Castlehouse Construction has the £7m main contract to build three industrial units totalling 29,950 sq ft for Carnworth Estates adjacent to the Pheasant Fields Lane retail park in Skelton. The project also included the construction of a car park for approximately 70 vehicles, plus soft and hard landscaping. Each industrial unit will have its own surface‐water management system to collect rainwater and surface water run‐off. These all feed into a central sub surface attenuation tank located under the road near the development’s main entrance.

Marshalls Civils & Drainage supplied 32 precast concrete MC2010 STKA box culverts laid in a double run to create the attenuation tank for storage and management of surface water from the three units. From receiving the order to delivery of the first units, Marshalls had a tight lead‐in time of less than 10 weeks. Marshalls was selected to supply the precast units for the attenuation tank on two main criteria: quality and availability.

The ability to supply standard units from existing stock was a key factor in keeping construction of the attenuation system on schedule.

The underground tank comprises 32 MC2010 culverts laid in a double row. Twenty of the culverts were standard designs which could be delivered immediately ex‐stock, while the remaining 12 were bespoke units manufactured to order. “Being able to use a stock product allowed us to speed up the programme,” explains Marshall’s Business Development Manager (Special Projects) Billy Fairhurst.

Castlehouse dug the excavation and cast the base slab for the attenuation tank and was able to start installing the standard MC2010 culverts without delay. Meanwhile Marshalls began manufacturing the 12 bespoke units for delivery on a just‐in‐time basis. The bespoke units included four end‐wall culverts with custom designed access holes and connections plus another eight units manufactured with special penetrations to connect the two parallel runs and to collect water flowing in from gulleys.

Dave Crozier, Project Manager with Castlehouse Construction, praised the quality of the Marshalls product as well as the support provided by Marshalls during the installation phase: “Marshalls kept us fully up‐to‐date with the manufacture of the specials and provided helpful advice to make the installation easier for us,” he says. It only took seven days to install all of the units, backfilling the excavation as we went,” he noted, “It took us only two weeks to finish the entire job.”