Water Quality from Above-Drainage Underground Mines Over a 35-YEAR Period (original) (raw)
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Journal American Society of Mining and Reclamation, 2001
The duration of acid mine drainage (AMD) flowing out of underground mines is important in watershed restoration and abandoned mine land reclamation projects. Past studies report that AMD flows from underground mines for hundreds of years with little change, while others find that poor drainage quality only lasts 20 to 40 years. In northern West Virginia, 20 above-drainage underground mines with AMD discharges were located and sampled during 1968, 1980, 2000, and 2005. Water flow, pH, acidity, Fe, Al, and sulfate were measured at all sampling times. From earlier work, 33 out of 44 sites (77%) were found to improve in drainage quality between 1968 and 2000. The results of the 2005 water sampling period confirmed these earlier findings. Out of 20 sites in the present study, only nine sites gave sufficient flow for water samples to be taken again in 2005. Of these nine discharges sampled in 2005, two showed a 22% and 32% increase of acidity, while the other seven sites (78%) decreased in acidity between 64 to 93%. Further sampling will quantify acidity changes of the original 44 above-drainage underground mine sites and more water samples will be collected during all four seasons of the year, which will represent both wet and dry periods. In this way, quantification of the effects of flow on underground mine chemistry may be evaluated.
Changes in Water Quality of 34 Above Drainage Mines in West Virginia
Journal American Society of Mining and Reclamation
Acid mine drainage (AMD) is one of the most prevalent pollution problems in the Appalachian region of the United States. The acidity concentration of AMD from a particular source is influenced by many different factors. Some researchers have shown that acidity concentrations in abovedrainage underground mines vary over time, with large fluctuations relating to the season of year or flow characteristics. The objectives of this study were to determine the changes in acidity, Fe concentrations, and flow over 38 years from 34 Upper Freeport underground mines in West Virginia. Water analyses were compiled from studies in 1968, 2000, and 2006 to evaluate these changes. The 34 underground mines were separated into three groups based on sampling season. Flow, acidity, and Fe values were averaged for each sampling year within each group. All three groups of mines had decreases in flow since 1968. Group 1 decreased by 69%, Group 2 by 84%, and Group 3 by 47%. All three groups also showed large decreases in acidity concentrations. Group 1 decreased by 80%, Group 2 by 73%, and Group 3 by 83%. Five mines were also selected to determine changes in Fe concentrations over time, which showed an average decrease of 83%. Further sampling of these sites will continue to quantify the effects of time on discharge amount and quality, and will help in determining the length of treatment and costs.
Trends in Acid Mine Drainage at Active Mines in West Virginia- 20001
1996
Abstract: WVDEP has inventoried water quality at active coal mine operations every other year since 1994. This 4th study details trends since the original study. Inspectors collected raw water samples at problematic sources and described the cause, quantity, and means of treatment. Laboratory analyses for pH, acidity, total iron, manganese, and aluminum were tabulated. Although there have been new sources of poor water quality identified in each study, the quantity of sources, permits involved, flow, and metals loads have declined since 1994. The water quality at a large number of sources has improved, allowing them to be deleted from the inventory. A much smaller number have been revoked. Approximately 5 % of all coal related outlets exhibit the potential to discharge poor water quality without some form of treatment. High volume, pumped, alkaline deep mine drainage dominates the flow, but represents a small percentage of sources. Roughly half the current sources representing three...
Longevity of Acid Discharges from Underground Mines Located above the Regional Water Table
Journal of Environment Quality, 2004
276 000 ha (682 000 acres) have been surface mined in the state (L. Bennett, personal communication, 2003). The duration of acid mine drainage flowing out of underground Therefore, extensive underground areas have been dismines is important in the design of watershed restoration and abanturbed in this region, thereby influencing water supplies doned mine land reclamation projects. Past studies have reported and water quality. that acid water flows from underground mines for hundreds of years with little change, while others state that poor drainage quality may Acid mine drainage (AMD) is a serious problem in last only 20 to 40 years. More than 150 above-drainage (those not areas of extensive surface and underground coal mining, flooded after abandonment) underground mine discharges from Pittssuch as the Appalachian region, where pyrite and other burgh and Upper Freeport coal seams were located and sampled metal sulfides are found within the coal and associated during 1968 in northern West Virginia, and we revisited 44 of those rocks. About 10 000 km of streams have been affected sites in 1999-2000 and measured water flow, pH, acidity, Fe, sulfate, by AMD in Pennsylvania, Maryland, Ohio, and West and conductivity. We found no significant difference in flows between Virginia (USEPA, 1995). Many mines currently dis-1968 and 1999-2000. Therefore, we felt the water quality data could charging AMD were operated and abandoned before be compared and the data represented real changes in pollutant conenactment of the Surface Mining Control and Reclamacentrations. There were significant water quality differences between tion Act (SMCRA) of 1977. The act provided standards year and coal seam, but no effect of disturbance. While pH was not for environmental protection during mining operations significantly improved, average total acidity declined 79% between 1968 and 1999-2000 in Pittsburgh mines (from 66.8 to 14 mmol H ؉ and placed the responsibility of AMD control and treat-L Ϫ1 ) and 56% in Upper Freeport mines (from 23.8 to 10.4 mmol H ؉ ment on the operator (United States Government, L Ϫ1 ). Iron decreased an average of about 80% across all sites (from 1977). The SMCRA also provided a means for reclaiming an average of 400 to 72 mg L Ϫ1 ), while sulfate decreased between 50 abandoned mines by taxing current coal operators, and 75%. Pittsburgh seam discharge water was much worse in 1968 which generates funds for abandoned mine land reclathan Upper Freeport seam water. Twenty of our 44 sites had water mation programs. Even with millions of dollars spent quality information in 1980, which served as a midpoint to assess the in reclaiming abandoned mine lands, these abandoned slope of the decline in acidity and metal concentrations. Five of 20 mines still generate more than 90% of the AMD in sites (25%) showed an apparent exponential rate of decline in acidity streams and rivers in the region and most of this acidic and iron, while 10 of 20 sites (50%) showed a more linear decline. drainage flows from underground mines (Faulkner, 1997; Drainage from five Upper Freeport sites increased in acidity and iron.
Effect of Flow Rate on Acidity Concentration from Above-Drainage Underground Mines
High flows during spring runoff and snowmelt can increase the concentrations of contaminants in the discharge or dilute them. In the Appalachian region, March tends to be a time of high flows from underground mines, May has moderate flow rates, and July has low flows. The objective of this study was to determine the effect of flow rate on water quality from five acid-producing, above-drainage underground mines in West Virginia. We measured flow rates and acidity twice a week for 3 weeks in March, May, and July 2007. As expected, flow rates in March (average of five sites) were significantly higher at 32 L s-1 than flows in May and July at 18 and 6 L s-1. Flows during weeks within months were not significantly different. Acidity concentrations for March and May (high and moderate flow months) were significantly lower at 342 and 400 mg L-1 (as CaCO 3) than those in July at 524 mg L-1 (as CaCO 3). Similar to flow, acidity concentrations during weeks within the same month were not significantly different. In general, this data supported the 'dilution' concept, where higher flow rates resulted in lower acidity concentrations from above-drainage underground mine discharges.
Acidity Decay of Above-Drainage Underground Mines in West Virginia
Journal of Environment Quality, 2010
Acidity of water from abandoned underground mines decreases over time, and the rate of decrease can help formulate remediation approaches and treatment system designs. The objective of this study was to determine an overall acidity decay rate for above-drainage underground mines in northern West Virginia from a large data set of mines that were closed 50 to 70 yr ago. Water quality data were obtained from 30 Upper Freeport and 7 Pittsburgh coal seam mines in 1968, 1980, 2000, and 2006, and acidity decay curves were calculated. The mean decay constant, k, for Upper Freeport mines was 2.73 × 10 -2 yr -1 , with a 95% confidence interval of ± 0.0052, whereas the k value for Pittsburgh mines was not significantly different at 4.26 × 10 -2 yr -1 ± 0.017. Acidity from the T&T mine, which was closed 12 yr ago, showed a k value of 11.25 × 10 -2 yr -1 . This higher decay rate was likely due to initial flushing of accumulated metal salts on reaction surfaces in the mine, rapid changes in mine hydrology after closure, and treatment. Although each site showed a specific decay rate (varying from 0.04 × 10 -2 yr -1 to 13.1 × 10 -2 yr -1 ), the decay constants of 2.7 × 10 -2 yr -1 to 4.3 × 10 -2 yr -1 are useful for predicting water quality trends and overall improvements across a wide spectrum of abandoned underground mines. We found first-order decay models improve long-term prediction of acidity declines from above-drainage mines compared with linear or percent annual decrease models. These predictions can help to select water treatment plans and evaluate costs for these treatments over time.
Journal American Society of Mining and Reclamation, 2001
Acid-Base Accounting (ABA) is an analytical tool to determine the acid-or alkalineproducing potential of overburden rocks prior to coal mining. This procedure was developed by Dr. Richard M. Smith and associates at West Virginia University in the late 1960s. After the passage of laws requirin g an assessment of mining on water quality, ABA became the preferred method to predict post-mining water quality, and many permitting decisions for surface mines were and are based on the values determined by ABA. As a post-mining water quality predictor, ABA is best used as a qualitative assessment of the site's potential to produce acid mine drainage. Several studies have attempted to adapt ABA to a quantitative assessment of the site's postmining water quality. By this approach, the mass of acid-producing rock is compared to the mass of alkaline-producing rock and a prediction of the water quality (amount of acidity or alkalinity) is obtained. Such analyses have given variable prediction success. We gathered information for 28 sites in West Virginia and estimated overburden amounts and ABA parameters on each site based on ABA data and topographic maps. Maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP/MPA ratios were determined for each site based on ABA and correlated to post-mining water quality from springs or seeps on the mined property. On our 28 sites, total NNP varied from-12.7 to 106 tons per thousand tons (t/1000 t) and NP/MPA ratios varied from 0.2 to 21. We found no relationship between MPA with post-mining water quality, while NNP and NP/MPA ratio showed the best correlation. Six sites gave NP/MPA ratios of <1; four of them (67%) gave net acid post-mining water quality, while the other two sites were only slightly net alkaline. Five sites had NP/MPA ratios of 1.1 to 1.6, and only one of these sites had net acid water quality and only slightly so. The remaining 17 sites had NP/MPA ratios >2.2 (all of which should produce alkaline water) and three of the 17 sites produced acid drai nage. Two sites with NP/MPA ratios of <1 gave net alkaline water, while 18 out of 22 sites (82%) with NP/MPA ratios >1 gave net alkaline water quality. ABA is a good tool to assess overburden quality before mining and to predict post-mining drainage quality after mining. Most sites followed the prescribed patterns of prediction.
Longevity of Mine Discharges from Above-Drainage Underground Mines
The duration of acid mine drainage flowing out of underground mines is important to watershed restoration and abandoned mine land reclamation projects. Reclamationists usually employ remediation strategies once (land regrading, revegetating, and installing water treatment) with the hope that these methods will adequately improve the water for a long time. An understanding of the changing acid water conditions from these portals over time will help in designing treatment methods. 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. Several factors are important in making a prediction of the drainage quality over time, such as coal seam characteristics (primarily sulfur content), time since mine closure, flooding, mining method and amount of coal remaining, collapse of roof and other disturbances within the mine, and subsequent nearby surface mining. Over 50 above-drainage (those not flooded after abandonment) underground mine discharges were located and sampled during 1968 in northern West Virginia, and we revisited those sites in 2000 and measured water flow, pH, acidity, alkalinity, Fe, Al, and sulfate. Most of the discharges were from mines in the Pittsburgh and Upper Freeport coal seams, both seams were extensively mined in this area during the past 70 years. There was no significant difference in flows between 1968 and 2000 from these discharges, so we felt that the water quality data could be compared. Across all sites, significant changes in water quality were found between 1968 and 2000 for all parameters: pH increased from 3.1 to 4.0, average acidity declined from 1,140 to 295 mg/L (as CaCO 3 ), Fe decreased from 352 to 61 mg/L, Al decreased from 143 to 38 mg/L, and sulfate declined from 2,918 to 1,037 mg/L. Pittsburgh seam discharge water was much worse in 1968 than Upper Freeport seam water and drainage water from both seams improved from 70 to 80% over 32 years (roughly 1800 and 750 mg/L as CaCO 3 in 1968 compared to 375 and 250 mg/L as CaCO 3 in 2000). The implications of this research provide a framework for estimating time periods when underground mine drainage will have less impact on nearby streams and rivers.
Acidity Decay Curves of 40 Above Drainage Mines in West Virginia
Journal American Society of Mining and Reclamation, 2012
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.