Blackpool Coastal Defence Scheme

Client: Blackpool Town Council
Duration: 4 years
Value: £62 million

Project Brief
To provide bespoke precast concrete units and ready-mixed concrete for the construction of Blackpool's coastal defence scheme.

Background
For over 100 years the old sea wall has provided Blackpool with protection from coastal erosion
and flood alleviation. But constant bombardment from winter storms has taken its toll and much
of the defensive structure now needs to be replaced.
The new seawall is the town's biggest ever civil engineering project, funded by the Department for Environment, Food and Rural Affairs (DEFRA). The four-year contract will see the old structures replaced with 65,000 m3 of in situ concrete and 44,000m3 of precast concrete in grey, white and sand colours to blend in with the sea, beach and promenade.

 

Logistics
When complete, Tarmac will have supplied a total of 44,000m3 of precast concrete and 65,000m3 of ready-mixed concrete to the Blackpool and Cleveleys sea defences contract. This comprised 2,791, 5m by 3.5m step units to cover a 3.3km stretch of beach (each unit weighing 20 tonnes, containing 8m3 of 'macro fibre' reinforced concrete and placed using a specially designed vacuum lift system) and 16 tonne "wave wall" sections 2.5m by 1.5m. This commitment (in addition to ensuring a continued supply to the local market) is being met through Tarmac's existing ready-mixed concrete plants on the Fylde coast but this required the refurbishment of existing cement silos, the installation of a new, freestanding silo for white cement, new admixture tanks, new aggregate storage bays, hot water facilities and a new microsilica dispenser system to give a combined output of 90m3 of ready-mixed concrete per hour.

Challenges
Not only are these North Fylde Coast sea defence contracts architecturally and aesthetically demanding but the variety of concretes required to fulfil client specifications has created unusual operational and manual handling challenges. Specifically, the specifications require large amounts of colour conditioners and fibres to be added to certain concretes and separate storage for white cement.  As with most sea defence schemes, tidal working provides only a narrow window for deliveries when construction takes place within the tidal zone. There is therefore an overriding need to ensure that all supplies are handled efficiently. Tarmac coordinates daily requirements through a dedicated distribution office via a single point of contact.

Materials
To ensure that the solution meets performance and aesthetic demands, each of the concretes was developed by Tarmac specifically to meet client specifications and limiting factors for durability. These include water: cement ratio, minimum cement content, colour and inclusion of structural fibres. Tarmac Toproc AA has also been supplied, as the Cleveleys Coastal Defence Scheme requires a concrete capable of withstanding the constant abrasion and scouring characteristic to the North Fylde coast.
Tarmac has undertaken a long period of pre-contract trials and experimentation to optimise the concrete mixes - all of which are filed and processed through Tarmac's electronic distribution system which is linked directly to the concrete plants, ensuring that only approved mixes are sent to site.  The benefits of precast concrete in construction are well accepted - low whole life costs, fast and efficient builds, low maintenance, strength and durability and good environmental credentials.

Councillor Fred Jackson, Portfolio Holder for the Urban Environment, said:
"The placing of the first of the stepped units was a landmark in this exciting project, which aims not only to provide coastal defence protection, but also to create a 21st Century seafront which will be a magical experience for all."

Images have been provided by Birse Coastal, who worked on this project in conjunction with SLP.

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