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Abstract motion golden colors background, shining lights, sparks and fireworks like particles, seamless loop able. Shutterstock Footage offers a growing library of royalty free stock footage, stock clips, and stock video for use in film, television, commercials, interactive web sites, and other multimedia productions. The generation, release, mobility, and attenuation of acid rock drainage (ARD) is a complex process governed by a combination of physical, chemical, and biological factors (see Chapter 2).
In this chapter, the term “ARD” refers to drainage types that are affected by the products of sulphide oxidation, including acid, neutral and saline drainage. What are the significant pathways that transport contaminants to the receiving environment and can those contaminants be attenuated along those pathways? Figure 4-1 shows how the information presented in this chapter is integrated with other chapters of the GARD Guide in the development and execution of a site characterization program to address these questions. To address these key questions, expertise from numerous disciplines is required, including geology, mineralogy, hydrology, hydrogeology, geochemistry, biology, meteorology, and engineering (Figure 4-2). Because the geologic and mineralogic characteristics of mineral deposits exert important and predictable controls on the environmental signature of mineralized areas both before mining and during mining (Plumlee, 1999), a preliminary assessment of the potential for ARD is typically made based on review of geologic data collected during exploration.
The initial assessment of ARD potential is refined during mine development and operation as detailed characterization data of the waste and ore materials are obtained. Table 4-1 describes the phases of mine development from exploration through to post-closure.
Table 4-2 and Table 4-3 present the chronology of a characterization program and identify the data collection activities typically executed during each mine phase. The primary objective of exploration is to locate a potentially economic ore body or energy resource.
Exploration data collected to determine the economic value of a mineral deposit also provide information useful in the assessment of environmental impacts from mining. Plumlee’s (1999) summary of how the geologic characteristics of a mine deposit affect its environmental signature is reproduced as Table 4-4.
Samples collected during the exploration phase (core, rejects and pulps) should be cataloged and saved for potential future use. To decide whether a project will progress, the economic viability is assessed during the mine planning phase.
During this phase, the intensity of site and source material characterization is usually high.
Environmental characterization programs need to be integrated with activities of other mine departments to optimize both data collection efforts and the design of the mine facilities. Characterization during the mine planning phase must be sufficient to allow estimation of any significant long-term costs of ARD management for inclusion in the economic evaluation of the project.
Initial design considerations for mine closure should begin as soon as possible during the mine planning phase. Detailed design typically occurs coincidently with and subsequent to the ESIA review by regulators, communities and other stakeholders, and the securing of mine permits. The characterization programs initiated during the mine planning phase are usually continued during this construction and commissioning phase. During the operational phase, source and watershed characterization data collected during operations are reviewed on an ongoing basis and compared to expected conditions and compliance requirements. The decommissioning phase involves activities aimed to reestablish premining conditions (to the extent possible) or conditions suitable for beneficial post-mining land use. Water table rebound and surface water inflow during the decommissioning phase present an opportunity to assess actual pit lake or flooded underground mine water quality. With the advance of mine waste management techniques, the post-closure phase is usually characterized by the absence of a continuous presence of personnel on the mine site, though some operations might require ongoing water management and treatment. The disturbances and wastes resulting from mining and processing are the primary sources of ARD. The selection of mining and mineral processing methods defines which sources of ARD are present (Figure 4-2). This section describes how the geometry, physical properties, and structure of common mine and process facilities influence or control the production and pathways of ARD.
Mining of relatively shallow deposits or very large low-grade deposits often employs surface open-pit mining techniques.
Figure 4-3 schematically illustrates the primary water pathways and geochemical reactions that occur within an open-pit mine during operations. The quality of pit wall runoff and groundwater inflow to the pit is a function of the composition and reactivity of the rocks these waters encounter and the contact time. Sulphides exposed to atmospheric oxygen on the pit walls or blast fractures oxidize, causing generation of acid that may result in ARD.
At the cessation of mining, a pit lake will form if total water inflow to the pit is greater than water outflow, including evaporation (Figure 4-3).
Open-pit mines in arid regions with limited surface water resources, low groundwater discharge rates, and high evaporation rates may take tens to hundreds of years to achieve a steady-state lake level, extending lake filling conditions well into the post-closure phase. Pit lake water quality can present a long-term environmental concern, especially considering the volume of water that some pit lakes contain. Because pit lakes may potentially represent a long-term source of ARD that persists after mine closure, prediction of the quality and environmental impacts of these lakes is a key part of the ARD management plan.
Additional references on pit lake characteristics, predictive modeling, remediation and post-closure utilization include Geller and Salomons (1998), Castendyk and Eary (2009), and Bowell (2003). Underground mining typically involves blasting, stoping, mucking (excavating), hauling, and where a shaft is used, skipping (vertical haulage) of waste and ore to surface. Similar to open-pit mining, dewatering activities are typically required to remove groundwater from the underground workings, commonly through use of dewatering wells and sump pumps. Mining exposes sulphides present on mine walls or blast fractures to atmospheric oxygen that enters the underground workings through shafts and other openings that intersect the land surface.
Figure 4-4 shows the water pathways and geochemical reactions associated with underground mines.
At the cessation of mining, dewatering ceases and groundwater inflow into the underground workings may begin to accumulate and flood the workings. As the water table rebounds, the underground workings may transition from a groundwater sink to a groundwater source.
Smith and Beckie (2003) provide a comprehensive summary of the hydrologic and geochemical processes occurring in a waste rock pile constructed by the traditional end-tipping from lift heights greater than about 10 m. Many of these facilities, especially large-volume ones, are a legacy of the mining industry due to problems associated with vegetation failure and poor water quality, and require significant effort and cost to mitigate.
The basis for design should be to construct waste piles to control the generation and leaching of sulphide oxidation products through segregation and controlled placement within a waste rock storage facility. Precipitation falling on a waste rock pile will evaporate, flow over the surface of the pile as runoff, or infiltrate into the pile.
To prevent infiltration of waste rock seepage into the underlying groundwater system, waste rock piles may be sited in areas where surficial soils have low permeability. Ore stockpiles are essentially temporary storage facilities that are established to provide feed to a processing plant or for direct transfer to markets, such as iron ore and some coal. High grade or run of mine (ROM) ore may only be stockpiled for a short period and ARD management generally relies on early processing before ARD conditions develop and, in some cases of high reactivity, the capture and treatment of drainage. Lower grade stockpiles, that may or may not be processed, require careful consideration to ensure allowance is made for closure. Tailings are discharged to surface storage facilities by several methods, including subaerial slurry, subaqueous slurry, paste and dry deposition.
The tailings grain size, disposal method, and deposition history govern the hydrogeological characteristics of a TSF (Blowes et al., 2003). Discharges associated with tailings facilities include runoff and seepage for all disposal methods. Coal processing typically includes crushing, grinding, and sizing followed by physical separation of pyrite and shale (waste materials) by gravity or floatation. Figure 4-6 shows the flow paths and geochemical reactions occurring in a subaqueous TSF as well as the three methods typically employed for dam construction. Improper handling of both the leach solutions and the pregnant solution can result in the release of acidic or alkaline process solutions to the environment. When leaching is concluded, the drain down water or rinse water must also be handled properly. Sulphide minerals remaining in the pile after conclusion of leaching can also contribute to acid formation, depending on the residual sulphide mineral content and climatic conditions. Solution mining makes use of a series of injection and recovery wells to circulate a leach solution through an ore zone. A conceptual site model (CSM) describes what is known about the release, transport, and fate of contaminants at a mine site. The CSM describes the sources of potential contaminants, the mechanisms of their release, the pathways for transport, and the potential for human and ecological exposure to these parameters. Atmospheric oxygen is essential for oxidation of sulphides and to begin the ARD evolution process. A conceptual site model can be developed at any stage of a mine’s life; however, development typically begins in the early phases of a project and is continually validated, revised and updated, as necessary, over the life of the mine as site characterization data and operational monitoring data are collected. Where regulatory approval for new mine development is required, early involvement by these agencies and other stakeholders, including the local communities, in the development and validation of the model is key, and should be encouraged. This section presents a summary of the components and methods commonly used to characterize ARD sources, pathways, and receptors. An approach for characterization, classification and prediction adopted by Earth Systems is documented in the Characterization Case Study.
A geo-environmental model of a mine deposit is defined as “a compilation of geologic, geophysical, hydrologic, and engineering information pertaining to the environmental behavior of geologically similar mineral deposits prior to mining, and resulting from mining and mineral processing” (Seal et al., 2002). Geo-environmental models provide a starting basis for the level of characterization that will be required at a mine site. The primary purpose of geochemical characterization of mine materials is to guide management decisions.
Geochemical characterization aims to identify the distribution and variability of key geochemical parameters (such as sulphur content, acid neutralizing capacity and elemental composition) and acid generating and element leaching characteristics. Reference to other mining operations in the region, particularly those situated in the same stratigraphic or geological units may provide empirical information on the likely geochemical nature of similar ore types and host and country rocks. This section outlines sample selection and number of samples required for a geochemical characterization program, and provides an overview of the testing programs and classification procedures. Sample selection is a critical task and must be given careful consideration at all stages of a project. Although drilling and sampling will focus on ore zones in the exploration and pre-feasibility stages, samples of host and country rock should be increasingly represented as the project develops, so that adequate data are available to produce block models and production schedules by geochemical waste types, where required.
The available sources of material for testing are typically related to the phase of mine development.
The project geologist is a valuable resource and should be consulted in the selection of representative samples for testing. As mentioned previously, any material with the potential to generate ARD or release contaminants should be characterized. Spatial Representation (x, y, z) – Sample selection should ensure good spatial representation (vertical and horizontal) of the area to be mined. Focused (Biased) versus Random Sampling – Use of focused or random sampling depends on the objective of the characterization program.
Standard operating procedures (SOPs) for geological logging and the collection and documentation of sample selection should be developed and followed. The mine geologic model and the block model may be used in the selection of representative samples. Initial estimates of sample numbers are typically based on professional judgment and experience. Table 4-5: Australian Guidance on Sample Numbers (adapted from Australian Government Department of Industry, Tourism and Resources, 2007).
By the end of the resource definition phase, there should be adequate information to accurately characterize the ARD potential of the ore body (high and low grade), although further test work will normally be required to characterize the ARD potential of waste rock and ore and hence tailings.
Static testing of several hundred representative samples of high and low grade ore, waste rock and tailings, the number dependent on the complexity of the deposit geology and its host rocks.
All drillhole samples analyzed must include sulphur analysis and identified representative metal ions. Surface water and groundwater analysis to include acidity as well as pH, EC and representative metal ions, including Al, Fe, Mn.
Where required, additional static testing as required for block waste resource model refinement – increase density of NAPP (or NPR) characterization. Statistical analysis of test results is advisable to confirm that a representative data set has been obtained. Laboratory and field testing is conducted to characterize the acid generation and metal leaching potential of mine materials. Static testing is the first phase of geochemical characterization, and is a precursor to kinetic testing.
Elemental analysis results are commonly compared to average crustal or mean world soil abundance values as a multiple or geochemical enrichment factor to provide a screening level assessment of elements that are enriched in the sample. An essential component of static testing is mineralogical analysis that, at a minimum, includes identification of all sulphur and carbonate minerals. ABA analysis typically includes analysis of paste pH, sulphur speciation, neutralizing potential (NP) or acid neutralizing capacity (ANC) and total inorganic carbon (TIC). Short-term extraction tests (such as 24-hour batch extraction tests using deionised water) provide information on the short term metal leaching potential. Although the results of static testing may indicate a potential for acid rock drainage or metal leaching, kinetic testing is commonly required to assess the relative rates of the various ARD and metal leaching reactions occurring, and to provide information on the evolution of ARD over time. Figure 4-8 shows the typical components and evolution of a geochemical characterization program for selected potential source materials. Because water is the primary pathway for transport of ARD, the quantity, quality, and movement within the mine’s watershed must be characterized. Although groundwater watershed divides are typically initially assumed to coincide with surface water divides, groundwater regimes and their boundaries can be complex. Characterization of the climatic conditions at a site typically begins with identification and review of available regional data.
Site precipitation data are typically compared to regional data collected concurrently to assess the representativeness of the regional data set. Stream flow measurements are required to characterize the amount and rate of flow to evaluate constituent fate and transport and to characterize aquatic habitat. Water quality sampling is conducted to characterize baseline water quality conditions (see Chapter 8). Albury has an urban population of 53,507 people.[1] It is separated from its twin city in Victoria, Wodonga by the Murray River. Albury is situated above the river flats of the Murray River, in the foothills of the Great Dividing Range.
Central Albury comprises the central business district (CBD) and lies between the railway line, the Murray River and Monument Hill. Forrest Hill lies directly north west and covers the saddle between Monument Hill and Nail Can Hill, whilst west over the ridge lies West Albury. South Albury is a mix of residential and industrial areas, with the floodplains south of the railway line and freeway still used for farming and grazing. North Albury was once covered by orchards and vineyards in the first half of the 20th century, as was a swamp where the James Fallon High School now stands, but after the second world war housing development in the area increased and Waugh Road was extended from David Street to the "Five Ways" intersection at Union Road, which ascribes the border between North Albury and Lavington. Lavington is the largest suburb of Albury, and the only suburb which has its own postcode (2641, as opposed to 2640 for the balance of Albury).
Thurgoona, to the east of Lavington, was established as a new residential suburb by the Albury Wodonga Development Corporation in the 1970s. The lake was created for irrigation purposes and has caused significant changes to the flow patterns and ecology of the Murray River. There are few remainders of the indigenous population of the area, although the Wiradjuri people occupied the area for many thousands of years before. The explorers Hume and Hovell arrived at what is now known as the Murray River at Albury on 16 November 1824 what their maps named 'Crossing Point'. Among the first squatters to follow in the steps of the explorers and settle in the district were William Wyse and Charles Ebden.


The first European buildings erected at the crossing place were a provisions store and small huts. By 1847, the Albury settlement included two public houses and a handful of huts, a police barracks and blacksmiths. In 1851, with the separation of Victoria from New South Wales and the border falling on the Murray River, Albury found itself a frontier town. Albury was at this time starting to grow substantially with German speaking immigrants using the area to grow grapes for wine. Albury's proximity to Wodonga has spurred several efforts to achieve some kind of municipal governmental union (see Albury-Wodonga). In 1888, the Smollett Street wrought iron arch bridge was constructed over Bungambrawatha Creek. The break of railway gauge at Albury was a major impediment to Australia's war effort and infrastructure during both World Wars, as every soldier, every item of equipment, and all supplies had to be off-loaded from the broad gauge and reloaded onto a standard gauge railway wagon on the opposite side of the platform. Fundamentally, the geologic and mineralogic characteristics of the ore body and host rock (or the coal seam and overburden) define the type of drainage generated as a result of mining. During the early stages of mine development, site-specific information may be limited and therefore a high level of uncertainty is present in site characterization. The bulk of the characterization effort occurs before mining during the mine planning, assessment, and design phase (referred to as the development phase throughout this chapter).
The techniques employed in mineral exploration include literature review, geologic mapping, geochemical sampling (rock, soil, and water sampling), geophysical testing, remote sensing surveys (surface, subsurface, airborne, and satellite), aerial photography, and drilling (SME, 2008). Determination of parameters such as sulphur and carbon during exploration, therefore, provides significant value at later stages of the project cycle by augmenting the ABA database from the geochemical characterization program. For example, the presence of acid generating and acid neutralizing minerals associated with the ore and host rock can be determined from mineralogical data.
This phase includes completion of a number of trade-off, design and prefeasibility studies, including the environmental and social impact assessment (ESIA) and the feasibility study (FS).
Laboratory testing programs aim to systematically evaluate the environmental stability of waste and ore materials, including the occurrence and nature of sulphide minerals and minerals with neutralization potential and their respective quantities.
It may not be possible to profitably mine some marginally economic ore bodies or coal deposits that have high ARD management and closure costs.
Integrated with the mine plan, the block model is used to estimate the quantity and production schedule of the identified geochemical waste types.
Modifications to the ARD management plan may be made as a result of this consultation to reflect stakeholder input and permit conditions. The quality of water removed in association with dewatering activities should be characterized, even if recycled, to understand the effects on site water quality, and if discharged, the need for treatment.
Additional data collection and evaluation, including modeling, may be required to refine long-term water quality predictions and assess the need for mitigation measures, including water treatment.
During the post-closure phase, land use is commensurate with requirements of permits and expectations from adjacent land users and regulatory agencies. This typically involves blasting, excavating, loading, hauling of waste rock and ore, with the construction of permanent waste rock storage facilities and temporary (low-grade) ore stockpiles.
Diversion of surface water or dewatering activities to lower the groundwater table may be required to access the ore body. When necessary, dewatering wells are sited around the perimeter of the pit to lower the groundwater table to beneath low stability rock units and mine working areas. Therefore, if the pit is to be filled and reclaimed after mining is completed, and if mining is proceeding laterally as for a surface coal mine, the backfilling process should be coordinated with excavation to minimize the amount of time that the mineral sulphides are exposed. The groundwater table may rebound to near the premining level and, if the pit has not been backfilled, produce a pit lake that can act as a source to groundwater. For example, the Island Copper Pit in British Columbia, Canada was flooded with sea water in less than half a year and a similar approach is planned for the Lihir Gold Mine in Papua New Guinea.
Alternatively, open-pit mines in such conditions may not contain water at all if the natural groundwater table is below the pit bottom or the evaporation exceeds inflows.
Acidic conditions may develop within a pit lake because of the oxidation of sulphides in wall rock, flushing of reactive waste materials backfilled in the pit, the addition of ARD in runoff or groundwater, and the precipitation of iron hydroxide minerals within lake water. If impacts are predicted, mitigative options should be considered, including accelerated flooding, raising the flooded water level, and batch treatment such as nutrient addition to facilitate bioremediation. In some cases, a drainage tunnel can be constructed below the mining level that permits gravity drainage of groundwater to land surface. The underground workings, as well as the ore and waste piles generated by mining, are a potential source of ARD. Dewatering activities during operations alter groundwater flow paths near the underground workings. The loading process and truck vibrations during hauling result in segregation of the rock into layers of similar grain size, a process called sorting. Siting such facilities is best accomplished by an assessment of the entire development site to map the levels of permeability for the purposes of determining the optimum location of all facilities. The sulphide content of the tailings and the availability of oxygen will govern the reactivity of sulphidic tailings.
Underground disposal may simply fill void spaces or may be designed to provide structural support for ongoing mining. Runoff and seepage quality are a function of tailings composition, reactivity, and contact time. The waste material (locally known as coal refuse, gob, slurry, etc.) from coal beneficiation (also known as coal cleaning, washing, or preparation) generally has a higher acid generation potential than the coal itself because sulphide minerals contained in the coal and waste rock are concentrated in the waste during the coal cleaning process.
In both leaching processes, cobble-sized or finer grains of ore materials are placed onto lined pads, either directly from the mine or after size reduction. Leakage through the lined or unlined base of the leach pad could impact groundwater quality, while seepage flowing from the toe of the facilities and direct runoff may impact surface water. Acidic leaching solutions and drainage may precipitate very fine-grained acid-generating secondary minerals such as jarosite and melanterite, onto grain surfaces particularly under dry conditions. If an alkaline cyanide solution is used for ore leaching, some cyanide compounds may remain sorbed to grain surfaces or dissolved in pore waters after leaching concludes.
The most important potential sources of ARD at mine sites are the mine pit (walls, benches and floor), exposures in underground workings, waste rock, ore (including any low grade stockpiles) and process residues (tailings and rejects). Indirect exposure may occur along the food chain (for example exposure of bioavailable metals to animals that graze on vegetation in contact with contaminated soils). The ability of the model to accurately describe the release, transport, and fate of ARD is a function of the amount of available characterization data, which generally is proportional to the mine phase. A comprehensive listing of the tools used in environmental assessments of mining projects, including references and a description of their use, is presented in Plumlee and Logsdon (1999). The key elements of the model include deposit type, deposit size, host rock, wall-rock alteration, mining and ore processing method, deposit trace element geochemistry, primary and secondary mineralogy, topography and physiography, hydrology, and climatic effects. Drill core is the most common material source for geochemical testing during the early stages of mine development. Determination of the appropriate disposal methods for wastes generated during exploration necessitates initiation of testing early in the mine life.
Construction materials for roads and site infrastructure are often quarried from the area around a mining development.
The exploration geologist should be consulted regarding the initial definition of mine units and material types. In practice, sample locations may be restricted to a one-dimensional line defined by a borehole or mine tunnel, or a two-dimensional plane, such as the wall of an open pit or cross section through the deposit. Personnel tasked with sample selection must be familiar with the geological characteristics of the deposit, including rock types, fracture patterns, weathering, alteration, and mineralization. For example, sample selection may target areas with visual sulphides to provide an indication of worst-case drainage quality. Preference regarding the use of weathered or fresh materials for testing must be determined.
The number of samples required commonly increases during each of the early phases of mine development as the knowledge base and project needs develop.
Table 4-5 provides an example of Australian guidelines for the number of samples during the early phases of the mine life. Surface water and groundwater analysis to include acidity as well representative metal ions.
Sampling density is dependent on complexity of ore deposit and host rock geology interval of representative drill holes but should be restricted to single rock units or lithologies - include minimums. For example, histograms may be used to ensure that the entire distribution has been captured in sample selection (Runnells et al., 1997) and samples with “extreme” characteristics have not been overlooked.
Characterization programs must be designed to provide adequate information to make cost-effective, sustainable, and environmentally protective decisions regarding the management and disposal of waste materials. Geochemical characterization programs typically follow a phased approach, beginning with laboratory testing followed by field testing.
The objective of static testing is to describe the bulk chemical characteristics of a material.
A high concentration of a particular element does not necessary imply that this element will be mobilized in concentrations that may lead to environmental or health impacts, but it does highlight an issue that should be further investigated. TIC is used to calculate the carbonate neutralizing value (CNV) or carbonate NP (Ca-NP), and allows assessment of the fraction of NP or ANC attributed to carbonate mineral phases.
Any waste, construction, or process stream residues that have the potential to generate ARD must be included in the mine characterization program so that appropriate disposal practices and mitigation measures can be employed.
When mining in an area with karst, investigations should be conducted very early in the site characterization program to identify karstic limestone features within the watershed boundary. Site-specific climatic data are obtained by installing a meteorological station to record daily values of temperature, precipitation, wind speed, wind direction, and relative humidity. Surface water quality, quantity, and direction of flow within the watershed boundaries are characterized. If possible, water quality sampling should precede any land disturbances such as exploration drilling. Much commercial activity is concentrated here, with Dean Street forming the axis of the main shopping and office district. West Albury is primarily a residential area, but it is home to the First World War Memorial (locally known as the Monument), Riverwood Retirement Village, Albury Wodonga Private Hospital (which lies on the corner of Pemberton Street and the Riverina Highway), and the Albury sewerage treatment plant. The Mungabareena Reserve lies on the Murray south of the airport, and is considered an Aboriginal cultural site of some significance.
Flood mitigation works in the 1990s have dramatically reduced the risk of flooding in the residential areas of South Albury. The locality of Glenroy is adjacent to North Albury, west of the Bungambrawartha Creek, and housing development was developed in the 1970s, including a significant Housing Commission public housing estate.
The suburb was originally named Black Range in the 1850s and 1860s, before being renamed Lavington in 1910.[10] Originally within the boundaries of Hume Shire, it was absorbed into the City of Albury Local Government Area in the 1950s.
In the 1990s a new campus of the Charles Sturt University was established here, as was an office of the Murray Darling Freshwater Research Centre. The Hume Dam (colloquially termed the Weir locally) wall construction took 17 years, from 1919–1936.
Before the construction of the Hume Weir, flows in normal (non-drought) years were low in summer and autumn (though still significant overall), rising in winter due to seasonal rainfall and reaching a flood-peak in late spring due to snowmelt in the Murray and tributaries' alpine headwaters.
Little history is documented about the relationship of Aboriginal people and the European settlers. They named the river the Hume River and the next day inscribed a tree by the riverbank before continuing their journey south to Westernport in Victoria. A survey for a town was commissioned in 1838 by Assistant Surveyor Thomas Townsend who mapped out Woodonga Place (the present Wodonga Place) as the western boundary, Hume Street as the northern boundary, Kiewa Street to the east and Nurigong to the south, with Townsend Street being the only other north-south road, and Ebden and Hovell Streets being the other two east-west roads. With increase in commerce with Melbourne, the first bridge was built in 1860 to the design of surveyor William Snell Chauncy. Albury boasted by the 1870s a butter factory, flour mill, wineries and locally brewed cider and soft drinks. The city's first mayor James Fallon was an innovator of the Public School, funding a demonstration High School to be built on Kiewa Street.
In 1973, Albury-Wodonga was selected as the primary focus of the Whitlam federal government's scheme to redirect the uncontrolled growth of Australia's large coastal cities (Sydney and Melbourne in particular) by encouraging decentralisation. Smollet Street was extended westward through the botanical gardens to give direct access from the Albury Railway Station to Howlong Road by a straight street. Originally, New South Wales and Victoria had different railway gauges, which meant that all travellers in either direction had to change trains at Albury. Check out the video for “Plans & Reveries,” from Rush, and a remix of that tune by London-Paris electro group The Teenagers. Identification of potential environmental impacts during this phase and incorporation of appropriate prevention and mitigation measures is intended to minimize environmental impacts and serves as a foundation for the environmental and social impact assessment. Exploration data are compiled to characterize the ore deposit, including the deposit’s size, grade, mineralization style, and the alteration assemblages present. Intensive baseline monitoring is conducted to characterize existing environmental conditions.
Optimal siting of waste facilities should integrate information from multiple disciplines, including mining engineering, metallurgy, geochemistry, hydrogeology, hydrology, geology and geotechnical. Issues such as reduced mine footprint, ARD prevention in waste rock and tailings (and coal refuse), and the avoidance of long-term water treatment should be integrated into the mine design to ensure that the economic model for mine development fully considers the true costs of the whole lifecycle, including post-closure. Incorporation of ARD and other geochemical indicator parameters into the block model facilitates consideration of environmental risk in ore development plans, waste production scheduling, and potential segregation of waste as part of an ARD management plan.
Field-scale testing programs may also be initiated at this time, including large test plots of mine waste and pilot testing of water treatment options. Site reclamation and rehabilitation activities are often conducted during mine operations (progressive reclamation) but their breadth and intensity increases substantially during the decommissioning phase.
The requirements for post-closure monitoring vary with the post-closure objectives and the remaining facilities. The mine plan and process waste management plan describe the size and location of these facilities. Fractures generated during blasting alter the hydraulic properties of the host rock and may change groundwater flow patterns. ARD neutralization may occur due to dissolution of buffering materials, when they are present. Depending on the depth of the workings, the primary source of groundwater inflow into the mine may be from the regional groundwater system (deep mines) or the local groundwater system (shallow mines).
In some cases, these openings are plugged to prevent discharge to surface and to further raise the water level (ERMITE-Consortium, 2004).
Waste rock dumping from the crest of a steep slope further enhances sorting because large grained material travels further down slope than fine grained material.
In potentially sensitive areas, drilling, test pitting and geophysical investigation to fully understand the subsurface conditions may be required. Water covers, in the case of subaqueous disposal, act as a barrier to significant oxygen ingress into the tailings. Reagents may be added to increase strength or improve environmental stability before backfill. Facilities may be sited in areas with low permeability surface soils or an engineered liner may be constructed to prevent migration of tailings seepage.
Coal reject piles, largely consisting of fine-grained shale and pyrite, are typically located near the coal processing plant. For stability reasons, tailings dam embankments are commonly designed to be unsaturated and well drained so if they are constructed with sulphide-bearing waste rock or tailings, the tailings dam embankments may be particularly prone to ARD generation. The leaching fluid, applied to the top of the pile, infiltrates through the material, dissolving the ore bearing mineral. During rain events, these secondary minerals will readily dissolve, releasing the stored acidity and metals. At the cessation of mining, cyanide present in gold heap leach piles can be removed by rinsing or can be allowed to degrade naturally (SME, 2008). Price (1997, 2009) presents guidelines for the development of a characterization program, including laboratory testing and interpretation of test results. Geo-environmental models are empirical data compilations that are best used as guidelines for the potential range of environmental impacts at a site (Seal et al., 2002) and should not be used to predict pH or element concentrations that will develop at a site or in lieu of site characterization (Plumlee, 1999).
Because exploration drilling programs target discovery and delineation of the ore zone, the selection of samples to characterize waste material must include careful examination of the spatial coverage of the drill core relative to the anticipated extents of the pit or underground workings (Downing and Mills, 2007).


The geochemical characteristics of these materials should also be evaluated before construction. Based on the results of the geochemical characterization program, material type classifications may require further refinement.
Additional boreholes increase the distribution of sample points and improve the definition of mine units.
Similarly, focused sampling may be more effective in ensuring a sample set with a complete range of compositional characteristics than random sampling. Sample size should be large enough to provide material for all potential geochemical tests and sample for archiving purposes. In this case, a comprehensive set of samples would be needed to build the geostatistical model. Ultimately, for sites characterized as having an ARD potential, a full geostatistical model often provides the basis for control plans where material segregation is part of the mine plan. Although characterization testing is likely to occur during all phases of mine development, the peak of the laboratory testing programs often occurs during the feasibility phase. For materials with an uncertain ARD potential, resolution of this uncertainty by additional characterization efforts may not be necessary if a decision is made to manage the waste with the assumption that the material has ARD potential.
The design of most testing programs is dynamic, with each successive phase building on the results of previous phase or phases. These tests are designed to evaluate the potential of a particular rock type to generate acid, neutralize acid, or leach metals. Sulphur speciation data, which includes information on the presence of non-acid generating sulphur minerals, are used to calculate the acid generation potential of the material.
Topographic maps and site reconnaissance are used to determine the surface water boundaries, or divides, that separate the watershed containing the ore deposit from surrounding watersheds. Karst features can be major preferential flow paths which can govern local groundwater regimes and the transport pathways of any seepage from tailings and waste rock containment areas.
Information on the amount, temporal distribution, and form of precipitation (rain or snow) is used in association with temperature data to characterize the quantity and seasonal distribution of recharge to a watershed. Baseline conditions are characterized before exploration or, more commonly, during the development phase. Multiple sampling events may be required to capture baseline conditions and seasonal variation in water quality related to seasonal variation in flow. A cultural precinct is centred around QE2 Square, including the Albury Library Museum, Albury Regional Art Gallery, Albury Performing Arts Centre and Convention Centre, and the Murray Conservatorium.
A hydro-electric power plant supplies 60 megawatts (80,000 hp) of power to the state grid.
The flow is effectively reversed now, with low flows in winter and sustained, relatively high flows in late spring, summer and early autumn to meet irrigation demands, although the spring flood peak has been virtually eliminated. In 1829, explorer Captain Charles Sturt discovered the Hume River downstream at its junction with the Murrumbidgee River. Albury at this time became a customs post between the two colonies as New South Wales held a protectionist stance on gaining its constitution in 1856.
New South Wales and Victoria had different railway gauges until 1962, when the first train ran straight through from Sydney to Melbourne.
Grand plans were made to turn Albury-Wodonga into a major inland city and large areas of the surrounding farmland was compulsorily purchased by the government. Albury became the stop over, where passengers on the Melbourne-Sydney journey changed trains until 1962, when a standard gauge was opened between the two capitals. The exploration geologist maps the lateral and vertical distribution of material types across the deposit. The depth to water and quantity of water encountered during drilling are information that may be used to characterize groundwater occurrence and flow conditions. This may include establishment of surface water, groundwater, sediment, and climate monitoring stations. Routine surface water, groundwater, sediment, climate, and biological receptor monitoring programs begin during baseline data collection and continue to be implemented during the construction and commissioning phase. Typically, there is a period of at least five to ten years of performance monitoring over which there is a decreasing frequency of activity, based on achieving the predicted performance for chemical and physical stability. Because waste facility design must consider the potential for these facilities to produce environmental impacts, material characterization and facility design is an iterative process involving multiple disciplines as explained previously. Precipitation falling within the pit capture zone becomes pit wall runoff, or infiltrates into the unsaturated zone. Sulphide oxidation products, which accumulate on pit walls and fracture surfaces, are flushed by groundwater or surface runoff.
Fortunately, pit lakes with these extreme characteristics are rare on a global scale and appear to be limited to some porphyry copper deposits with high sulphur contents and minimal carbonate or other neutralizing lithologies. The shallow groundwater flow system is recharged by precipitation that falls within the underground working capture zone and infiltrates into the ground. Consequently, waste rock piles are generally composed of inter-layered beds of coarse grained material and fine grained material inclined at the angle of repose (33 to 37 degree angle). Compared to waste rock, tailings are homogenous with a more consistent distribution of acid generating and acid neutralizing minerals.
In cold climates, migration of the permafrost into the base of the facility may prevent generation and movement of ARD.
Because of the mineral composition, grain size, and high-surface area of these wastes, coal reject piles may be strongly acid generating depending upon their sulphur content (SME, 2008). Precipitation onto the surface of the facility contacts the tailings beaches (tailings exposed to atmospheric oxygen), the dam, or falls directly on the tailings pond.
The metal-bearing solution (pregnant solution) is collected from the bottom of the pile and processed to recover metals. Maintenance of the residual alkalinity (pH 10 to 11) from cyanide leaching through the addition of a cover may also provide environmental benefits. Blasting may be conducted in boreholes before injection to increase the permeability of the ore zone.
Because water is a primary pathway, aquatic resources generally are the receptor of most interest. Other sources of material for testing that are frequently available include rock chips from borehole drilling, hand samples from outcrops, samples from existing waste facilities, development rock, ore composites, and residues from metallurgical testing.
Due to the spatial extent of placement, use of construction materials with ARD potential may result in a widespread source of ARD. For instance, a classification suitable for mineral extraction may not be sufficient to identify the environmental characteristics and corresponding ore and waste management requirements of the various material types. Because mine plans change, the spatial representativeness of samples should be reassessed throughout operations. For this reason, characterization of process tailings typically requires fewer samples than characterization of waste rock. For example, detailed characterization of the sulphide content of tailings over time may not be necessary if the tailings will be placed in a contained impoundment with a water cover. A brief summary of the testing approach is provided below, with significantly more detail presented in Chapter 5. Geographic information systems (GIS) and digital elevation models (DEM) may be used for this task. Evaporation pans or empirical equations are used to estimate site evapotranspiration rates. Monitoring is conducted during the construction and operations phases, and possibly during decommissioning and post-closure phases to assess impacts.
The initial water quality survey should be spatially comprehensive, with samples collected throughout the watershed, both upstream and downstream of the ore deposit and future land disturbances. Frosts are commonplace in winter, with approximately 20 days per year featuring minimums of below freezing. In the same block are the Post Office, Police Station and Courthouse, as well St Matthew's Anglican Church which was rebuilt after being destroyed by fire in 1990. The only remnant of this is Horseshoe Lagoon to the south-west of the suburb, which has been declared a Wildlife Refuge by NSW Parks & Wildlife and incorporated into the Wonga Wetlands.
Prior to 2007, the Hume Highway – also known as Wagga Road – passed north-east through the suburb, with Urana Road passing north-west though the suburb from the "Five Ways" or "Roundabout" road junction.
The states could not initially agree which should be the transfer point so they had an expensive and attractive iron lattice bridge sent from Scotland which accommodated both gauges.
Some industries were enticed to move there, and a certain amount of population movement resulted.
The broad gauge section of track between Seymour and Albury has now been converted to standard gauge; there is no longer a break-of-gauge at Albury station. After World War II, in an attempt to overcome the difference in gauges and speed up traffic, a bogie exchange device lifted freight wagons and carriages allowing workers to refit rolling stock with different gauged wheel-sets. Ongoing monitoring refines the knowledge of the site, allowing adjustments for new technologies that may evolve during the mine life and whose incorporation will reduce closure costs and better manage associated risks. Soil, water, and sediment sampling provide information on the occurrence and mobility of trace metals in the watershed. The biological receptors within the watershed are identified and their habitats characterized. Source characterization during operations often includes collection of runoff and seepage samples from potential ARD sources. Following performance monitoring, some sites may require longer term monitoring and maintenance of, for example, physical structures such as tailings dams, water retaining structures, or covers. The solubility of the ore material determines whether heap leaching or in situ solution mining is an option (SME, 2008). When sulphides are present within the surrounding rock, dewatering and blasting activities may expose them to atmospheric oxygen, initiating oxidation and acid generation.
Infiltration flows downward to the groundwater table or horizontally toward the pit wall, where it discharges as seepage.
Abandoned coal mine pits in eastern Germany and Pennsylvania, USA, and uranium mines in central Canada have also developed acidic waters. The quality of groundwater inflow is a function of the composition and reactivity of the rock it encounters and the contact time. However, because of the heat generated during sulphide oxidation, the permanence of the permafrost below waste facilities requires evaluation. During large storm events, discharge through an overflow drain or discharge down the face of the dam may occur. Best operating practices from closed heap leach sites in Nevada have demonstrated that preserving the alkaline conditions, which were essential during the cyanide leaching operations, is best achieved by not rinsing the heaps. Solution mining has been used in uranium, copper, manganese, halite, potash, nahcolite, and sulphur mining (SME, 2008).
The potential for land disturbances associated with the construction of mine facilities to expose rock with ARD potential should also be considered.
For example, if the location of the pit wall changes, additional testing may be required to characterize pit wall runoff. In this context, “random” still implies a rationale-based program, which may be part of a phased program but lacks adequate samples to be geostatistically complete.
Groundwater watershed divides are initially assumed to coincide with surface-water divides, with refinements added based on the results of subsequent hydrogeological investigations. Typically, samples are collected above and below the confluences of each relevant tributary in the watershed, as well as above and below any historical mine features and natural exposures of ARD. In 2007, an internal bypass of the Hume Freeway was opened,[11] with the former name of the Hume Highway section officially reverting to the commonly used "Wagga Road". Both names persisted for some time, Hume falling into disuse eventually in favour of Murray. However, the current population of approximately 101,597 residents is far below the 300,000 projected by Whitlam in the 1970s. Three-dimensional digital representations of material types, called block models, are generated from borehole data to develop the economic ore estimation models (see Chapter 5).
Remote sensing data may provide information on the distribution of secondary minerals formed from weathering of mineral deposits. High-porosity blast-generated fractures within the adjacent rock zone and historical mine tunnels intersecting the open pit provide preferential pathways for groundwater flow and can create a zone of groundwater depression around the pit. Neutral to basic waters have developed in pit lakes hosted in limestone deposits, where the dissolution of calcite buffers pit lake pH. Oxidation of exposed sulphides in the underground workings (mine walls or blast fractures) results in the accumulation of sulphide oxidation products. Where it is deposited dry, it should be compacted frequently to minimize the ingress of oxygen.
However, an engineered cover may be needed to limit infiltration of precipitation and prevent natural leaching of alkalinity to a level that could allow ARD, NMD or SD processes to begin depending on the nature of the material.
Mining may also extend into areas that were not characterized during feasibility testing and such mining may encounter new materials. Ultimately, if a major ARD problem is predicted from earlier phase test work, the waste should be characterized by a geostatistical model, which includes an adequate number of samples as well as a geological interpretation.
Compositing may be useful for identification of the characteristics of a sample representing a larger core interval or rock volume, such as an open-pit mine bench depth or waste zone. For example, a change in ore type over the mine life may produce process tailings with different characteristics. The suburb of Lavington also includes the localities of Springdale Heights, Hamilton Valley and Norris Park. These soluble mineral phases are flushed during storm events and may release metals, sulphate, and acidity, depending on their characteristics. Saline waters also occur in pit lakes, particularly in extremely arid environments where the evaporative loss raises the concentration of dissolved solids.
During mining, a constant supply of oxygen is maintained through the ventilation system and mine shafts and adits that intersect the land surface. Further information is presented in Chapter 2, which contains detail on oxygen transport into and within waste rock piles. Infiltration through the tailings enters into the subsurface or is captured in a seepage collection system. From this model, one or more key indicators can then be selected for the operations to use in separating materials. However, information on the smaller-scale characteristics may be lost due to the “smearing” of geochemical properties and analytical results. Operational monitoring (see Chapter 8) should include a program of systematic ongoing tailings testing to identify changes and implement alternative waste management practices, if required. Some of the sampling sites in the initial survey will become part of a long-term monitoring program if and when a mine is developed.
As is the case for pit lakes, underground mine pools are frequently stratified (Wolkersdorfer, 2008). The seepage rate is a function of the permeability of the underlying natural or engineered materials and the infiltration rate through the tailings. This “smearing” may lead to samples with anomalous qualities not being recognized, even though it may be those materials that govern the composition of a mine or process effluent.
With this in mind, siting of sampling locations should consider the locations of future mining features. Water on the floor of the pit may infiltrate into the groundwater system, evaporate, or be actively removed by pumping from sumps. In Pennsylvania, USA, water levels in flooded underground coal mines show considerable fluctuation in composition responding to variability in meteoric conditions and local groundwater pumping. During operations, ARD is not normally a concern (except with extremely reactive tailings) because most mill circuits add lime to the tailings. In general, it is recommended to collect discrete samples with clearly-defined characteristics.
Sample sites should be surveyed with a satellite based navigations system such as Global Positioning System (GPS), GALILEO (European Global Satellite Navigation System), or GLONASS (Global’naya Navigatsionnaya Sputnikovaya Sistema [global navigation satellite system]).



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