Sustainable Development Initiatives At Oparure Quarry

By Darcy Madden, quarry manager, McDonald’s Lime, and Greg Slaughter, sustainability manager, Holcim (New Zealand) Ltd

This paper — which earlier this year was awarded The Institute of Quarrying’s 2009 Caernarfon Award — outlines four examples from McDonald’s Lime Oparure Quarry where voluntary initiatives focused on sustainable development have proved that what is good for the environment is also good for business.

First, water management at the quarry, through water recycling and specialized stone washing, has resulted in reduced water consumption, cleaner discharges, reduced costs and improved product quality. Secondly, large areas of the 67ha site have been rehabilitated for agricultural purposes and are now in a condition better than that present prior to quarrying. Thirdly, carbon-management initiatives have been adopted to measure and reduce energy consumption and carbon dioxide (CO2) emissions from the quarry operations. And fourthly, cave conservation and community involvement have demonstrated the company’s strong commitment to corporate social responsibility.

As a result of these initiatives, McDonald’s Lime have not only enhanced the quality of the surrounding environment and their reputation within the local community, but they have also increased the sustainability of their business.

Background

McDonald’s Lime is a subsidiary of Holcim New Zealand (75%) and New Zealand Steel (25%). The company’s Oparure Quarry, which is located 5km south of Waitomo village and 7km west of Te Kuiti, is the largest lime-producing quarry in New Zealand, supplying over 750,000 tonnes of high-quality limestone each year for commercial and agricultural uses throughout the North Island (fig. 1.). The site occupies an area of 67ha, which includes excavated areas, the processing plant, pastoral and forestry land, rehabilitated areas and a limestone cave complex.

The quarry is part of the Waitomo District, known for its karst formations of very pure limestone deposits. The high quality of the limestone is one of the reasons why the quarry is located in this area; however, it is also the reason why there are numerous individual cave and karst features of national and international significance within the district (including Waitomo Caves, Lost World and McDonald’s own Mason’s Dry Cave). McDonald’s Lime have developed long-term partnerships with the local community and indigenous people by focusing on protecting
and enhancing the district’s unique environment.

Recently McDonald’s Lime achieved certification to the international standard for environmental management ISO14001 at Oparure Quarry. The adoption of this standard has helped the company drive initiatives regarding environmental management and sustainability focused on water management, rehabilitation, minimizing waste, working with the community, and carbon management. As required by the standard, the quarry sets specific environmental targets each year against which progress is measured and externally verified.

Water management

Water for the quarry is carefully managed and improved to ensure surrounding catchment water quality and quantity is maintained and enhanced. Improvements in stone washing, truck wheel washing, water harvesting and treatment processes have not only reduced the environmental impact of quarry operations, but have also increased the overall productivity and energy efficiency of the quarry.

The installation of a stone-washing screen in 2005 was commissioned to remove fines and clay accounting for 4.3% of the unwashed product at the quarry. This gave direct savings from reduced cartage of fines and lower costs associated with cleaning conveyor tunnels, chutes and blockages at McDonald’s lime processing plant at Otorohanga. Due to the pre-washing, there is reduced settlement pond maintenance at the Otorohanga plant and less transportation of sludge back to the quarry for disposal. This has helped reduce the silica concentration in the final product as most of this was from the fines and clay.

The water used for washing the stone is discharged through a maze of small treatment ponds, before being held in a large storage pond (fig 2). Water from the storage pond is accurately monitored using a v-notch weir system (fig. 3) before being continually recycled. Much of the storm water from the quarry is also recovered and fed into the storage pond for subsequent use. For every tonne of stone requiring washing, some 2m3 of water is needed, but by recycling the water in this manner, a significant amount of water is saved. This form of water harvesting is considered both environmentally important and commercially beneficial for the quarry’s operation.

The truck wheel wash is another voluntary environmental initiative that prevents quarry vehicles exiting the quarry from tracking fine lime aggregate on to Oparure Road. The truck wash at the quarry is very effective and represents a best-practice approach, given that it also recycles the water used (fig. 4).

In the event of significant rainfall, water is designed to discharge from the storage pond in a controlled manner, via a vegetated swale, before entering the Mangawhitikau river. During these events, quarry staff monitor the quality of the discharge to ensure compliance with the conditions of consent. McDonald’s have also recently planted native riparian plants along the Mangawhitikau river to help enhancement of the river margin in partnership with the local iwi, Maniapoto Maori Trust Board.

Rehabilitation

Oparure Quarry’s aim is to rehabilitate the land to a better condition than that present prior to quarrying. Up to 1 million tonnes of overburden are stripped each year to meet the operational demands of the quarry, which presents various challenges to the quarry operations.

After removal of the topsoil the gullies are lined with limestone cap rock, which allows natural storm water runoff to effectively percolate through the clean rock before reaching underground waterway systems. Siltstone is compacted over the cap rock to provide a solid bed for the volcanic ash to follow. At strategic intervals, cap rock sumps ensure all water runoff reaches its normal discharge stream so that underground water tributaries within the karst system are not effected. This rehabilitation programme has improved the quality of the surrounding waterways, ensuring an effective filtering system for the water before it discharges into creeks and streams.

Prior to rehabilitation, gullies were previously being farmed with difficulty due to steep slopes and limestone bluffs where stock would often be lost. The restoration plan was to return these areas to pasture but with a contour that would not appear out of place and would be conducive to the type of farming being undertaken.

Involving the farmer at an early stage of the rehabilitation assisted McDonald’s Lime in identifying areas to be used for grazing. Rolling terraces were designed to support the intensive farming style, and special grass seed types and a rigorous soil-analysis programme were selected to enhance dairy grazing. Quarry management controlled the grazing movements, fertilizer and lime applications for 12 months before handing the land over to the farmer for full productive use.

Carbon-management initiatives

McDonald’s Lime acknowledge that they are a company operating in an energy-intensive business, and they recognize the need to reduce greenhouse-gas emissions and energy consumption while fostering economic and social development. They understand that climate change is a risk to business that cannot be ignored. As such, the company has adopted a ‘measure to manage’ approach to CO2 and has begun measuring its emissions per tonne of quarry product as a key performance indicator (table1).

McDonald’s have benchmarked these specific CO2 figures with other quarries internationally. In particular, data from Aggregate Industries in the UK indicate comparable specific CO2 at between 4.0–5.0kg/tonne. However, initiatives that are being undertaken during 2008/09 to further reduce CO2 emissions from production include the following:

• A cone crusher was purchased in early November 2007 to maximize the use of total stone resources and to present the right quality, quantity and grade of stone for processing. In addition, re-screening during the first washing removes unwanted material, while reduced fall distance from the head drum minimizes segregation. This allows stable kiln operation, which in turn has led to production and efficiency gains.
• Installation of a wash plant has improved product quality and reduced the volume of product transported from the quarry for processing at Otorohanga by 4–5%.
• The purchase of a Volvo loader that consumes 9 litres/h less fuel than its predecessor (fig. 6). This machine uses one of Volvo’s new Advanced Combustion Technology engines, which complies with the stringent US Tier 3/EU Stage IIIA emission requirements. The quarry has subsequently saved 27,000 litres of fuel per annum (based on 3,000h expected work).

The effectiveness of these measures is being tracked on a monthly basis and has started to show not only reductions in emissions, but also a reduction in production costs.

Work with the community and indigenous people

Oparure Quarry is an important member of the Oparure and Waitomo communities and has been extensively involved with many projects aimed at corporate social responsibility.

The quarry has held regular open days which have become a highlight of the community’s calendar. Over 200 visitors came to the relatively remote quarry location during the last open day. Visitors included neighbours, customers, key suppliers, iwi, and regulatory bodies. At these events, visitors are given a tour of the operations, watch lime-spreading, stabilization and blasting demonstrations, and enjoy a barbecue.

The quarry also hosts secondary school visits, where geology and chemistry students get the chance to view, first hand, raw material resource extraction methods and the final uses of these materials. The reason behind encouraging the local community to visit the site in this manner is to help inform stakeholders that the quarrying industry is not a dirty industry, and that Oparure Quarry, in particular, is a well-managed and professional operation.

Moreover, the area surrounding the quarry has a long and significant cultural history. Recently, McDonald’s Lime have undertaken an initiative to formalize their existing relationship with the local iwi (indigenous tribe) Ngati Maniapoto. In 2008 the company signed a Memorandum of Understanding with the Maniapoto Maori Trust Board to help allow both parties to work together in good faith for their mutual benefit (figs. 9 & 10). The Memorandum states that McDonald’s will manage operations, as far as practicable, so as to avoid, remedy or mitigate any adverse effects on cultural value. It is planned that the document will help Maniapoto and McDonald’s Lime to develop and maintain an ongoing and meaningful consultative relationship long into the future.

Given the importance of the local karst and cave areas, McDonald’s Lime have also undertaken a lot of work (in combination with Prime Explosives) in optimizing blast patterns to ensure the minimum amount of explosives are consumed to achieve optimal stone size and to minimize ground vibration per tonne of rock. Recent blasting has achieved a powder factor of 0.28kg/m3 (ie, 0.11kg of explosive per tonne of rock). McDonald’s have also committed to the monitoring of vibration caused by future blasting. To date the company has been successful in avoiding damage or nuisance vibration effects to neighbouring cave systems.

The company is also extensively involved with a cave-conservation project and tourism operation in Mason’s Dry Cave (also known as Spirit Cave or TeAna o Te Atua), which is located on land north-east of the quarry that was purchased by McDonald’s Lime Ltd in 2000. Before the company purchased the cave, its natural features had suffered significant damage under the previous ownership.

The cave was purchased by McDonald’s at this time to prevent any further degradation and to help manage visitors. McDonald’s Lime worked with local commercial cave operators ‘Spellbound’ to clean up and rehabilitate the cave to its natural state and to operate it as popular tourist attraction with over 2,000 visitors each year (figs. 11 & 12).

The cave is part of the Mangawhitikau System and now features all-weather access, full wheelchair accessibility, cave lighting and a complete fossilized moa skeleton. In 2005 the cave hosted two BBC film crews, led by Sir David Attenborough, who were amazed by the dense and magnificent display of glow-worms in the cave. Indeed, one crew member described the Spellbound Waitomo Glow-worm Cave as one of the world’s top-10 natural spectacles (www.glowworm.co.nz/) (fig. 13).

Summary

McDonalds Lime’s are committed to going beyond compliance in developing sustainable development practices at their Oparure lime quarry. To date, these sustainability-focused initiatives have not only provided significant benefits to the environment, but have also contributed to company’s business success. McDonald’s Lime plan to continue these environmental initiatives and the involvement of the community well into the future.