tank being lowered into the ground


The 52,000-litre Carat XXL tank range makes its mark for Kier.

When it came to finding an underground firefighting water tank big enoughfor the job there was only one manufacturer main contractor Kier could go to – GrafUK.

The sustainable water management specialist, better known for itsrainwater harvesting and wastewater treatment systems, supplied a super-sized 52,000-litrerecycled plastic Carat XXL tank for an extension to Oak View School inLoughton, in Essex’s Golden Triangle.

And that’s not the biggest tank Graf can supply – its firefighting modelscan be designed to suit whatever the design capacity is on a scheme, utilisingmultiple adjoined tanks from the Carat XXL range or alternatively adapting itsmodular attenuation tank systems.

This tank was required because pressure from the local water main wasinsufficient which is one of the fire safety requirements of the 2010 BuildingRegulations. These allow an alternative source of water supply, in this case astatic water tank with a minimum capacity of 45,000 litres.

Kier senior site manager Mac McKenzie said: “I was late to the contractbut I believe Graf were the only manufacturer who could supply the capacityrequired. I think cost also played a role and the fact that Graf supplied thecomplete package.”

The tank, complete with fire hose connection to BS336, was supplied byGraf distributor Southern Tanks and installed by specialist sub-contractor MADivane complete with access turrets, maintenance and inspection ladder, and suctionpipework, in just a couple of days.

Preparing the excavation, on a steep hill and in challenging conditions,and then finishing with EWS (Emergency Water Supply) signage approved by EssexFire Brigade took a total of a couple of weeks.

The tank, believed by Mac to be the biggest he has worked with, waslowered into the excavation using slings supplied with it, onto a gravel baseand backfilled with gravel instead of the more traditional concrete, to savetime and therefore money on site.

Mac McKenzie added: “Graf were a good company to work with and providedexcellent follow-up support. They came down during the works and were veryhelpful.”

Oak View School is a SEN (Special Educational Needs) provider and thestandalone extension on its former car park was required due to its successwith students with moderate, severe and complex needs within the autisticspectrum.

The CaratXXL is the largest tank supplied by Graf, offering storage capacitiespreviously only available with concrete and steel tank models. As well asfirefighting water, its modular concept enables it to store and retainrainwater and function as a wastewater tank for local wastewater disposal.This, combined with its light weight, allows for more flexibility throughdesign, planning and installation when compared with a concrete or steel tankoption.

The lightweight also saves time and money during installation as there is no need to laygravel for truck and crane access – so often the case with concrete or steeltanks. It can be easily mobilised with a stationary crane or excavator, savingeven more time and money.

Requiring anearth covering of just one metre, the ribbed construction of the Carat XXLmeans it can be driven over by a vehicle weighing up to 40 tonnes, and it can alsobe installed in groundwater up to its midway point. In appreciation of this quality,Graf offers the Carat XXL with up to a 25-year warranty.