Construction Roxburgh Dam

1 construction

1.1 unsolicited offer
1.2 call tenders
1.3 downer s takeover
1.4 lake filling
1.5 electrical equipment
1.6 transmission
1.7 construction village
1.8 project cost

construction
unsolicited offer

the ministry of works government department designed , constructed power station had identified had shortage of engineering , drafting staff undertake large amount of power station construction government had committed in north , south islands. unsolicited bid received british consortium consisting of civil engineering contractors richard costain, electrical manufacturers , contractor english electric , insulated callender cables design , build power station using imported workers. ministry of works had reservations lack of guaranteed completion date, difficulties divided responsibility if consortium undertook both design , construction, potential cost higher if competitive tenders called , give consortium monopoly on future projects of similar nature. state hydro-electric department didn t want restricted 1 electrical equipment manufacturer , saw offer threat transmission line construction staff. taking these concerns account , wishing avoid using precious overseas funds offer formally rejected in september 1949 minister of finance in labour government. meanwhile, work continued on site on building construction village , creating diversion channel 200 ft long, 100 ft wide , 70 ft deep. progress slow, completion of diversion instead not expected until 1953 instead of planned 1951.

call tenders

in 1949 newly elected national government, ideologically favoured private enterprise, appointed stan goosman both minister of works , minister of state hydro-electric department. 1951 projected project delays serious enough draw criticism electrical supply authority. aware of projected energy shortfalls , shortage of government resources complete 6 other hydroelectric projects underway complete roxburgh, goosman s response announce on 25 september 1951 tenders called interested parties undertake civil aspects of project. required rapid production of tender documents , specifications short staffed government design staff. bidders had choice of offering on either bill of quantities basis or nominating target estimate plus 4% fee. in type of contract government met costs , contractor received fee of 4% of total cost target estimate. if cost varied estimate, 25% of change added or subtracted fee. no loss clause meant if cost overruns high enough contractor lose entire fee not suffer further loss, other not meeting agree completion dates. 8 tenders received. 3 fixed price bill of quantities , remainder target estimates. ministry of works had estimated work cost £10,198,000 , average 7 of bidders £10,068,838. lowest bid £7,4412,419 holland, hannen & cubitts of england. government engaged sir alexander gibb & partners of london assess ability of bidders undertake work.

after negotiations hannen, holland & cubitts of england joined s conrad zschokke revised bid received , on basis contract target estimate of £8,289,148 , 4% fee of £331,566 awarded on 25 july 1952. contract had provision bonus of £350,000 completion. there penalty late division of river , £1000 penalty each day past july 1955 power station not ready service. target completion date 1 june 1955.

by late august 1952 ministry of works had completed 2 cableways used carry concrete workface. manufacture concrete on site ministry of works purchased johnson concrete batching plant had been used united states navy in reconstruction of pearl harbour after japanese attack in 1941. came operation in april 1953. upon completion of roxburgh plant transported first benmore power station , later aviemore power station , pukaki dam mix aggregate penstocks, spillways , other concrete structures.

the consortium bought overseas 82 engineers, supervisors , administration staff , 322 workmen project , took on civil aspects ministry of works on 29 sept 1952. stage ministry of works had completed diversion channel , consortium took on these workers.

prior involvement roxburgh project hannen, holland & cubitts experience had been limited commercial , residential buildings. zschokke had expertise in construction of hydraulic structures limited providing engineering services while cubitts personnel filled management roles.

by march 1953 ministry of works became concerned @ progress being made consortium , management team lacked experience construct hydro power station, highlighted large amount of rework being undertaken. progress not helped government directing employment of large number of assisted immigrants many of whom had little construction experience , limited english. in 1953 @ government s expense consortium flew out 309 workers great britain. october 1953 clear consortium not meet contracted july 1955 date generation of first power. in attempt improve progress contractor replaced number of senior project staff. labour relations deteriorating due uncertainty on management changes, reduction in working hours 40 per week , impact of cost overruns on workers pay. in november 200 british workers demanded either 70-hour working week or tickets great britain.

downer s takeover

with having been necessary in 1953 introduce power rationing in south island due shortage of generation government decided slow progress couldn t continue , requested 2 directors of downer & co, major new zealand construction company attend in 2 days time meeting @ prime minister s summer cottage on 24 april 1954. @ meeting attended representatives of consortium, arnold downer , arch mclean downers requested government enter project managing partner 25% interest. after spending £4 million existing contract cancelled , schedule of rates contract agreed upon renamed cubitts zschokke downer planned completion date of late 1956.

as result of forming of new consortium arnold downer put in charge of site activities.

the preliminary works diversion of river got off bad start when explosive charge used in mid-june remove upstream dumpling damaged steel sheet pile cofferdam downstream of it. cofferdam has been constructed ensure water didn t carrying blast debris upper dumpling sluice channel. debris , cofferdam removed, allowing unrestricted flow down diversion channel. in 12-hour operation on 30 june 1954 river diverted using 12 bulldozers diversion channel despite flow down river having increased far higher level studies had indicated optimum. if diversion hadn t been able have been undertaken before peak winter flows project have incurred 9 12-month delay.

once river diverted on next 3 months cofferdams constructed upstream , downstream of dam, water pumped out between them , excavation placing of foundations commenced.

in july 1954 downer replaced 20 senior contractor staff had inherited people of choosing, many morrison-knudson co. significant appointment of a. i. smithies, experienced hydro construction engineer morrison-knudson co construction superintendent. under downer s management pace of construction increased weekly concrete pour rapidly improving. improved management allowed workfare reduced 1107 when downers took over, 850.

the dam constructed in 50 ft wide concrete blocks 5 ft wide slots between them constructed in 2 profiles, associated penstocks had additional section containing intakes , screens downstream slope support penstock while other profile had flatter slope , wide enough @ top house road across top of dam. in conjunction block sizes, different concrete mixes , cooling coils through passed cold water used maintain block temperature @ 10˚c (50˚f) , cracking of concrete. cracking can allow water body of dam can lead allow uplift , instability during earthquakes. once blocks had reached final stable temperature slots filled concrete.

once concrete in block stable coils filled grout. 20 ft (1.86 m) deep low pressure consolidation grout curtain installed on upstream side of dame , extending both abutments improve strength of rock under dam , prevent leaks. drainage holes constructed downstream of grout curtain under power house 40 pressure gauges installed record pressure on structure.

during construction large gravel filled hole discovered in centre channel or gullet of river bed. gullet 50 ft (4.6 m) deep , varied in width 50 100 ft (9.3 m) dug out , filled mix of pozzolana (fly ash) , cement under dam while under powerhouse prepakt concrete used reduced demand on batching plant occupied supplying concrete dam blocks. total of 700,000 cubic yards (535,188 m3) of concrete used in construction of dam , spillway consuming 600,000 cubic yards (458,733 m3). cement sourced millburn s bankside plant @ dunedin while aggregate obtained clutha river @ commissioner s flat. water came river.

the penstocks manufactured stevenson & cook of dunedin. after rolling plates in factory in dunedin, transported truck site , fabricated sections on site in purpose built workshop. welds x-rayed during fabrication , radiographed after installation pressure tested except concrete encased section @ intake.

in november joints in stator windings of generators discovered faulty. fortunately sufficient time became available re-make joints when 24 november 1955 23 work days until christmas break members of new zealand workers union on strike in support of union crane driver had refused lower load being carried crane when siren went tea break contractors estimated delay commencement of lake filling 2 months.

lake filling

with power cuts being applied across south lsland june 1956 minister of works requested contractors concentrate resources on work bring forward lake filling far possible. encourage workforce government offered bonus of £2 per week plus £1 per day lake filled before 19 august. @ midnight on 21 july 1956 lake filling began , lake level commenced rising @ average of 3 ft hour.

as lake began fill increasing levels of water began flow drainage channels behind grout curtain in right abutment, indicated grout curtain faulty. investigations concluded further grouting have performed (which took fortnight) before lake raised final level. decision made allow lake fill no further crest of spillway while contractors began drilling , inserting more grout.

by 11:20 on 23 july 1956 lake had filled crest of spillway water. desperate shortage of electricity effecting south island, commissioning of no 1 machine commenced. once engineers satisfied machine fit service connected @ 6 pm national grid. due reduced head machine s output limited 30 mw. end of next day no.2 machine had completed commissioning , connected system. allowed 220 kv line islington bought service 2 machines needed provide sufficient reactive power charge long length of line. third machine commissioned on 18 august 1956 , fourth machine on 11 december 1956. power station officially opened on 3 november 1956 stan goosman.

delivery of machines 5 8 began late in 1959.

the commissioning of roxburgh removed need power restrictions in south island , ensure surplus of power many years.

electrical equipment

the state hydro-electric department undertook design, purchase , installation , commissioning of electrical equipment. tenders supply of major electrical plant issued in october 1949 contracts awarded in may 1950 @ cost of £1,000,000 first 4 machines. possible equipment shipped on dunedin-roxburgh railway line roxburgh , there transported road power station. because of line larger tunnels on waikaka branch railway line turbine runners , generator bearing support transported on line. line s terminus @ waikaka, transported road power station using specialized transporter.

the state hydro department established on site in june 1953. access undertake activities first provided in august 1954 , erection of first machine began first scroll case concreted in march 1955.

transmission

to connect new power station major load centres, 52-mile-long (84 km) new 110 kv wood pole line first built gore. linemen commenced constructing 89-mile-long (143 km) double circuit 110 kv overhead transmission line using lattice steel towers halfway bush substation @ dunedin completed in july 1955 @ cost of approximately £500,000.

the principal connection, however, new 266-mile-long (428 km) 220 kv single circuit overhead transmission line built using lattice steel towers roxburgh new substation @ islington on outskirts of christchurch. 1949 surveys line under way 1951 construction camps established , material on order. 1954 first section of line had been completed, allowed carry power tekapo christchurch. second section far south waitaki valley helped improve supply conditions during winter. roxburgh-islington line cost approximately £1,000,000 , completed winter of 1956.

construction village

to house workforce ministry of works first built in 1947 single men s camp , cookhouse on west bank of river. in 1949 single-lane bailey bridge installed connect new temporary village being constructed on east bank of river. village grew 724 houses complete 90-bed hostel, 600-child primary school, cinema, social hall, 17 shops, 3 churches, fire brigade , ambulance building, 4 tennis courts, swimming pool , piped sewage scheme. in addition there 4 single men s camps (two on east , 2 on west bank) containing total of 1000 huts. these facilities cost total of £2,241,925.

as otago central electric power board s network not provide sufficient power village , project, government built temporary power station containing 2 1 mw , 1 0.4 mw diesel generators, supplement supply.

project cost

in december 1947 government expected project cost total of £11,500,000. september 1949 when final location , type of dam had been chosen cost had increased £17,000,000.

a contract of £8,620,074 awarded hannen, holland & cubitts in association conrad zschokke. target estimate contract no loss clause . in may 1954 contract re-negotiated include downer & co principal. new contract based upon schedule of rates @ value of £10,120,000.

the final total cost of project £24,102, 800 of £19,151,700 civil engineering, £445,000 on bulkhead caissons , stage 2 civil works, £4,506,100 on purchase , installation , commissioning of 8 generators , outdoor switchyard. included in civil engineering cost £900,000 completion bonus , £35,900 on expediting programme.

a total of 3,500 drawings produced between ministry of works, state hydro-electric department , contractors build power station.