Lake Margaret: Conservation of a 1914 Tasmanian Hydro-Electric Power Scheme

Transcription

1 Lake Margaret: Conservation of a 1914 Tasmanian Hydro-Electric Power Scheme Sandra Hogue, Environmental Programs Manager, Hydro Tasmania Summary: The Lake Margaret Power Scheme (LMPS) is located approximately 10 km north of Queenstown on the Yolande River on Tasmania s west coast. Its history is closely linked to that of the Mt Lyell Mining and Railway Company, at one time the largest copper producer in the British Empire and the longest operating mining venture in Australia. In 1914 hydro electric power generation commenced at Lake Margaret. This was one of the earliest hydro electric power stations in Australia and showed great foresight and confidence in the Mount Lyell Copper Mine by the Directors. The power scheme includes two power stations, an employee s village and other ancillary sites. A significant feature of the site was its isolated nature with the only access for around 50 years being by an 11 km tramway. The site has been listed on the Tasmanian Heritage Register and been nominated to the National Heritage Register. A number of studies into future redevelopment options have been commissioned including a recent Conservation Management Plan. The power scheme was decommissioned in June 2006 due to major concerns about the safety of a 2.2 km King Billy woodstave hilltop pipeline, one of the most significant heritage features of the site. This pipeline dates from 1938 replacing an earlier woodstave pipeline. Hydro Tasmania released a feasibility study for public comment in October The feasibility study canvassed two main options for the scheme: o o refurbishing the existing upper power station; or installing a new generator adjacent to the upper power station. Both options require the replacement of the woodstave pipeline with both steel and woodstave being considered. This paper highlights some the challenges Hydro Tasmania has experienced in attempting to incorporate heritage values in a major upgrade of an historic power scheme which has strong community interest and involvement. Key words: hydro-electric power scheme, timber (woodstave) pipeline, conservation practice for operating assets 1. INTRODUCTION As a major hydro electric generator for almost 100 years Hydro Tasmania (HT) now has a number of assets identified as having significant cultural heritage values. A Cultural Heritage Program established in 1994 has been systematically identifying these heritage values and developing plans and procedures to help manage the values. The Heritage Program has also recognised that many of these sites have social value for the communities who have lived and worked in these often isolated places. This paper examines one of Hydro Tasmania s oldest assets, the Lake Margaret Power Scheme (LMPS). Investigations of how to manage this asset into the future have presented major challenges due to the safety risks of heritage features of the site, particularly a 2.2 km King Billy Pine woodstave pipeline, as well as considering the costs of investing in an aging asset. The paper provides a brief history of the Lake Margaret Power Scheme, describes its heritage significance, outlines safety issues leading to a station down and the care and preservation planning required following the shutdown. It concludes with an overview of future options for the site. 2. BACKGROUND The Lake Margaret Power scheme is located on Tasmania s West Coast to the north of Queenstown. Figure 1: Location of Lake Margaret

2 The scheme was originally built by the copper mining giant, the Mt Lyell Mining and Railway Company. The potential of hydro power had been recognised early in the company s history, and after thirty years of utilising local timber supplies for power generation, the company looked for a more permanent source of power. Lake Margaret was selected due to the high rainfall and suitable head of water from the Yolande River to power turbines. The Mt Lyell workforce, including Maltese immigrants, began by constructing a two foot tramway into the site. Specialised Maltese stonemasons were involved in the construction of dry stone walls and cutting a bench around a cliff for the tramway to the dam. At commissioning in 1914 the power station building had four turbines (single runner, single jet Pelton type water turbines manufactured by Boving in England). The station began by transmitting power to the mining company s works at Queenstown with considerable transmission losses over the line. Figure 3: Lake Margaret completed c For over fifty years the village remained relatively isolated - the tramway (or walking) the only way in or out. During an oral history commissioned in 2006, Molly Groves, a resident of Lake Margaret, recounted how the rail cars would run children into school at Queenstown, leaving at twenty past eight in the morning and returning at five o clock at night. Wednesday was ladies day and the rail car would take the women of Lake Margaret to Queenstown for shopping. In 1948, Queenstown was connected to the grid, and for the next twenty years little changed apart from regular maintenance and upgrade work to the generating equipment. The big change to Lake Margaret came in 1964 when the tramway was replaced by a road, thus ending the isolation of the village. Figure 2: Lake Margaret Power Station under construction Soon after the opening of the station a new penstock and two more generating sets were added, creating additional generation capacity. The 1920s was a period of consolidation with minor repairs and upgrade work. A permanent village of prefabricated houses grew out of a sea of tents and temporary accommodation providing permanent homes for workers at the station and their families. During the 1930s another power station (using one Boving Francis turbine) was constructed to utilise the water flowing down the Yolande River. In 1938 the upper Oregon woodstave pipeline was replaced due to severe deterioration after only 24 years of operation. This time the woodstave was built out of King Billy Pine harvested and milled locally after an investigation that considered both steel and woodstave replacements. The construction costs of both were similar. In the 1970s major works were undertaken. A new penstock was added, new headworks and connections into the station, upgrades to the dam and replacement of some of the outdated equipment. In 1985 the scheme was sold by Renison Goldfields Ltd, the owners of the Mt Lyell Mining and Railway Company Ltd, to the Hydro-Electric Commission (HEC) (now Hydro Tasmania) through the Tasmanian Government. 3. DESCRIPTION OF THE POWER SCHEME SITE The Lake Margaret Power Scheme is one of the oldest hydropower schemes in Australia. The scheme is based on the catchment of a small glacial lake of the same name located in the coastal ranges north of Queenstown in a region of very high rainfall. The scheme covers a site of around ha and consists of the following major assets: the Lake Margaret Dam (post-tensioned concrete gravity dam);

3 2.2 km King Billy Pine wood stave pipeline, transporting water from the dam to the penstock; penstock; upper Power Station; lower Power Station and supporting infrastructure, decommissioned; and Lake Margaret Village, including 7 cottages and a community hall. The Upper Power Station contains seven pelton machines each having a capacity of 1.2 MW. The overall station capacity is thus 8.4 MW with a flow rate of approximately 3.4 m 3 /s. The Lower Power Station, decommissioned in 1994, has a single Francis machine with a capacity of 1.5 MW. This machine has been mothballed. In June 2006 the average annual energy production from Lake Margaret was GWh. This represented an average of just over 5MW average production over the whole year or about 0.5% of Tasmania s total output. For the purpose of assessing heritage values and providing policy direction, the Lake Margaret site has been divided into a number of separate but related areas or precincts (see Figure 4). Precinct 2: Precinct 3: Precinct 4: Precinct 5: The village and area to the west of the river including roads and infrastructure. The core site around the power station defined by the river and covering the penstock, entry road, lower weir, residence no 1 and the immediate setting. The lower penstock, hilltop valve house, winch house and lower power station. The entry roads and surrounding bushland areas that comprise the balance of the site. 4. HERITAGE SIGNIFICANCE A Heritage Study commissioned by the HEC in 1994 by Godden Mackay has provided a detailed assessment of the assets on the site as well as a statement of heritage significance. The statement of significance was updated in 2006 by Paul Davies Pty Ltd during preparation a Conservation Management Plan (Davies 2006a). The Lake Margaret power station complex is a place of outstanding cultural heritage value. It encapsulates the early development of power generation in Australia and Tasmania and the pioneering enterprise of the West Coast of Tasmania that was integrally linked to mining development on a site of great natural beauty and value. The development of the Mt Lyell Mining and Railway Company mines (an icon mining venture in Australia) and Queenstown was dependant on the operation of the station. The place is one of the earliest power schemes in Australia whose value is enhanced by its continued operation. It is the last privately built and operated scheme in Tasmania and marks a major change from private to public power generation in the State. The site is a rare and intact example of not only the power generating plant with its rare set of early generating and control equipment but the associated infrastructure of dam, pipelines, headworks, the village and the very rare second station added in Lake Margaret has the ability, more than any other hydro power station in Tasmania, to demonstrate all aspects of its history and operation within an accessible wilderness area. It is a place that has very high interpretative value. Figure 4: Lake Margaret Conservation Precincts Source: Davies 1996a, volume 1 Precinct 1: The upper penstock and dam including the tramway, hilltop valves and winch houses. The Lake Margaret Power Scheme was provisionally listed on the Tasmanian Heritage Register in August 2006 with final listing on 28 February The site has also been nominated to the National Heritage List (pending assessment). The detailed history and assessments contained in the Conservation Management Plans provided valuable input into the data behind both the listings.

4 The Management Plan also assisted in developing an exclusion agreement with the Tasmanian Heritage Council (THC) to allow on-going maintenance activities to occur without the need for individual applications for permits to the THC. 5. POWER STATION SHUTDOWN, JUNE 2006 Due to concerns about the safety of King Billy Pine woodstave pipeline, in December 2005 a decision was made by the HT Board to shutdown the upper power station on 30 June The pipeline had been leaking profusely for a number of years and operation and maintenance costs were high due to the manning levels required and a number of OH&S issues. Maintenance activities on the woodstave pipeline included: board replacement after blowouts; replacement of steel hoops when hoop failure occurs; patching and driving timber wedges into leaks stabilisation of foundations (rock walls); and remedial work on steel support structures. In the earlier stages of the life of the pipeline the steel hoops were periodically tightened. For the last 20 years the condition of the corroded steel nuts and band threads have been such that tightening of the steel hoops had not been a suitable method of reducing leakage in the pipeline. Figure 5: Leaking King Billy woodstave pipeline Around the time of the shutdown there was considerable stakeholder and community interest in its closure and Hydro Tasmania came under intense criticism for closing the station with no clear plans for future development. A Lake Margaret Community Liaison Group was established in October 2005 and included representatives of the West Coast Council, people with tourism and heritage interests from the west coast community and staff from Hydro Tasmania. It has met regularly since. The Group has considered a range of heritage conservation issues and projects as well as the feasibility of future development options for the Lake Margaret scheme. 6. CONSERVING LAKE MARGARET S HERITAGE VALUES A number of detailed conservation and design papers have guided management of the site in conjunction with 2006 Conservation Management Plan. Three key papers are summarised below, that is the Care and Preservation Plan, the Heritage Impact Assessments and the detailed Design Report for preservation of sections of the woodstave pipeline. A number of other papers have been prepared to support heritage conservation on the site and provide guidance such as an Interpretation Plan (Terry and Tiddy, 2006) and an Indicative Assessment of Tourism Potential (Inspiring Place, 2006). 6.1 Care and Preservation Plan Prior to the shutdown, the 2006 Conservation Management Plan was used to prepare a detailed Care and Preservation Plan. The works identified and implemented from this plan are designed to ensure that the power station is capable of redevelopment in the future. A key aspect of this Plan was providing for preservation of three sections of the King Billy woodstave pipeline to allow for future interpretation on the site. Following decommissioning, Hydro Tasmania continues managing the site in accordance with the 2006 Conservation Management Plan. The Care and Preservation Plan covers detailed actions for: the dam (including crest raising to minimise the potential for overtopping and impact on heritage infrastructure down stream); the pipeline (including preservation of 3 sections); retaining water in the penstock to ensure that internal coal tar coating is preserved; works to the hilltop valve, valve house, winch, haulageway and tramway; securing and reducing water damage to the houses and hall in the village; mothballing of machines in the upper power station building; and works to the lower power station building and infrastructure to decrease the rate of deterioration. A number of activities were also identified that ensure that site remains secure to minimise the potential for vandalism and theft from the site. There is an on-going presence by operators at the site and three of the houses in the village are still occupied. 6.2 Heritage Impact Assessments A procedure introduced into HT s Environmental Management System in December 2005 as part of the Cultural Heritage Program requires that all sites or assets of high or very high significance have a of Heritage Impact Assessment prepared and endorsed

5 prior to undertaking works. While the Conservation Management Plan for Lake Margaret provides broad strategic and policy direction, the Heritage Impact Assessment identifies the specific conservation requirements for the proposed works. Paul Davies prepared a Heritage Impact Assessment (HIA) during May 2006 which was endorsed prior to the shutdown. The HIA covers the works detailed in the Care and Preservation Plan, describes the conservation options and makes recommendations about the preferred options. The HIA has been used as supporting documentation for applications for permits for removal of the woodstave pipeline required from both the West Coast Council as well as the Tasmanian Heritage Council. While both these processes were subject to public notice and community concern, the detailed requirements of the HIA were not disputed. A second HIA was completed for 300 mm crest raising works required to ensure that the dam did not overtop due to increase water levels resulting from the power station shutdown. During the life of the power station the dam spilled infrequently. Overtopping the dam could result in impacts on heritage infrastructure down stream or other environmental issues such as erosion. During the assessment careful consideration was given to, as far as possible, matching new works with the existing dam. In addition, historic inscriptions on the original dam wall needed to be protected during the works. The crest raising was completed in August. removal of another section of pipeline for Queenstown museum; and establishment of The Lake Margaret Furniture Collection (a West Coast trust be formed to manage an annual/biennial event with display of select furniture manufactured from the King Billy pine). Following dewatering it is likely that the woodstaves will shrink due to drying. As was experienced with a woodstave pipeline to the lower station, it is inevitable that the pipe will collapse if preservation measures do not occur. Despite being dewatered on 8 July 2007 (three days before the scheduled date due to collapse of a rock wall under one of the saddles), at the time of writing the pipe was still relatively intact, probably due to dewatering occurring in the winter. It is expected that sections of the pipe will collapse when the timber dries out in the summer. Figure 7: Section of collapsed rock wall July 2007 To ensure that the three sections identified for preservation it was necessary to internally reinforce the woodstave pipeline and to upgrade the bracing of the supports. Galvanised steel bands were installed on the inside of the pipe to provide internal support counteracting the external steel bands. Figure 6: Recently completed dam crest raising works (note the water level) 6.3 Preservation of Pipeline sections Following shutdown of the power station, removal of all but three sections of the woodstave pipeline is planned. The actual removal of the pipeline and salvage of the highly valuable timber is not planned to occur until the time of redevelopment. The Lake Margaret Community Liaison Group is currently considering a variety of projects for the salvaged timber including: manufacture of a violin by a local artisan; removal of a compete section of pipeline for West Coast Pioneers Museum at Zeehan; Longitudinal reinforcement has been installed inside the pipe. External reinforcing was required on one of the three sections and was designed to be sympathetic to the existing nature of the steelwork. End caps were constructed to prevent access inside the pipeline, hide internal reinforcing and reduce the risk of fire damage. The individual woodstaves have been staggered at the pipe ends to depict the construction of the pipeline. These were carefully designed to ensure that there were no shelves that would capture embers in the event of a bushfire. Other key fire management tactics are detailed in the Lake Margaret Woodstave Fire Management Plan (Lawless 2007). Aspects include a program of strategic fuel management, wrapping in protective materials and installation of sprinklers.

6 Coating of the timber has been investigated to attempt to prolong the life of the preserved sections. However, the scouring required to prepare the timber for coating may reduce the patina and change the appearance. Testing of coatings is occurring on sections of woodstave not identified for preservation. Preservation of the three sections was completed in September One of these sections is shown in figure minimalist refurbishment of the existing power station 2- build a new power station with a single generator adjacent to the existing power station 3 -Combined refurbishment of upper station together with redevelopment of new lower station. All options include a replacement woodstave pipeline. It should be noted that on financial criteria alone the redevelopment of this power station is marginal. However, the Board can consider the community interest in this project when determining whether to proceed. The project will be competing with a range of capital works priorities in a time of drought where storages of other hydro electric schemes are low and the business needs to maximise production. A summary of the three options is provided below. Option Generation capability Upfront capital cost range $M Figure 8: Preserved Section of Woodstave Pipe 1. Minimalist refurbishment of existing power station 51.5 GWHrs pa FUTURE PLANS FOR LAKE MARGARET Future options for the scheme have been considered concurrently with the conservation works planned and implemented during the shutdown phase. In November 2006 HT released a feasibility study for redevelopment of the LMPS. Two main options were considered to be feasible: build a new power station; or refurbish the existing upper power station. 2. New power station approx 10 MW 3 Combined minimalist refurbishment of upper station with redevelopment of lower station 56GWHrs pa 72 GWHrs pa Both options require construction of a new low pressure pipeline to replace the woodstave pipeline. The two preferences were for a woodstave or steel replacement. Preliminary cost estimates indicated that both were similar in cost. A fibreglass pipe was also considered but dismissed due to cost. The Lake Margaret Community Liaison Group and the general public were consulted on the feasibility study. It received 19 submissions with the community preference being for the power station to be refurbished and for a woodstave replacement pipe. At the time of writing, a detailed business case was being finalised for a decision by the HT Board at its meeting in November During development of the business case a third option has also been canvassed, that is consideration of redevelopment of the lower power station. This third option was requested by the Community Liaison Group. The three options now are: 7. CONCLUSIONS Conservation of the Lake Margaret Power Scheme has presented significant challenges for Hydro Tasmania. While the scheme s considerable heritage values have been recognised since 1994, it has not been easy to justify the significant expenditure required to overcome the operational and occupational health and safety issues with running a station that is 93 years old. Substantial community interest in the future of the scheme has meant that Hydro Tasmania has needed to consult with key stakeholders throughout consideration of redevelopment options. The Conservation Management Plan and other supporting preservation and conservation reports along with in-house expertise through the cultural Heritage Program has been invaluable in incorporating heritage requirements in planning processes at a relatively early stage.

7 8. ACKNOWLEDGEMENTS Over the last few years a number of Hydro Tasmania staff has made a substantial contribution to developing the design and conservation options for Lake Margaret including Tony Field, Brad Turner, Joshua Chugg, Sarah Waight, Matthew Lawless, Nicola Woolford, Terry Dooley and Scott Newett. The support and advice of the Lake Margaret Community Liaison Group is also acknowledged. Over the years many others have taken a keen interest in the heritage values at Lake Margaret and have contributed to the debate about future options, there are too many to mention here. I hope their visions of a continued life for Lake Margaret are realised. 9. REFERENCES Bird T and Petersen M, 2006 Assessment of the Thickness and Condition of the Timber Staves in the Pipeline for the Lake Margaret Upper Power Scheme Colman, R., 2006, Notes on structural shortcomings of the Lake Margaret upper hilltop pipeline, Hydro Tasmania - Assets & Engineering Group Godden Mackay, 1994, The Lake Margaret Cultural Heritage Study, Hydro Tasmania, 2006, Lake Margaret Feasibility Study Volume 1: Main Report and Volume 2: Appendices Inspiring Place, 2006, Indicative Assessment of Tourism Potential for Lake Margaret Lawless, M., 2006, Lake Margaret Woodstave Pipe Preservation: Detailed Design Report, Hydro Tasmania Consulting Lawless, M., 2007, Lake Margaret Preservation Fire Management Plan, Hydro Tasmania Consulting Paul Davies Pty Ltd, 2006a, Lake Margaret: a Conservation Management Plan Volume 1: and Volume 2: Appendices Paul Davies Pty Ltd, 2006b, Lake Margaret Power Scheme: Heritage Impact Assessment of works related to the shutdown of the station SKM, 2006, Lake Margaret Pipeline Review, October 2006 Terry I and Travis T, 2006, Lake Margaret Hydro- Electric Scheme Interpretation Plan Woolford, N. and Chugg, J., 2006, Lake Margaret Care and Preservation Plan Decommissioning Phase, Hydro Tasmania Consulting