Quarrying & Mining Magazine

The big rebuild at Isaac Construction

The massive effort being deployed to restore Christchurch’s infrastructure has created opportunities for a number of aggregate suppliers in the region, including Isaac Construction, a long-standing supplier of aggregate to the region.

With the onset of the city’s rebuild, Isaac Construction, drove its equipment and production staff to their limits, until it became apparent it had to expand its production facilities.
Set up in 1957, Isaac Construction’s McLean’s Island quarry is one of the oldest quarries in Christchurch. The quarry converts its raw material feed of incredibly hard, ancient river gravel into coarse natural concrete aggregate, blended sand (natural and Barmac dust) as well as sealing chip. Located just 18 kilometres from the centre of Christchurch, the quarry is ideally placed to efficiently supply its products for the city’s reconstruction work.
After the 2010-11 earthquakes, Isaac Construction ramped up production and was eventually running double shifts to meet the increased demand for concrete production and road-building materials. However, the plant’s production capacity and reliability started to become a major issue. This sometimes resulted in the need to buy in products to satisfy supply obligations. So towards the end of 2011 the company’s management team agreed that an upgrade was required to treble the quarry’s production capacity from 100 to 300 tonnes per hour.

Peter Newfield, Metso Australia (left) with David McCaffrey and Mike Higgins from Isaac Construction.
Peter Newfield, Metso Australia (left) with David McCaffrey and Mike Higgins from Isaac Construction.

A tender process was initiated in February 2012 and, after months of bid reviews, Isaac Construction awarded an $11 million contract to Mimico for Metso equipment.
The plant was designed, fabricated and installed by QMI Engineering, a Mimico subsidiary and the upgrade was completed in three stages. Work on the primary and secondary sections started in early 2013 and was completed in September 2014. The tertiary section was started in November 2014 and was completed by May 2015.
This project represented a significant investment for Isaac Construction and it wanted a payment arrangement that would not impact on the continuity of funding for the company’s long-established community and environmental trust operations.
“To avoid the need for Isaac’s to make large lump sum payments, such as a 10 percent deposit and other significant milestone payments that are typical in such large scale projects, we offered a monthly payment arrangement,” says Rex Davies, Mimico’s managing director.
“This required careful planning on our side because we needed to synchronise the project’s progress with the payments as best as we could. Obviously there were instances when it wasn’t possible to get the timing right, so financially it would be a bit tough for us for a month or two as we still needed to continue paying our suppliers on time.
“This was a great result for Isaac’s, as quite uniquely, the arrangement allowed them to make all of their payments from cash flow. I am quite certain that our payment package was an important factor in the decision to award us the contract.”
The feedstock from McLean’s Island quarry is infamous for its hardness. This factor alone made designing an optimal plant complex. Contributing to this complexity, were shifting market demands both in terms of volume and variety of product.
The finished project delivered numerous optimisations, cost savings, and process efficiencies for Isaac Construction, says Rex.
“An example of how the new plant has reduced costs is the elimination of the load and carry aspect of the process. Previously the plant consisted of three sections and so at any one time there would be four or five wheel loaders moving product between sections for the next stage of processing – doing up to 120 kilometres a day. Not only did this mean high fuel and maintenance costs, but it was also a big capital outlay. The new plant has a network of conveyors, removing this requirement completely.”
For plant manager Mike Higgins the flexibility of the new plant is what impresses him most.
“We have a fairly unique situation in this region, at times it’s a real challenge to produce what the market needs from the feed gravel we have available to us. The gravel is very hard, and this makes it expensive to produce large volumes of fine-crushed material.
“Thanks to this project, we have been able to optimise our costs far better than other quarries. Lower costs and the ability of the new plant to easily change the product specification have made us very competitive in meeting market demands.” 

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