LECA® LWA geotechnical fill from Leca® UK helped the £80 million transformation of Blackpool’s seafront … and saved the council hundreds of thousands of pounds.
Some 4,000m³ of LECA® LWA was used, for the first time by Birse Coastal, to fill the void between the existing sea defences and a new sea defence wall. The new 7m high sea wall of precast concrete units was constructed immediately in front of the existing defences, limiting the space for foundations. The only way around this would have been to break out the old wall which would have added serious costs to both temporary and permanent works.
Through value engineering workshops held with Birse Coastal, consultants Halcrow Group discovered LECA® LWA was 66% lighter than its closest rival and considerably more cost effective. Anthony Burgess, regional engineering manager with Birse Coastal, estimates that not having to break out the existing sea defences saved Blackpool Council some £250,000.
“We hadn’t used a lightweight fill before but the LECA® LWA product performed very well. We were a little concerned at first about using lightweight material because of the exposed environment. We thought it might blow away in the wind or float away on the tide.
“But we got a lot of support from LECA® LWA and when we trialled it slowly on the Blackpool project, it proved very effective and simple.”
To assist with minimising costs a dedicated shipment of 10-20mm LECA® LWA was received into Goole docks and trucked across the Pennines to Blackpool on walking floor vehicles carrying average loads of 86m³. More economies of scale were realised with the walking floor vehicles which negated Birse having to work around its ban on articulated tipper trucks.
Gareth Robertshaw, principal coastal engineer with consultants Halcrow Group, said: “We had a real design challenge with the Section 7 works. The new wall was to be built immediately in front of the existing sea defences, limiting the space for foundations.
“Without adding serious additional temporary works costs associated with breaking out the existing defences, we couldn’t get a design to work using standard materials. Using LECA® LWA meant we were able to reduce the weight of the new construction by up to 40% and support the weight of the new wall within the available footprint of the original revetment design.
“Overall, this has allowed the delivery of this critical element within programme and budget which is a real success given the initial challenges.”
No settlement period was required before a concrete cap was then cast and the new promenade finished off with a decorative concrete.
Birse Civils is one of six contractors working on the final phase of the six-year redevelopment of Blackpool’s seafront into the “best seafront and promenade in the UK”.
LECA® LWA is a lightweight expanded clay aggregate formed by heating and firing natural clay in a rotary kiln at temperatures up to 1150º centigrade to create a ceramic granule. With an average density after compaction of just 300kg/m³, LECA® LWA is free-draining, chemically inert and resistant to extreme temperatures.
LECA® LWA is used in many civil engineering and geotechnical fill scenarios helping to reduce weight loadings by up to 75% on retaining structures and wiping out lengthy settlement periods in bulk fill applications. With site production up to 16 times faster than traditional fills, LECA® LWA proves itself an economical alternative.