CONTRACTOR DEMPSEY WOOD CIVIL is approaching the completion of the $2.3 million contract to create 10,000 lineal metres of uncovered, terraced, embankment seating above existing terraced seating at what was once an iconic speedway and concert venue in Auckland.
THE CONTRACT INVOLVES Dempsey Wood earth-working a 1.2 hectare site and an approximately 5000 cubic metre cut to fill to create a uniform a 1:2.7 batter of solid clay at Western Springs Stadium in Auckland.
The work is being done for Auckland Stadiums, a Council Controlled Organisation responsible for three stadia across Auckland – Mount Smart and QBE (formerly North Harbour) stadiums as well as Western Springs.
Head of business improvement for Auckland Stadiums James Parkinson says work will result in safer and more comfortable seating options for patrons in the short term and, in the long term, will offer additional seating for sports events.
The council hopes to redevelop “the Springs” and has been in discussions with Speedway to move its events to Mount Smart, which is Council’s preferred option. This, says the council, would solve issues with noise levels at Western Springs, more events could be held in a season, and more seating at Mt Smart would be available for speedway events.
Dempsey Wood is an industry leader in shear-key construction and has extensive experience in carrying out bulk earthworks operations in steep terrain and devising methodologies to mitigate the problems this presents. It has been responsible for the whole job.
“We prefer to be the main contractor on any job,” explains managing director Conal Dempsey, who started the company 21 years ago.
Obviously, it’s a “pretty technical” job, he says, made possible through the use of very accurate machine control equipment used at all stages.
This has included the initial topographic surveying work as well as ongoing construction survey gear using everything from a robotic total station complemented with a rover and base station, to GPS-based automated Leica machine controls for dozers, graders and excavators, supplied by Global Survey.
“The design is supplied by the consultant,” explains Dempsey Wood’s surveyor Stephen Wardle. “This goes into the Leica 3D machine control software which is operated using GPS, and ensures our earthworks are cut to precise depths and angles without needing to use pegs.
“I share the same design data on my iCON robotic total-station which allows me to operate as just one person. By checking my readings against the excavator’s anywhere on site, we’re able to guarantee independent cross-checking of each and every cut.”
Using a single supplier, Global Survey, and single brand, Leica, for all positioning, measurement and machine control technology means everything on site integrates seamlessly, and as a result return on investment has been very rapid, says Conal Dempsey.
The extremely steep slope means working conditions are not for the faint hearted.
“It’s challenging work,” says Conal. “Machines are working on very steep clay terrain – so steep they need grip cleats on their tracks.”
Being on solid clay also means that rain can interrupt work at any time because the slope immediately becomes extremely slick. With Auckland’s reputation for four seasons in one day, that’s a real challenge.
“Doing stabilised cut to fill on a steep slope in such a confined area provided a real challenge,” says Dempsey Wood’s site project manager Michael Lunjevich.
“We were able to achieve it by having a methodology in place that always ensured safe plant access across the slope and kept the stabilising and compacting activities to flat temporary benches as we progressed up the hill. The safety of our guys is paramount so it was important to have their input when putting the methodology together.
“Being able to rely on the Leica GPS enabled excavator for trimming also adds a safety advantage to our operation. It eliminates the need for a person to be controlling trim levels and having to work in close proximity to large machinery which is especially beneficial on our compact site.”
Luckily the speed the company has been able to work at has meant residents surrounding the site have had their weekends significantly less disturbed than they would have been even five years ago.
“Without using the latest technology, we couldn’t have made such accurate cuts without taking a lot more time and using a multitude of pegs and such. Having well maintained plant also helps to reduce our noise output.”
Getting the scoria up to the top retaining wall was one of the first tasks that needed to be completed and was another challenge, says Stephen. The scoria had to be embedded behind the existing concrete wall between private properties and Western Springs.
The site has been divided into thirds, in cut and fill operations. This was an environmental requirement that also added to the challenge.
Some additional drainage has been incorporated into the design, complementing the existing drainage which remains intact.
Like the Yarrow Stadium in New Plymouth on which the design was based, seating will be uncovered.
Subtle retaining walls are incorporated into the seating design and unlike the existing concrete terraces, these framework supported terraces are just 400mm deep by 170mm high. Six stairwells are spaced across the development, compared to four on the larger existing levels.
Once seating has been blocked out and wooden stairwells completed, the slope will be covered in artificial turf. “Council agreed this will be longer lasting than the ready-lawn they were originally considering,” Conal explains.
Dempsey Wood has been very aware of the health and safety challenges presented by the project, and the company undertook morning prestarts to review procedures and safety requirements. All the safety provisions in the world are no use if they’re not being used, though.
Conal agrees. “Our company recognises the challenges and limits the risks by using common sense, safe and intelligent methodologies which are then clearly communicated to the staff. Project first, safety always.”