Helping to rebuild Christchurch: quarry upgrades to meet the demand

The South Island of New Zealand is one of the most pristine environments on earth; crisp clean air, emerald green pastures, vividly blue rivers with crystal clear water and snow-capped mountains — a picture of paradise. Life in the island’s capital city, Christchurch, seems tranquil and unrushed. People here are polite and friendly, and they actually respect the speed limit. But a visit to the city’s central business district is a stark reminder that things haven’t always been so tranquil in Christchurch.

Already weakened by a 7.1 magnitude earthquake in 2010, the city was struck by a 6.3 magnitude earthquake on 22 February 2011. As well as causing widespread damage to buildings, roads and infrastructure, tragically the quake claimed 185 lives. This disaster was compounded by two additional earthquakes in June and December of the same year. Over 100,000 homes were damaged, many of which were condemned. More than two-thirds of the shops, hotels and office buildings in the heart of the city had to be demolished. The devastation was so widespread that it took nearly two years to fully quantify all of the damage. Early in 2013, the New Zealand government announced its total damage estimate came in at a staggering NZ$40 billion (AU$38 billion).

The massive effort being deployed to restore the city’s infrastructure has created a need for a huge amount of resources. This unprecedented demand has continued to grow, challenging local building companies and construction material suppliers to step up their production. Isaac Construction has been a longstanding supplier of construction materials to the Christchurch region for many years. Much of the company’s quarry product is consumed in concrete and bitumen production. Isaac Construction is one of the companies that took on the challenge of meeting this ever-increasing demand to help rebuild Christchurch. Initially the company achieved additional volume through a lot of hard work, driving its production staff and existing equipment to their limits. However, it soon became apparent that the need to expand the company’s production facilities was inevitable to ensure its ability to reliably meet demand over time.

MacLean’s Island quarry — combining construction with conservation

Established by the Isaac family in 1957, Isaac Construction’s MacLean’s Island quarry is one of the oldest established 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 for roads. Located just 18 km from the centre of Christchurch, the quarry is ideally placed to efficiently supply its products for the city’s reconstruction work.

Caring for the interests of the community and environment has long been part of Isaac Construction’s business approach. The company’s slogan “Combining Construction with Conservation” is proudly demonstrated through the work of The Isaac Conservation and Wildlife Trust, which was established by Sir Neal and Lady Diana Isaac in 1977.

Upgrading to meet market demands

After the 2011 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 and boldly decided to treble the quarry’s production capacity from 100 to 300 tonnes per hour.

A tender process was initiated in February 2012 and after months of detailed bid reviews, Isaac Construction awarded a NZ$11 million contract to MIMICO — Metso’s exclusive distributor in New Zealand. The contract included the design, supply, installation and commission of a new plant based on Metso’s crushing and screening equipment as well as its wear protection system. The plant was designed, fabricated and installed by QMI Engineering, a fully owned subsidiary of MIMICO. Commissioning was undertaken by MIMICO’s in-house service team. 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.

Knowledge, experience and a proven track record

Stu Cameron, Isaac Construction’s maintenance supervisor, explained from his perspective why choosing MIMICO as the supplier of the new plant was a good move. “A big factor was the confidence we had in the working relationship. All the key people on the project from QMI engineering and MIMICO knew our plant and company.

“Another important factor was the reliability of our existing Metso crushers. In our old plant, we had a Metso HP100S and an HP200; both machines were close to 20 years old and were still running strong,” he said.

Colin Welsh founded QMI in 1989, and has been personally involved with Isaac Construction since 2000. He said, “When we first started doing work for Isaac Construction it was just maintenance over their Christmas shutdown period. Over the years this grew into doing refurbishments and small upgrades to improve production rates, or to add the capability to produce different products. There is no doubt that our long-term relationship played a big part in us being awarded the contract.

“On our side, we had developed a deep trust for the people at Isaac Construction. This was a significant factor in our risk evaluation of the payment arrangement for the contract.”

David McCaffrey (L) and Mike Higgins (R) make adjustments to production parameters via the plant’s SCADA user interface.

Project challenges

The feed stock from MacLean’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. This forced Isaac Construction to change the required project specifications. While changes like this are understandably unpopular with contractors, David McCaffrey, MIMICO’s process equipment engineer, believes that his company’s ability to quickly interpret changes, adapt process models and select suitable equipment helped them to win the project.

“BRUNO is Metso’s easy-to-use software tool for planning and simulating the crushing process. It helps us to quickly explore various machine combinations for different applications. We use it extensively. On this project, I created many alternative models in BRUNO before proposing our overall design,” said McCaffrey.

“When Isaac’s advised us about expected increases in sales production volumes for various products, I quickly made changes to input and output parameters and within minutes was able to assess the performance of the various models I had previously built. This allowed me to quickly understand what changes we needed to make to our offer.

“We also excelled in addressing the uncertainty of Isaac’s feed stock hardness, as we have our own laboratory which conducted extensive crush tests for us. The combination of using accurate crushability data and presenting BRUNO process models gave the management at Isaac Construction a high degree of confidence in the reliability of our design,” he said.

A strong focus on safety

Talking about the project and its outcomes, Cameron said, “Overall things went really well, so it is hard to try to single out anything that stands out. I would say though, that the advanced safety levels in the new plant have really impressed me.

“Based on what I have seen, I think it has possibly worked out cheaper to install new plant than to try to get the existing plant up to the same safety standards required to comply with New Zealand’s latest safety rules,” he explained.

Mike Higgins, Isaac Constructions industries manager, is responsible for the running of all of the company’s production facilities. Mike believes that the high level of safety provided by the new plant has ignited a wave of safety awareness.

“Suddenly we all started looking at things differently and have become very proactive in increasing our safety performance,” he said.

Plant efficiency and flexibility delivers a competitive advantage

The project delivered numerous optimisations, cost savings and process efficiencies for Isaac Construction.

“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 km 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,” said Rex Davies, MIMICO’s managing director.

“I am very satisfied with the way that our team has performed and the outcomes we have delivered for Isaac Construction. Our collaboration throughout the project has strengthened our relationships. I’m pleased to say that through the process we have established a good, loyal and long-term customer.”

For 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.”

Top image: Infamous for its hardness, the quarry’s feedstock contributed to the complexity of the plant’s design.