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Coal Surface Mining and Reclamation

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Environmental Effects of Coal Surface Mining and Reclamation on Land and Water in Southeastern Kansas

by Jerome E. Welch and William W. Hambleton

with contributions to sections by Harold P. Dickey, David A. Grisafe, Lawrence L. Brady, and Donald O. Whittemore

Cover of book; beige paper with green text.

Originally published in 1982 as Kansas Geological Survey Mineral Resources Series 7. This is, in general, the original text as published. The information has not been updated. An Acrobat PDF version (20.5 MB) is also available.

Authors

The authors are all affiliated with the Kansas Geological Survey at The University of Kansas, Lawrence, Kansas. Jerome E. Welch is a soil geochemist in the Geochemistry Section. William W. Hambleton is a geophysicist and Director of the Survey. Harold P. Dickey is a soil scientist with the Soil Conservation Service, assigned to the Environmental Geology and Geophysics Section of the Survey under a cooperative agreement. David A. Grisafe is a ceramic and material scientist in the Mineral Resources Section. Lawrence L. Brady is a coal geologist and Chief of the Mineral Resources Section. Donald O. Whittemore is a water geochemist in the Geochemistry Section.

Executive Summary

Introduction

The Kansas Geological Survey undertook a study of the soil and water environments of a surface coal mine site in southeastern Kansas for the purpose of comparing data from unmined land to those of reclaimed and unreclaimed mined land.

Bore-hole records of the Kansas Geological Survey, numerous records of coal-company drillings, and high wall channel sites were used to characterize the overburden of the unmined land. Rock-core samples were analyzed by x-ray diffraction and fluorescence. Soil samples were taken at depth to determine the morphological, physical, and chemical properties of the predominant natural soil and minesoil in the area. Surface samples of these soils were also taken for fertility analysis. Soil samples were analyzed by x-ray diffraction for their mineral composition. Surface waters were sampled in unmined land and in reclaimed and unreclaimed mined land at the mine site. Concentrations of major and minor constituents and trace elements were determined in these samples. Two observation wells were drilled to investigate recharge to ~he shallow aquifers in unmined land and reclaimed mined land.

Geology

The rocks at the mine site consist of shale, siltstone, sandstone, coal, underclay, and several thin beds of clay-ironstone nodules of the Krebs Formation, Cherokee Group, Desmoinesian Stage, Middle Pennsylvanian Series. The lowermost unit of the measured section is the Rowe coal, which ranges in thickness from 14 to 18 inches. Strata between the Rowe coal and the overlying Dry Wood coal consist mostly of shale and underclay beds, ranging from 6 to 9 feet in thickness. The Dry Wood coal ranges in thickness from 0.25 to 1.25 feet. Above the Dry Wood coal is a dark-gray shale several feet thick, and a thin coal bed locally known as the "pilot coal." Above this coal is a dark-gray silty shale with interbedded light-gray shale and very finely laminated siltstone. The upper part of the shale interval also contains interbedded sandstone considered to be equivalent to the Bluejacket sandstone.

The interval between the coals thickens appreciably to the east. The coals are absent in places. Circular depressions and ridges, which are typical of the area, occur in the coals, possibly reflecting an older karst surface. The most prominent structural feature is a southwest- to northeast-trending trough or syncline that plunges to the northeast. The deeper parts of the syncline are not mined because of the increased overburden thickness.

X-ray diffraction analysis showed that clays, quartz, and feldspars are the predominant minerals. Kaolinite and illite are the predominant clay minerals, with appreciable amounts of montmorillonite found in places. Calcite, iron oxides, pyrite, and siderite are also present. X-ray fluorescence analysis indicated the absence of any elements of economic importance in the rocks.

Coal

The Rowe and Dry Wood coals from the mine site were ranked as high-volatile A, bituminous coals. Both these coals average a higher ash content and lower heat of combustion and contain more total sulfur than the average southeastern Kansas coal. Most of the sulfur in the Rowe and Dry Wood coals is present as pyritic sulfur. Compared to the Rowe coal, the Dry Wood coal contained higher amounts of 31 of the 43 elements analyzed. The Rowe and Dry Wood coals are both markedly enriched on an average basis in arsenic, lead, and selenium. The Dry Wood coal is additionally markedly enriched in cadmium and zinc. The extremely high amounts of cadmium and zinc in the Dry Wood coal seem to be related to sphalerite mineralization in the Tri-State Mining District.

The average ash content of the Kansas Dry Wood coal is 12.9 percent higher than the average ash content of Interior Province coals, and the average carbon content of the Kansas Dry Wood is 10.9 percent less than the Province average. As a result, of the above, the average heat of combustion of the Kansas Dry Wood is less than that of the Province average. The Rowe and Dry Wood coals both average more total sulfur than Interior Province coal, and their average pyritic sulfur contents are 3 times those of Interior Province coal. Both the Rowe and Dry Wood coals average more iron, copper, mercury, nickel, and lead than Interior Province coal. Additionally, the Dry Wood also contains more silicon, aluminum, potassium, titanium, cadmium, cobalt, gallium, strontium, vanadium, yttrium, ytterbium, and zinc. Comparisons of reported average enrichment values of elements in Interior Province coal based on crustal abundance and those calculated for the Rowe and Dry Wood coals at the mine site show both the Rowe and Dry Wood coals are more enriched in arsenic, mercury, and lead. Additionally, the Dry Wood coal is more enriched in antimony.

Compared to the Rowe coal from Missouri, the Kansas Rowe contains an average of 4.0 percent more sulfur, of which 3.6 percent is pyritic sulfur, and more iron, manganese, arsenic, lead, strontium, and zinc. The Missouri Rowe contains more cobalt, lithium, molybdenum, selenium, uranium, vanadium, and zircon. The Kansas Dry Wood coal contains an average of 10 percent more ash, 13 percent less carbon, 5 percent more sulfur, and more calcium, iron, manganese, arsenic, cadmium, cobalt, copper, gallium, mercury, lanthanum, neodymium, nickel, lead, strontium, yttrium, and zinc than the Missouri Dry Wood. However, the Missouri Dry Wood coal contains more boron and selenium.

Soil

The principal soil of the unmined area is the Parsons silt loam, a deep, somewhat poorly drained, moderately acidic, upland soil, with well-developed and contrasting horizons. Weathering of the soil was found to extend to a depth of 8 to 12 feet. Extensive leaching has resulted in the accumulation of calcium, magnesium, sodium, and potassium with depth. Less-soluble elements such as zinc, iron, copper, and manganese were concentrated in the surface. Fertility analysis of the surface showed the Parsons soil to be low in calcium, nitrogen, phosphorus, potassium, and boron, and high in zinc, iron, copper, and manganese.

The most prominent characteristics of the minesoil were the absence of well-developed horizons and the presence of large amounts of rock fragments. Minesoil samples showed variation within and among sites, reflecting the mixing of soil and overburden that occurred during mining and releveling. The only pedogenic development observed in the minesoil was the physical weathering of surface shale fragments.

The particle-size distribution of the minesoil varied within and among sites, again reflecting the mixing of soil and overburden that occurred as a result of the mining and releveling operations. The minesoil has greater amounts of material in all particle-size ranges except the <0.074 mm fraction. The size range with the greatest amount was 2-0.074 mm , The minesoil contained 85 percent (by weight) material <2 mm, whereas in the Parsons soil nearly all the material (98-99 percent) was <2 mm. Silt and clay were more uniformly distributed with depth in the minesoil. However, when averaged over depth, the amounts of clay in the minesoil and Parsons soil were essentially identical, whereas the amount of silt in the minesoil was less than that of the Parsons soil.

The bulk density of the minesoil decreased with depth, whereas that of the Parsons soil increased with depth. The bulk density of the 0-12 inch depth of the minesoil was higher than that of the 12-40 inch depth, due to filling of void spaces by fine materials during smoothing of the minesoil and tilling of the minesoil for planting.

The surface 12 inches of the minesoil contained 35 percent (by weight) less plant-available water than the Parsons soil. However, the water data and the high wheat yields indicate that the minesoil supplied sufficient water to the wheat.

In terms of the usual measures of fertility the minesoil differed markedly from the Parsons soil. The pH of the minesoil was more acid than the Parsons soil. Consequently, the liming requirement of the minesoil was also greater. The cation exchange capacity of the minesoil was less than for the Parsons soil, but exchangeable magnesium was 5 times greater in the minesoil. Boron was slightly more abundant in the minesoil and extractable iron and manganese were 1.5 and 10 times greater respectively. The lower pH and the greater amounts of the above elements in the minesoil were attributed to the weathering of pyrite-containing shale particles in the surface of the minesoil.

Water

Comparisons of the quality of surface waters draining from unmined land and from the reclaimed and unreclaimed mined land showed major differences. Water in the tributary draining the unreclaimed mined land was severely affected by strip pit drainages (overflow and seepage). The water was highly acidic, extremely hard, and had very high concentrations of most of the major and minor dissolved constituents and trace elements. The high acidity makes this water unsuitable for most uses. As a result of the low pH, many minor and trace-element concentrations exceeded recommended permissible levels for various uses. Recommended concentrations in irrigation water were exceeded for iron, manganese, nickel, zinc, and fluoride. National Drinking Water Contaminant Levels were exceeded for iron, manganese, sulfate, zinc, and fluoride. Effluent Limitations for Coal Mining Point Sources were not met or were exceeded for pH, manganese, and iron.

Water draining from the reclaimed mined land was appreciably better in quality than that from the unreclaimed mined land, but not as good as water draining from the unmined land. The concentrations of iron, manganese, and sulfate were still too high for most uses.

Dilution and partial neutralization of waters draining from both the reclaimed and unreclaimed mined land occurred with mixing of the water in the larger creeks that drain the area. However, even after dilution, the concentrations of iron, manganese, and sulfate were too high for most uses.

Water-level measurements of observation wells in the unmined land and in the reclaimed mined land showed a relatively rapid recharge from rainfall of the shallow aquifer in the reclaimed mined land. Recharge of the shallow aquifer in the unmined land was slight. Thus, the quantity of water available from reclaimed mined land should be much greater than that from unmined land in the area.

Land Reclamation

Wheat yields from the 5 fields showed that wheat was well suited to the minesoil and produced relatively high yields where good management practices were employed. Among these practices were the burial of dark-colored acid-producing shale fragments, good seedbed preparation, the use of quality seed, and the proper application of sufficient amounts of lime and fertilizer, as indicated by soil-fertility tests.


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Kansas Geological Survey, Geology
Placed on web Oct. 25, 2018; originally published 1982.
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