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Limestone / Cement
Limestone is the most widely used industrial mineral. Limestone is mainly calcium carbonate and forms on the bed of the sea from the remains of sea shells and other marine organisms. Beds of limestone are common throughout New Zealand. Limestone is used as a base for fertilisers with phosphate and other minerals such as potassium, salt, sulphur and serpentine being added. High quality lime is used in industry. Limestone is the basic material used to make cement. It is heated to remove carbon dioxide and water, and then shale or clay are added. When sand and gravel and water are added concrete is produced. Limestone has a wide range of other uses, many of them far removed from its origins
Holcim's Westport Cement Works began operation in 1958. The plant runs 24 hours a day and is capable of producing approximately 500,000 tonnes of cement annually.
Two bulk cement carriers, MV Milburn Carrier II and MV Westport, transport cement from the storage silos at the port of Westport to the eight marine terminals. Both vessels are able to carry used oil products back to Westport to be used as fuel in the clinker kilns. Each vessel makes around 300 port calls per year.
Each of the marine terminals has multiple silos to store bulk cement and most also operate a cement bagging facility to service the surrounding region.
Holcim New Zealand operates a fleet of cement tankers to distribute cement from its marine terminals to the ready mixed concrete plants and large scale roading and construction projects.
In addition, small volumes of cement are transported by rail from Westport to South Island depots on a regular basis.
The company's cement manufacturing operation at Westport involves quarrying the raw materials from a resource near Cape Foulwind. This quarry supplies the main component, limestone, and the secondary component, marl.
Quarrying operations can have a major impact on the surrounding environment, and on nearby communities. At Cape Foulwind the adjacent seal colony that attracts 100,000 visitors a year must also be a consideration.
In the mid 1980s Holcim carried out restoration work that mitigated the visual impact of the quarrying operations, and also began planting native species to restore the quarry surrounds to native bush. The quarry rehabilitation plan at this stage included the concept of indigenous forest, a lake within the area of the quarry workings, and adjacent wetlands.
In the early 1990s Holcim began work with David Norton from Canterbury University School of Forestry. Dr Norton is Associate Professor at the School and is an expert in the ecology of New Zealand plant communities. Dr Norton supervised projects assessing the re-establishment of native species in the quarry environs. In 1992 he presented the report Concept Plan for the Restoration of the Cape Foulwind Limestone Quarry and Environs to Indigenous Forest and Wetland.
The report outlined rehabilitation in four zones: the coastal restoration zone, mainly farmland adjacent to Tauranga Bay; the wetland restoration zone of the planned lake and associated wetlands; the quarry restoration zone, areas of workings not flooded and quarry slopes; the inland restoration zone of land adjacent to the road and inland farmland. The report outlined the constraints on restoration, as well as giving a pathway to successful rehabilitation in parallel to continued quarrying.
The restoration plan encouraged the setting up of a nursery at Cape Foulwind to raise indigenous species in local conditions. This nursery is leased to local a nursery manager who provides Holcim with up to 50,000 plants a year on contract, as well as growing for general sale.
The decade since the Norton report has seen thousands of natives planted, mainly in the coastal restoration zone, and inland restoration zone. These plants are already converting parts of the quarry environs to fully restored indigenous vegetation.
The goal of restoring this area to a complete, functioning, natural ecosystem is well underway.
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