Johnson & Johnson
Johnson & Johnson Head Office
Johnson & Johnson TarmacDry access road
Johnson & Johnson TarmacDry
Johnson & Johnson
The Project Brief required no change to the site’s natural system of drainage
Johnson and Johnson required the construction of a short section of new access road within their facility whilst also providing a durable paved surface to an existing 500m long unbound chalk access track.
Conscious of the need not to affect the natural balance of how rainwater currently soaked away, Johnson and Johnson requested a system that would not simply channel water into the site’s drainage system but continue to allow it to percolate naturally into the ground.
Tarmac provided design and technical input to meet the site constraints
GL Projects were the groundworks subcontractor for ongoing developments on the site and asked Tarmac for design advice that would meet these environmental requirements. They were aware of the concept of porous pavements but required advice about what this was and how it should be installed. After site visits by Tarmac’s technical representatives the TarmacDry system was proposed and accepted.
Tarmac offered and provided a full technical assessment, proposing a structural design that would meet the individual loading requirements of Johnson and Johnson whilst also taking into consideration the existing differences in levels along the access track both longitudinally and transversely. A visual inspection was sufficient to prove the subgrade without the need for plate bearing tests to determine CBR values.
The Client also wanted to incorporate new precast concrete edgings along both sides of the road that were sat on a conventional concrete bed and surround. Our design ensured this bed did not affect the hydraulic conductivity of the system.
The works were completed on programme without any site disruption
Following three months of liaison, discussions about the overall works programme and the agreement of an acceptable quote for the work, a 150mm deep layer of porous sub-base was shaped and profiled onto the existing surface of the track. To prevent future weed growth and in the absence of any geotextile membrane the surface was treated prior to placing the subbase. The new concrete edgings were then installed, followed by machine laid porous Base and surface courses on dates previously agreed to the main contractor’s own programme of works. During all those periods of time when TarmacDry was being installed Tarmac maintained a site presence to provide further technical assistance and to supervise the works.
All materials were supplied from Tarmac’s own Quality Assured production units
In total over 2,000m2 were surfaced with porous materials and the work was completed in July 2007.
Hydraulic conductivity testing proved the system’s capabilities
An aspect of this contract was the need to undertake extensive hydraulic conductivity testing prior to laying the surface course. This was done with the full approval of Johnson and Johnson and was undertaken by specialists from Tarmac’s own Technical Centre. The locations of each test were logged in a Technical Report and will be monitored to assess future performance.
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