Morrisons Kidderminster
TarmacDry Geomembrane
TarmacDry Geomembrane and granular reservoir
TarmacDry granular reservoir
Tarmac National Contracting
Tarmac National Contracting laying the TarmacDry binder course
TarmacDry binder course
TarmacDry binder course
Paver laying TarmacDry surface course
TarmacDry surface course
TarmacDry surface course
Drainage of the system
TarmacDry hydro test of the system
Hydro test of the system
Morrisons supermarkets PLC have created a new store within the town centre of Kidderminster. The site was previously factory and warehouse units and lies close to two converging rivers that run through the site. The project brief was to pave part of the car park with TarmacDry and the rest of the area in conventional paving with positive drainage.
The Contract
The original specification for the stores car park was to use permeable block paviors but due to time constraints and the need to reduce construction time on-site the main contractor approached Tarmac National Contracting to explore if using TarmacDry could bring their build schedule back on track. The complexity of the project and the clients desire to reduce programme time placed additional pressures on the project team. The car park was prepared, laid and completed in 15 days bringing the store opening back on track.
Tarmac's Solution
The project utilised collaborative working with the client's projects engineer, architect and Tarmac's teams, leading to a engineered solution that was then installed by Tarmac National Contracting.
As part of our service, if required, the permeability of the system will be monitored periodically by Tarmac. During this process, should the client or Tarmac deem it appropriate to clean the system and restore hydraulic conductivity then Tarmac will use specially designed cleaning equipment.
System Performance
In principle, the TarmacDry system offers several key benefits, many of which deliver sustainable construction objectives:
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Shallower construction depths over other systems often reducing both bulk excavation on-site and material volumes
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Faster construction times thereby condensing programme durations and reducing contract management costs
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Delivers a SuDS approach through infiltration or attenuation techniques, providing complete control over rainwater management. This technique is called 'source control' and is considered best practice by the Environment Agency.
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High rainfall porosity levels through the system achieving on average a minimum 5,000mm per hour at installation, compared to a 1 in 100 year storm event which generates rainfall of around 150mm / hr.
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Provides both first and second stage rainfall treatment through settlement and then bacterial action.
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Minimises the need for conventional drainage, again reducing costs and saving construction time.
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Low cost and rapid maintenance through a specialised high pressure suction cleaning machine.
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A fully integrated approach - Quality assured design, supply and installation through Tarmac National Contracting.
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TarmacDry porous asphalt surfacing course can be coloured to add visual impact or demark safety zones.
Tarmac's solution
The TarmacDry system was required to provide sufficient attenuation to deal with run-off from the 1 in 100 year plus 20% climate change event. Collection and treatment of run-off from the car park was provided by the TarmacDry system. Attenuation of run-off is provided within the specially designed granular reservoir below the car park.
The car park drainage system connects into the highway drainage system for the adjacent access road, which subsequently discharges into the adjacent River Stour. The total discharge rate from the car park and the access road was restricted to 26 l/s. When this discharge rate is exceeded, flow is allowed to back-up from the highway drainage system into the car park granular reservoir layer storage. A diffuser system was installed within the granular reservoir layer to facilitate the two-way flow of water into and out of the granular reservoir storage layer. The drainage system was also designed to operate under conditions when the outfall is submerged by a 1 in 100 year flood level in the River Stour.
This tanked system has additional storage capacity which attenuates rainwater from both the car park area and the access road. This additional storage ensures a controlled release of rainwater into the river. Hence, during a heavy storm when the river level rises, this part of the development will not be putting additional water into the river, reducing pressure on this part of the system and reducing the risk of flooding to properties further down river.
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