Front Cover Story
Maccaferri water
attenuation lagoons
reduce flood risk at new
energy from waste plant
A network of high capacity rainwater run-off lagoons has been installed by geotechnical specialists Maccaferri at
Lincolnshire’s new, state-of-the-art Energy from Waste (EfW), recycling plant at North Hykeham, Lincoln
attenuation ponds. These would normally be used to allow return
of surface water run-off from the buildings and surrounding hardstanding to the sub-soil through natural percolation.
To manage building run-off and surface water drainage at
Lincoln’s new Energy from Waste recycling plant, Consulting
Engineers, Arup devised a two stage system of ground level
‘wet & dry’ holding lagoons, constructed by Maccaferri.
To resolve the drainage issues, Consulting Engineers, Arup
proposed a two stage system of ground level ‘wet & dry’
holding lagoons - the smaller wet feeding and larger dry lagoon.
Commenting on their design, Rhodri Lea, Arup Senior Civil
Engineering Technician said, “The surrounding countryside is
criss-crossed with minor streams and waterways and we needed
to slow the surface-water discharge rates to around 10.0 litres per
second to prevent them being overloaded. The two-stage plan
gave us the required rainwater attenuation, even scaled up to a
once in a 100 year event”.
The Lincoln EfW plant, which is designed to treat 150,000
tonnes of domestic waste per year and generate enough
electricity to power 15,000 homes is built on a low lying
brown-field site with a high local water table.
At planning stage, Environment Agency requirements
stipulated that the development should have a maximum
surface water discharge rate no greater than that of a
comparable green-field site.
To help with the detailed design Arup turned to Maccaferri whose
experience in watercourse management and erosion protection
proved invaluable in the construction of lagoons.
Limited availability of space within the site ruled out the use
of a conventional SUDS-style system of large ground-level
The Maccaferri solution centred on impermeably
lining the two ponds using the Company’s Bentomat,
reinforced geosynthetic clay liner and enclosing
them within 2.0m high stone filled, twisted-wire
Gabion retaining walls. These near vertical walls help
maximise the holding capacities of the ponds within a
tight overall footprint.
The connected lagoons take advantage of slight falls
in levels; the higher and smaller ‘wet’ lagoon, roughly
35.0m long x 5.0m wide and 2.0m deep, accepting
initial storm surge from roofs and surrounding hard
pavement before gravity discharge through pipe-work
to the much larger and lower ‘dry’ lagoon.
Installation of the Maccaferri
Bentomat impermeable liner to the
larger, dry lagoon
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