Preserving a piece of mining history

Already basking in the glow of the Waikato Sustainable Business Award it won in August 2006, Newmont Waihi has further cause to celebrate its commitment to the local community with the completion of the relocation of the historic 1840 tonne Cornish pumphouse.   BY HUGH DE LACY

The 21 metre tall concrete shell of Newmont Waihi’s Cornish pumphouse reached its final resting place above the town’s main street on November 8 after a 301 metre journey that began on August 7.

It was built in 1904 to house the steam engine pumping water from the 600 metre deep underground gold mine on the edge of Waihi. Without the move the pumphouse, which is protected by a Category One rating with the NZ Historic Places Trust, would eventually have toppled into the Number Five mineshaft.

Indeed, by as early as 1905 the Number Five shaft collar had already sunk 350mm into the tunnel-riddled ground, and in 1913, the year electricity replaced steam, 200mm had to be cut off the main pumping rod because the pumphouse was descending at a rate of 25mm a year.

Because the miners didn’t trust electricity, the steam engine and pumphouse were kept in working order until 1929, after which it was progressively stripped of its equipment until it became the teetering Gothic shell that has cost Newmont about $4 million to shift and preserve.

With its giant Hathorn-Davey C pump, the pumphouse design was based on similar installations servicing the tin mines of England’s Cornish coast, and when it began to tilt alarmingly in 2004, planning to save it was begun.  Under its Martha Pit mining licence, Newmont was required to take “whatever precautions are necessary” to preserve the historic landmark.

Planning took two years and involved consultations with the building’s owner, Land Information NZ, as well as the Historic Places Trust, the Hauraki District Council and the Ministry of Economic Development. Dunning Thornton, which in 1993 moved the 3000 tonne Museum Hotel 200 metres along the Wellington waterfront, was appointed consultant, and another Wellington-based firm, Building Solutions, won the moving contract.

There was no alternative to moving the building as nothing could be done to stabilise the ground around it, which was shifting in large-scale blocks into the old mine workings. Nor was there any possibility of shifting the building in pieces as this would have compromised its integrity and value.

Relocation of the entire building by rail, as had been done with the Museum Hotel, was abandoned in favour of strengthening the pumphouse with internal steel bracing, then sliding it on a combination of cast–in-situ and relocatable concrete slider beams.

Several moving options and new sites were evaluated to pick a way through the hazards of collapsed shafts, 50 metre wide chimney subsidences and unfilled stopes. A two-stage shift – 26 metres to the southeast, followed by an eight degree turn to the southwest and a 270 metre run to the permanent site – was finally settled on.

Geotechnical investigation and design was carried out through the winter of 2005, with option selection completed by December of that year. The internal steel bracing was completed by Mount Maunganui Engineering in the four months to March this year, and Building Solutions started the on-site relocation work in April.

The concrete beams, along which the building was pushed by hydraulic rams, were topped by stainless steel strips, while flatjacks and Teflon pads supported the weight and provided the lubrication.

Considering the range of potential hazards, the actual relocation was largely problem-free, and Newmont is meeting the cost with gold recovered during the stabilising of the walls of the 200 metre deep Martha Pit – currently under way and expected to take at least two more years – preparatory to its being filled with water to form an amenity lake for the town.

While both the preservation of the Cornish pumphouse, which is to be formally opened in February, and the stabilisation of the Martha Pit were required under the company’s mining licences, it was the beyond-compliance investment in the local community that so impressed the judges in the Waikato Sustainable Business Awards.

These initiatives, some of which were inherited from Normandy Mining when Newmont bought the Martha Pit and associated permits and licences in 2002, run into millions of dollars, and can be broadly categorised as environmental, heritage and community investments.

They include:

Environmental

• The Dotterel Watch Partnership with the Department of Conservation which began in 1995 after staff noticed that the endangered New Zealand dotterel had begun nesting on the waste-rock embankments beside the two kilometre haul road between the Martha Pit and the processing plant. The funding, which includes provision of a vehicle, costs $60,000 a year.
• The Bridge-to-bridge Riparian Planting Project, started in 1995 and completed 10 years later at a cost of $2 million, involved establishing a walkway to the summit of Black Hill and the establishment of 200,000 native plants along the Ohinemuri River and its tributaries between the Golden Valley and Coronation bridges on State Highway 2.
• The Habitat Enhancement and Landcare project, to which Newmont has contributed $95,000 to raise environmental awareness among children.
• The KauriBank project, costing $95,000, which has established 3200 kauri trees in the Waihi area.

Heritage

• Assistance to the Victoria Battery Tramway Society in setting up a display area in the old stamping battery’s transformer building.
• Two $10,000 grants for research on the historic Union Hill workings.
• The Oral History Project, begun last year, to record the memories of local elderly people and former mineworkers.

Community

• The Waihi Gold-mining Education Trust through which the company has donated over $350,000 to Waihi College.
• Martha Mine tours conducted by the company, and which yield about $10,000 a year to community groups.
• Grants totalling $45,000 since 1997 to the six local primary schools, and upgraded last year to annual grants of $10,000 to each.
• Six open days at the Martha Mine which have earned the Waihi Lions Club $100,000 in entry charges.
• The Education Centre which, since mid-2000, has been providing curriculum-linked educational programmes to primary, secondary and tertiary teachers and students.
• The Golden Legacy Centre adjacent to the Martha Pit viewing platform, manned by company volunteers hosting 20,000 visitors a year.
• The Waihi Community Vision forum, to which the company gives annual funding of $250,000, and which serves as a communication point between company and community, and also funds community projects.
• Property support totalling $6 million by which the company bought at market rates the properties of the victims of the 2001 ground subsidences, caused by historic rather than the company’s mining activities.
• Annual funding of $150,000 for a variety of other community projects.