Predicting total dissolved solids release from central Appalachian coal mine spoils.

Appalachian USA surface coal mines face public and regulatory pressure to reduce total dissolved solids (TDS) in discharge waters, primarily due to effects on sensitive macroinvertebrates. Specific conductance (SC) is an accurate surrogate for TDS and relatively low levels of SC (300-500 µS cm(-1)) have been proposed as regulatory benchmarks for instream water quality. Discharge levels of TDS from regional coal mines are frequently >1000 µS cm(-1). The primary objectives of this study were to (a) determine the effect of rock type and weathering status on SC leaching potentials for a wide range of regional mine spoils; (b) to relate leachate SC from laboratory columns to actual measured discharge SC from field sites; and (c) determine effective rapid lab analyses for SC prediction of overburden materials. We correlated laboratory unsaturated column leaching results for 39 overburden materials with a range of static lab parameters such as total-S, saturated paste SC, and neutralization potential. We also compared column data with available field leaching and valley fill discharge SC data. Leachate SC is strongly related to rock type and pre-disturbance weathering. Fine-textured and non-weathered strata generally produced higher SC and pose greater TDS risk. High-S black shales produced the highest leachate SC. Lab columns generated similar range and overall SC decay response to field observations within 5-10 leaching cycles, while actual reduction in SC in the field occurs over years to decades. Initial peak SC can be reliably predicted (R(2) > 0.850; p < 0.001) by simple lab saturated paste or 1:2 spoil:water SC procedures, but predictions of longer-term SC levels are less reliable and deserve further study. Overall TDS release risk can be accurately predicted by a combination of rock type + S content, weathering extent, and simple rapid SC lab measurements.

Hardwood tree growth after eight years on brown and gray mine soils in west virginia.

Surface coal mining in Appalachia disturbs hundreds of hectares of land every year with the removal of valuable and ecologically diverse eastern deciduous forests. After the passage of the Surface Mining Control and Reclamation Act in 1977, coal mine operators began planting a variety of grasses and legumes as a fast and economical way to reestablish a permanent vegetative cover to meet erosion and site stabilization requirements. However, soil compaction and competitive forage species have arrested the recolonization of native hardwood tree species on these reclaimed sites. Three 2.8-ha demonstration plots were established at Catenary Coal's Samples Mine in Kanawha County, West Virginia, of weathered brown sandstone and unweathered gray sandstone. Half of each plot was compacted. Each plot was hydroseeded with a low-competition herbaceous cover and planted with 11 hardwood tree species. After eight growing seasons, average tree volume index was nearly 10 times greater for trees grown in the brown sandstone treatments, 3853 cm, compared with 407 cm in gray sandstone. Trees growing on compacted treatments had a lower mean volume index, 2281 cm, than trees growing on uncompacted treatments, 3899 cm. Average pH of brown sandstone was 5.2 to 5.7, while gray sandstone was 7.9. The gray sandstone had much lower fine soil fraction (<2-mm) content (40%) than brown sandstone (70%), which influenced nutrient- and water-holding capacity. Brown sandstone showed significantly greater tree growth and survival and at this stage is a more suitable topsoil substitute than gray sandstone on this site.

Survival and growth of chestnut backcross seeds and seedlings on surface mines.

Some scientists consider the loss of the American chestnut from forests in the eastern United States as one of the greatest forest ecological disasters in the 20th century. The American Chestnut Foundation has been attempting to restore chestnut by backcrossing blight-resistant Chinese chestnut to American chestnut and selecting those strains with blight resistance. Third-generation backcross seeds and seedlings have been produced and planted by researchers. Surface-mined lands provide a land base where these backcross chestnut seedlings may be introduced back into forests. In 2008, seeds of two parent species of chestnut (100% American and 100% Chinese) and three breeding generations (BF, BF, and BF backcrosses) were planted into loosely graded mine soils with and without tree shelters. First-year establishment from seeds averaged 81%. After the fourth year, survival without shelters declined for all chestnut stock types except for Chinese (80%): American 40%, BF 70%, BF 40%, and BF 55%. Survival with shelters was only slightly better after the fourth year (average, 60% with shelters and 57% without). Height growth was not different among stock types, and average height after the fourth year was 43 cm without shelters and 56 cm with shelters. In 2009, seeds and seedlings of the same chestnut stock types were planted into brown (pH 4.5) or gray (pH 6.6) mine soils. Only six out of 250 seeds germinated, which was very poor considering 81% average seed germination in 2008. Transplanted chestnut seedling survival was much better. After the third year, seedling survival was 85% in brown and 80% in gray soil, but significant differences were found with stock types. Survival was significantly higher with American, Chinese, and BF stock types (75%) than with BF and BF (60%). Height after the third season averaged 90 cm on brown and 62 cm on gray soil. Chestnut backcrosses displayed no hybrid vigor and were not better in survival and growth than the parent stock. All five stock types grew on mine soils in West Virginia, and we found surface mines to be promising sites for introducing blight-resistant chestnut backcross trees into the Appalachian forest.

Acidity decay of above-drainage underground mines in West Virginia.

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 x 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 x 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 x 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 x 10(-2) yr(-1) to 13.1 x 10(-2) yr(-1)), the decay constants of 2.7 x 10(-2) yr(-1) to 4.3 x 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.

Survival and growth of hardwoods in brown versus gray sandstone on a surface mine in West Virginia.

Surface mining in West Virginia removes the eastern deciduous forest and reclaiming the mined land to a productive forest must consider soil depth, soil physical and chemical properties, soil compaction, ground cover competition, and tree species selection. Our objective was to evaluate tree survival and growth in weathered brown sandstone and in unweathered gray sandstone. Brown and gray sandstone are often substituted when insufficient native topsoil is available for replacement. Three 2.8-ha plots were constructed with either 1.5 or 1.2 m of brown sandstone, or 1.5 m of gray sandstone at the surface. Half of each plot was compacted with a large dozer. Percent fines (<2 mm) in the upper 20 cm was 61% for brown sandstone and 34% in gray. Brown sandstone's pH was 5.1, while gray sandstone's pH was around 8.0. In March 2005, 2-yr-old seedlings of 11 hardwood species were planted. After 3 yr, tree survival was 86% on 1.5-m gray sandstone, 67% on 1.5-m brown sandstone, and 82% on 1.2-m brown sandstone. Survival was 78% on noncompacted and 79% on compacted areas. Average volume of all trees (height x diameter(2)) was significantly greater on brown sandstone (218 cm(3)) than gray sandstone (45 cm(3)) after 3 yr. Black locust (Robinia pseudoacacia L.) had the highest survival (100%) and significantly greater volume (792 cm(3)) than all other tree species. Survival of the other 10 species varied between 65% for tulip poplar (Liriodendron tulipifera L.) and 92% for redbud (Cercis canadensis L.), and volume varied between 36 cm(3) for white pine (Pinus strobes L.) and 175 cm(3) for tulip poplar. After 3 yr, brown sandstone appears to be a better topsoil material due to the much greater growth of trees, but tree growth over time as these topsoils weather will determine whether these trends continue.

Acid soil indicators in forest soils of the Cherry River Watershed, West Virginia.

Declining forest health has been observed during the past several decades in several areas of the eastern USA, and some of this decline is attributed to acid deposition. Decreases in soil pH and increases in soil acidity are indicators of potential impacts on tree growth due to acid inputs and Al toxicity. The Cherry River watershed, which lies within the Monongahela National Forest in West Virginia, has some of the highest rates of acid deposition in Appalachia. East and West areas within the watershed, which showed differences in precipitation, stream chemistry, and vegetation composition, were compared to evaluate soil acidity conditions and to assess their degree of risk on tree growth. Thirty-one soil pits in the West area and 36 pits in the East area were dug and described, and soil samples from each horizon were analyzed for chemical parameters. In A horizons, East area soils averaged 3.7 pH with 9.4 cmol(c) kg(-1) of acidity compared to pH 4.0 and 6.2 cmol(c) kg(-1) of acidity in West area soils. Extractable cations (Ca, Mg, and Al) were significantly higher in the A, transition, and upper B horizons of East versus West soils. However, even with differences in cation concentrations, Ca/Al molar ratios were similar for East and West soils. For both sites using the Ca/Al ratio, a 50% risk of impaired tree growth was found for A horizons, while a 75% risk was found for deeper horizons. Low concentrations of base cations and high extractable Al in these soils translate into a high degree of risk for forest regeneration and tree growth after conventional tree harvesting.

Longevity of acid discharges from underground mines located above the regional water table.

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.

Acid-base accounting to predict post-mining drainage quality on surface mines.

Acid-base accounting (ABA) is an analytical procedure that provides values to help assess the acid-producing and acid-neutralizing potential of overburden rocks prior to coal mining and other large-scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requiring an assessment of surface mining on water quality, ABA became a preferred method to predict post-mining water quality, and permitting decisions for surface mines are largely based on the values determined by ABA. To predict the post-mining water quality, the amount of acid-producing rock is compared with the amount of acid-neutralizing rock, and a prediction of the water quality at the site (whether acid or alkaline) is obtained. We gathered geologic and geographic data for 56 mined sites in West Virginia, which allowed us to estimate total overburden amounts, and values were determined for maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP to MPA ratios for each site based on ABA. These values were correlated to post-mining water quality from springs or seeps on the mined property. Overburden mass was determined by three methods, with the method used by Pennsylvania researchers showing the most accurate results for overburden mass. A poor relationship existed between MPA and post-mining water quality, NP was intermediate, and NNP and the NP to MPA ratio showed the best prediction accuracy. In this study, NNP and the NP to MPA ratio gave identical water quality prediction results. Therefore, with NP to MPA ratios, values were separated into categories: <1 should produce acid drainage, between 1 and 2 can produce either acid or alkaline water conditions, and >2 should produce alkaline water. On our 56 surface mined sites, NP to MPA ratios varied from 0.1 to 31, and six sites (11%) did not fit the expected pattern using this category approach. Two sites with ratios <1 did not produce acid drainage as predicted (the drainage was neutral), and four sites with a ratio >2 produced acid drainage when they should not have. These latter four sites were either mined very slowly, had nonrepresentative ABA data, received water from an adjacent underground mine, or had a surface mining practice that degraded the water. In general, an NP to MPA ratio of <1 produced mostly acid drainage sites, between 1 and 2 produced mostly alkaline drainage sites, while NP to MPA ratios >2 produced alkaline drainage with a few exceptions. Using these values, ABA is a good tool to assess overburden quality before surface mining and to predict post-mining drainage quality after mining. The interpretation from ABA values was correct in 50 out of 52 cases (96%), excluding the four anomalous sites, which had acid water for reasons other than overburden quality.