History and monitoring of the Cornish Pumphouse – up to December 2005
The Cornish Pumphouse was built around 1904 to house steam-driven pumping machinery needed to dewater the mine.The pump was used until 1913 and kept in working order until 1929. After this it was abandoned, the machinery removed and the steel beams inside removed for scrap.
photo taken about 1950
In 1961 the collar of No. 5 shaft west of the pumphouse collapsed leaving the structure on the edge of a potentially dangerous void.
This aerial photograph taken from the south in the mid 1980s shows the collapsed No.5 shaft on the left (west) of the picture.
In 1987 Waihi Gold Mining Company fenced the area around No.5 shaft for public safety. Construction of Martha Mine had begun and a viewing platform was placed next to the pumphouse. Paths were constructed and the area planted with native trees and shrubs.
With the town’s Information Centre and the Martha Mine Education Centre operating close to the pumphouse the area further developed as a significant tourist attraction.
The autumn colouring of the Virginia Creeper accentuates what had become a tourist icon.
By 1995 regular monitoring of the building and surrounding area by Waihi Gold Mining Company showed that the pumphouse was slowly tilting, and that the ground on which it was built was also moving.
In 1999 access to the pumphouse was restricted following a series of nearby ground subsidences and the increased danger of a similar subsidence of No.5 shaft immediately adjacent to the structure.
By the beginning of 2005 it was obvious that the pumphouse was tilting dangerously and the ground on which it sat was continuing to move. Experts advised that if it was to be saved the building itself would have to be moved. All interested parties met to consider the future of the structure. In June 2005 conservation architects responsible for moving the Museum Hotel in Wellington got a close look at the condition of the 100 year-old structure.
A 100 tonne capacity crane was brought on site to secure the weight of a small drill rig above the partially collapsed No.5 shaft. The rig drilled into the shaft to investigate ground conditions.
A flat rack container platform supported the small drill rig above the partially filled No. 5 shaft. The platform was suspended from the crane. Staff wore fall arrest equipment attached to a rail above the platform.
A large range of possible relocation sites and transport routes was considered. A geoprobe vehicle investigated the condition of the ground along which the pumphouse may travel. This information allowed geologists to determine how much preparation each section of the route would require.
Scaffolding was installed inside the pumphouse ready for detailed investigations of the structure and the installation of internal steel beams to brace the building.