Penalties for lane closures are focusing contractors' minds on maintenance minimisation, as work begins on Newport's £55M privately financed southern distributor road.
Andrew Bolton reports.
A landfill site in south east Newport is concentrating the minds of contractors as they begin work on the city's privately financed £55M southern distributor road. Part of the road will run right across the landfill, and Morgan Vinci, the joint venture between Morgan Est and French contractor Vinci Grands Projets is determined to come up with a long term, settlement free solution for the carriageway. If it fails, and the road has to close for extended maintenance, the two companies face financial penalties.
The 9.3km southern distributor road is intended to take local traffic around the southern edge of Newport and over the River Usk. Although it begins and ends at junctions with the M4, Newport City Council's agent Capita Gwent Consultancy stresses that the road is not a bypass for the motorway. This would seem to be borne out by the number of at grade roundabouts connecting it to local roads along the route.
The project is in three main sections. To the east it is mainly a widening job, with 5.5km of new carriageway now under construction in space which was set aside next to the existing road when it was originally built in the 1970s. South of the city centre the road will cross a new 190m span steel bowstring arch viaduct with composite deck over the Usk, before joining the 3.8km western section, which be a newbuild project including the landfill portion of the route.
Morgan Vinci jv is building the road for a joint venture company called Morgan Vinci Ltd - set up by the two contractors to take on the 40 year design build finance and operate (DBFO) concession.
Building on landfill is never ideal, because of the risk of settlement caused by compacting waste. Ensuring that the approximately 400m long landfill section of the road is settlement free is of paramount importance to Morgan Vinci because it will lose revenue if the road has to be closed while settlement problems are sorted out.
Newport City Council will spread payment for the road over 40 years, paying Morgan Vinci Ltd an annual fee. The payment mechanism is based on a formula developed by the Highways Agency for the DBFO upgrade of the A13 in east London.
Newport decided that 68% of the payment would be determined by the contractor's ability to keep the road open. If the road has to be closed for maintenance, the contractor will have money knocked off this part of the payment.
In addition, 27% of the fee is a shadow toll - paid according to the number of vehicles using the road. Another 3% is determined by the road's accident record and 2% is paid if things like lighting and grassed areas are maintained to agreed standards.
As an additional constraint, the road must be handed back to Newport with a residual life of 10 years after the end of the 40 year concession. This means that materials must be easily replaceable or very long lasting.
'The availability charge focuses the mind, ' says Morgan Civil Engineering operations manager Aidan Brannan. 'The key challenge is that we have got to construct a road that will live for 50 years.'
This has concentrated attention on ways of taking the road across the landfill. Final details of the solution are still being worked out, but Brannan says the contractor will use concrete columns inserted into the waste tip to hold it stable and limit settlement. The road will then run on an embankment across the consolidated ground.'
The payment mechanism has also had a major impact on the road's maintenance regime. The concession agreement allows Morgan Vinci to close lanes for maintenance between 9pm and 7am during the week, between 8pm and 8am on Saturdays and all day on Sundays. The wearing course is 25mm thick Tough Grip asphalt, chosen in part because it can be quickly planed off and replaced.
On the western section, the contractor also has to carry out a series of major services diversions. This includes relocating oil filled 132kW power cables.
Again the availability payment has driven Morgan Vinci's approach. It does not want to be penalised for allowing utilities to dig up the road to access their cables and drainage culverts.
'If the statutory undertakers go into the carriageway, availability is affected, ' says Brannan. To avoid this problem it has set up a forum for utilities affected by the road's construction. Its aim is to pool ideas and anticipate future needs. This is so that work can either be done before the road is completed or, if excavation is unavoidable, work can be co-ordinated. The contractor has also used ground radar to find uncharted services, so they can be accounted for if necessary.
Construction of the road itself involved overcoming other constraints. Work in the river is not allowed between March and June as this is the breeding season for indigenous Shad, Lampray and Bullhead fish. This places constraints on the construction of a pair of temporary piers which will be used to support the viaduct deck during construction. The contractor must also provide 7m clearance above the river's mean tide level, to allow barges and pleasure craft to reach an upstream wharf.
The Anglo French alliance between Morgan Est and Vinci Grands Projets is nothing new. The two have worked together on around £500M of projects mainly under their previous guises of Miller and Dumez GTM. The firms worked under these names on the Channel Tunnel Rail Link viaduct across the Medway in Kent, plus Contract 310 Thurrock to Dagenham. They are also working on a baggage handling tunnel at London's Heathrow.
Several of Vinci's French staff are familiar with south Wales, having worked in the Laing GTM joint venture which built the Second Severn Crossing, just down the road.
Another string to Newport's bow
'Newport was looking for a significant bridge to complement the other bridges along the Usk, ' says Capita Gwent Consultancy's Reg Ball, who acts as Newport's representative for the project.
Newport's collection of Usk crossings includes the historic transporter bridge, one of the few remaining examples of its kind.
Newport is also home to the George Street bridge, Britain's first cable stay structure.
To maintain the tradition, Newport City Council drafted in architect Ronald Yee Associates to develop the concept.
The result is the striking 190m span bowstring arch.
Keen to preserve Yee's vision, Morgan Vinci has taken him on as an advisor.