Constructing an award-winning, terraced amphitheatre on an extremely steep site alongside the Waikato River was not without challenges. Richard Silcock explains.
Demolishing derelict building foundations, removing contaminated earth and constructing a unique public amphitheatre suitable for staging outdoor concerts and events on a 45-degree sloping, 4000 square-metre site that faced the Waikato River in the heart of Hamilton’s CBD was no easy task!
The scene was set by the Hamilton City Council to turn the unused site into a worthwhile public venue. The overgrown site had lain derelict for some considerable time and was regarded as an eyesore by the general public and local businesses over-looking it.
Enter Hamilton based Schick Civil Construction, the construction act of the project, who in just over six months of solid and intensive work transformed the space into a splendid facility that the client, Hamilton City Council and the people of Hamilton as patrons can be justifiable proud.
With a set designed and structured in a ‘V-shape’ with tiered, terraced concrete seating cascading down the slope, the aptly named Victoria-on-the-River facility (it is accessed from Victoria Street) features granite and rock-salt finished concrete paving, a hardwood boardwalk, corten steel garden accents, state-of-the-art Italian lighting, landscaping and extensive plantings.
The project provided Schick with a ‘value-engineered’ end-to-end complex construction challenge that required thinking and planning well outside the box.
Schick’s Waikato regional manager, Ryan Smith, says the project was an exercise in logistics, careful planning and working in an extremely collaborative way with the architects (Edwards White), the consulting engineers (Aecom), suppliers and specialist sub-contractors, the council and the nearby commercial businesses.
“Not only was the project challenging due to the site’s steepness and design complexity, but being right in the heart of the city also brought its own particular challenges,” says Ryan.
“It meant all our vehicle movements to and from the site needed to be carefully orchestrated to avoid peak traffic times and minimise disruption to pedestrian flows. We also had to be mindful of the adjacent office buildings and apartment blocks, minimise noise and vibration and work within, and be compliant with, the resource consent.
“This also meant being vigilant, not only of the steep site from a health and safety perspective but also in not allowing any soil or silt run-off contaminating the river.”
Initially a lot of the preparatory work necessitated extensive site clearance. Contaminated earth covered much of the area and had to be removed down to subgrade level with over 3000 cubic-metres of soil excavated and carted in covered truck and trailer units to a controlled waste-disposal dump on the outskirts of the city.
In addition, the old concrete and brick foundations of the former Waikato Times building and a public car park that had occupied part of the site had to be broken up, excavated and removed to allow for the terracing to be formed and the drainage and services trenches excavated.
“We also discovered a second gas main, in addition to the one noted on council plans,” says Colin Vette, Schick’s project and contract manager. “It was buried to a depth of one-metre, so made tracking difficult. In addition water pipes and an old sewer coming from a nearby building were found to be connected to old brick manholes that had no lids, so we replaced these along with a new sewer line.
“With most of the old utilities running down a service lane to where the former Waikato Times building was located, it was a case of testing each pipe or cable to ascertain whether it was ‘live’. A gas main also had to be replaced as it ran directly over and around the sewer main, and the asbestos pipes that we encountered had to be removed and replaced in a controlled manner.
“The actual earthworks and formation of the terraces was a challenge for our machine operators, not only because the ground composition varied between sand, soil, rock and concrete, but also because the design called for a semi-circular-like amphitheatre to be formed along with the provision of wheel-chair ramps for people with a disability,” says Colin.
Once formed the terraces were overlaid with 6721 non-square concrete panels which were pre-cast by Ultimate Precast in New Plymouth.
“These three-tonne panels were laid to form the seating with none being at the same angle,” says Colin. “The original design specified the panels be seated on a compacted GAP20 base, however we adopted a more efficient method of installation. This entailed pouring concrete micro-piles, 300mm in diametre under each panel to provide a stable base and allowing us to achieve an accuracy tolerance of within one-millimetre.”
Colin says it allowed them to install 65 panels in only two days – which was far quicker than the original specification.
“Apart from the various angles and finishes a further unique feature of the concrete was the porous, rustic surface finish which was achieved by applying rock salt when pouring then washing it off 24hours later. This was the first time such a finish has been used for a commercial project in the city with some 1250 square-metres of concrete finished in this way.”
Two-hundred, driven timber plies were used as the base for the boardwalk sub-floor which connects the terraces to an existing river-side walkway. To provide the eight-tonne piling rig with a platform from which it could safely drive the six-metre long piles, an access way had to be created down the unstable slope.
The timber and materials for the boardwalk were craned down from above using a 100-tonne crane and then dragged into position.
Most of the decking was constructed of imported hardwood (purpleheart from South America) and was fixed in place using over 18,000, 90mm long screws in pre-drilled holes.
All the electrical wiring, which runs underground from a central supply point, connects the lights along the terraces, pin lights on the boardwalk, feature lighting in the landscaping and ‘fairy ‘ lights on the steel portals. Power was also required for security installations.
“It was clear from the start that doing everything to a high standard was paramount and would only be achieved by having a robust quality control system in place that had hold points and sign-offs along the way,” says Colin.
“This minimised the chance of any errors and helped maintain standards.”
“For instance, the chance of having a concrete panel at the wrong height or angle had the potential to seriously impact the build process.”
The initial lump sum styled contract called for the project to be completed in six months with all risks lying with the contractor. Inherent in that was the risk of wet weather, soil conditions and dealing with the contamination, supply of materials and other risk factors. Following negotiation with the council, the risk was subsequently spread between the council and contractor. Despite the soil contamination and an abnormally wet winter, Schick were able to deliver, with only a slight extension of time, a project of high quality and finish.
At a cost of $4.9 million it was completed in January this year and has not only provided an exciting and functional venue for the staging of various events but has also become a popular roost for lunch time office workers. As was the councils’ desire, it has also reconnected the inner city with the river, one of the city’s most noticeable and endearing assets.
Comments from the ‘critics’ have been complementary with praise for both the design, the high level of construction finish and accuracy, the selection and use of materials and its overall pleasing ambiance and functionality.
A worthy awards winner indeed.