7344 – White Cart Flood Prevention Scheme Contract 1 – Flood Storage Areas
7344 – White Cart Flood Prevention
Scheme Contract 1 – Flood Storage Areas
• 1,710 residential properties at risk
• 40 businesses at risk
• 20 significant floods in last 100 years
• Last significant flood in 1990
• Events in January 2005 and October
2008 were close to flooding property
• Flood damages estimated >£100M
Project Scope
• Contract 1 comprises the construction of:
• 3 earth embankment dams
• 2 road bridges
• 275m flood defence walls
• Extensive environmental works
• Contract awarded to Carillion plc
• Starting date February 2008
• Planned completion in winter 2010
• 1,710 residential properties at risk
• 40 business at risk
• 20 significant floods in last 100
years
• Last significant flood in 1990
• Events in January 2005 and
October 2008 were close to
flooding property
• Flood damages >£100M
Spillway Crest
Vortex flow control
Screen
Screen
Culvert
Embankment dam
Typical cross section
Spillway protection –
articulated concrete mattress
Vortex flow control
Environmental mitigation
• Wetlands constructed at all sites
• Culverts designed for fish and mammal passage
• Extensive tree and shrub planting
• Replacement hedgerows
• Artificial badger sett
• Artificial Sand Martin bank
• Re-meandering of straightened channel
• Bird and bat boxes
Protecting the environment
Culverts – boulders
and baffles for fish
passage
Searching for bats
Otter survey in progress
Site issues – Kirkland Bridge
• Access to Mains Farm to be maintained at all times
• Early completion of flood defence walls required
• Large flows in the White Cart Water
• Sandmartins
• Tame deer
An uninvited visitor is
sent to get a yellow
vest and hard hat
Nesting Sandmartins in
face of excavation
Kirkland Bridge – habitat creation
Kirkland Bridge – October 2009
Borrow
pit Wetlands
Already the future benefit is clear?
• Numerous badger setts to be avoided
• Artificial sett to be created
• Service diversions and protection
• Overhead sewer
• Close to residential properties
• Very ‘flashy’ river
Site issues – Kittoch Bridge
Kittoch Bridge – habitat creation
Kittoch Bridge – October 2009
Borrow
pit
Wetlands
Site Issues – Blackhouse
• High voltage overhead power lines
• Right of way to be maintained
• Poor access from main transport routes
• Access to Blackhouse Farm to be maintained during
bridge construction
• Impacts on existing wetland to be minimised
• Imported fill for embankment construction
• Ground improvement required
Blackhouse – June 2009
Blackhouse – October 2009
Wetlands
Facts and figures
• Combined storage volume
• Peak flow reduction
• Flow controls
• Maximum dam height
• Earthworks
• Wetlands
– 2.6M cubic metres
– circa 45%
– 5 Hydrobrakes
– 15 metres
– 175,000 cubic metres
– 90,000 square metres