TPD Mini Hydro Project. Moawhango Concept Design Report

Transcription

1 TPD Mini Hydro Project Moawhango Concept Design Report

2 Contents 1. Introduction 1.1 Short history of the project 1.2 Structure of this report 2. Site Investigation 2.1 Structures and tailrace 2.2 Intakes and valves 2.3 Transmission 2.4 Communications 3. Design Concepts 3.1 Moawhango Mini Hydro Concept 3.2 Protection from spillway 3.3 Access 3.4 Generation potential 3.5 Regulation of compensation flow 3.6 Intake, pipework and valves Intake Pipework 3.7 Turbine 3.8 Generator 3.9 Civil works 3.10 Auxiliary mechanical plant 3.11 Electrical systems 3.12 Generator Protection 3.13 Station Control and communications 4. Construction Phase 4.1 Contract Structure

3 4.2 Contract Interfaces 4.3 M & E Installation Mechanical installation Electrical and Controls installation 4.4 Potential Contractors 4.5 Supervision and Commissioning Appendix A Drawing Schedule

4 1. Introduction 1.1 Short history of the project Lake Moawhango was formed during the construction of the Tongariro Power Development project by the construction of a 60 m high concrete arch dam across the Moawhango River, about 10 km north east of Waiouru. Lake Moawhango stores water diverted from the south eastern slopes of Mt Ruapehu via the Wahianoa Aqueduct and the Mangaio tunnel, and also from the surrounding catchment of the lake. The following figure shows the location of the lake and dam 1. 1 This figure is taken from the July 2002 Tongariro Power Development Assessment of Environmental Effects Figure 4.2 The Eastern Diversion. Most water from the lake is diverted northward via the Moawhango Tunnel to the upper Tongariro River and the headpond of the Rangipo Power Station. However, a compensation flow of 600 l/s is released from the dam down the Moawhango River. This project is to install a mini hydro at the base of the Moawhango dam and utilise the compensation flow to generate electricity. In August 2003, XXXX Power commissioned a feasibility report for the Mangaio and Moawhango Mini-hydro Schemes by Bryan Leyland Consulting Engineer and Pickens Consulting Ltd. The present scheme is based on their feasibility report. Both Bryan Leyland and Alan Pickens have been retained by XXXX to provide guidance and assistance in the preparation of the current work, which is the subject of this report.

5 1.2 Structure of this report The remainder of this report is divided in three sections. Section 2 summarises the main features of the existing plant that are pertinent to the proposed development. This information has been derived from drawings, from queries XXX has directed to XXXX, and from several site visits. Section 3 describes the concept design to date. It also describes some of the alternatives considered. This section should be read in conjunction with an examination of the concept drawings listed in Appendix A. Section 4 outlines a suggested construction methodology. This requires careful planning as the compensation flow must be maintained during construction, and work will need to be carried out in the vicinity of the present release point.

6 2. Site Investigation 2.1 Structures and tailrace There are two fixed cone valves located on the downstream face 12 m above the bottom of the dam, which terminate pipes running directly through the dam. The valve diameters are 84 and 18. The larger one, rated at 65 cumecs, is for rapid dewatering of the lake, and the smaller, rated at 2.5 cumecs, is for compensation flow. The valves are located within a protruding dormer structure, integral with the sloping downstream face of the dam. This valve house structure is provided with two levels. The upper level houses a hydraulic pumping unit, control panels, and a valve actuator. The lower level is divided into two smaller spaces, an isolation valve pit, and a discharge valve gallery. The lower level spaces are accessed from the upper level via floor plates and fixed ladders. The discharge valve gallery is open on the downstream side, and is provided with a safety handrail. Below the valve house is the lowest point of the spillway apron at the foot of the dam. The apron includes an integral raised concrete block plinth, approximately 3.6 m square and 1.2 m high. The upstream side of the plinth is joined to the downstream face of the dam. During construction of the dam, the plinth was provided at the outfall of the dam diversion opening. The diversion opening was plugged after completion of the dam, leaving the plinth exposed and presently redundant. This has been selected as the preferred location for the turbine. 2.2 Intakes and valves The intake to the pipes supplying the discharge valves is located on the vertical upstream face of the dam, slightly to the true right of the bottom of the old Moawhango River channel. The intake is approximately 11 m up the face of the dam. A single arched steel screen covers the entry to both discharge valve pipes. The screen has a total face area of approximately 50 m 2, and a bar gap of 127 mm. The average screen velocity at compensation flow is clearly quite negligible. However, higher local velocities in front of the compensation flow pipe would be expected. Nevertheless screen head loss will be minimal. Although the bar gap is insufficient to stop debris large enough to block a small turbine, this is not considered to be a significant problem. The water is relatively clean, most debris during normal inflows to the lake will accumulate at the entry to the Moawhango Tunnel, and the intake is at an intermediate depth between the bottom and surface of the lake, where both floating and sunken debris are unlikely to enter the intake. The pipe to the compensation flow discharge valve comprises an 18 m length of 2-10 diameter pipe, a 0.9 m long conical transition down to 450 mm NB pipe, and a 2.6 m long section at 450 mm NB, which includes an 450 mm NB gate valve for isolation of the discharge valve. The pipe has an elliptical entry bell-mouth, and is embedded in concrete over most of its length. It was made up of flanged short spools, most of the flanges now being embedded in the concrete. The bell-mouth, and also the exposed spools that mate with the valves are constructed of cast iron. The remaining spools which are embedded are fabricated stainless steel 2. The 8-0 diameter pipe for the draw down valve is similar. However, it is mainly constructed using stainless lined mild steel pipe. Both pipes terminate at the discharge valves. The discharge valves are of the fixed cone type; a type often referred to as Howell-Bunger valves. Both discharge valves have upstream isolation valves.

7 The 450 mm NB discharge valve is electrically actuated, and the 84 discharge valve and its isolation valve are both hydraulically actuated. The 450 mm NB isolation valve is a manually operated gate valve, and the 84 isolation valve is a butterfly valve. It is proposed to divert the compensation flow, presently released at the 450 mm NB discharge valve, to a hydro turbine for generation of electricity. 2.3 Transmission The Moawhango generator will be connected to the existing Tokaanu-Moawhanga 33 kv transmission line system that ends about 800 metres from the Moawhango dam. The backbone of this existing 33 kv system effectively consists of two sections; a 13 km, single circuit 33 kv overhead line that runs from the Tokaanu substation to the Ta Hanga switching station, and a 38 km double circuit 33 kv overhead line that runs from Ta Hanga to the Moawhanga Dam. Presently the line has nine small capacity transformers distributed along it's length (total capacity of 980 kva). These transformers provide electrical supply to the Tongariro tunnel system intakes, Tukino repeater site, and Rangipo dam. 2 While it is not completely clear from the drawings obtained by XXX if these 18 pipe spools embedded in the dam are stainless steel, this is most likely, as the larger 8-0 diameter draw-down pipe is stainless faced on the inside surface. Both pipes are of course very difficult to maintain or replace. 2.4 Communications The data communications requirements for Moawhango machine monitoring and control are minimal and these could be met by interfacing the machine controller to the Kingfisher RTU that has radio microwave communications with Tukino. We understand that the present communications system between Moawhango dam and Tokaanu consists of a Kingfisher telemetry data link connected to a microwave link for data and voice (and video). Discussions with Tokaanu C & I staff confirmed that any new communications installation would also follow this standard. Discussions with the XXXX Microwave contractor, Kevin Box, confirmed these systems are currently utilising Aprisa SE 4RF microwave units for data, voice and WAN interconnections.

8 3. Design Concepts 3.1 Moawhango Mini Hydro Concept Below the valve house on the downstream face of the dam is the lowest point of the spillway apron at the foot of the dam. The apron includes an integral raised concrete block plinth, approximately 3.6 m square and 1.2 m high. The mini hydro turbine and the vertical induction generator will be mounted on this concrete slab. A 450 mm NB steel pipe will be installed from the existing compensation flow valve to connect to the turbine inlet, as shown in drawing AP00821-M-501, a part of which is shown below. The compensation flow valve will be relocated further down the pipe to provide space for a 450 mm NB magnetic flowmeter. In addition, a new turbine isolation valve will be installed below the compensation valve Tee off: 3.2 Protection from spillway The generator-turbine unit would be located near the lowest point on the downstream side at the foot of the dam, which is also under the spillway crest. A deflection slab protruding above the valve gallery will provide shelter against spillway flow from directly above. However, during spilling, the generation plant will be deluged by spillway flow cascading down the spillway apron s stepped banks which border either side of the centre channel. A steep sided gorge just downstream of the dam rules out any possibility of building the hydro station further downstream. It is proposed to locate the generator-turbine unit centrally in the plinth that remained after the diversion opening was plugged, as described in 2.1. The generator-turbine unit will be partly protected from side flows by deflection at the walls of the plinth, and also the location is central under the deflection slab at the top of the valve house which enhances the protection from above.

9 The draft tube will be recessed into a cavity that will be cut into the plinth. The surrounding plinth concrete protects the draft tube, and the cut-out cavity conveys the turbine discharge to the lowest point of the channel, thereby gaining the maximum head. As a final protection the generator-turbine unit will be covered with a robust protection structure. The protection structure is fabricated with a 200 mm universal-column steel frame, and is formed in a truncated A-frame shape. The sloping sides of the A-frame will be covered with heavy steel plates. The upstream end face is partly covered with a removable steel plate panel, and the truncated top face is also plated but with a 500 mm diameter ventilation hole provided. The downstream end is left open apart from a frame cross member for strengthening. The completed protection structure will be a single fully integral unit strongly bolted to the concrete using chemset injection anchors. The unplated openings will allow access for inspection and minor maintenance, but for major disassembly the protection structure unit will be unbolted from its base, and craned clear of the generator-turbine unit. Similarly the generator-turbine unit would also then be unbolted from its base, and craned to a suitable locality for disassembly. Minor components could be craned to the upper level of the valve house for maintenance, using the in- situ monorail crane. However, cranage from the crest of the dam, and transport to a fully equipped workshop is probably preferable. The top surface of the plinth provides a convenient point of anchorage for the turbine, the protection structure, and the bottom of the penstock pipe. 3.3 Access The controls and most of the valves are located well inside in the existing valve house space, and can be safely reached using existing access arrangements via the dam galleries. The bypass valve is mounted in an exposed position, and this will require a special provision. The generator-turbine unit is also located in a position where easy access is not presently possible. This is especially so during winter months when the apron of the dam is ice covered. It is envisaged that the required access to the above equipment should be fairly infrequent. The following options for access have been considered: 1) Bypass valve: crane suspended personnel cage or bucket; permanent stainless steel fabricated platform mounted at the same level as the existing discharge valve gallery; demountable fabricated platform bolted to fixed brackets; harness. rigger clamber access using a safety 2) Generator-turbine unit: crane suspended personnel cage or bucket; a permanent stainless steel caged-ladder from the existing discharge valve gallery down to the mounting plinth; access via a downstream abutment and down the spillway apron steps. We are not presently sure how feasible this would be, and it is assumed that some improvements and extensions to the steps and ladder presently installed, are likely to be required.

10 The above access options as well as any other alternatives, should be examined during the HAZOP phase of the project. Moawhango Concept Design Report 3.4 Generation potential The generation will depend on the future management of storage in the lake. Modelling using historic daily lake levels, from January 1993 to January 2004 as shown in the figure below, indicated an average annual generation of approximately 2.1 GWh pa. 3.5 Regulation of compensation flow The current water permit requires that a minimum compensation flow of 600 l/s is maintained at all times. Conversely avoidance of excess compensation flow from the diversion is an important commercial requirement. The water captured in Lake Moawhango is used to generate electricity in the XXXX Energy Rangipo and Tokaanu hydro stations then, via Lake Taupo, all nine Mighty River Power Waikato River hydros. Previous estimates by ECNZ valued the water captured in this diversion at $149 MWh/(cumec.day). Therefore an accurately regulated release is required, and also a discharge valve must still be retained to release the compensation flow if the generation plant is unavailable. Three options for achieving a constant 600 l/s compensation flow have been considered: A regulated turbine, with a bypass valve for discharge when the turbine is not available,

11 An unregulated turbine sized for 600 l/s at the maximum storage level, with a bypass valve for supplementary discharge when the lake level is lower than maximum storage. In this arrangement the bypass valve would discharge virtually all of the time, An unregulated turbine sized for 600 l/s at the minimum storage level, with a bypass valve for discharge when the turbine is not available. In this arrangement the net head at the turbine would be kept constant by dissipating head through the turbine isolation valve when the lake level is higher than minimum storage. The generation that could be expected from each of the above options was modelled using historic lake levels. The modelling results are tabulated below: The regulated turbine achieved significantly more generation even though the modelling allowed for unregulated turbines having higher efficiency. The modelling suggests that the extra generation from a regulated turbine is likely to justify the extra cost of this option. The actual generation achieved from the Moawhango scheme will be dependent on the future storage management of the lake. 3.6 Intake, pipework and valves Intake No modifications to the existing intake are proposed. Although the screen bar gap of 127 mm is insufficient to stop debris large enough to block a small turbine, as described in 2.2, this is considered unlikely to cause any problems. The possibility of sedimentation build-up at the intake has also been raised. Unfortunately we did not identify any sediment surveys of the lake. However, most sediment from the tributaries would be expected to deposit as dunes near the point of entry to the lake, where the water velocities become low. Also the compensation flow intake is 12 m above the old river bed, and most of the lake outflow goes through the Moawhango Tunnel. To date there has not been any sediment observed in flows from the intake 3. If the sediment ever gets high enough in the future to cause problems, an environmentally acceptable approach may be to open the 84" drawdown valve during floods (when the dam is already spilling). This would probably keep the entry to the compensation flow pipe relatively clear, since the base of the drawdown valve entry bell is approximately 1.2 m lower than for the compensation valve Pipework

12 General All of the proposed new pipework will be installed downstream of the existing isolation valve for the compensation flow valve. Installation of the intake bulkhead during construction should not be necessary. Drawings AP00821-M-502 and AP00821-M-503 show the proposed pipework. The pipe route is kept in close to the face of the dam, and is mostly under the shadow of the valve house. Materials The penstock will be constructed using an 18" (450 mm NB) standard weight ANSI B fabricated carbon steel pipe, which will be extended from the present terminal flange, (where the existing 450 mm NB fixed cone valve is currently installed), down the face of the dam to the proposed turbine. GRP pipes were considered. However, because of the unusual erosion problems that have historically occurred in the TPD structures, it has been decided to continue with a proven conventional steel pipe design. The bends and the tee branch will be made from off-the-shelf forged 1-1/2-diameter-radius buttwelding pipe fittings to ANSI B Flanges will be Class 150 slip-on flanges flat-faced with full-face sheet gaskets. Gasket jointing will probably be an aramid fibre reinforced rubber binder type, as commonly used on water piping. Bolting will be 1-1/4 bolts, to a similar strength as Grade 8.8 galvanized bolts. The pipe will have epoxy coatings inside and out. Possibly an epoxy zinc-rich primer, and vinylacrylic top coatings, as recently proposed for Tuai, could be considered. Pipework equipment items At the existing discharge valve gallery, the following items of pipework equipment will be installed: 450 mm NB magnetic flow meter; tee-branch and relocated 450 mm NB compensation flow valve; wafer-style 450 mm NB butterfly valve for isolation of the turbine. Due to space constraints none of these items have optimum lengths of straight constant diameter pipe upstream. This is not considered problematic, as the velocity at 0.6 m 3 /s is only 3.65 m/s, which is relatively low. However, if higher compensation flows are required in the future, it is likely that the present 2.5 m 3 /s capacity of the compensation flow valve will not be achievable. The actual limit could be established after commissioning, by determining the head/flow limits at which vibration or unstable operation becomes apparent. Strength rating Modelling of the proposed pipework using Autopipe software, applying ANSI B 31.5 design criteria, shows that it will be strong enough with four standard pipe supports anchored to the dam concrete work 4. No additional support framing is necessary.

13 The 450 mm NB pipe will also support smaller external pipe ducts for hydraulic hoses and generator cables. Three 80 mm NB pipes are proposed. One pipe is for the hydraulic hoses, and two for the generator cables. Two multicore flexible and waterproof cables, connected in parallel, are envisaged for the generator main connections. 4 A seismic factor of 0.7, 8 bar gauge design pressure, and temperature range from 5 C to + 35 C was applied. 3.7 Turbine The turbine is expected to be a small (300 kw) vertical Francis unit, with hydraulically actuated regulation, and a vertical cone draft tube. The scroll case will have integral brackets for anchoring directly onto the top of the existing concrete plinth (as described in 3.2). Anchoring using chemset injection anchors, or similar, is envisaged. The scroll case will have a long life surface coating provided by the manufacturer. The scroll case will also have access nozzles to allow clearance of minor debris from the stay vanes and guide vanes. It is possible that the regulation linkages will be located on the underside of the scrollcase for better physical protection. Preliminary turbine operational data is as follows: Rated power: 278 kw Net head and flow at rated power: 52 m at 0.6 m 3 /s Expected speed: 1,000 rpm Best efficiency head: 47m 3.8 Generator The generator will be an IP 68 rated, close-coupled, AC 3 phase motor. It is proposed to specify the motor so that it will operate as a generator at the rated power without requiring an external cooling fan. The generator will be capable of operating both submerged in water and in air. It will not be reliant on internal water circulation for its cooling. A double mechanical shaft seal, incorporating leakage detection, as used in submersible pumps will also be specified. The close-coupling should permit relatively simple disconnection of the generator, complete with the turbine runner, from the scroll case. This will allow access to remove any debris that becomes jammed in the runner after penetrating through the guide vanes. This type of disassembly for cleaning is very common on larger sewage pumps. The generator will be rated to operate for a sustained period at the maximum runaway speed of the turbine. This will avoid the need for a hydraulic accumulator for fast closure of the guide vanes, and/or for the turbine-isolation valve. 3.9 Civil works The civil works are minimal for this scheme, comprising only the concrete cutting of the mounting slab to accommodate the draft tube, turbine and the penstock anchors. The strength of the mounting plinth, after concrete cutting, will be determined at the detail design stage, and additional reinforcement or special long anchor bolts may be required Auxiliary mechanical plant

14 The only auxiliary mechanical plant is the hydraulic oil system. We have not yet determined whether the existing drawdown valve hydraulic pumping unit and reservoir will be utilisable for the mini hydro turbine and valve actuators. If this is the case, it is likely the only modifications that will be required will comprise a new hydraulic valve panel, and probably additional and updated oil filtering/monitoring Electrical systems The Moawhango dam electrical services are presently supplied from the 33/0.4 kv 50 kva transformer T70, located about 800 metres from the dam on the pole mounted end structure of the dual circuit 33kV overhead line. The existing 400 V underground cable from this transformer to the dam will be retained as the station services supply. A new single circuit 33 kv overhead line erected from the 33 kv end structure to the western end of the dam. The mini hydro generator output will be connected to the 33 kv line via short length of 33kV cable from a ground mounted 400/33 kv 400 kva power transformer. The following figure shows the intended route for the Moawhango and Mangaio 33 kv line extensions: TPD Minihydro Transmission line extensions (lower section of Tokaanu-Moawhango 33kV system) Mangaio powerhouse site New 0.7km 33kV Mangaio line The proposed single line diagram for the Moawhango scheme is shown on drawing AP00821-E-501, part of which is repeated below:

15 A 33 kv air break fuse switch will be installed at the terminal pole next to the transformer. A 33 kv air break switch will be installed at the existing Moawhango end structure to allow isolation of the new 33 kv line. The generator output of nominally 300 kw will be switched, at generator voltage, by a suitably rated moulded case circuit breaker installed in a switchboard in the dam valve house, located on the west wall next to the recently installed Kingfisher RTU control panel. The mains cable from the generator will terminate in this switchboard. The cable from the switchboard to the generator transformer will be run through the dam galleries along the same route as the existing cables. The generator voltage will be determined on receipt of the generator tenders. There is a potential cost saving in the interconnection cabling from the generator to the 33kV generator transformer if the generator is rated for operation at 600 V rather than the more common 400 V as used in New Zealand. The finally selected voltage will also be the low voltage winding voltage for the generator transformer.

16 3.12 Generator Protection Drawing AP00821-E-502 shows the intended protection concept for the Moawhango generator. This system will be based on two multifunction relays as shown in the diagram below. Both relays will be mounted in the Generator switchboard. Relay 1 - Generator protection: Neutral Overcurrent, Negative Phase sequence, Phase overcurrent, Overload, Winding overtemperature, Bearing overtemperature. Relay 2 - Interconnector protection: Under/over frequency, Under/over voltage, Reverse power, Neutral voltage displacement.

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18 Auxiliary supplies, at 400/230V AC, for the Moawhango hydro turbine will be taken from the existing dam distribution panel. A battery backed 24V DC supply will be used for controls, in a similar manner to that proposed for Mangaio Station Control and communications Although the Moawhango mini hydro scheme is conceptually very simple, the control and monitoring system is not significantly less complex than that for Mangaio. The control equipment and a PLC will be installed in a separate control panel located next to the generator switchboard in the dam valve house. A 450 mm NB, full bore, magnetic flowmeter will be installed in the compensation pipe, upstream of the turbine and compensation valve, to monitor the instantaneous flow through the pipe. The flowmeter signal will be used by the PLC to control the station flow. The station will operate fully automatically by monitoring the water flow in the discharge pipe and maintain the set flow of 600l/s by controlling the turbine and/or the compensation valve output. If the turbine trips off, the control system will regulate the position of the compensation valve to maintain the required compensation flow. We expect to achieve very accurate flow control from the station. The station control system is expected to utilise a Unitronics Vision 280s PLC, ( with integrated graphics touch screen. Monitoring and control of the turbine/generator system and compensation valve will be possible from the graphics panel. Suggested control system architecture is shown on drawing AP00821-E-003 Data Communication Block Diagram and is described below: Moawhango generator PLC with graphic panel located in the valve house control panel, RS232 serial communications from the PLC to the existing Kingfisher RTU located in the valve house, Existing RS485 serial communications from the existing Kingfisher RTU located in the valve house to the existing Kingfisher RTU located in the dam gallery entrance, Remote communications to Tokaanu via microwave from the existing Kingfisher RTU located in the dam gallery entrance, Software Driver at the Tokaanu Plantscape HMI using Unitronics OPC Server or similar software. The station will be controlled by the programmable logic controller in the valve house which will provide all the necessary control facilities and also monitor and log bearing and winding temperatures, protection conditions and the like. Remote supervision would be provided from the Tokaanu Plantscape HMI. The station output and status will be transmitted to the Tokaanu control room at regular intervals. In the event of an alarm or trip, someone could travel to site to solve the problem.

19 XXXX will also be able to control the flow set point, stop and start and trip the station from the Plantscape HMI at Tokaanu. Control and protection power supplies will be dual 24V dc battery systems with automatic changeover on primary battery failure. If the 33 kv power supply was lost, the station would trip off and go to bypass mode, maintaining flow control via the compensation valve. If the station programmable logic controller failed, the station would continue operating at the last flow setting and send an alarm to the Tokaanu control room. If the electrical protection operated or a bearing temperature was excessive, the station would trip off. This implies that the PLC cannot be used for bearing temperature trips etc that are required to allow the machine to continue running. The use of a Multifunction electrical protection relay with RTD temperature inputs meets this requirement.

20 4. Construction Phase 4.1 Contract Structure Recent meetings between XXXX Energy and XXX have resulted in an agreement that the Mangaio and Moawhango mini hydro projects will be structured in the following way: 4.2 Contract Interfaces Turbine and Generator contracts may be awarded to separate suppliers, depending on the results of the tender evaluation. Coordination between the equipment suppliers will be carefully controlled by XXX in accordance with the requirements of the technical specifications. It is unlikely that a separate civil contractor will be necessary for the Moawhango project. The M & E contractor can arrange for the civil works associated with the turbine mounting slab cutout and then commence preparation for the installation of the turbine, generator and balance of plant. It is likely that the construction of the 33kV transmission lines will be undertaken by specialist subcontracts to the M & E Installation Contractor. Due to the simple nature of the Moawhango contract, a Contract Termination Point Diagram and accompanying schedule have not been created for this project. 4.3 M & E Installation Mechanical installation The main considerations during mechanical installation that will need special attention are: ensuring satisfactory working conditions, i.e. safe access, and a dry site; maintaining the compensation flow during construction; prevention of watercourse pollution, (concrete cutting, and any site painting being particular areas of concern); availability of services, e.g. temporary power supply from the valve gallery, or craned-in portable gen-sets, etc. One methodology is to prepare the site as follows: install special ladders, and handrails, etc. as may be required to permit safe pedestrian access from the dam abutments down to the mounting plinth (all equipment will be craned in using a mobile

21 crane on the dam crest, although some minor lifting may be possible using the valve house monorail); prefabricate and install a special anchored mounting frame for the fixed cone valve, that will allow the valve to be temporarily installed on one of the apron steps downstream of the plinth, and access route (the frame will also include a simple adjustable link mechanism to allow manual regulation of the valve); prefabricate special temporary reducing fittings, with extension pipe stubs which can be bolted onto the existing terminal flange, and the fixed cone valve flange; deploy a 300 mm contractors hose string, with flanged ends, and around 30 to 40 m total length; crack open the drawdown valve, and close the 450 mm NB isolation valve; then relocate the fixed cone valve on the special mounting frame, and (using the hose and reducing fittings) reconnect to the terminal flange at the valve gallery; close the drawdown valve, and open the 450 mm NB isolation valve. It is envisaged that the mechanical installation will proceed as follows: contractor review of drawings and completion of prefabrication site measurements; prefabricate and surface coat most of the pipework, (postponing selected shop-welds-to-precisefield-measurement as deemed prudent); manufacture hydraulic actuator for fixed cone valve, and new hydraulic valve panel; concrete cut the proposed draft tube cavity in the plinth; install and anchor turbine and generator unit; install and anchor protection structure; install and anchor penstock pipe up as far as the lower flange of the turbine isolation valve; obtain precise measurements of the flange to flange dimensions to allow accurate shop fabrication of the upper penstock assembly (the magnetic flow meter, bend with tee-branch, and turbine isolation valve); complete fabrication and trial shop fit-up, and surface coating of the upper penstock assembly; install hydraulics for actuation of fixed cone valve and turbine isolation valve; crack open the drawdown valve, and close the 450 mm NB isolation valve; then install the upper penstock assembly, and commission the hydraulic actuation of the fixed cone valve and turbine isolation valve; close the drawdown valve, and open the 450 mm NB isolation valve and the fixed cone valve; complete installation of generator cables, and turbine hydraulics; complete remaining electrical work, and commission the turbine and generator Electrical and Controls installation The Electrical and Controls installation for this project is relatively straight forward and within the capability of several leading contractors.

22 The long lead time items are the generator transformer and generator. All other items are likely to be available at less than 6 weeks delivery. Off site fabrication of the generator control panel and the generator switchboard will be specified. Following delivery of all items to site, an on-site construction period of about four weeks is probably sufficient for this section of the project. Off site programming and testing of the control PLC will be specified. The configuration and testing of the Tokaanu HMI interface will also be undertaken off site, prior to installation. 4.4 Potential Contractors Discussions with XXXX Energy Tokaanu management and XXX knowledge of suitable contractors have resulted in the following list of potential contractors for the M & E work: 4.5 Supervision and Commissioning XXX will provide skilled and experienced engineers to observe the construction and provide the technical interface between the Contractors and the XXX design team during the site construction, precommissioning, and commissioning of the mini hydro station. XXX recommend the following staff be provided on a part time basis to ensure adequate control during the construction phase: Hydro Mechanical erection supervisor Hydro Mechanical engineer Electrical and Instrumentation engineer Commissioning will require the services of XXXX operations staff, the Hydro Mechanical erection supervisor, a Hydro Mechanical engineer and a Hydro Electrical and Instrumentation engineer.

23 Appendix A Drawing Schedule