Water Quality Improvements Over Time and Longevity of Acid Mine Discharges From Underground Mines in Northern West Virginia

Demchak, Jennifer; Skousen, Jeff; McDonald, L.A.

doi:10.21000/jasmr01010174

Cited by 7 publications

(10 citation statements)

References 11 publications

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“…It is also possible that the accumulated and stored metal salts within the mine could be flushed out soon after mine closure, which would cause a rapid increase in acidity (more closely approximating the higher 5% decay rate), followed by a rapid decrease as these salts leave the mine environment (approximating the 2% decay rate). The percent change in acidity/year from 1968-2006 was observed to be similar to the previous research of Demchak et al (2001) and Ziemkiewicz (1994) (Table 3). While there is no way to quantify these changes because we do not have acidity values from these mines at the time of closure, we therefore estimated the values of acidity that could have been present at mine closure based on the decay rates of acidity, had those decay rates remained constant since mine closure.…”

Section: Decay Curvessupporting

confidence: 88%

“…This is expected, as these two parameters are mostly derived from the oxidation of pyrite within the mine. Demchak et al (2001) other researchers showed similar decline rates of S over time. Ziemkiewicz (1994) used a similar rate of 2% to determine changes in AMD discharges over time.…”

Section: Introductionsupporting

confidence: 62%

“…Table 2 shows mean acidity concentrations for each group of mines. The 2% curve was used due to its similarity to research done by Demchak et al (2001) and Ziemkiewicz (1994) and the 5% and 10% decay curves were used as comparisons. The six Pittsburgh sites had a decay curve slope of -0.044, which gave a curve that was more similar in shape to the 5% decay rate curve (Fig.…”

Section: Decay Curvesmentioning

confidence: 99%

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Acidity Decay Curves of 40 Above Drainage Mines in West Virginia

Mack¹,

Skousen²

2008

ASMR

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Several measurements of acidity concentrations from 40 abovedrainage underground mines over 38 years were plotted against a range of acidity decay curves. The objective of this study was to determine the average amount of acidity lost over time. Ideal acidity decay curves of 2, 5, and 10% were used for this comparison. The 40 sites were split into two main groups by coal seam (Upper Freeport and Pittsburgh). Acidity values from the 34 Upper Freeport sites were split further into four different groups (by 1968 acidity) and an exponential trend line was drawn through the data to determine how well the groups matched the ideal decay curves. Both the Pittsburgh and Upper Freeport groups most closely matched the 5% decay curve. Acidity values from the T&T #2 mine, which was closed 12 years ago, were also plotted against the same three decay curves. T&T most closely matched the 10% decay curve during its first 12 years after closure. This is likely due to the relatively short time since mine closure of T&T compared to the 50-70 years since mine closure for the 40 sites. In addition, T&T is likely still going through its initial flushing phase, which includes the flushing of accumulated metal salts from the mine. Additional

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Section: Decay Curvessupporting

confidence: 88%

Section: Introductionsupporting

confidence: 62%

Section: Decay Curvesmentioning

confidence: 99%

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Acidity Decay Curves of 40 Above Drainage Mines in West Virginia

Mack¹,

Skousen²

2008

ASMR

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“…While predictions for annual acidity declines or decay rates have not been made here, such as those made by Ziemkiewicz (1994), Younger (2000), and Demchak et al (2001), these predictions have proved helpful in determining remediation strategies and costs. For example, given the scenario that the first 15 to 20 yr after closure will probably produce the highest acidity levels (as was found here), suitable chemical treatment systems can be installed to treat the low pH, metal‐laden water.…”

Section: Resultsmentioning

confidence: 99%

Longevity of Acid Discharges from Underground Mines Located above the Regional Water Table

Demchak¹,

Skousen

McDonald

2004

J of Env Quality

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The duration of acid mine drainage flowing out of underground mines is important in the design of watershed restoration and abandoned mine land reclamation projects. Past studies have reported that acid water flows from underground mines for hundreds of years with little change, while others state that poor drainage quality may last only 20 to 40 years. More than 150 above-drainage (those not flooded after abandonment) underground mine discharges from Pittsburgh and Upper Freeport coal seams were located and sampled during 1968 in northern West Virginia, and we revisited 44 of those sites in 1999-2000 and measured water flow, pH, acidity, Fe, sulfate, and conductivity. We found no significant difference in flows between 1968 and 1999-2000. Therefore, we felt the water quality data could be compared and the data represented real changes in pollutant concentrations. There were significant water quality differences between year and coal seam, but no effect of disturbance. While pH was not significantly improved, average total acidity declined 79% between 1968 and 1999-2000 in Pittsburgh mines (from 66.8 to 14 mmol H+ L(-1)) and 56% in Upper Freeport mines (from 23.8 to 10.4 mmol H+ L(-1)). Iron decreased an average of about 80% across all sites (from an average of 400 to 72 mg L(-1)), while sulfate decreased between 50 and 75%. Pittsburgh seam discharge water was much worse in 1968 than Upper Freeport seam water. Twenty of our 44 sites had water quality information in 1980, which served as a midpoint to assess the slope of the decline in acidity and metal concentrations. Five of 20 sites (25%) showed an apparent exponential rate of decline in acidity and iron, while 10 of 20 sites (50%) showed a more linear decline. Drainage from five Upper Freeport sites increased in acidity and iron. While it is clear that surface mines and below-drainage underground mines improve in discharge quality relatively rapidly (20-40 years), above-drainage underground mines are not as easily predicted. In total, the drainage from 34 out of 44 (77%) above-drainage underground mines showed significant improvement in acidity over time, some exponentially and some linearly. Ten discharges showed no improvement and three of these got much worse.

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“…Various analytical methods have been proposed for the quantification of the first flush from underground mines (Demchak et al, 2001;Frost, 1979;Gzyl and Banks, 2007;Mack et al, 2010). The approaches in these studies relied mainly on the contaminants' time dependent decay rates in mine water fitted with decay curves.…”

Section: Introduction and Previous Investigations On Mine Floodingmentioning

confidence: 99%

Modelling the hydrogeochemical evolution of mine water in a decommissioned opencast coal mine

Huisamen

Wolkersdorfer

2016

International Journal of Coal Geology

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Highlights• Kinetic geochemical modelling calibration method proposed-calibration against leaching test data was successful.• Transient source term transport modelling successful -calibrated against existing groundwater monitoring data.• Improved confidence in numerical transport modelling of the initial flush from opencast mines• Contaminant plume calibration in numerical models is possible using the proposed methodology. AbstractA method for the geochemical modelling of transient contaminant release from rehabilitated opencast coal mines, including calibration against existing data, is proposed. The need for such a methodology is illustrated by a directive received by a decommissioned opencast coal mine in Mpumalanga, South Africa. Groundwater monitoring data, geochemical analyses, numerical flow modelling and geochemical modelling are used to model the hydrogeochemical evolution of mine water over time. Models presented in this study are based on a conceptual model detailing groundwater levels and flow directions, hydraulic conductivities, groundwater chemistry, precipitation, evaporation, surface water bodies and potential sources. Additional to this, mineralogical analyses, leaching tests and acid-base accounting were performed to obtain a better understanding of the site geochemistry. A geochemical model was constructed which was used to obtain a statistically representative mineral assemblage based on laboratory data which was calibrated against leaching test data. This assemblage was simulated in field conditions as input to a numerical flow and transport model. The transport of sulfate was modelled accordingly and sulfate concentrations from monitoring data were used for chemical calibration. Following this, long term contaminant release was simulated. Calibration graphs from the transport model indicated concentrations within a 20 mg/L error margin, showing that the proposed methodology can be used to calculate contaminant concentrations in an aquifer over time within an acceptable range. This approach could provide an improved estimate of the duration of the first flush 2 which, upon completion, will transform decommissioned collieries into large scale reservoirs of utilisable groundwater.

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Water Quality Improvements Over Time and Longevity of Acid Mine Discharges From Underground Mines in Northern West Virginia

Cited by 7 publications

References 11 publications

Acidity Decay Curves of 40 Above Drainage Mines in West Virginia

Acidity Decay Curves of 40 Above Drainage Mines in West Virginia

Longevity of Acid Discharges from Underground Mines Located above the Regional Water Table

Modelling the hydrogeochemical evolution of mine water in a decommissioned opencast coal mine

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