Downer engages Synergys’ PaveSmart Grade Control

Downer recently engaged Synergy Positioning Systems’ survey consultancy service and PaveSmart grade control system to ensure time and cost savings on resurfacing a lengthy section of Christchurch arterial road.

In addition to the resultant logistical benefits to the project, utilising Synergy Positioning’s PaveSmart grade control system also resulted in a NAASRA count unlike anything recorded so far in the busy Christchurch infrastructure redevelopment scene.

Synergy Positioning’s Survey/Software Manager Gavin Greenhalgh says that after initial construction and Membrane work was completed along Russley Road – a major connecting route to the city’s International airport and freight precinct – a NAASRA survey recorded a less-than-satisfactory result.

“The build spec required a NAASRA count of 50-60, but with Membrane Sealing already laid, initial results were well above that. We sat down with the client and came up with a methodology for proceeding with remedial work, which included a detailed as-built survey of what was already there.”

Following an initial survey using a Topcon Robotic Total Station to accurately measure paving depths, Gavin then employed the PaveSmart grade control system – which was fitted to Downer New Zealand’s paver to control hydraulic levels – to meet the required asphalt paving depths across the road surface with absolute precision to adhere to kerb revel, ride and tonnage constraints.

“Not only does the PaveSmart system work to incredibly accurate tolerances, meaning that surface specification always complies with or exceeds what’s expected, it will also adjust and allow for the effects of differential asphalt compaction,” says Gavin.

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“We also decided that, rather than proceed with smoothing the road profile from the shoulder to the medium in one grade, we’d work the profile lane-by-lane. This method of surveying enabled us to develop a grid table for each lane, allowing us to see where mix was needed, whilst constraining additional tonnage use.”

The ability to provide an accurate map of the material requirements meant that Downer New Zealand’s project Asphalt Manager was able to lock down tonnage rates before the job even commenced, resulting in cost savings for the job.

“The profile accuracy really sped up the remedial work,” says Gavin. “Downer New Zealand was obviously impressed with that aspect and NZTA were impressed with the finished result.”

While the overall NAASRA count was above the required mark before Synergy Positioning employed the PaveSmart system, the score afterwards caused an equal amount of raised eyebrows.

“We got a 13 from one lane on the initial post-pave survey run,” laughs Gavin.

“That was so good, several project personnel couldn’t believe it, so we took the NAASRA vehicle out again and on the southbound inside lane scored a 15, with an average over the four lanes paved of 18.25.

“As I understand it, the country’s previous best NAASRA count across the board was 19.25, which was achieved on the Hobsonville Motorway project in Auckland, although it needs to be stated there are variables which mean we’re not comparing apples with apples.

“Regardless though, the Russley Road project was a great result for the client and a good illustration of what can be achieved with this technology.”