The Gordon River Underground Power Station
The Gordon River Underground Power Station 1974 by Clifton Townsend
The Gordon River Underground Power Station is the largest project undertaken by the Hydro. Formed by a large machine hall 67,373m3 carved out of quartzite and schist rock, 183m below the surface of the switch yard. This cavern has no structural lining, the ceiling and walls are secured by heavy duty galvanised mesh, rock bolted, plated and then coated with gunite a concrete mix with additives for strength and quick drying, sprayed on under pressure and produces a very strong hard crust. This prevents walls, ceiling from scaling, cracking and loose material from falling. Gunite can still be viewed today, on walls around the area set aside for turbines 4 and 5 and photographs provided with this story.
Access to the machine hall is via a lift shaft for power station operating personnel. Vehicle and large component access is via 1000m+ tunnel with a 13.4% gradient with a rail line embedded in concrete. This rail line was surveyed by Hayden Dwyer and me on a 12 hour shift rotation. This rail line had its small problems, second hand rail was used of varying size and some pieces had buckled lengths that had to be straightened as we surveyed on site.
Hans Lindner, surveyor in charge, and I were privileged surveyors to be chosen to carry out all the survey work necessary for this major task of establishing the number 1 and 2 turbines and associated works starting at the floor level of an empty 2,105m2 machine hall. Slowly day by day we watched and experienced the growth of this very important project to its present operating level today.
Surveying underground, the temperature remained constant; cap lamps were used to signal commands back and forth from surveyor to chainman (surveyors offsider) with experience the smallest of moves could be made using this method. Dim artificial lighting always posed a problem especially with target shadows when extreme accuracy was required. Most of our survey control points were established on the 90 tonne crane rail line high above the machine hall floor and room was limited for surveyor and equipment.
Occasionally the power would go off and without a cap lamp things were extremely dark and dangerous, quiet because the foul air and dust exhaust extraction fans have stopped, followed by a large water flow back noise, this noise occurred because the pumps had stopped that carried the water up the access tunnel for disposal running back to the sumps.
Surveying techniques and calculations during my time working on the underground power station in the mid-seventies were being revolutionised by the introduction of the Hewlett Packard calculator, this made computations and checks on survey work much easier. Hans was amazed what I could do with that calculator. I spent a few nights in my room at the Chalet studying the reference books and started to do short equations that would help Hans and I to be more proficient and productive on the job.
The magnitude of the components used for the turbine installation are mind blowing, a 116 tonne stop valve is used to turn the water on/off for each turbine. Compared to the stop tap we use to turn water on/off at the kitchen sink for example.
The underground excavation works carried out over many years. The surveys were carried out by numerous survey parties. These surveys included the intake tower, lift shaft, access tunnel, power tunnel, draft tubes, tailrace tunnel, adits, and the machine hall.
I was pleased to be able to attend the Hydro Centenary Celebration open day tour of the underground power station on 21 September 2014. The tour was conducted in a very professional and courteous way. We were shown a lot by the operational staff and experienced the power station operating.