of materials in accordance with the CL:AIRE Protocol to minimise demand on landfill sites.

The project attracted a visit from the British Dam Society, with a group of almost 40 people visiting in March 2013. Completion of the works within the strict timescales set by UU in order to avoid any disruption to the planned Haweswater Aqueduct outage.

Client Feedback

“The skill, professionalism and commitment of all those involved in delivering this multi- million pound project successfully was outstanding. Exceptional progress was made against a tight programme whilst maintaining a key focus on health, safety and positive engagement with local residents and stakeholders.”
Jonathan Clarke
Project Manager at United Utilities

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