- Mine Site Rehabilitation
- River Diversions
- Water Balance Modelling
- Erosion Management
- Environmental Impact Statements
- Surface Water Management
- Integrated Waterway Management and Monitoring
- Flood Assessment
- Sediment Transport Assessment
- Water Quality Monitoring and Modelling
- Coastal Assessment
Condensate Spill Fate and Transport (PNG)
In the Southern Highlands of Papua New Guinea, a natural gas (condensate) pipeline links the Hides Gas Condensate Plant and the Central Processing Facility. It was anticipated the pipeline would traverse four major rivers and six lesser watercourses and numerous minor watercourse crossings. The length of the pipeline is approximately 109 km and includes steep terrain, regions of high rainfall and flooding, and sensitive cultural areas and ecological habitats.
As part of the mitigation planning, and in the event of a release of condensate to surface waters along the pipeline, an understand of the impacts and transport through the local environment was required. Water Technology was engaged to undertake condensate fate and transport modelling for the Papua New Guinea Liquefied Natural Gas (PNG LNG) pipeline project at Lake Kutubu, and the waterways along the pipeline route. The modelling assessed dilution and volatile losses, the spill effect and surface water drainage pathway flow duration, with the results were used to provide information for the development of site specific spill response plans.
The modelling considered condensate loss to the atmosphere, residence within the water column and the formation, and maximum size, of the condensate plume at the water surface. To do this, the condensate was modelled separately in the near-field and far-field. The reason for modelling these zones separately was to enable an understanding of the dynamics of a spill plume both close to the spill location and as it is transported further downstream. The focus of the near-field modelling was on the geometry and dilution characteristics of the initial spill mixing zone, while the emphasis of the far-field modelling was to track the spill plume as it is transported away from the spill site by the flow.
The modelling involved detailed assessment of near-field plume mixing using the package CORMIX, coupled with extensive 1D models (MIKE 11) of the river network in the Southern Highlands. The lake was modelled in 2D (MIKE 21) in order to describe the lake hydrodynamics and mixing in more detail. Based on the outcomes of the modelling a toxicology assessment was undertaken to describe the potential ecological effects and potential impacts of any condensate spill.
Key Services Provided
- Hydrological Assessment
- Near-field and far- field spill and transport modelling
- 1-D and 2-D Hydrodynamic modelling
Fortescue Metals Group – Flood Modelling Support
Fortescue Metal Group own and operate four iron ore mines in the Pilbara, Western Australia. The region has an arid subtropical climate with highly variable rainfall that is seasonally impacted by monsoonal activity and tropical cyclones (Bureau of Meteorology; WA Govt). Understanding, and mitigating against, the impacts of flooding in this region is critical for Fortescue’s operations and infrastructure.
Water Technology completed flood modelling support for Fortescue’s mining operations in the Pilbara, Western Australia. The project involved Water Technology staff working within Fortescue’s Perth offices in a secondment style arrangement. Fortescue’s mining operations include large open pits and raised haul roads that are significantly impacted by the creeks flowing from the Chichester Ranges into the Fortescue Marsh. Tasks included developing detailed flood models to quantify and mitigate the impacts of flooding on infrastructure and to minimise changes to the overall hydrological regime.
The flood modelling support included large scale TUFLOW rain-on-grid hydraulic models along with smaller, more detailed models for the design of culvert and floodway structures. Water Technology staff were able to improve Fortescue’s flood modelling techniques and processes to increase the efficiency and reliability of future flood impact assessments. The scope of work also including reviewing and applying Pilbara hydrology techniques developed specifically for the region.
Key Services Provided:
- Catchment Hydrology – Review, modelling and analysis
- Rain-on-grid Hydraulic Modelling with TUFLOW
- Flood impact assessment
- Flood Risk Mapping
- Waterway and Flood Infrastructure Modelling and Assessment
Water Technology was commissioned by Groote Eylandt Mining Company (GEMCO) to undertake a river sedimentation analysis for the Angurugu River, Groote Eylandt.
Groote Eylandt is situated on the western side of the Gulf of Carpentaria, approximately 50 km from mainland Australia. The Angurugu River flows between the main GEMCO mining leases, and is fed by a total catchment area of approximately 117 km2. The river discharges into Milner Bay and the tidal influence is known to extend as far up stream as the Haul Road Bridge.
Concerns have been raised that increased sedimentation in the river is occurring as a result of changes associated with the Haul Road Bridge and/or mine operations. In order to understand the sedimentation processes in the river, this assessment focussed on analysing the river planform, flow characteristics and sediment transport potential prior and post construction of the Haul Road Bridge.
Work undertaken included a geomorphic assessment, combined with hydrologic and hydraulic modelling along with sediment transport modelling through the river system.
Key Services Provided:
– Geomorphic Assessment
– Hydrologic and hydraulic modelling,
– Sediment transport modelling
Water Technology prepared an integrated stormwater management assessment, including conceptual and detailed design of the stormwater management system for the Wodgina Mine Site (Global Advanced Metals and Atlas Iron) south of Port Hedland, WA.
The work undertaken included on-site assessment of flooding and stormwater constraints, flood modelling and identification of the impacts of flooding on proposed and existing mine developments. This information was then used to develop a site wide water management plan with design options including culvert locations and sizing, sediment pond location and sizing, surface grading and stormwater transfer channel location and sizing.
As part of the development application for the Mummaloo Mine site, Top Iron commissioned Water Technology to undertake a hydrological assessment of the site and adjacent catchment.
This involved a site assessment to determine key surface water features, followed by detailed hydrologic and hydraulic modelling to determine surface-water flow paths and potential impacts of the mine development on the unique ecosystem of the areas.
Following the development application, Water Technology developed, and is, undertaking on-going monitoring of surface water quality across the tenement with the data to be continued during active mining of the site.
The Mt Morgan mine, located some 30 km south-west of Rockhampton, is arguably the world’s richest current or historical gold mine. The site has been subject to both underground and surface mining operations since the late 1800’s. Poor quality surface and subsurface runoff from disturbed areas, and seepage from storages, has resulted in substantial environmental damage to the nearby Dee River. Mt Morgan has the dubious distinction of being classified as the largest and worst abandoned mine pollution problem in Queensland.
Water Technology staff undertook a study which quantified the existing hydrologic behaviour of the Mt Morgan mine site. Three numerical models were developed and calibrated against recorded data; a rainfall-runoff model, a groundwater model and a behavioural (storage) model. Once calibrated, a number of model runs were undertaken using 100 years of historical daily rainfall; this considered the impact of different sequences of wet and dry years. The results of these runs were used to develop statistics of mine water balance behaviour for use in site management and rehabilitation planning.
The water balance model was used to evaluate the effectiveness of a range of mine site management and rehabilitation options, inform the rehabilitation plan and assess the impact of a proposed reprocessing operation on the mine site water balance.
The Mt Todd mine site is located within the Edith River catchment and is currently a significant source of Acid and Metalliferous Drainage (AMD). Downstream from the mine the Edith River flows into the Fergusson River, which ultimately flows into the Daly River system. During the wet season (December to April), runoff from the Mount Todd site drains either directly to the Edith River or indirectly through Horseshoe and Batman Creeks, that flow into Stow Creek and then into the Edith at the south east of the site.
For the remainder of the year, runoff does not occur from the site. At the time that mining operations ceased in July 2000, there had not been any significant remediation works undertaken. This left the site with a legacy of large volumes of mining wastes with the potential to generate AMD. Over the past few years, Batman Pit (RP3) has been used to store contaminated water primarily from RP1 and the Heap Leach Pad. This pumping combined with the Batman pit’s own catchment means that it is a net accumulator of water. A recent review of pit water levels, rainfall data and pumping records indicated that the storage capacity of Batman Pit is likely to be exhausted in the 2012-13 wet season.
The Department of Resources (DoR) requested that Water Technology Pty Ltd develop a water balance model of the mine to assist with mine site planning. In particular, the water balance model was to be used to determine the probability of uncontrolled releases from the pit and all mine site retention ponds during the 2012-13 wet season and to investigate the efficacy of various management options. This report describes the development of the water balance model.
The former Rum Jungle mine site is located 105km by road south of Darwin, near Bachelor in the Northern Territory. Uranium, copper, nickel and lead were mined and processed at various times between 1934 and 1971. The mining operations led to significant environmental impact within and downstream of the site, primarily from the long-term generation of acid and metalliferous drainage (AMD).
In 1982, an $18.6 million financial assistance agreement was established between the Commonwealth and Northern Territory Governments for the Territory to rehabilitate the site. Rehabilitation was followed by environmental monitoring programs, which spanned 12 years. At the time, the Rehabilitation Project’s objectives were considered to have been achieved. However, recent studies have documented the gradual deterioration of those original works.
In 2003, the former Department of Infrastructure, Planning and Environment and the former Department of Industry, Tourism and Resources entered into a Memorandum of Understanding to better define the current state of the environment at the site. On 7 October 2009, the Northern Territory and Commonwealth Governments entered into a National Partnership Agreement (NPA) on the management of the former Rum Jungle mine site. The Department of Mines and Energy (DME) is responsible for the overall management and coordination of projects to achieve the objectives and outcomes of the NPA which include site maintenance activities, environmental monitoring programs and investigative studies to develop an updated site management and rehabilitation strategy for the site by mid-2013.
The DME commissioned Water Technology Pty Ltd to assist with surface water investigations for the Rum Jungle mine site rehabilitation project. In particular, this included:
- -Development of a rainfall-runoff model of the East Finniss River catchment to assist with calculation of pollutant loads and dilution rates for pollutants leaving the site and entering the river.
- Delineation of mine site surface water catchments.
- Estimation of rainfall infiltration rates into the waste rock dumps and Dyson’s Backfilled Open Cut.
- Flood study to assist the rehabilitation program.
- Geomorphic stability assessment.
Water Technology (WT) were commissioned by BHP Mitsui Coal Pty Ltd (BMC) to develop a diversion strategy at the South Walker Creek (SWC) mine to secure mining access to the Mulgrave coal resource area associated with the Kemmis Pit. The Kemmis Pit area represents one of the northern operation areas at the SWC mine and the Mulgrave coal resource is understood to be a high value coal reserve. The Mulgrave coal reserve is transected by Carborough and Walker Creeks. Carborough and Walker Creeks are major tributary systems of the larger Bee Creek catchment, which ultimately flows to the Fitzroy River via the Isaac and Mackenzie Rivers to discharge to the Coral Sea in Rockhampton. The project scope has included the identification of the preferred creek diversion options; Surface water assessments involving hydrological and hydraulic analysis; and fluvial geomorphologic assessments of the waterway systems.
In total, some twenty diversion channel alignment options were identified as part of the study. The alignment options considered a range of scenarios involving channel length, channel grade, diversion take-off and re-connection locations, etc. The diversion options also included short term versus long-term diversion strategies, with the short-term options generally representing the shorter length diversion options. The alignments reflect the nature of the key controls at the site and specifically the local topographical conditions whereby the options have been structured to minimise excavation quantities. The initial diversion options were considered by BMC’s Project Steering Committee and a process of shortlisting of the options was undertaken. Conceptual diversion channel arrangements including channel form and shape and earthwork quantities for five shortlisted options were prepared for consideration by BMC. Two preferred diversion options were ultimately chosen to proceed with more rigorous assessments.
Expert staff from Water Technology’s Brisbane office joined the McArthur River Mine Independent Monitor team, under the management of ERIAS Group. The Independent Monitor (IM) team includes experts in the fields of groundwater, geochemistry, hydrology, hydraulics, ecology, geotechnics, geomorphology, water quality, soil and sediment quality, and mine closure. In addition to ERIAS Group, the team consists of six consultancies from across Australia:
- Water Technology
- Pell Sullivan Meynick
- Groundwater Resource Management
- Environmental Geochemistry International
- Low Ecological Services
- Integrated Design Solutions
The IM was first established in 2007 with the aim to assess the environmental performance of the McArthur River Mine and the Department of Mines and Energy. The IM was renewed this year under the management of ERIAS Group. The assessment is based on the review of:
- Environmental assessments and monitoring activities undertaken by the mine operator (MRM Pty Ltd).
- Environmental assessments and audits undertaken by the mine regulator, the Department of Mines and Energy (DME).
This is a five-year project for the new team, beginning in 2014 with a site visit to familiarise the team with the Mine, DME and associated staff. The Independent Monitor Audit Report for 2014 (2013-2014 operational period) was released in October 2014 and is available for download at the MRM-Staging Website.