RICHARD SILCOCK takes a look at a quarry that, after being mothballed for a number of years, was reopened in 2008 following a decision to invest in a sand, chip and aggregate plant to supply the expanding demands of the Christchurch and wider Canterbury markets.
The Fulton Hogan owned and operated Miners Road Quarry at Yaldhurst on the outskirts of Christchurch is one of the biggest in the South Island, producing on average around 700,000 tonnes of chip, sand and aggregate per annum.
It has been described as a state-of-the-art quarry by all accounts and was largely designed in-house by Fulton Hogan’s own quarrying specialists.
Originally developed, owned and operated by British Pavements in the 1970s and early 80s to supply aggregate for road construction in the region, the quarry passed into Fulton Hogan ownership following their purchase of the company in the mid-80s.
Mothballed for a number of years, it reopened in 2008 following a decision to invest in a sand, chip and aggregate plant to supply the expanding demands of the Christchurch and wider Canterbury markets.
“The quarry sits within Christchurch City’s established ‘quarry zone’ and lies astride the former Waimakariri River flood plain so there is only 0.5 to one metre of overburden that needs to be removed,” says Jared Johnston, Fulton Hogan’s quarries divisional manager.
“Due to the predominately flat topography the alluvial deposits are readily accessible and do not require deep extraction.
“The success of the quarry can largely be attributed to our own people and their technical expertise in designing the quarry which is a bit unique and to the plant setup which is fairly advanced in terms of technology, ease of operation and maintenance.
“With these components put together we are able to achieve, on average, a throughput of around 400 tonnes per hour. This is a pretty significant amount of extracted resource and maintaining this output week to week can be attributed to our on-site team who bring considerable skills to the job and have an intimate knowledge of the site and the know-how to operate efficiently.
“Although there are some really clever quarry modelling programmes available these days, they are not tailored to the local environment.
“Using our own in-house knowledge the whole operation at Miners Road has proven to be highly efficient. Our quarry managers and supervisors know the site and the resource pretty well and by utilising suitable plant, such as our long field aggregate conveyors, we can move product pretty rapidly from the extraction point to the crushers for processing.”
The Miners Road Quarry essentially occupies two, 40-hectare sites, separated by the road. Rather than utilising dump trucks to transport the mined product to the crushers, Fulton Hogan has opted for designing and constructing an underpass beneath the road through which a 700-metre long conveyor transports the aggregate to the crusher. As the mining perimeter extends, the conveyor will be further extended out to 1.5 kilometres in length.
“Our technical people designed and built the conveyors for our particular requirements,” says Jared.
“While there was significant start-up capital required to build the conveyor system, the huge reduction in dump truck movements along with other operational efficiencies, such as the reduction in the amount of diesel used, have easily offset this cost.
“The crushing plant itself consists of three Metso cone crushers (two HP200s and one GP300) and a Barmac.
“Everything except the actual crushers and the specialty sand plants was designed and built by ourselves, including the screens and feed bins.
“We opted for the GP300 crusher as our primary unit given the small nature of the stone and in considering the noise impacts. The overburden is stripped by CAT excavators and then extracted by six, 34-tonne CAT and Volvo loaders which operate throughout the quarry. A couple of Volvo A40E dumper trucks and a tractor trailer unit make up the rest of the fleet.”
Nine permanent staff work at the quarry under the supervision of Blair Ferguson, who has been with Fulton Hogan’s Quarry Division for 10 years.
“Quarries are deemed to be pretty high risk areas and there have been some unfortunate accidents in the past at some other quarries,” says Blair.
“We’ve had no accidents at Miners Road and this can be attributed to our staff buying-in and adhering to our strict safety procedures. We are like a large family and really look out for each other.”
To combat dust at the site, Fulton Hogan has invested in sealing the access roads and operating a 22,000 litre water cart on the unsealed sections.
At the recent MIMICO Environmental Excellence Awards at the Quarry NZ Conference held in Blenheim back in July, the Miners Road Quarry took out a silver award for ‘leadership in environmental policy and sustainable practice’ (refer Q&M Aug-Sept 2016).
The quarry caters to a range of markets in the Canterbury region and actually sells more aggregate to external clients than it supplies to the other divisions of Fulton Hogan.
“We have, for example, a contract with Allied Concrete to supply most of their sand and aggregate requirements,” says Blair.
“We also supply asphalt aggregate and road sealing chip along with top-course and M4 graded basecourse product to a large customer base in the region.”
Aggregate is currently extracted down to a depth of eight metres and it is estimated that the quarry has sufficient resource to mine for the next 15 years.
To meet projected future demand a group of Canterbury quarries in the area, including those owned by Fulton Hogan, have recently sought resource consent to mine below the highest groundwater level.
This has however been rejected by the Environmental Commission (on behalf of Environment Canterbury, the Christchurch City Council and the local DHB) citing a potential risk to untreated drinking water sourced from the deep aquifers fed by the Waimakariri River (refer Q&M Oct-Nov 2016).
Fulton Hogan has also recently commissioned an additional quarry at McLeans Island for sand and aggregate and a top-course plant at Pound Road, with the latter having a ‘drive-over’ feed bin to maximise efficiency. Both facilities have also been designed in-house, of course.