When defects arise, it is often debated whether it is a design or workmanship issue. When both are at fault, complications arise. This issue arose in a recent case and the contractor decided to commence proceedings against its designer.
Kent County Council had engaged Jacobs Engineering to design two new dual-carriageway roads, the A256 and A299, in east Kent. Hochtief and Volker Fitzpatrick were appointed JV principal contractor and in turn appointed Atkins to complete the design elements. Atkins’ scope of work included the permanent civil and structural design for the Cottington Road Bridge and the Cliffsend Underpass.
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Following completion of the bridge in 2011, surface settlement of the carriageways on the north and south sides of the approach embankments was discovered, forming localised depressions. Between 2012 and 2014 remedial works were carried out.
The underpass was completed in March 2012. A month later signs of leakage were discovered including rust staining on the headwall beam and the west end of the underpass, icicles above the carriageway and fine cracking to the concrete face of the headwall. In June 2013, remedial works were carried out.
The JV issued proceedings against Atkins for breach of contract and negligence in carrying out the design of the structures. Damages of £802,475.35 were claimed for remedial works to the bridge and £122,559.82 for the underpass.
On the bridge, the JV alleged Atkins failed to design or specify any adequate system of drainage of sub-surface water from above or adjacent to the membranes. On the underpass, it alleged Atkins failed to specify an adequate waterproofing system for the joints between the elements of the west end.
The bridge works
Experts for each side referenced guidance for the use of chalk fill and drainage relevant to the bridge works. The recommendations included provision for sub-surface drainage to remove water that may permeate through the pavement layers of roads. It was explained that when chalk was compacted to form a fill, like in this case, the permeability of the material is reduced and this can cause collapse compression following wet conditions. This meant that chalk fills needed to be protected against water inundation.
Here, the design was revised over time from a graded granular fill to one that included an impermeable layer and chalk fill that did not incorporate drainage around the edges of the membrane to transport water away. It was claimed that Atkins intended that the membrane was built to a 1:40 fall that would enable drainage but this was not actually specified on the drawings.
But the situation became more complicated because the JV did not follow the design precisely. So what contributed to the defect?
Mrs Justice O’Farrell held that the compression of the chalk fill was caused by excessive water penetration due to Atkins’ failure to design adequate sub-surface drainage for water accumulating on the membranes and percolating into the chalk fill. She said Atkins’ bridge design was inadequate, negligent and in breach of the subcontract because it was responsible for the design, it failed to follow industry guidance and the risk of collapse settlement of chalk fill was a widely recognised risk Atkins should have been aware of.
The justice also agreed with the damages claimed for the remedial works, which she described as reasonable and necessary.
The underpass
However, the underpass yielded a different result. It was alleged that the water ingress was caused by Atkins’ inadequate waterproofing design. But photographs of the as-built works confirmed there was grout interjected between the underside of the headwall beam and the deck. This had displaced the fill but created voids between the grout and the beams. There were also steel sheets that should have been removed from any gaps to facilitate grouting to fill the gaps and create a watertight seal.
The experts felt additional waterproofing measures should have been specified but the grouting workmanship contributed to the water seepage. The justice found that this was a specialist activity, saying if the JV had any concerns it should have raised them with Atkins, but failed to do so. She therefore dismissed this claim. So in the event, it turned out both design and workmanship were at fault, leading to a costly dispute.
Theresa Mohammed is a partner at Trowers & Hamlins
