The 6 mile 688 feet long, 30’ diam. horseshoe shaped Tail race Tunnel will exit spent waters from the West Arm Underground Power House to the sea at Deep Cove in Doubtful Sound.
Commencing at 16’ below sea level (B.S.L.) at West Arm the tunnel descends at a grade -3% to 110’ B.S.L. thence at grade -1% to 132’ B.S.L. From this lowest point it ascends to exit at Deep Cove at 30’ B.S.L. The descending-ascending grades are designed to diminish the water’s exiting force.
Utah Construction & Mining Contractor excavates 4/5 mile of the tunnel; the remaining 5¼ miles, and concrete lining, by Utah-Williamson-Burnett, the Deep Cove Contractor.
Initial excavation on the West Arm contract was semi-circular as shown, later being fully excavated to the designed 30’ diam. horseshoe shape. Excavation was accomplished with two specially built, three tiered, drilling Jumbos as shown.
Service lines on the right deliver air and water, and discharge the ever present water seepage. The steel arches are designed to ‘hold’ the tunnel in weak rock areas and will be included in the finished concrete lining.
The 705 feet (design) deep Service Shaft was originally excavated at 6’ x 9’ by Thiess Bros. of Australia for underground exploratory purposes. thiess Bros. reamed part of the Shaft to the designed 14’8” diam; the reaming was completed by Utah Construction & Mining.
Initial use, after exploratory purposed was primarily the removal of underground excavated rock facilitated by the Headframe shown here and the accompanying Winch House out to the right. Rock was hauled in a 5½ cubic yerd capacity ‘muck-skip’, on a 2 min. 15 sec. return trip cycle for the 1,690’ distance, and deposited in a holding hopper thence into ‘Tournopull’ earth-moving machines. The Shaft also carried air, water, and concrete delivery lines and water discharge lines.
In the completed state the Shaft will hold New Zealand’s tallest elevator system, delivering personnel to the Underground Power House.
Seven, 446’ deep, 16’ diameter Vertical Penstocks deliver water from the Power Intake Throats to the Turbines in the Machine Hall.
Each Penstock was initially excavated as a 6’ diameter raise using the Alimak Raising Climbing machines, and later reamed to the designed 16’ diameter by winch-controlled drilling platforms, seen in the lower part of this penstock. Rockbolting and meshing of the entire shaft progresses with reaming.
After lining of the lower section with steel liners the penstocks are slipformed to a diameter of 12 feet.
(Slipforming is a method of concrete pouring areas using a hydraulically operated concrete form which is raised slowly on jacks as the poured concrete sets. Rate of slipforming is approximately 2 feet per hour.)
Machine Hall August 1967
The Machine Hall floor seen here requires a further seven feet of depth excavation before completion to 25 feet below sea level. The seven penstocks are at the left.
Upper crane columns are being places on the north and south walls by a P. & H. 655 Crane. South wall columns are capped by the crane-rail beams.
A ‘Barford’ Dump truck awaits load from the ‘Cat 977’ Mucker.
The Emergency Exit tunnel appears at the top of rear wall and the inspection walkway for the permanent metal arch-ceiling extends forward.
Machine Hall September 1967
The Machine Hall has reached its maximum depth of 25 feet below sea level on the left bench and 48.5 feet in the central turbine pit.
Seven Penstocks enter on the left beneath incomplete south wall crane columns; seven draft tubes exit on the right beneath completed crane columns.
Overhead the arch ceiling inspection walkway forwards from the Emergency Exit Tunnel high on the rear wall. the concrete delivery line awaits the first pour in Unit 1.
West Arm Camp
One of the two company launches, the ‘Endeavour’ departs West Arm for Supply Bay, 20 miles away at eastern lake end.
The two camps, comprising 794 huts, are divided by the prominent recreational building at left, housing gymnasium and indoor basketball court, cinema, dry and wet canteen, with T.V. Lounge, card rooms, bowling room, library and chaplain’s office comprising the first floor. The camp Post Office is overshadowed at real of hall whilst the cookhouse continues cap division to the right. Staff hostels share left far side of Wilmot Pass Road with the guest house and B.P.C.L. Staff Hostels. B.P.C.L. Offices at left near side of road foreground additional B.P.C. L. Hostels. In the centre foreground at lake edge is warehouse with U.C.M. wharf facilities to left, and U.C.M. Offices behind. Left of this office block is heavy equipment storage yard and to the right are the medical clinic and workshops. In the background, behind camp, is the permanent materials warehouse surrounded by storage yards. The Wilmot Pass Road moves out at top right to Deep Cove.
Machine Hall August 1966
Photo shows ceiling, at 79 feet above sea level, and the ‘Centre-Cut’, a continuation of the Emergency Exit Tunnel. The Centre Cut was the initial excavation, the left and right ribs following, resulting in the formation of the completed Machine Hall ceiling.
‘Airtrack’ Drilling Machine at right is drilling for rockbolt emplacement, patterned to support the ceiling rock. An ‘Austin-Western’ crane in the Centre0Cut affords a platform for rockbolt emplacement. The Airtrak Drilling Machine mounted on a ‘Barford’ Dump Truck is used for excavating the left and right ribs.
The metal squares in the ceiling, surrounded by ‘in place’ rockbolts, house ‘flat jacks’, rock movement detectors.
Machine Hall March 1967
The gunited and completed ceiling is left behind and walls are formed as the invert deepens.
Controls for the metal arch ceiling are seen down each wall at ceiling-wall junction
A raise miner demonstrates the safety boots which allow for descent should the ‘Alimak’ break down. the boots clamp to the Alimak rail sections, bolted to the shaft wall, an employ friction braking.
Rail sections carry air and water delivery lines for drilling purposed, and communication cables.
The Alimak, driven by compressed air, climbs on a sprocket system, and to maintain efficiency, the shafts were raised from three levels.
Concrete Batching Plant
A transit-mix roars out from the Concrete Batching Plant to supply concrete to a Gate Shaft pour whilst another awaits its load.
The Crushing unit behind the plant supplies various aggregate, crushed from underground excavated rock, to the aggregate bins at upper left. the tower at right contains cement, bulk transported from Deep Cove, whilst further cement supply is held in the two cylindrical hoppers.
The plant is capable of producing 70-75 cubic yards of concrete each hour, and will eventually supply approximately 91,000 cubic yards (design) total.
The Batch Plant viewed from the rear of the preceding photograph shows the crushing plant at left upper. Tunnel rock, after crushing, is sorted and conveyed to stockpiles. Required aggregate is loaded into the hopper at the bottom right and further conveyed to the aggregate bins atop the Batching Plant.
The Access Tunnel portal is obscured out to the left (a 1.26 mile, anti-clockwise, spiralling tunnel giving access to the underground areas.) The upper road leads to the Switchyard, the lower to the Headframe seen in the background, and the project powerhouse to its right. Below this lower road is seen the Gate Shaft and Power Intake area.
Machine Hall January 1967
With the ceiling fully excavated now the excavation follows a centre-cut and side-strip pattern to the design depth. Whilst excavation progresses the rail mounted work deck allows for guniting of the ceiling and grouting of the ceiling rockbolts.
Machine Hall July 1967
Rigger and welder attach an upper column to its wall support on the south wall of the Machine Hall.
Their swinging workdeck is suspended from the boom of a Japanese P. & H. 655 Crane. Further crane columns on the Machine Hall floor await placement.
Penstock entries are seen along the south wall floor junction.
‘Airtrak’ Drilling Machines rest in the background.
Machine Hall September 1967
The first of two ‘Savigliano’ manufactured Machine Hall cranes is being readied at the far end. Beneath is the temporary Machine Hall bridge for crane unloading of materials.
The floor on the right is at completed level, the central Turbine Pit area has yet to be fully excavated.
Overall dimensions of the Machine Hall are 364 feet long, 59 feet wide, 104 feet high from main floor and 127.5 feet high from bottom of Turbine Pits.
Machine Hall January 1968
At the west end of the Machine Hall the Unit No. 1 Penstock liners enter on the left. The Draft Tube liners on the right, which will exit the water through the Draft tube Manifold thence into the Tailrace, await the cone section which will connect them to the Turbine scrollcase. A Dresser coupling will connect the Penstock liners to the scroll.
Manufactured by Harland Engineering Co Ltd., Scotland, the four scrollcases where delivered to the Deep Cove wharf in Doubtful Sound by the ‘Australia Star’.
Their West Arm destination entailed a heavy Transporter journey over the tortuous 14 mile Wilmot Pass Road rising to a summit of 2,200 feet through dense rain forests of Fiordland National Park.
Each scrollcase was delivered in two sections: the inlet section (as shown on Transporter) weighing 65 ton, and the smaller section weighing 37 ton.
Machine Hall April 1968
Unit No. 1 at rear shows concrete pour encasing the scrollcase.
Unit No. 2 in the foreground shows scrollcase encircling the Draft Tube cone; concrete yet to be placed. The Penstock liner, entering the Machine Hall through left wall, awaits coupling to the scrollcase. In the completed state, water will enter the turbine through this penstock and scrollcase after falling through 446 feet of vertical penstock shaft, and exit through the Draft Tube at a lower level on the right.
Subcontractors Wismer & Becker – Wilkins & Davies are responsible for the Draft Tube liners, Scrollcase, Turbine, and Generator emplacement.
Machine Hall April 1968
Units 3 & 4 in foreground await scrollcases whilst Unit 2 at rear awaits concrete pour around scrollcase.
The Transformer Vaults are seen on the north wall (right) midway of columns.
One of the two Machine Hall permanent gantry cranes delivered by ‘Savigliano’ of Italy rides the crane rails supported by the columns.
A concrete conveyor belt below the right hand end of crane delivers to all concrete pours.
Machine Hall June 1968
The metal arch-ceiling is being installed above Units 1 to 4.
Units 5, 6, & 7, seen here, are nearing completion in preparation for Turbine scrollcase installation at a later date under a separate contract.
The Service Bay nears completion in the background.
Seven cable shafts, each 6’ diam. and 775’ deep, rise from the seven Transformer Vaults in the north wall of the Machine Hall.
Permanent platforms are installed at 15’ intervals to carry ladder and lighting systems, and to provide attachments for the 200 K.V. power cables carrying generated power from the Transformer Vaults to the Surface Switchyard.
'Alimak' Raise Climbing Machine
Of Swedish design the Alimak raise climber is used for excavating vertical or sloping shafts, in this case the initial 446 feet high vertical penstock shafts. The 6’ x 6’ initial shafts were later reamed to the designed 16 feet diameter.
The lower cage provides protection for the two operators when the Alimak is in motion, the upper workdeck being reached through a trapdoor. The compressed air hose supplying the operating air motor tails out to an obscured, automatically operating, hose real. The Alimak rails, rockbolted to the arch of the tunnel and walls of the shaft, show clearly the triple-pipe construction carrying air and water for drilling, and communications.
The lower vertical curve section of the fully reamed 16’ diameter Penstock here enters the south wall of the Machine Hall.
The rails are a continuation of those seen in the preceding photograph and allow for operation of the drilling platforms as well as delivery of, and a base for, the steel liners.
The Penstock entry into the Machine Hall seen in the preceding photograph now has the steel liners places and set in concrete. The inspection hatchway is seen on the liner crown.
A Dresser Coupling will complete the connection between the liners and the Turbine scrollcas
[Photograph missing from book.]
Fletcher-Bernard-Smith Subcontractors places the 12 steel liner sections in each Lower Penstock.
The varying 10’-11’ diameter steel liner sections are placed from above the Lower Penstock curve to the junction with the Turbine Scrollcase to withstand the water forces after their 446’ vertical fall.
The liners are installed to exacting specifications after which they are set in concrete.
Two ‘Euclid’ Dumptruck-mounted Drilling Jumbos were fabricated on site primarily for excavation of the West Arm Tailrace contract although use extended to many other underground excavation areas.
Each Jumbo permitted drilling from three levels, each deck carrying two hydraulically operated, air-activated, drilling units.
Draft Tube Manifold
The rail-mounted Gunite Jumbo allowed for grouting of the Draft Tube Manifold ceiling rockbolts and guniting of the arch, (Gunite is a sand-cement mixture sprayed on under pressure), to prevent water seepage.
The Draft Tube Manifold receives the spent waters from the Turbines through the seven Draft Tubes on the right hand wall and sends them on their 6¼ mile exiting journey through the Tailrace to Deep Cove (towards viewer). Surge, caused by additional water received, as when a Turbine is brought into use, is accommodated by a 1510’ long, 33’ wide, horseshoe shaped Surge Chamber out to the left, and a 102.5’ high, 28’ diam Surge Shaft behind Jumbo, until this additional water is included in the exiting waters.
Switchyard Retaining Wall
The first concrete construction of note on the project was the Switchyard Retaining Wall, designed to build up to required level the south east corner of the Switchyard and with-hold it from the Service Shaft.
The Headframe, used to exit the major proportion of excavated underground rock, stands over the 704’ (design depth) deep Service Shaft; the muck-skip cables extending over the wheels to the Winch House obscured out to left.
Of historical note is that the Winch House and Headframe were manufactured in Great Britain in 1927, both being purchased by Utah Construction and Mining from Australia where they had rested for many years.
The Transmission Line Access Road winds upwards and across the mountain slopes across the lake.
The ornate handrails are indicative of the age of the winch – manufactured in Great Britain in 1927.
The 1130 Brake Horse Power Metropolitan Vickers electric motor on the right drives the 13’ diameter winch drum carrying the 2” diameter cable for lifting the Service Shaft ‘muck-skip’ and its counterweight through their 845 feet hoisting distance. Rate of lift is in the vicinity of 1100 feet per minute.
A transit-mix delivers concrete to a pour in Gateshaft No. 4.
The seven, 95’ deep, 22’ diameter, Gateshafts contain hydraulically operated gates to control inflow of water through the Power Intake Throats to the vertical Penstocks. A gantry crane spanning the shafts at surface will lower another set of gates, the Bulkhead Gates, thereby halting inflow of water and allowing maintenance on the water control gates.
Power Intakes August 1968
The waters of Lake Manapouri are held back by the Intake Dyke on right allowing excavation of, and finishing work to be accomplished on, the seven Intake Throats in the centre trench. These Water Intake Throats, with No. 7 at far end, enter the Gate Shafts and Upper Penstock area through the rock face on the left side of the trench.
The crane and transit-mix are assisting with a concrete pour in No. 6 Gate Shaft. Seven, 22’diameter, Gate Shafts, which will house hydraulically operated water-flow control gates, descend 95’ from this level to the Intake Throat level.
Above the Gate Shaft area rises the Switchyard.
Following completion of the Water Intake Throats, the Intake Dyke will be blasted out and removed by barge-mounted dragline. Meanwhile, powerful pumps return lake seepage to their origin.
Switchyard August 1968
Now at the finished level, construction of Tower footings, Cabletray Gallery *centre) and Cable Shaft Terminal Building (left) proceeds.
The Cable Shaft Terminal Buildings span the seven Cable Shafts, each 6’ diam. and 766’ deep, to receive the 220K.V. power cables from the underground Machine Hall. These cables continue through the Cable Tray Gallery along the Switchyard centre to the Service Building at far end. Cables from here eventually link to the four take-off-towers and thence across the 3828’ (Av.) span of lake to the Transmission-Line Receiving Towers.
The Service Shaft Headframe stands at rear with the Project Power House to its left.