Civil Infrastructure

Power Station Pipeline

Lower Lake Margaret

Task

Restoring the Lower Lake Margaret Power Station to the grid of Tasmania's highly ecologically sustainable hydro-based electricity system has seen a masterful combination of old and new technologies. A mix of "on the job smarts" and "solid engineering principles" brought about a set of practical solutions to a series of economical, environmental and community issues, not to mention the construction tasks of working in a rugged landscape with slopes of 38 degrees and temperatures ranging from -3 to 25 degree Celsius.

Hydro Tasmania initially looked to re-commission the Lower Lake Margaret Power Station using steel pipes or possibly fibreglass pipes on the two-kilometre hilltop section. But it faced considerable community opposition to replacing the century old wood stave pipe - despite its obvious poor condition. The solution was one that addressed not only these community concerns, but also a more pressing practical one - cost.

The answer, replace the wood stave pipeline with a wood stave pipeline for the two-kilometre hilltop section. And on the crucial penstock section leading to the power station inlet valve, the decision was taken to replace the old steel pipeline with fibreglass reinforced plastic, leading to a world first in the above ground use of this type of composite pipe. The solution addressed not only these community concerns, but also a more pressing practical one - cost.

The task of blending these two technologies, separated in their development by thousands of years, harnessed Shaw’s broad expertise across a range of civil engineering practices to complete what many would see as two complete projects in one.

Challenges

The logistical complexity of the project was acknowledged by Hydro Tasmania as being one of the most significant features of the job. Integrating the completely different types of technologies and different methodologies into the one project, within a tight timetable to meet a series of changing deadlines, also added another level of complexity.

On the environmental side, the area had been listed by Heritage Tasmania.  This meant that every step of the process had to be approved by the listing authority and changes to the approved plans had to be submitted for acceptance before progressing. The 10-page listing included both natural environmental features, such as flora and fauna, varying from rain forest sections through to sub-Alpine regions, as well as the "built environment" of the old Lake Margaret Village, the old tramway tracks, the wood stave pipeline, heritage bridges, old camp sites and the historic power stations.

Outcome

When full, the pipe will hold three million litres of water on its way to the penstock, which, although officially rated at 1600 kilopascals, has been tested up to 2000 kilopascals pressure down the 38-degree slope to the rejuvenated Lower Lake Margaret power station. The project was finished on time, on budget and on target to rejoin Hydro Tasmania's electricity network, but it also became one of the prime pieces in the jigsaw of Tasmania West Coast Wilderness Tourism Trails.

Erosion Stabilisation

Detention River

Task

The site at Detention River in Northern Tasmania was situated on the outside of a river bend that coincided with a local community. Constant erosion of this river bank was exposing properties to undermining as well as exposing essential services; sewerage and electricity, to possible damage and subsequent contamination.

Initially the community and council of the Detention River precinct sought out a design and construct model package for a revetment wall to stabilise the existing bank and prevent further erosion. Shaw Contracting a concept design, sought some design support and a solution was presented to all parties. Upon securing reasonable funding, the community approached Shaw Contracting to design and construct the wall based on the available funds.

Challenges

Shaw Contracting then set about assessing the site and the most feasible option of an Elcorock shoreline protection system was the chosen ‘engineered solution’, due partly to its soft amenity and ability to rapidly construct within the tight confines of the site.

Shaw Contracting engaged Geotas Pty Ltd and Geofabrics Australia for supply and support in constructing the first ever Elcorock project in Tasmania.

Outcome

Placement and filling of the Elcorock containers was completed on time and on budget without any incidents, loss to performance or amenity to the structure. The successful completion of the first Elcorock project in Tasmania at Detention River represents an effective work method for other problem sites such as this across the state.

Basslink Converter Station

George Town

Task

Site preparation to final completion with detailed earth works associated with construction of the HDVC transmission facility at George Town that links the Tasmanian and Victorian electricity supplies.

The project included excavations and preparation of the land in readiness for the civil construction.

Construction included, the control building, valve hall and transition yard each including air conditioning, heating, fire detection, all electrical works, concrete works, steel structures and cladding, masonry and finishing works and sanitary.

Shaw installed a number of precast cable trenches to take the cables installed around the site, and 22 in-ground concrete pipes, each 2.5m diameter and 25m long, which will be used for oil containment in the event of a spill. The oil is contained so that it can be pumped out, thereby reducing any potential risks to the environment.

Challenges

Each converter station consists of a control building, valve hall including transformer bays, auxiliary buildings, foundations in reinforced concrete for buildings and equipment in switchyard, external works, road and walkways, transition yards.

Approximately 2,000m³ of earth were removed for the pipes to be laid and back filled to specifications. The total earth moved in the 500m x 500m converter site was approximately 25,000m^3.

The switchyard work involved the construction of approximately 420 bored concrete piles and pile caps, with holding down bolts set into them for installation of other structures necessary to complete the electrical switchyard.

Outcome

Shaw Contracting completed this project on time and on budget. Shaw’s detailed Quality System and exceptionally skilled workforce allowed it to not only meet, but also exceed the very arduous project specification

Red Hills Creek Diversion

Red Hills

Task

Hydro Tasmania has taken up the challenge to identify and develop opportunities from the current system, which could be captured to restore lost water inflows rather than just accepting a reduced system capacity. On this basis a target to identify 1000 GWh of additional energy from system enhancements of the Hydro Tasmania’s assets was set. The Red Hills Creek Diversion Project is part of targeted catchment diversion and diversion upgrades.

An objective of the project was to increase existing storages, such as Lake Plimsol, to capture grater inflow to be release during drier periods. Lake Plimsol was reduced in size in the mid 1990s due to the need to cut costs. This project is part of Hydro Tasmania’s plan to upgrade or redevelop existing power stations, some of which are up to 70 years old.

Positioning two structures on the Red Hills Creek and Number 1Creek to capture the natural overland run-off and that of several creek tributaries, the project sees a V drain which catches the overland flow and channels it through a series of pipes which ultimately diverts the flow under a roadway and to a tunnel portal into a natural watercourse.

The catchment goes into an eight-kilometre tunnel from the Anthony Dam and then into the underground Tribute Power station. Development of the Red Hills Creek diversion tunnel utilised hand held machine and drill and blast techniques. This provided the following advantages:

• A minimum of soil to be removed
• Tunnel slope to allow natural drainage, eliminating the need for a pump during the excavation cycle
• Hand held development to provide greater control over the finished contours of the tunnel design
   

Charging and blasting was carried out with the aim of minimising damage to the walls and backs of the tunnel. This required careful selection of explosives and charging to conform to the rock type and geotechnical conditions.

Challenges

One of the major challenges facing the project was the weather. In one week more than 250mm of rain fell on the site making conditions extremely difficult for heavy machinery. Also, as a design and construct project a number of design changes were required as the project developed. Unexpected variations in rock structure required the need for alternative structures to be developed.

Outcome

The Red Hills diversion project will contribute an additional five percent output on the existing power station while contributing to Hydro Tasmania’s objective to source an additional 1000 GWh of additional energy from its existing generation assets.

Launceston Waste Centre Extension

Launceston

Task

The project was to take place at the existing Launceston Landfill Site and consisted of two parts:

1. Construction of a new landfill cell including a new leachate barrier system.  The leachate barrier incorporated a combination of clay lining, geosynthetic placement and underground drainage confined within a drainage blanket.
2. Construction of a new perimeter road around the existing landfill site.

Challenges

In construction of the landfill cell it was essential that quality was maintained throughout the project while ensuring that the most economical solution was found for the Council. 

The construction of the clay liner was carried out to stringent compaction and moisture content control to ensure an impermeable barrier was achieved.  Materials were varied and later in the project on site borrow pits used to ensure that the project was as economical as possible.

Elcoseal X1000 had been specified for the Geosynthetic Clay Liner.  This specialist product was imported to Tasmania from the mainland in a just in time basis.  Scheduling of site resources for its installation was then critical. It was essential to install the liner material and confine it on the same day. 

On the perimeter road it was essential for the road design levels to be maintained.  Large sections of the road were to be excavated in sheet rock.  Due to security issues on site and likely interaction with the public it was not practical to use drill and blast techniques to achieve this.

Outcome

Some 29,000m3 of clay material was placed on site with 20,000m3 from an on site borrow pit and 9,000m3 imported material.  Imported material was used to ensure timely delivery at the project outset prior to testing and confirmation of the test results for the onsite borrow.

Over 50,000m2 of Elcoseal X1000 was used on the product and this was confined by 22,500m3 of single sized aggregate. Significant resources were used to ensure that this went smoothly.  Comprehensive quality records were kept with product position and traceability retained throughout the project.

Some 4,175m of sub soil drain were installed in to the clay liner.

Shaw broke out a total of 13,150m3 of rock on the perimeter road.  Shaw purchased an ACCO 1000 rock breaker, the largest rock breaker in Tasmania for the project.  The addition of the rock breaker to the project enabled all of the rock to be excavated by mechanical means.  No blasting was carried out across the project, eliminating risks to the general public.

Due to the high level of competence demonstrated by the Shaw staff Launceston now has a state of the art landfill site meeting all environmental and regulatory requirements. 

Building & Office Complex

Alinta Energy

Task

Following Shaw’s successful completion of the major earthworks and civil works for Alinta Tamar Valley, Shaw was then engaged to design and construct a complex suitable for the main operating centre of the power station.

Shaw provided four building design options in the initial design phase for the client to select which would best suit their requirements.

Shaw then worked up the architectural design to obtain council approval. However, as there was no sewerage outlet facility on site, planning approval could not be achieved without a Waste Water Treatment Plant.

Shaw was in turn, engaged by the client to design a suitable Waste Water Treatment Plant that would meet site and council requirements.

The Shaw team designed a class A Kelair Blivett, environmentally friendly system that completely irrigates processed sewerage onto a designated vegetated area onsite.

Challenges

This project was to be fast tracked and Shaw was expected to meet a tight completion time frame.

Following the successful design and approval process, Shaw commenced construction of the Control Building Complex.

This complex consisted of the subsequent features:

• A 600m² Structural Steel and Trim deck Clad Warehouse.
• 465m² Control Building suitable to accommodate 30 – 40 employees.
• Control & Equipment Room with office and kitchen facility featuring a 300m set down floor for major telemetry and system management equipment fitted with a false floor and soundproof, fire retardant wall cladding system.
• Open plan office space suitable to facilitate 25 workstations.
• Male, female and handicapped bathrooms with multiple toilet, basin, shower and locker room facilities.
• Lunchroom with kitchen.
• Office reception area.
• 1 large and 2 small meeting rooms.
• 1 large work area used to undertake maintenance on highly sensitive equipment.

Shaw Contracting also designed and coordinated the installation of electrical, data, lighting and mechanical services for this project.

Outcome

Shaw met the tight time and budgetary constraints of the D&C project and provided the client with a state of the art Control Building that will service this Power Generation Plant well into the future.