Sand mining case studies in NZ

The Hauraki Gulf is currently the site of the biggest seabed mining operations in NZ waters. Pakiri and Mangawhai have been compromised by nearly 80 years of nearshore suction dredging, in waters from 5-20 metres deep. This has had multiple visible impacts including the loss of dunes and surrounding vegetation. The quality of the surf has been adversely affected and the fishery disturbed.

Currently two permits are active allowing extraction of 76,000 cubic metres of sand per year (near-shore Pakiri). In 2006, sand mining at Pakiri Beach was extended for a further 14 years by the Environment Court. This case highlights the frailties of relying on supposed scientific evidence for solutions to problems, as despite all the anecdotal evidence being negative; despite all the objections from a vast majority of residents, allied with a body as significant as the ARC; and despite the huge investment made by them in the form of a nearby regional park; and despite the comparatively small return in revenue from the mining company, the law can still allow an activity like this to take place. What was the worst aspect of this was that it appeared to be up to the residents to prove that mining was responsible for erosion to their coast, rather than the appellant.

“In a reserved decision, the court dismissed objections to continued mining from the Auckland Regional Council and Friends of Pakiri, made on the grounds of serious environmental effects. McCallum Bros and Sea Tow appealed to the court after the council turned down their application to take 76,000cu m of sand a year for 20 years near the shore at Pakiri. The companies sought to renew consents to take the sand from where the water was 5m to 10m deep in the Mangawhai-Pakiri bay area. In court, the firms disputed the claim of the council and experts that the bays formed a closed system and no new sand was coming in. The ARC said continued extraction would eventually lead to beach and dune erosion and would spoil the significant natural character of the coastline. But the companies said that despite huge volumes of sand having been extracted from the Pakiri inshore area over the past 85 years, no significant erosion or change to the coastline could be blamed on the extraction. The firms sought 20-year terms because of the quality and value of the Pakiri sand, which is needed for Auckland construction projects. It has also been used to replenish the beaches at Mission Bay, Kohimarama and St Heliers.

Judge David Sheppard said no link between sand extraction and environmental damage had been shown. He authorised coastal permits for the mining for 14 years. ARC environment chairman Dianne Glenn said last night she was disappointed by the decision. In December, the council paid $20 million to create a regional park at Pakiri and the dunes there have two threatened bird species – the NZ fairy tern and the NZ dotterel. The Government takes $1.70 in royalties for each cubic metre of sand mined here and at Pakiri, and the sand is sold for about $50 a cubic metre. The ARC hearing drew 678 submissions about the proposal – 658 were against and 20 for.”

NZ Herald, “Mining at Pakiri extended for 14 years” | Article

Little Barrier

One permit for 2,000,000 cubic metres is currently operational in the seabed area north east of Little Barrier island, with no annual limit, but additional impact assessment requirements where quantities exceed 1,200,000 cubic metres in a 24 month period, (off-shore east coast near Little Barrier Island). Current extraction rates are approximately 151,000 cubic metres per year for the entire east coast sector

Kaipara

Two permits are currently active within the Kaipara harbour, totalling 400,000 cubic metres per year, for five years, then increasing quantities after meeting further conditions, (Kaipara Harbour entrance, flood tidal delta). Current extraction rates are 219,000 cubic metres per year. We have heard 250,000 cubic metres described as a building the size of a rugby field and twenty storeys high. Sand from the Kaipara Harbour entrance currently contributes over 50% of the concrete sand requirements for Auckland.

Port Waikato North Head

At Port Waikato, BHP mines 6 M tpa of ironsand from the North Head, which is concentrated on site to produce 1.2 M tpa of titanomagnetite concentrate. Mining of the deposit began in 1969, and production to the end of 2000 is about 18 Mt of concentrate. The concentrate is slurried 18 km to the steel mill at Glenbrook where it is blended with Huntly sub-bituminous coal in the ratio of about 1.8:1 and heated in reduction kilns to form sponge iron containing 70% Fe. The sponge iron is melted in an electric arc furnace to produce molten pig iron. The resultant steel products are for domestic consumption and for export, and include very high-purity stainless steels. A vanadium-rich slag is separated as a valuable by-product. Currently 12,000 t/yr is produced and exported to China, representing 1% of the world’s vanadium production. Estimated in-ground ore resources at Waikato North Head are in the region of 140 Mt of concentrate.

Taharoa

At Taharoa, ironsand is mined by dredging beach and dune sand to produce concentrate averaging 40% titanomagnetite. Annual production has been about 1.4 Mt since the operation opened in 1972. The concentrate is slurried through a 3 km long pipeline to an offshore loading facility for export. Total exports to the end of 1996 were 31 Mt, mainly to Japan, with small quantities to South Korea and China. Estimated in-ground ore resources at Taharoa are about 208 Mt of concentrate.

Waipipi

A small land-based mining operation in the dunes behind the beach here was begun in 1971 and wound up in 1987. Like at Taharoa, ore was slurried via a pipe to ships moored offshore and transported to Japan and China. Extraction of 15 million tonnes of ore created a vast hole, which is now filled with water. A new beach-side subdivision now covers part of the site. XXXXX? Currently has a permit for prospecting and exploration here.

There has been a long history of mining gravel and aggregate directly from the beaches of Hawke’s Bay, beginning during the earliest period of settlement. Not having been monitored, there is only anecdotal information concerning these early beach-mining activities. For example, large volumes were extracted during the construction of the railway, needed to raise its bed. This extraction was not limited to local needs of sand and gravel; for example, in the construction of the huge concrete pier in Tolaga Bay north of Gisborne, the gravel in its concrete came from the Hawke’s Bay beaches. In recent years the most significant extraction of beach sediment has taken place at Awatoto, which has averaged 47,800 cubic metres per year; during the 30 years from 1973 to 2002, for which we have the best records, this extraction removed a total volume of nearly 1,500,000 cubic metres of beach sediment, and continues today although this annual removal is scheduled to decrease during the next ten years, and to cease altogether after that. The significance of this commercial extraction at Awatoto is that it has exceeded the quantities of gravel reaching this stretch of shore, from the Tukituki River and from sea-cliff erosion along Cape Kidnappers. As a result, the total quantity of gravel and sand contained within the beach between the Cape in the south and Bluff Hill and the Port’s breakwater in Napier has significantly decreased over the years, making this stretch of shore more susceptible to property erosion and flooding.

Hawke´s Bay Today, “Gravel firm making erosion worse” | Archived Article

Whiritoa

Whiritoa has been substantially transformed form its original state, when it featured huge heaped dunes. Early Māori communities removed most of the original coastal forest and dune plants. European farmers then introduced stock to the dune area, disturbing the native sand-binding grasses and causing severe wind erosion. Most of the sand reserves eroded, reducing the height of the dunes and caused sheets of sand to move more than 200m inland, then was mined for over 50 years; in total more than 180,000m³ of sand has been removed. Since the 1960s coastal subdivision has covered most of what remains of the sand dune reserves.