Many of the mine workings abandoned by the Westport-Cardiff, Seddonville State and Mokihinui mines have been reopened at different times, often by small cooperative parties who have been able to make a living when there was a strong demand for coal. They were aided by the development of hydraulic mining techniques, which were pioneered in the Seddonville area.
A hydraulic mining pioneer
Mining using water (called hydraulic or hydro mining) was common in the West Coast goldfields, but was applied only slowly to the mining of coal. There are major advantages in coal mining, as water minimises dust as well as the risk of explosion and fire. Westport entrepreneur and engineer Tom Moynihan was associated with a number of mines in the Seddonville area from the 1920s onwards, and developed hydraulic mining techniques for coal that are now widely used.
The adoption of hydraulic mining technology was opposed for many years by the unions because they feared the loss of jobs, especially in trucking coal. The Seddonville coalfield was Moynihan's laboratory – one of the few areas where he was able to develop and test his ideas in working coal mines away from union influence.
Transporting coal
The earliest attempts at hydraulic mining involved transporting coal from the mine mouth to the nearest road or rail transport. For example, in 1924 a flume (water race used for carrying coal) was constructed from the mouth of the Cardiff Bridge mine to the railway at Seddonville, a distance of 1.6 km. It was soon discovered that wood was rapidly worn away, so the flume was lined with iron sheets. By the end of the year the flume was successfully transporting 120 tonnes of coal a day.
There was a major advance at the same mine in 1927 when water was piped directly to the coal face. The coal could then be transported all the way to the bins, thus eliminating the work of filling and trucking.
The old Seddonville State Mine workings were converted into a hydraulic mine in 1936 (renamed the Hydro mine). A flume was laid along the line of the old railway, about 1.7 km, to bins at Seddonville. There was still considerable coal left in pillars, originally thought to be too crushed to be mined and sold. After blasting, this was sluiced to the bins. Use of water allowed the fine material to be washed away, so that only clean coal was stored in the bins.
Lifting coal
The Charming Creek mine, converted to hydraulic working after 1952 under the supervision of mine manager J.W. (Red) Duncan, was the best example of how this technology can simplify mining. After blasting, the coal was sluiced from the working face through a flume into an underground holding tank. It was then raised to the surface by high pressure water and passed through a rotating screen to remove fine material before being held in a storage bin.
