The Hattah Lakes wetland no longer floods as regularly as it once did, posing a threat to the area’s ecological balance. A vast project to create artificial flooding undertaken to solve this issue was threatened when rivers rose to 40 year levels during construction, but a collaborative approach between the stakeholders and contractors ensured that the job was completed on time.
Hattah Lakes is an extensive wetland complex covering approximately 13,000 ha within the 48,000 ha Hattah-Kulkyne National Park. It is located in Victoria on the River Murray between Robinvale and Mildura. The key threat to the environmental values of the Hattah Lakes is the reduction in the frequency and duration of flooding, caused by the diversion and regulation of flow upstream. There has also been a minor shift in the seasonality of flows with the majority of peaks now occurring in August, one month later than under pre-development conditions. The lakes are now rarely filled and floodplain vegetation, which depends on flooding, is in poor health.
In 2010, a briefing paper on the economic value of Australian wetlands was commissioned by the Conservation Foundation. This paper found that by applying the concept of Total Economic Value (TEV) to the Hattah Wetlands asset, the range of attributable values (‘direct use’, ‘indirect use’, ‘option’ and existence’) to the asset including ecosystem services totaled over $14.5 million per annum.
Goulburn-Murray Rural Water Corporation (G-MW), the statutory corporation that manages resources for northern Victorian water systems identified the need for works as part of The Living Murray (TLM) Hattah Lakes Environmental Flows Project to address deficiencies related to environmental flows in the Hattah Lakes and improve the ecological condition of the Hattah Lakes as well as protect the economic value it holds for the local region and Victoria in general.
The works proposed included lowering sills in Chalka Creek to increase the frequency of natural flows, constructing a series of regulators and stop banks on the floodplain to retain water; and constructing a permanent pumping station at the mouth of Chalka Creek to top-up natural floods and fill the lakes during long dry spells. The intention is that these works will improve the ecological condition of the lakes system by increasing frequency, duration and extent of wetland and floodplain inundation. Ultimately the Messenger Creek Pump Station can supply 1050 mega litres of water every day (12,000 litres per second) into the wetland system.
Comdain Infrastructure was awarded the prime contract for this project which included complete project management of the works, survey, all site supervision, and construction works (earth, road, concrete, river and mechanical), mobilisation and demobilisation. After award Comdain also assumed the contract responsibility for the construction of the required 5.2km 22,000 volt underground electricity supply to the Messenger Pump Station ensuring the continuity of the overall project.
The total value of the project was $19M (ex-GST) with plant and labour contributing over $7M of the total and the specialised axial flow pumps for the Messenger Regulator over $2M of the total.
Overall the scope of works delivered by Comdain’s project group included site mobilisation and site clearing including grubbing of trees, setting out of works and construction of all works, including but not limited to:
- Messengers Works Regulator;
- Messengers Works Pump Station which includes seven 300kw, 32 metres long two-stage axial flow and driven pumps;
- Messengers Works Motor Control and Telemetry Room which includes pump variable speed drives, local Human Machine Interface control and telemetry/WAN interface to GMW’s flow office in Mildura;
- Lake Kramen Works comprising a pipeline and regulator structure;
- Little Lake Hattah Regulator Refurbishment;
- Chalka Creek Works comprising Lowering of sills at various sites and rock-lined fishway channels at the confluence of the Murray;
- Breakout works comprising a stop bank (levee) which replaces the existing road;
- Cantala, Oateys and Bitterang Works comprising variously a Regulator, Stop Bank and Access Tracks.
Temporary works, as required for the construction of the works including:
- Set down areas at Messengers, Cantala, and Oateys;
- Site office accommodation/facilities for both the Contractor and G-MW
- Borrow areas (for soil deposition) at some or all of Orchard Partners, Kulkyne and Bitterang;
- Temporary Concrete Batch Plant site;
- Access track maintenance and passing bays for construction vehicles
The remote area, harsh climate and controls needed to mitigate damage to environment and cultural heritage values required a comprehensively planned construction methodology coordinated with multiple stakeholders. Scheduled delivery duration was just over 10-months (18 October 2012) from contract award (1 December 2011) but the highest recorded river level increases in 40-years threatened this already tight delivery time-frame. The effective use of river level modeling and prompt decision making by the Comdain Project Team around mobilisation and protection works for the site ensured the project reached practical completion ahead of time and on-budget.
A collaborative approach to every possible element of this project and its works has been a key reason for its outstanding success:
According to Comdain Infrastructure Managing Director Peter Coen, “Comdain has been very proud and grateful to work with stakeholders ranging from Goulburn Murray Water and Murray Darling Basin Authority through to indigenous land owner representatives, environmental groups, government agencies and the broad range of users of the lakes area.”
Tony Morse GM Assets MDBA commended Comdain Infrastructure writing “I would like to thank Comdain on their professionalism on managing the Hattah Lakes Environmental Flows project to meet project schedule, come in under budget, respecting indigenous people and their cultural heritage, respecting the environment and building strong relationships.”
Andrew Reynolds Project Director GMW expressed their gratitude writing, “constructing these large scale infrastructure works in the environmentally sensitive Hattah Kulkyne National Park presented unique sets of risks and challenges that Comdain’s diligent and systematic approach to managing them contributed significantly to the successful deliver of this project.”