An upgrading and widening programme on State Highway 58, which began in February, is being done in various stages. Costing $25 million, the first stage (the middle section) was awarded to Fulton Hogan. RICHARD SILCOCK explains the work involved.
A 5.1 KILOMETRE SECTION of State Highway 58 near Wellington, locally known as the Haywoods Hill route, currently sees around 15,000 vehicles per day use it as a connection between the Hutt Valley, Porirua and the Kapiti Coast.
While not seen as a feeder route to the Transmission Gully Motorway when that is completed in mid-2020, SH58 will provide an alternative route out of Wellington and the Hutt Valley, but the main focus of the project is on improving road safety. SH58 has a very poor safety record with over 156 crashes recorded since 2009, a number of which were fatal.
The NZTA’s regional performance manager, Mark Owen, says SH58 is a challenging piece of road. With multiple hazards including a number of sharp curves, undulations, gradient changes and some steep banks dropping off to the stream running close by, it was important to make it safer and more forgiving, so that simple driver mistakes didn’t result in serious injury or further fatalities.
“Realistically this road will always be a bit of a challenging drive, but this does not mean we should accept that death and injury are inevitable,” Mark says.
“We recognise that people can make mistakes, so the road needs to be more forgiving so driver error does not lead to tragic consequences.”
Upgrading this section entails taking out a tight blind curve by excavating a hillside (considered the most dangerous part of this road with two fatal crashes), realigning and straightening several other poor line-of-sight curves, widening the road throughout the section, and shoring-up and repairing parts of the road where, over time, the road’s integrity has been compromised by wash-outs caused by a nearby stream eroding some edge foundation.
The installation of wire rope safety barriers between the lanes of opposing traffic and along some drop-off edges, pavement sealing and road marking are also included in the upgrade.
Considerable earthworks have been required by the contractor to cut back eight metres of the hillside to take out the sharp curve and enable realignment of the road. It took around 24 weeks to complete this, with the 25,000 cubic metres of earth trucked to nearby Queen Elizabeth Park on the Kapiti Coast for use in the construction of a cycleway.
Sediment ponds were constructed at the site to alleviate environmental contamination and considerable work to improve rain water run-off and drainage was also completed.
Work came to a halt in June through September due to wet weather, which Contractor understands caused some stabilisation issues with the new embankments. This necessitated closing the site down and imposing a temporary speed restriction of 50 kilometres per hour for traffic over one kilometre of the highway.
“Due to a period of extremely wet weather we had some issues with the embankments and we’ve had to put the pavement sealing work on hold until mid to late spring when hopefully the weather will improve, temperatures will lift and conditions will be more suitable for attaining a good bind for the pavement seal,” a Fulton Hogan spokesperson says.
“Once that is completed we will get on with the lane marking and install 700 metres of centre-aligned wire rope safety barrier.”
The NZTA says work has been timed to align with the construction work that will take place for an interchange where the highway will intersect with the Transmission Gully Motorway near Pauatahanui, and the grade-separated interchange at the intersection with SH2 in the Hutt Valley.
Other sections of the highway upgrade will involve further extensive earthworks, widening and curve realignment, and constructing a roundabout at the junction with Moonshine Road. While the agency could not confirm a start date for these next stages, Contractor understands work will start before Christmas on Stage 2 at the Hutt Valley end of the highway. (The successful tenderer for this stage was due to be announced at the time Contractor went to print.)
Several passing lanes on the existing highway are also being removed to avoid potential accidents as traffic re-merges, and a 1.5 metre-wide shoulder will also make it safer for cyclists.
The NZTA, Porirua City Council and Hutt City Council had been collaborating for several years over planning the upgrade of this highway and following a report by consultants MWH Global in 2010 and public consultation at the end of 2014, they came up with this realignment solution to make the highway a much safer stretch of road.
The cost of the total upgrade is expected to be in the region of $33 million plus and will take just over three years to complete.