Mining and Sediment Impacts
Adverse environmental impacts can arise from the accelerated entry of sediments into receiving waters, and mining developments have the potential to create such problems.
When a surface mine is excavated, originally consolidated overburden material is fractured, removed and then backfilled as a heterogeneous mixture. This results in a large mass of permeable material (mining spoil) subject to weathering and erosion that may affect the quality of water intercepted by the spoil or receiving its drainage waters.
EnviroGulf Consulting can make predictions of the magnitude, frequency and duration of suspended sediment concentrations in receiving waters under different flow regimes. These data may then be used in a probabilistic assessment of aquatic biological effects.
The following analyses can be performed by EnviroGulf Consulting's subcontracted analytical and geochemical laboratories or measured in the field:
- Secchi disc.
Sediment physical properties:
- particle size grading.
- soil moisture content
Sediment chemical properties:
- multi-scan elemental analysis.
- metal sequential extractions.
- aeration/dilution extractions.
- elutriate tests.
- batch leaching tests.
- total cation analysis.
- net acid production potential (NAPP).
- acid neutralising capacity (ANC).
- nutrient status, cation exchange capacity (CEC), pH, Eh, carbonate content, sulphur content etc.
The assessment of the effects of mine-derived sediments entering receiving waters is complex. EnviroGulf Consulting uses a multidisciplinary approach comprising consultation with the client's in-house mining engineers and the use of subconsultants (hydrologists) having a proven track record in the analysis of sediment transport capacity.
EnviroGulf Consulting offers the following services to clients in association with subconsultant hydrologists:
- Catchment erosion and erosion risk assessment.
- Flow duration analysis and synthetic flow estimates.
- Sediment rating curves.
- Sediment transport capacity.
- Prediction of suspended sediment (SS) concentrations in receiving waters.
- Prediction of physical effects of sediments on aquatic organisms and populations:
- algae, seagrass and other macrophytes.
- deep-sea benthos.
- Prediction of sediment impacts on aquatic resource use:
- floodplain plants and crops.
- subsistence, artisanal and commercial fisheries.
- drinking water quality.
- Field surveys.
- Design, planning and execution of sediment sampling and monitoring programs for receiving waters.
The Principal of EnviroGulf Consulting has carried out numerous sediment impact assessment and evaluations, for example:
- Nambonga Portal Decline Project (2018 - ongoing) - Review and assessment of suspended sediment loading of rivers downstream of construction activties for an underground mining portal, waste rock dumps, laydown areas, clay borrow pits, temporary stockpiling of soils and a new or upgraded road network and assessment of impacts on water quality and aquatic life (for Coffey Pty Ltd to Wafi-Golpu Joint Venture, Papua New Guinea).
- Wafi-Golpu Project (2016 - ongoing) - Peer reviews of baseline studies of freshwater ecology, marine ecology and ecosystems services. Assessments of residual freshwater ecology impacts of onshore pipeline construction and residual marine ecological impacts of Deep Sea Tailings Placement (DSTP) on Huon Gulf submarine slope, seabed and water column habitats, flora and fauna (for Coffey to Wafi-Golpu Joint Venture).
- Waisoi Copper and Gold Project, Fiji (2016 - ongoing) - Review and gap analysis of existing baseline information. Environmental impact assessment of project construction and operations on riverine water quality and freshwater ecology (to Coffey for Newcrest (Fiji) Limited).
- Ok Tedi Mine Pit Shell Variation (PSV) Project, PNG (2014 - 2015) - Review and assessment of the Riverine Aquatic Ecology Program for mine life extension and technical and textual inputs to the proposed Ok Tedi Environmental Management Act (OKTEMA) (to Coffey Environments for PNG Department of Environment and Conservation).
- Ok Tedi Mine Life Extension Project, PNG (2013) - Review and assessment of the appropriateness, completeness and certainty of predictions for future changes to fish biomass and diversity downstream of the Ok Tedi mine under mine life extension scenarios compared to closure in 2015 (to Coffey Environments for PNG Department of Environment and Conservation).
- Frieda River Gold/Copper Project - Assessment of the aquatic environmental impacts of project construction, mining and hydro-electric dam operation on downstream aquatic habitats and biological communities (to Coffey Environments for Xstrata Frieda River Limited).
- PNG LNG Project: Assessment of the potential impacts of construction corase and fine sediments on fish, invertebrates and algae in estuarine (mangrove) and marine waters (to Coffey Natural Systems for Esso Highlands Limited).
- Bell Bay Pulp Mill Project: Assessment of the potential impacts of construction and resuspended sediments on fish, invertebrates and algae in estuarine and marine waters (to Gunns Limited).
- Koniambo Nickel Project: Assessment of the potential impacts of mine surface sediments on fish and invertebrates, and formulation of suspended solids effects threshold criteria for the protection of freshwater aquatic life (to Roche Limited Consulting Group for Falconbridge Nouevelle Caledonie).
- Basslink Project: shallow- and deep-water marine biological impacts of construction sediments from subsea cable installation and sea electrode emplacement (with NSR for Basslink Pty. Ltd.).
- Sepon Gold Project: review of riverine biological impacts of fugitive sediments in mine construction runoff waters (to NSR for Oxiana Resources Limited).
- Ramu Nickel Project Environmental Plan: riverine, shallow- and deep-water marine biological impacts of sediments in mine runoff waters and from Deep-sea Tailings Placement (DSTP) (to NSR for Highlands Pacific Limited).
- Misima Gold Mine: marine biological impact of sediment-laden mine runoff waters from the open-pit (with NSR for Placer Pacific).
- Lihir Gold Project: marine biological impact of mine-imposed sediments (with NSR for Kennecott-Niugini Joint Venture).
- Wapolu Gold Project: impact of exploration sediment-laden runoff on mangrove swamp (with NSR for City Resources).
- Ok Tedi Gold and Copper Mine: impact assessment of mining sediments on coastal mangroves and coral reefs at Fly River mouth (to OTML).
- Ok Tedi Gold Mine: monitoring and impact assessment of mine-derived sediments on Fly Riverecosystem (to OTML).
- Porgera Gold Project: sediment impact predictions on Strickland River system (with NSR for PorgeraJoint Venture).
- Hidden Valley Gold Project: sediment impact predictions on Watut and Bulolo river systems (with NSR for CRA).
- Wafi Gold Project: sediment impact predictions on Wafi Creek and Bulolo River system(with NSR for Elders Mining).
- See Principal's CV for others.
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