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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 CHAPTER 3 AFFECTED ENVIRONMENT......................................................................... 3-1  3.0  Introduction .......................................................................................................... 3-1  3.1  Mineral Resources and Mining ............................................................................ 3-1  Geology and Seismicity ....................................................................................... 3-1  3.2  3.3  Soils...................................................................................................................... 3-1  3.4  Geomorphology and Fluvial Processes................................................................ 3-1  Topography .......................................................................................................... 3-1  3.5  3.6  Surface Water Hydrology .................................................................................... 3-1  3.6.0Introduction .................................................................................................. 3-1  3.6.1Appalachian Basin ....................................................................................... 3-3  3.6.1.1  Climate ............................................................................... 3-3  Hydrology........................................................................... 3-7  3.6.1.2  3.6.1.3  Water Quality ................................................................... 3-13  3.6.2Colorado Plateau ........................................................................................ 3-20  3.6.2.1  Climate ............................................................................. 3-20  3.6.2.2  Hydrology......................................................................... 3-24  Water Quality ................................................................... 3-25  3.6.2.3  3.6.3Gulf Coast .................................................................................................. 3-26  Climate ............................................................................. 3-26  3.6.3.1  3.6.3.2  Hydrology......................................................................... 3-31  3.6.3.3  Water Quality ................................................................... 3-32  3.6.4Illinois Basin .............................................................................................. 3-32  3.6.4.1  Climate ............................................................................. 3-32  Hydrology......................................................................... 3-36  3.6.4.2  3.6.4.3  Water Quality ................................................................... 3-38  3.6.5Northern Rocky Mountains........................................................................ 3-40  3.6.5.1  Climate ............................................................................. 3-40  3.6.5.2  Hydrology......................................................................... 3-44  3.6.5.3  Water Quality ................................................................... 3-45  3.6.6Northwest ................................................................................................... 3-47  3.6.6.1  Climate ............................................................................. 3-47  3.6.6.2  Hydrology......................................................................... 3-48  3.6.6.3  Water Quality ................................................................... 3-48  3.6.7Other Western Interior ............................................................................... 3-49 
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CHAPTER 3 TABLE OF CONTENTS

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Table 3.6-1 

3.6.7.1  Climate ............................................................................. 3-49  3.6.7.2  Hydrology......................................................................... 3-54  3.6.7.3  Water Quality ................................................................... 3-55  3.6.8Surface Effects of Underground Mining.................................................... 3-59  Potential Impacts on Streams and Surface Waters ........... 3-60  3.6.8.1 

TABLE OF TABLES
Regression Equations for Estimating Mean Flows at Ungauged Sites. .............. 3-9 

Table 3.6-2  Regression Equations for Estimating Peak Discharges in the Appalachian Plateau of Pennsylvania ............................................................................................................ 3-10  Table 3.6-3  Regression Equations for Estimating Peak Discharge in Maryland Streams ... 3-10 

Table 3.6-4  Regression Equations for Estimating Peak Discharges in Selected Portions of the Monongahela River Basin.......................................................................................................... 3-11  Table 3.6-5  Regression Equations for Estimating Peak Discharges in West Virginia Portion of the Monongahela River Basin. ................................................................................................... 3-11  Table 3.6-6  Comparison of Percentiles of Dissolved-Solids Concentrations in Streams Draining Undisturbed and Mined Basins. ................................................................................. 3-14  Table 3.6-7  Table 3.6-8  Comparison of Sulfates for Unmined and Mined Areas .................................... 3-16  Median Water Quality Constituents Related to Land Use ................................. 3-16 

Table 3.6-9  Selected Median Water Quality Constituents for Streams in the Allegheny and Monongahela Formulations....................................................................................................... 3-17  Table 3.6-10  Table 3.6-11  Table 3.6-12  Table 3.6-13  7-Day 2-Year and 7-Day 10-Year Low Flows ....................................... 3-37  Estimation of Peak Flood Magnitude .................................................... 3-38  Erosion Rates for Natural and Reclaimed Heavy, Medium, and Light Soils ................................................................................................................ 3-46  Flood Frequency Equations for Kansas and Missouri Streams ............ 3-54 

TABLE OF FIGURES
Figure 3.6-1  Appalachian Basin Region 1 Mean Total Precipitation (Annual) ....................... 3-4 
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Figure 3.6-2  Appalachian Basin Region 1 Mean Evapotranspiration (Annual) ...................... 3-5  Figure 3.6-3  Appalachian Basin Region 1 Mean Daily Average Temperature (Annual) ........ 3-6  Figure 3.6-4  Appalachian Basin Region 1 Mean Wind Speed (Annual) .................................. 3-7  Figure 3.6-5  Composite Flow-Duration for Streams in Eastern Coal Province Area 5. (Adopted from Herb et al., 1981) ................................................................................................. 3-8  Figure 3.6-6  Relation of the Dissolved Solids Concentration and Specific Conductance Values for Area 13. ............................................................................................................................ 3-15  Figure 3.6-7  Histogram of Maximum Specific Conductance in Selected Streams ................. 3-17  Figure 3.6-8  Ranges and Means of Specific Conductance for Selected Continuous- Record Stations, 1977 and 1978 Water Years ........................................................................................ 3-18  Figure 3.6-9  Colorado Basin Region 2 Mean Total Precipitation (Annual) .......................... 3-21  Figure 3.6-10  Figure 3.6-11  Figure 3.6-12  Figure 3.6-13  Figure 3.6-14  Figure 3.6-15  Figure 3.6-16  Figure 3.6-17  Figure 3.6-18  Figure 3.6-19  Figure 3.6-20  Figure 3.6-21  Figure 3.6-22  Figure 3.6-23  Figure 3.6-24  (Annual) Colorado Basin Region 2 Mean Wind Speed (Annual) ......................... 3-22  Colorado Basin Region 2 Mean Evapotranspiration (Annual) ............. 3-23  Colorado Basin Region 2 Mean Daily Average Temperature (Annual) 3-24  Gulf Coast Region 3 Mean Total Precipitation (Annual) ...................... 3-27  Gulf Coast Region 3 Mean Evapotranspiration (Annual) ..................... 3-29  Gulf Coast Region 3 Mean Daily Average Temperature (Annual)........ 3-30  Gulf Coast Region 3 Mean Wind Speed (Annual) ................................. 3-31  Illinois Basin Region 4 Mean Total Precipitation (Annual) .................. 3-33  Illinois Basin Region 4 Mean Evapotranspiration (Annual) ................. 3-34  Illinois Basin Region 4 Mean Daily Average Temperature (Annual).... 3-35  Illinois Basin Region 4 Mean Wind Speed (Annual) ............................. 3-36  Specific Conductance ............................................................................. 3-39  Northern Rocky Mountains Region 5 Mean Total Precipitation (Annual) ... ................................................................................................................ 3-41  Northern Rocky Mountains Region 5 Mean Evapotranspiration (Annual) .. ................................................................................................................ 3-42  Northern Rocky Mountains Region 5 Mean Daily Average Temperature ................................................................................................................ 3-43 

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Figure 3.6-25  Figure 3.6-26  Figure 3.6-27  Figure 3.6-28  (Annual) Figure 3.6-29  Figure 3.6-30  Figure 3.6-31  Figure 3.6-32  Figure 3.6-33  Overburden

Northern Rocky Mountains Region 5 Mean Wind Speed (Annual) ....... 3-44  Other Western Interior Region 7 Mean Total Precipitation (Annual) .. 3-50  Other Western Interior Region 7 Mean Evapotranspiration (Annual) .. 3-51  Other Western Interior Region 7 Mean Daily Average Temperature ................................................................................................................ 3-52  Other Western Interior Region 7 Mean Wind Speed (Annual) .............. 3-53  Mean Specific Conductance ................................................................... 3-56  Percentage of Drainage Area Strip Mined ............................................ 3-57  Suspended Sediment Concentration ....................................................... 3-58  Five Zones for High Extraction Mining Impacts on Mined Roof ................................................................................................................ 3-60 

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Chapter 3 Affected Environment
3.0 3.1 3.2 3.3 3.4 3.5 3.6
3.6.0

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INTRODUCTION MINERAL RESOURCES AND MINING GEOLOGY AND SEISMICITY SOILS GEOMORPHOLOGY AND FLUVIAL PROCESSES TOPOGRAPHY SURFACE WATER HYDROLOGY
Introduction

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9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

The topics addressed in this section are climate, with an emphasis on precipitation, and hydrology and water quality of undisturbed, mined and reclaimed areas (where published analysis is available). Due to the current interest in specific conductance with respect to impact on specific biota both specific conductance and total dissolved solids (TDS) have been emphasized along with contributing constituents of sulfate and bicarbonate. Additionally, selenium is the primary metal that is addressed. Iron and manganese concentration associated with mining are well documented in other publications, have been regulated since the inception of SMCRA and treatment processes well understood. Also, acid mine drainage has been researched for over thirty years and therefore geochemistry, overburden analysis, influence of geology, special handling and treatment processes are well document (PADEP, 1998). The predominant sources of information for this chapter are refereed journal articles and government publications that have presumably been subjected to at least internal peer review and quality control/quality assurance procedures implemented. It should be noted that the majority
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of applied research and data acquisition of mined and reclaimed lands occurred from approximately 1977 through 1984 and that there are few peer-reviewed studies of hydrology and water quality associated with coal mining within the last two decades. Only very limited funding through federal, state and industry has been directed towards such applied research and sitespecific data acquisition; therefore documentation of hydrology and water quality contributions on mined and reclaimed lands is limited. It is not possible to account for the influence of specific mining or reclamation techniques on the hydrologic regime or water quality constituents except for a few selected studies that have been published. The hydrology section varies somewhat among regional descriptions depending on availability of published, peer-reviewed articles and government reports. Hydrologic components that are addressed are a general description of streamflow linked with precipitation and evapotranspiration, peak flow predictions based on regression equations and flow-duration and low flow predictions/data. Storm water management and sediment control are highly integrated with active mining and are similar throughout all mining regions. The primary controls consists of water conveyance by diversions (clean water by-pass and sediment laden), culverts and sediment ponds. Sediment ponds are located down-gradient of disturbed areas and have various configurations such as bench ponds (in conjunction with contour mining), excavated ponds usually with a small embankment (used in area, open pit and mountaintop removing mining) and embankment ponds (used throughout mining methods) and always near the toe of conventional lift-type valley fills, head of hollow fills and durable rock fills). The use of best management practices, which are near-source erosion and sediment control systems, and geomorphic landscape design have gained wider acceptance especially in the Northern Rocky Mountains and Colorado Plateau Regions. The hydrologic analysis for probable hydrologic determination traditionally emphasized only peak flow reduction for the 10-year 24-hour design storm, during active mining and early stages of reclamation such that the peak flow of undisturbed (pre-mining) areas was not significantly exceeded (usually no more than a 10 percent increase allowed). Some regions prefer to contain the entire design storm event and subsequently discharge when water quality constituents can be achieved. The predominant water quality constituent is sediment with most mining regions required to achieve less than 0.5 mL/L settleable solids for storm events less than the 10-year 24hour design storm. There are also iron, manganese and pH effluent values that are required. These are achieved through mining methods that emphasize source controls (water and material handling) and/or through treatment systems, when needed. Modeling, such as SEDCAD (Warner, 1998) and design procedures such as SWROA (WV reference to be inserted) are commonly used for hydrologic analysis and SEDCAD is primarily used by the Office of Surface Mining, State mining programs, industry and engineering consultant firms for hydrologic, erosion and sediment control designs. It should be noted that in other large-scale land disturbance activities and in mines that emphasis sustainable mining practices that simply addressing peak flow is not considered sufficient and that the pre-mining hydrologic regime (peak flow from various return period storms, runoff
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volume, hydrology shape (runoff temporal distribution) and seasonal flows) is attempted to be matched during active mining and throughout all phases of reclamation.

3.6.1

Appalachian Basin
3.6.1.1 Climate

The Appalachian Basin has a humid climate with abundant rainfall. Precipitation averages about 45 inches annually (see Figure 3.6-1). Rainfall is greatest in the mountain areas. Precipitation is generally greatest during the spring and summer and least during the fall and winter. October is usually the driest month. Thunderstorms occur on the average 40 to 50 days per year and are more frequent during June and July. These storms sometimes produce intense local rainfall and cause flooding in the narrow valley bottoms. Intense storms rarely encompass large areas but are frequent over small areas. The 10-year 24-hour rainfall is approximately 4 inches (Ehlike et al., 1982).

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Figure 3.6-1

Appalachian Basin Region 1 Mean Total Precipitation (Annual)

2 3 4 5 Evaporation averages approximately 38 inches and therefore there is a rainfall excess of approximately 7 inches (see Figure 3.6-2). Evaporation in May through October exceeds average monthly rainfall. Average annual temperature values are shown in Figure 3.6-3.

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Figure 3.6-2

Appalachian Basin Region 1 Mean Evapotranspiration (Annual)

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Figure 3.6-3

Appalachian Basin Region 1 Mean Daily Average Temperature (Annual)

2 3 4 5 6 Precipitation distribution is influenced primarily by the prevailing westerly wind and by topography (see Figure 3.6-4). During the spring and summer, the area is also affected by winds moving in from the Gulf of Mexico. Winds approaching the mountains are subjected to orographic lifting which intensifies precipitation.

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Figure 3.6-4

Appalachian Basin Region 1 Mean Wind Speed (Annual)

2 3 4 5 6 3.6.1.2 Hydrology Streamflow in the area generally follows a pattern that varies seasonally with precipitation and evapotranspiration. In late October, streamflow generally increases and maintains a high runoff rate through May. This is due to precipitation through rain and some snowmelt and a decrease in
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evapotranspiration. An increase in evapotranspiration beginning in May reduces the amount of runoff until the low flow season begins in August and runs through October, (Kiesler et al., 1983). The area’s general topography is one that is conducive to producing severe floods. The area is characterized by steep slopes with narrow valleys. When this topography is coupled with intense storms, floods of short duration with large magnitude are common. With data taken from 33 gauging stations in the Pennsylvania, Maryland and West Virginia areas, a composite flow duration curve was created for ungauged streams. Flow duration curves allow one to predict the flow discharge knowing the drainage area of a given stream. The flow estimations are for a drainage area no larger than 90 mi², due to database. Figure 3.6-5 presents the flow duration curve for the area, (Herb, et al., 1981). Figure 3.6-5 Composite Flow-Duration for Streams in Eastern Coal Province Area 5. (Adopted from Herb et al., 1981)

14 15 16 17 18 The shaded area encompasses the uncertainty associated with the data, and the solid dark line through the shaded area represents the mean of the data. It is worth noting that the results from the curve can be subject to large errors if data from a stream with a drainage area greater than 90 mi² or a stream outside of the study area is used.
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Annual and monthly mean flows can be estimated at ungauged streams in the area through use of regression equations (see Table 3.6-1). These equations were derived for streams in Pennsylvania but can be used to estimate most streams in the vicinity. The equations are accurate for streams having drainage areas greater than two square miles (Herb, et al., 1981). The equations are based on drainage area, mean annual precipitation, annual potential evapotranspiration, and mean basin elevations. Not all parameters are required for each calculation, but vary by period. Table 3.6-1 Period Annual October November December January February March April May June Regression Equations for Estimating Mean Flows at Ungauged Sites. Estimating equation Standard Error of Estimate (Percent) 11 33 23 14 13 11 11 10 16 26

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QA = 0.117 DA.99 APX.91 Q10 = 0.022 DA1.04 APX1.03 Q11 = 0.022 DA1.00 APX1.33 Q12 = 0.094 DA.95 APX1.14 Q01 = 0.150 DA1.03 APX.89 Q02 = 0.320 DA1.00 APX.72 Q03 = 0.822 DA.98 E.38 APX.44 Q04 = 0.340 DA1.00 E.21 APX.67 Q05 = 0.561 DA1.00 E.48 APX.31 Q06 = 0.805 DA.99 E.55 Q07 = 0.012 DA1.02 E.54 July 32 APX1.42 1.05 1.071 Q08 = 0.020 DA APX 22 August Q08 = 0.005 DA1.17 APX1.302 21 1.12 1.12 September Q09 = 0.008 DA APX 41 DA = drainage area, in square miles E = mean basin elevation, in thousands of feet APX = annual precipitation excess, in inches QA - Q09 = mean discharge for period, in cubic feet per second. Subscript identifies month: 01 = January, 02 = February, and so forth. Subscript A identifies mean flow for entire period of record.

Flood peaks can be estimated at ungauged streams in the area by using regression equations that have been specifically developed for Pennsylvania (see Table 3.6-2) and western Maryland (see Table 3.6-3) (Herb, et al., 1981). Table 3.6-4 can be used for unregulated non-urban streams having drainage areas larger than 2 miles but may not be applicable in watersheds that have been extensively strip mined. Table 3.6-5 equations are applicable to streams in the area having drainage areas from 2 to 300 mi², (Herb, et al., 1981). As these equations were developed over 30 years ago, the user should consider the potential effects of land use change (type and extent) on peak discharge prior to using these equations.

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Table 3.6-2 Regression Equations for Estimating Peak Discharges in the Appalachian Plateau of Pennsylvania Exceedance of Probability of Estimating Equation Peak (percent) 10 7.079 CWIDE1.473 4 10.641 CWIDE1.451 2 14.028 CWIDE1.437 CWIDE - Top width of bankfull channel, in feet Standard Error of Estimate (percent) 50 50 50

3 4 5

Table 3.6-3

Regression Equations for Estimating Peak Discharge in Maryland Streams Standard Error of Estimate (percent) 41 42 44 46 37

6 7 8

Exceedance Probability of Estimating Equation Peak (percent) 50 562 DA.769 E.339 F-.494 20 818 DA.751 E.325 F-.446 10 1040 DA.737 E.325 F-.418 4 158 DA.893 S.356 F-.357 2 19.2 DA.763 E.573 PI2.663 DA = Drainage area, in square miles E = Mean basin elevation, in feet F = Forest cover, in percent

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1 2 3 Table 3.6-4 Regression Equations for Estimating Peak Discharges in Selected Portions of the Monongahela River Basin. Exceedance Probability of Standard Error of Estimate Estimating Equation Peak (percent) (percent) 43 39.4 DA.827 APX.222 28 .789 .445 10 45.4 DA APX 25 4 45.3 DA772 APX.566 26 .759 .656 2 44.5 DA APX 29 751 .744 1 42.2 DA APX 31 DA = Drainage area, in square miles APX = Difference between mean annual precipitation and annual potential evapotranspiration

4 5 6

7 Table 3.6-5 Regression Equations for Estimating Peak Discharges in West Virginia 8 Portion of the Monongahela River Basin. Exceedance Probability of Standard Error of Estimating Equation Peak (percent) Estimate (percent) 50 496 DA.92 S-.21 E-.31 F.43 P.39 T1-.43 21 .97 .13 -.26 -.40 .40 -1.26 20 1200 DA L S E F T1 22 10 927 DA1.01 L.14 S-.34 E-.36 F.38 T1-1.08 24 1.04 .15 -.43 -.34 .39 -1.01 4 982 DA L S E F T1 27 1.01 .19 -.45 .33 -1.40 -.39 2 20900 DA L S F T1 SN DA = Drainage area, in square miles S = Main channel slope, in feet per mile L = Main channel length, from point of interest to drainage divide, in miles E = Mean basin elevation, in feet F = Forest cover, in percent T1 = Mean minimum January temperature, in degrees F SN = Average annual snowfall, in inches Since the predominant land use prior to mining is a forest the predictive equations provide above are primarily for pre-mining conditions. Forested watersheds typically have little surface runoff. Subsurface processes, such as interflow dominate (Sloan, 1984). Water that infiltrates into the forest soils is slowly released, thereby sustaining stream flow (Chang, 2003). Ten to 20 % of annual precipitation is intercepted by the forest canopy (Chang, 2003) and approximately 1 to 5% of the annual precipitation is absorbed by forest detritus (Helvey, 1965). The portion of the infiltrated flow that does not proceed as interflow primarily moves through stress-relief fractures in the weathered and unweathered underlying geological strata and is discharged through seeps. A portion of the flow migrates through deeper strata.
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The rainfall-runoff response for a storm is accounted for by the NRCS (formerly SCS) curve number (CN). Higher curve numbers produce higher runoff volumes and higher peak flows for a given unit hydrograph shape. Curve numbers are a function of soil hydrologic group (related to infiltration rate) and land use, such as forest, grasses, etc. The predominant land use in the Appalachian Region is a hardwood forest. Design professionals normally specify CNs based on NRCS tables or guidance promulgated by state agencies. For example, a CN of 73 is recommended for forest in Kentucky by KYDNR. Since CN is the most sensitive hydrologic design parameter with respect to runoff volume and peak flow, its selection is critical to determining the pre-mining hydrologic response. Curve numbers found in the literature for forested watersheds in eastern Kentucky ranged from 85 to 93 (Hawkins, 1993) and 86 to 88 (Springer, 1980) and was 77 in southern Ohio (Bonta, 1997). The mean curve number for Little Millseat in Robinson Forest watershed, an 80-year-old second growth forest located on the Cumberland Plateau in eastern Kentucky, based on 12 storm events, ranging from 28 to 68 mm, was 83 (Taylor, 2008). Curve numbers for West Virginia’s Watersheds 2 and 4, in the Fernow Experimental Forest, based on 3 and 4 storm events had means of 62 and 65, respectively (McCutcheon, 2003). The mean curve numbers for four forested watersheds in northern Georgia ranged from 64 to 81 (Tedela, 2008). 3.6.1.2.1 Mining and Reclamation The description and sequence of surface mining methods is provided in section 3.1.5 and consists of developing site access, installation of stormwater and sediment controls, clearing and grubbing, topsoil removal, excavation of overburden, excess spoil placement and coal extraction. Excess spoil, section 3.1.7, may be placed on fills (conventional lift-type sequence, head of hollow and durable rock fills). A combination method that incorporates conventional lifts and end-dumping is also used where the lowest lifts are constructed by conventional lift-sequence to constructed the rock chimney drain, the intermediate volume is end-dumped and the upper lifts are conventionally constructed lifts since rock segregation by the end-dump method requires approximately 70 ft height difference between the truck bed and the fill level. Excess spoil is also placed in previous mined areas, on benches and in side-fills. Reclamation activities encompass, section 3.1.7.7, backfilling, regrading, topsoil or topsoil substitute placement and revegetation with grass or grass and shrub mixtures. The Forest Reclamation Approach (FRA) has gained wide acceptance in recent years. For example, in 2008 the WVDEP approved 63 surface mine permits covering 12,833 acres. Fifty-five (87 percent) of these permits, covering 10,906 acres, had reclamation plans that require implementation of the Forest Reclamation Approach (OSM, 2009). There is limited data on the hydrologic response on traditionally compacted and reclaimed mine lands. Hydrology of mined lands is controlled mostly by the infiltration rate as it governs the amount of rainfall remaining on the surface. (Jorgensen, 1987).In West Virginia the water holding capacity of mined lands was found to decrease by over 50% from pre-mined conditions (Younos, 1980). An increase in hydraulic conductivity was noted for an Ohio surface mine (Weiss, 1984). The increase was attributed to the presence of voids in the spoil. Large pores in the non-compacted spoil facilitate more rapid infiltration and migration through the spoil (Rogowski, 1979). Compaction of any type of spoil reduced infiltration (Grandt, 1958). Thus,
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runoff potential is highly associated with infiltration rate which in turn depends on spoil compaction characteristics. Curve number (rainfall-runoff response) for compacted Appalachian mine spoil range form 83 to 88 in Pennsylvania (Ritter, 1991) and 87 to 97 in southern Ohio (Bonta, 1997). Mined watersheds had greater peak flows during severe storms than unmined watershed (Messinger, 2003). In eastern Kentucky analysis based on 42 runoff-producing events over a 28-month period resulted in a compacted spoil mean value of 85 (Warner, 2010). The ability to more accurately predict the correct CN for traditionally compacted mine spoil was determined by a storm-based CN approach that accounted for the temporal rainfall characteristics (Warner, 2010). There are very few studies of the hydrologic characteristics of loose-dumped spoil using the FRA. Three monitored sites were employed to determine the hydrologic response of loosedumped spoil at Starfire Mine in eastern Kentucky. No surface runoff was observed over a 2 year period. The infiltration rate was measured at an adjacent site using 38 lysimeters (5m X 5m) installed prior to end-dumping 2 to 3 m of loose run-of-mine (ROM) spoil. The average annual infiltration rate was 32.2% which is within the range of an Appalachian forest, 30 to 35% (Warner, 2009). Non-graded spoil had an infiltration rate ten times greater than graded spoil (Merz, 1951). A comprehensive hydrologic assessment of loose-dumped spoil was conducted at the Bent Mountain research site in eastern Kentucky on six 1-acre plots consisting of weathered sandstone, gray unweathered sandstone and ROM spoil. No surface runoff was observed an a mean curve number, based on interflow, of 77 was determined (Taylor, 2008). The loosedumped spoil demonstrated low discharge volumes, long durations of discharge (5 to 8 days) and low peak flow discharge rates (Taylor, 2009). Valley fill hydrology has not been adequately documented by site-specific data acquisition and is predominantly described through generalized terms. It is assumed that the crown of the fill should have similar characteristics as traditionally compacted spoil that is low infiltration rate and high runoff. The water that does migrated into the fill enters slowly through the crown of the fill and laterally through coal seams that have been intercepted by the fill. A more constant baseflow from fills has been observed compared to pre-mine forested conditions. The 90% flow duration value was 6 to 7 times higher than that of forested sites (Wiley, 2001). Daily streamflows at sites located down-gradient of valley fills were generally greater than forested areas during periods of low streamflow (Wiley, 2001). Surface flow in streams on forested watersheds did not have surface flow in the summer and fall when a drought occurred, but streams below valley fills continued to have surface flows during this timeframe (Green, 2000). Peak discharges after an intense storm were greater downstream of valley fills than in unmined watersheds (Wiley, 2003). 3.6.1.3 Water Quality The area observed contains sites with surface mining, underground mining, and no mining. Dissolved solids concentrations varied depending on the type of mining, or lack thereof, at each site. Ten sites were observed and studied for their dissolved solids content. The results are summarized in Table 3.6-6. The table shows that the sites without mining had the least dissolved
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solids content, followed by underground mining, followed by surface mining. The study showed that where mining did not occur, 90 percent of the dissolved solids concentrations fell within the range of 35 to 77 mg/L. In areas with surface mining, however, 90 percent of the dissolved solids concentrations fell within the range of 82 to 634 mg/L (Kiesler, et al., 1983).

5 Table 3.6-6 Comparison of Percentiles of Dissolved-Solids Concentrations in Streams 6 Draining Undisturbed and Mined Basins. Minimum 24 50 80 5 35 58 82 25 50 126 214 Percentile 50 75 52 60 240 350 366 533 90 77 497 634 Maximum 109 630 892

Natural Undergroundmine Surface-mine 7 8 9 10 11

Specific conductance values in the area ranged from 10 to 26,000 µS/cm with 90 percent of the values falling between 93 and 840 µS/cm and a median value of 336 µS/cm. A correlation was determined between specific conductance values and dissolved solids concentrations in the area (see Figure 3.6-6) (Kiesler, et al., 1983).

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Figure 3.6-6 Relation of the Dissolved Solids Concentration and Specific Conductance Values for Area 13.

3 4 5 6 7 8 9 10 11 Sulfate concentrations in streams are usually dependent on the presence of reactive minerals in the area, the length of time these minerals are exposed to weathering, and the amount of water draining the area. Due to this, sulfate concentrations are lowest during high flows, and highest during low flows. In the observed area, sulfate concentrations ranged from 3 to 18 times greater in areas where surface mining has occurred than where no mining had taken place. Areas with no activity had a range of concentrations from 4.5 to 32 mg/L with a median value of 18 mg/L. Conversely, areas with surface mining activities had a range of 15 to 580 mg/L and a median value of 230 mg/L (see Table 3.6-7) (Kiesler, et al., 1983).

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Table 3.6-7

Comparison of Sulfates for Unmined and Mined Areas 5 5.5 15.8 25 16 110 Percentile 50 75 18 20 230 310 90 27 440 Maximum 32 580

Undisturbed Surface Mined 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Minimum 4.8 15

Coal mining and older reclamation activities have been shown to influence low-flow water quality. Water quality data (1,476 observations) collected at 779 sites in eastern Ohio from June 1975 to September 1982 were analyzed to determine difference in water quality among 100% unmined, >50% abandoned (included active mining), >50% reclaimed, >50% deep-mined and mixed land uses. The purpose of the investigation was to relate surface water quality to land use. Both specific conductance and sulfate were of interest. The median value of specific conductance (see Table 3.6-8) for abandoned, reclaimed, deep-mined was statistically different from unmined lands at the 95% confidence level (Hren, et al., 1984). After reclamation, sulfate exhibited a pattern similar to and remained a major contributor to specific conductance. Reclamation did not reduce either sulfate or specific conductance to unmined levels. Reclamation reduced total iron to the levels found for unmined lands. Another objective of this study was to determine if downstream water quality constituents could be used to predict up-stream land use categories under base flow conditions. Seventy-nine percent of the time, the correct land use was predicted based only on pH and specific conductance (Hren, et al., 1984). Table 3.6-8 Land Use Category Abandoned Reclaimed Deep-mined Unmined Spec. Cond. mho/cm 2,000 1,900 1,850 400 Median Water Quality Constituents Related to Land Use pH 3.3 7.8 7.6 7.5 Bicarbonate mg/L 232 232 150 Sulfate (dissolved) mg/L 995 940 840 42 Iron (total) mg/L 8.6 0.4 5.4 0.4 Manganese (total) mg/L 21.0 0.3 0.4 0.1 TDS mg/L 1,627 1,560 1,760 -

18 19 20 21 22 23 24 25 26 27 The influence of coal formation and related mineralogy and geochemistry on water quality constituents was evaluated for the Monongahela and Allegheny Formations in the southern Ohio coal mine area over a 3-year monitoring period in the early 1980s. Streams draining the carbonate-bearing Monongahela Formation had significantly greater buffering capacity than streams in the Allegheny Formation. Alkalinity, bicarbonate concentrations and TDS were highest in streams draining the unmined Monongahela Formation compared to the Allegheny Formation (see Table 3.6-9) (Childress, 1985). There was a significant increase in specific conductance, dissolved sulfate and TDS for lands mined in both formations compared to unmined land water quality.

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Table 3.6-9 Selected Median Water Quality Constituents for Streams in the Allegheny and Monongahela Formulations Water Allegheny Quality Constituent Unmined Abandoned Reclaimed Spec. Cond. 510 1,680 1,670 µS/cm pH 6.8 3.3 6.7 Alkalinity (mg/L 53 0 43 asCaCO3) Bicarbonate 76 0 52 (mg/L) Monongahela Unmined 600 7.6 180 220 Abandoned Reclaimed 1,520 7.4 120 170 1,710 7.9 180 220

3 4 5 6 7 8 9 10 11 12 13 14 15 High levels of specific conductance was a common characteristic shared among the streams located in the Pennsylvania, Maryland and West Virginia area. The study conducted from June 1979 to April 1980 examined specific conductance of 134 sites in the area (Herb, et al., 1981). The range of specific conductance at the sites was 20 to 8,000 µS/cm with a median value of 220 µS/cm and a mean value of 465 µS/cm. Readings were generally taken during periods of moderate to high base flow. Daily readings were collected at four sites at different streams for two years. These data showed the difference in specific conductance from site to site and also within stream. For these four sites, the mean specific conductance values were 32, 86, 390, and 1080 µS/cm (see Figure 3.6-7 and Figure 3.6-8) (Herb, et al., 1981). Figure 3.6-7 Histogram of Maximum Specific Conductance in Selected Streams

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Figure 3.6-8

Ranges and Means of Specific Conductance for Selected ContinuousRecord Stations, 1977 and 1978 Water Years

3 4 5 6 7 8 9 10 11 12 13 14 15 16
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In the observed area, dissolved solids concentrations were higher in the northwest and lower in the southeast, according to data taken in 1979-1980. Samples were collected during moderate to high base flow in streams of the area. Dissolved solids concentrations in the northwest generally ranged between 50 – 200 mg/L; values were less than 50 mg/L in the southeast. In the overall area, the average maximum of dissolved solid concentration was 325 mg/L with a median of 120 mg/L. Dissolved solids and specific conductance were related as follows:

where ROE is the dissolved solids concentration in mg/L and SC is the specific conductance in µS/cm at 25°C. This relationship holds a correlation coefficient of 97 percent with a standard error of 88 mg/L (Herb, et al., 1981). For dissolved solids and dissolved sulfate, the relationship was described as follows:

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where SO is the dissolved sulfate concentration in mg/L. This relationship holds a correlation coefficient of 97 percent with a standard error of 78 mg/L dissolved solids (Herb, et al., 1981). Several prior studies have been performed using various water quality parameters to predict mining impacts. (Rikard and Kunkle, 1989) determined that sulfate and conductivity were both good indicators for detecting coal mining pollution during a water quality assessment study performed on three Appalachian streams located in the Big South Fork National River and Recreation Area, Tennessee and Kentucky. They concluded that measuring sulfate levels alone were an excellent water quality indicator of coal mining in the area, and that using the sulfate readings in conjunction with conductivity measurements provided an excellent combined index of the presence of coal mining drainage. They found that use of acidity and pH measurements were not dependable indicators of mine impacts. Rikard and Kunkle’s findings confirmed earlier studies by Parker and Carey, 1980 that dissolved sulfate could be used as a prime indicator for detecting coal mining. Downstream water chemistry from valley fills has recently been extensively monitored and as seen historically from mined lands has shown elevated concentrations of specific conductance and sulfates. Sulfates are conservative ions and as such are good indicators of up-gradient mining activities in this region. Mean values of specific conductance, sulfate, calcium (total), magnesium (total) and selenium for streams receiving flow from forested areas versus valley fills are 62 and 1,020 µS/cm, 16 and 696 mg/L, 7.5 and 138 mg/L, 4.3 and 122 mg/L, 0.0015 and 0.011 mg/L, respectively (Pond, 2008). Similar mean values specific conductance have been previously measured to account for seasonal variations comparing reference streams to streams down-gradient of valley fills. Overall means are 59 and 850 µS/cm for reference streams and valley fills, respectively. The seasonal range of means for reference streams was 58 to 140 µS/cm and 643 to 1,232 µS/cm for valley fills, with the higher means being associated with summer and fall low flow conditions (Green, 2000, Merricks (2007) and Hartman (2005)). Seasonal mean values of specific conductance for reference streams were 140, 91, 73 and 58 for summer (1999), fall (1999), winter (2000) and spring (2000), respectively. For streams below valley fills seasonal mean values of specific conductance were 1,232, 958, 836 and 643 µS/cm, respectively (Green, 2000). Again, similar results were found in eastern Kentucky with specific conductance values ranging from 30 to 66 µS/cm in reference streams and 420 to 1,690 µS/cm in streams below valley fills (Howard, 2001). Selenium was non-detect in reference streams and ranged from 0.001 to 0.011 mg/L, based on 18 samples, in streams below valley fills (Merricks, 2007). The leaching potential of unweathered and weathered spoil, from southwestern Virginia, was investigated by Orndorff, 2010. Specific conductance for unweathered spoil ranged from 400 µS/cm to 3,480 µS/cm. For weathered spoil specific conductance ranged from 200 to 560 µS/cm. These results are as expected since weathered strata has been subjected to leaching by infiltrated rainfall which should remove calcium and magnesium and sulfates should have been oxidized thereby reducing specific conductance.

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Selenium is a naturally occurring element and is widely distributed throughout most soils and natural waters. A major geologic source of selenium is coal and associated weathering of specific spoils. Selenium concentrates with the sulfur-containing minerals is organically bound in the coal such that it does not leach until weathering processes are initiated. Oxidized spoil is a primary source of selenium. There are regional-specific risk factors due to different species (chemical forms) associated with variations in selenium sources and transfer between solid and liquid phases. Selenium exists in a wide variety of chemical and physical forms that are linked to numerous biogeochemical transformation reactions (Chapman, 2010). Selenium typically exists in the environment in one to four oxidation states with selenate and selenite being found in oxidized areas and elemental selenium and selenides existing in anaerobic conditions and unweathered geologic formations. Reduced selenium species and strongly adsorbed selenium species are insoluble and are more susceptible to being attached to fine sediments than found in the dissolved forms. Drainage emanating from some spoil material and reclaimed areas can release selenium which can potentially reach aquatic ecosystems. Aquatic sediments represent complex processes where selenium speciation is based on chemical and physical properties of sediment and various biotic factors (Chapman, 2010). In discharge generated from mining areas selenium can be absorbed onto iron-manganese oxyhyroxides on the surface of sediments, desorbed when reduction of those oxyhydroxides occurs and mineralized within organic matter. Low redox conditions create low solubility as iron selenide or Se(0) phases are formed.

3.6.2

Colorado Plateau
3.6.2.1 Climate

A general description of the climate in this region is low relative humidity, abundant sunshine, large daily and seasonal variations in temperature, and increasing precipitation with elevation. The two major contributors to climate are a mid-latitude continental location far removed from any significant moisture sources and a high elevation combined with large local topographic variations, resulting generally in a semiarid climate. Mean annual precipitation ranges from about 10 to 16 inches in the semiarid basins to 40 inches or more in the humid mountains (see Figure 3.6-9). Seasonally, the semiarid lower elevations receive more precipitation during the summer, whereas the mountains areas receive precipitation more uniformly throughout the year. Winter precipitation is almost entirely in the form of snowfall associated with large storms moving from the west or northwest and is highly influenced by orographic effects (see Figure 3.6-10). Summer precipitation is generally produced by convective thunderstorms but since moisture is lacking the rainfall associated with these storms seldom exceeds 1 inch. In all areas, except perhaps the higher mountains, evaporation exceeds precipitation (see Figure 3.6-11). Most streamflow is derived from mountain snowpack. Daily temperature averages 25 °F during the winter to nearly 40 °F in the summer (see Figure 3.6-12).

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Figure 3.6-9

Colorado Basin Region 2 Mean Total Precipitation (Annual)

2 3

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Figure 3.6-10

Colorado Basin Region 2 Mean Wind Speed (Annual)

2 3
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Figure 3.6-11

Colorado Basin Region 2 Mean Evapotranspiration (Annual)

2 3

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Figure 3.6-12

Colorado Basin Region 2 Mean Daily Average Temperature (Annual)

2 3 4 5 6 7 3.6.2.2 Hydrology Most annual streamflow is from snowmelt runoff during spring and early summer; irrigation diversions affect streamflow during the summer growing seasons. Natural streamflow variations between basins result primarily from differences in basin physiographic and other physical characteristics, such as climate, altitude, vegetation, and geology. Man also can have an
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influence on streamflow variations through diversions for irrigation and use of water for livestock and domestic purposes. Seasonal streamflow variations within a basin primarily are the result of type and timing of precipitation and temperature. Many coal mines are in ephemeral stream basins; most of these streams receive the majority of their average annual discharge from snowmelt, although local thunderstorms also may contribute a significant proportion especially on streams in the drier western part of the area. An equation to estimate average annual flow is: QA = 0.00140A0.956St0.192P2.010ti-0.189 where QA is the average annual flow, in cubic feet per second; A is drainage area, in square miles; St is area of lakes and ponds, as a percentage of drainage area (plus 1 percent); P is average mean annual precipitation, in inches; and ti is average mean minimum January temperature, in degrees Fahrenheit (plus 11 degrees). Streams in the mountainous region have a greater average annual flow per square mile than streams in the semiarid region. This difference is due to the effects on streamflow of the mountains from which most streams in the eastern part of the area flow. The major effect of the mountains is to change the altitude-precipitation relation at higher altitudes. Melting snowpacks and reservoir releases also help augment low flow on some streams. Low flows on perennial streams are sustained primarily by ground-water inflows, although melting snowpacks and reservoir releases help augment low flow on some of these streams. Most peak flows occur in the spring months as a result of snowmelt or rainfall runoff with snowmelt. 3.6.2.3 Water Quality In coal-mining areas located in northern Colorado, pyrite and other sulfide minerals in sedimentary rocks and associated coal deposits can affect pH. Oxidation of these minerals may cause a decrease in pH. This process of acid mine drainage is not common in the study area because of the buffer capacity bicarbonate. Bicarbonate ions are the primary source of alkalinity in the surface waters of this area. Increased sulfate concentrations might also be expected as a result of coal mining, since this ion is present in acid mine drainage. However, because sulfate is a ubiquitous constituent in the soils of the area, caution must be used in applying sulfate concentrations as an indicator of acid mine drainage. Increased acidity can also result in the dissolution of certain trace elements in amounts greater than natural concentrations. Trace elements are found in coal and overburden formations in significant concentrations. Regionally, dissolved solids concentrations are generally greater west of the mountains. The lower dissolved solids concentrations are in the mountains. Documented studies in the area have shown that dissolved solid concentrations increased due to coal mining. Alkalinity buffers water against pH changes that may affect aquatic life, decreases toxicity of metals, and help prevent acid mine drainage. In areas of coal mining, buffering capacity is an important consideration because sedimentary rocks associated with coal deposits and the coal itself commonly contains pyrite and other sulfide minerals. When exposed to the atmosphere in spoil material, these minerals are oxidized producing sulfate and hydrogen ions. The acidity
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produced may be neutralized by any available alkalinity; however, if the production of hydrogen ions is large, the pH may be decreased possibly to 4.5 or less. The potential influence of surface mining on the water quality of the San Juan River, located in the southern region was investigated between 1963 and 1979. Eight analytical techniques were used in this quantification of water quality. None of these techniques showed any increase in TDS (total dissolved solids) or specific conductance in the river down-stream from the mines compared to up-stream values (Goetz, et al., 1987). The difference in water quality between spoil piles and reclamation plots was analyzed between 1978 and 1982 for mining operations at the San Juan Mine and the Navajo Mine. At the San Juan Mine, specific conductance, except for an excursion on April 23, 1982, decreased from 940 to 625 µS/cm one to four years after the spoil pile was graded. The specific conductance of the reclamation plot, again excluding the April 23, 1982 excursion, averaged 480 for five to eight years after reclamation was completed (Goetz, et al., 1987). At the Navajo Mine, specific conductance ranged from 590 to 1,120 µS/cm for the spoil pile three years after construction. Reclamation plots built in 1973 had specific conductivity decreasing from 410 to 275 µS/cm six to nine years after completion. Reclamation plots built in 1978 had specific conductance decreasing from 3,600 to 1,330 µS/cm measured just one year after completion. The specific conductance of the San Juan River, that receives runoff from the San Juan Mine, averaged 550 µS/cm throughout the monitoring period of 1973 through 1981 (Goetz, et al., 1987).

3.6.3

Gulf Coast
3.6.3.1 Climate

Generally, a maritime climate prevails along the Gulf coast. Average annual precipitation in the coastal mining area of Texas exceeds 56 inches and other areas have even greater precipitation (see Figure 3.6-13). Evaporation exceeds rainfall for a large part of the western area, reaching as high as 61 inches on the Texas coast (see Figure 3.6-14). There are two basic seasons consisting of a hot summer that may last from April through October, and winter that starts in November and usually lasts until March. Temperatures range from 48°F in January to 88°F (31°C) in August (see Figure 3.6-15). Winds are from the southwest (see Figure 3.6-16).

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Figure 3.6-13

Gulf Coast Region 3 Mean Total Precipitation (Annual)

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Figure 3.6-14

Gulf Coast Region 3 Mean Evapotranspiration (Annual)

2 3

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Figure 3.6-15

Gulf Coast Region 3 Mean Daily Average Temperature (Annual)

2 3

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Figure 3.6-16

Gulf Coast Region 3 Mean Wind Speed (Annual)

2 3 4 5 6 3.6.3.2 Hydrology Regression equations for estimating the 7-day 2-year and 7-day 10-year low flow of ungauged Alabama streams were developed based on geology, drainage area, and mean annual precipitation. The equations are only for natural streams and are applicable throughout the state
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(Bingham, 1982). The rate of stream flow recession was used to account for effects of geology on low flow regimes. The predictive equations are: 7Q2 = 0.24 X10-4(G-30)1.07(A)0.94(P-30)1.51 7Q10 = 0.15 X10-5(G-30)1.35(A)1.05(P-30)1.64 where G is stream flow recession index (cfs); A is contributing drainage area (mi2); and P is mean annual precipitation (inches). 3.6.3.3 Water Quality Surface runoff from three re-vegetated lignite mine spoils and nine native soils on three geologic deposits along the Texas Gulf Coast were evaluated from August 1977 through November 1979 to determine differences in water quality. The percentage of pyrite in the test pit mine spoils ranged from 0.078 to 0.452. Chemical characteristics of the surface runoff from the three revegetated plots were similar. The resulting electric conductivity in all runoff samples was less than 3.0 dS/m throughout the entire study period. Conductivities converged to background soil levels within one year of vegetation establishment (Brown et al., 1984).

3.6.4

Illinois Basin
3.6.4.1 Climate

Precipitation is mainly produced by low-pressure westerly systems entraining southerly winds bearing moist, warm air from the Gulf of Mexico. Occasionally, high pressure cells from the north also create rain, snow and sleet conditions. Average annual precipitation ranges from approximately 39 to 50 inches (see Figure 3.6-17). Precipitation occurs about 120 days per year. Monthly averages from August through October are 20% to 35% less than monthly averages for the remainder of the year. Intense storms usually cover large areas. Pan evaporation averages approximately 40 inches (see Figure 3.6-18). Annual temperatures averages approximately 55°F with a range in monthly temperature from 32 °F in January to 77°F in July (see Figure 3.6-19). Wind direction is primarily from the west (see Figure 3.6-20).

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Figure 3.6-17

Illinois Basin Region 4 Mean Total Precipitation (Annual)

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Figure 3.6-18

Illinois Basin Region 4 Mean Evapotranspiration (Annual)

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Figure 3.6-19

Illinois Basin Region 4 Mean Daily Average Temperature (Annual)

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Figure 3.6-20

Illinois Basin Region 4 Mean Wind Speed (Annual)

2 3 4 5 3.6.4.2 Hydrology Streamflow in the area generally follows a seasonal pattern. The yearly cycle begins in October, which is characterized by being the month of lowest precipitation and lowest streamflow.
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November has a period of increased streamflow, which is maintained through the spring months and into May. Precipitation increases and evapotranspiration decreases helps the flow through the winter months before the spring rains maintain a high level of runoff. The low flow season follows beginning in early June and usually extends into early October. During periods of little or no precipitation, many streams that have drainage areas less than 100 square miles will go dry. This is primarily due to the low permeability and low water storage characteristics of the underlying rock in the area. Drainage area, versus 7-day 2-year discharge, and 7-day 10-year discharge are given in Table 3.6-10 (Quinones, et al., 1983). Most of the sites with drainage areas less than 100 square miles generally have a flow less than 1 cfs for the 2-year discharge and a flow of 0 cfs for the 10-year discharge. Table 3.6-10 Site Number 1 2 5 8 15 27 29 40 49 66 78 82 98 103 117 130 131 132 133 136 140 141 143 144 Drainage Area (Square Miles) 5.34 36.4 357 85.4 30.8 94.3 90.5 42.0 124 194 149 58.2 255 2.1 2.26 8.12 5.16 137 116 20.1 109 88.3 62.3 166 7-Day 2-Year and 7-Day 10-Year Low Flows 7-Day 2-Year Discharge (Cubic Feet Per Second) 0.2 0.3 48 9.0 0.3 0 1.0 0.2 0 0 0 0.1 0.2 0 1.0 1.6 0.6 0.9 0.3 0 0 0 0 0 7-Day 10-Year Discharge (Cubic Feet Per Second) 0 0 36 5.7 0 0 0 0 0 0 0 0 0 0 0.8 1.1 0.4 0.5 0 0 0 0 0 0

12 13 14 The area is characterized by frequent flooding during the spring months. Due to the hilly topography, flash floods often occur in the headwater areas of streams. Floods peak slowly at
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sites with gentle stream gradient and relief and peak quickly on small streams with steeper stream gradients. The Ohio River also adds flooding from its backwater. Data recorded since 1930 at various sites in the area show maximum peak discharges from 17 to 117 cfs/mi² (Quinones, et al., 1983). Approximately 75 percent of flooding occurs between January and April (McCabe, 1962). Regression equations were developed to estimate the magnitude and frequency of floods for sites located throughout western Kentucky. These equations were based on the drainage area and geographical factor for each site. These equations were developed by McCabe (1962) and Hannum (1976) (see Table 3.6-11). In each equation, Q(x) is the discharge of the (x) year flood in cfs, A is the drainage area in square miles, and R is the geographical factor, which is related to the geology and topology. Table 3.6-11 Flood Frequency (years) 2 5 10 25 50 100 Estimation of Peak Flood Magnitude Flood Magnitude (cfs) Standard Error (%) 31.8 29.5 29.5 30.6 31.8 33.3

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 In this equation, Y is the dissolved solids concentration, in mg/L, and X is the specific conductance, in µS/cm. Specific conductance values ranged from 48 to 4750 µS/cm and dissolved solids concentrations ranged from 46 to 4,520 mg/L (Quinones, et al., 1983). The areas with the highest specific conductance and dissolved solids values were those located near mining operations. High sulfate concentrations in the waters of an area are usually an indicator of coal mine activity and drainage. For the observed area, the sites with coal mine activity had the highest concentrations of dissolved sulfates. These concentrations were in the range of 12 to 2,700 mg/L, with most having a concentration greater than 200 mg/L. Sulfate concentrations in areas
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3.6.4.3 Water Quality Specific conductance is often used to estimate specific ion concentrations in streams. The Illinois Coal Region, areas affected by mining have a higher dissolved solids concentration than areas that are unmined. A general correlation was found for the entire area, including both mined and unmined, and is presented by the following equation:

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with no coal mining activity or minimal coal mining activity had concentrations that were generally less than 30 mg/L. Sulfate concentrations were significantly correlated with specific conductance in the area (see Figure 3.6-21) (Quinones, et al., 1983). These data showed a higher correlation between sulfate and specific conductance at mined lands than at unmined lands. Figure 3.6-21 Specific Conductance

6 7 8 9 10 11 12 13 14 15 Surface mine lakes Surface mine lakes are primarily formed from the final dragline cut that is left to fill with runoff. However, lakes can also be formed through depressions of spoil caused by subsidence, topography associated with uneven backfill, and impoundments associated with coal processing. The water quality of 107 surface mined lakes in southern Illinois was assessed between June and August 1983. Lake size ranged from 8.8 to 210 acres. Of primary interest was the specific conductance of the lakes. Specific conductance ranged from 130 to 7,800 µS/cm. The largest specific conductance values ranged from 2,000 to 5,000 µS/cm, (Voelker, 1985). It should be noted that lake water quality may reflect mining methods that were prevalent in the 1980s.

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3.6.5

Northern Rocky Mountains
3.6.5.1 Climate

The climate in the area is significantly affected by the mountains along the Pacific coast and the Rocky Mountains. Annual precipitation in the mountains exceeds 25 inches and the plains receive approximately 10 to 16 inches (see Figure 3.6-22). Most precipitation occurs as snowfall from November through April with greater than 100 inches in the mountains and 30 to 75 inches in the plains. Much of the snow in the plains is sublimated. Precipitation during the summer months primarily occurs as light showers with occasional intense thunderstorms.

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Figure 3.6-22

Northern Rocky Mountains Region 5 Mean Total Precipitation (Annual)

2 3 4 Evapotranspiration is greatest in July and continues to be significant throughout the fall because of the warm soils (see Figure 3.6-23). Daily air temperature average 75 °F in July and 25 °F in
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January (see Figure 3.6-24). Wind highly influences the climate with westerly winds prevailing at an average velocity of 13 mile per hour (see Figure 3.6-25). Figure 3.6-23 Northern Rocky Mountains Region 5 Mean Evapotranspiration (Annual)

4
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Figure 3.6-24 Northern Rocky Mountains Region 5 Mean Daily Average Temperature (Annual)

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Figure 3.6-25

Northern Rocky Mountains Region 5 Mean Wind Speed (Annual)

2 3 4 5 3.6.5.2 Hydrology The average annual runoff volume, peak flow, and low flow characteristics of seven sites in the eastern Powder River Basin were determined prior to mining. The average annual runoff for the
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seven analyzed sites was 0.185 inches or 1.3 percent of the average annual precipitation of 14 inches. Annual runoff ranged from 0.069 to 0.392 inches for the sites (Martin et al., 1988). Peak flow (Q in cfs) for the undisturbed areas is related to drainage area (sq. mi.), average basin slope, Sb (ft/mi), maximum drainage basin relief, RM (ft) and main channel slope, S at 10 and 85% stream distance above point of interest (ft/mi). Peak flow relationships were developed for 2-, 5-, 10-, 25-, 50-and 100-year recurrence intervals (Craig and Rankl, 1978). These relationships were based on 8 years of data at 22 sites and extended to the 100-year storm using rainfall-runoff modeling techniques. The 10-year peak flow for undisturbed land is: Q10 = 32.99 A1.094 X Sb1.08 X RM-1.308 X S10/850.603 The above equation is valid for areas between 0.69 and 10.8 sq. mi., basin slopes between 240 and 929 ft/mi, channel slope between 59 and 204 ft/mi, and maximum basin relief between 173 and 752 ft. Similar equations were developed for watershed areas between 10.8 and 5,270 mi2, (Lowham, 1976). There is a 90 percent and 87 percent probability of having 1 to 3 and 7 to 14 consecutive days with no flow based on analysis of one flow monitoring station (Druse, et al., 1981). Ephemeral streams normally have small flows during spring snowmelt and during early summer rainstorms (Cannon, 1985). Infiltration rates can provide insight to subsequent changes in runoff potential due to mining. The infiltration rates, based on using a rainfall simulator, on natural soils that consisted of heavy, medium and light soils ranged from 0.6 to 2.6, 1.9 to 3.5 and 2.1 to 3.8 in/hr, for 1979, 1981 and 1983, respectively (Gifford, 1983). Much of the surface hydrology generated for the region is based on flow through spoil that has replaced the coal beds and sandstone aquifers. After mining the groundwater flow system is established within the placed spoils. Rainfall directly infiltrates into the spoil and additional water enters into the spoil through adjacent coal and limestone aquifers. The quantity of flow being discharged to streams is related to direct recharge from precipitation and the hydraulic characteristics of the spoil such as spoil porosity and permeability. The infiltration rates, based on using a rainfall simulator, on reclaimed soils that consisted of heavy, medium and light soils ranged from 0.7 to 2.8, 0.6 to 2.4 and 0.3 to 2.8 in/hr, for 1979, 1981 and 1983, respectively (Gifford, 1983). Thus, infiltration rates were lower than natural soils for the medium and light soils for the first year after reclamation and approached premining rates within six years after reclamation. 3.6.5.3 Water Quality Specific conductance for Otter Creek located in southern Montana had an average daily mean of 3,260 and 2,920 µS/cm for 1983 and 1984, respectively (Cannon, 1985). The calculated annual load was 7,311 tons of dissolved solids (Cannon, 1985) based on three years of records.

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The potential for an additional contribution of specific conductance from mine spoil was calculated based on a saturated extract assessment of 506 overburden samples. A regression relationship between dissolved solids and specific conductance was developed. TDS = 0.762 (specific conductance) -222 The TDS (mg/L) from the saturated extraction method for overburden predominately ranged from 1,510 to 7,375 µS/cm (Cannon, 1985). It is difficult to acquire statistically reliable median annual sediment yield data for semi-arid areas due to the infrequency of rainfall, especially for the small drainage area of ephemeral streams. Sediment records are often not of sufficient length for statistical analysis. Without a sufficient data base only general observations can be stated. Based on seven years of sediment yield data for an undisturbed area of nearly 500 mi2, the annual suspended sediment yield was 0.5 tons/mi2 (Martin, et al., 1988). Erosion rates of heavy, medium and light natural soils were obtained from a rainfall simulator study conducted in 1979, 1981 and 1983 (Gifford, 1983). The average erosion rates based on 10 plots, three timeframes, and three soil types decreased overtime (see Table 3.6-12). Such decreases in erosion rates were found in other studies and are often due to the early removal of easily eroded soil particles and subsequent armoring of the surface soil by rock fragments. Erosion rates for the reclaimed soil were 2 to 3 times, 5 to 20 times, and 5 to 10 times higher than natural soils for the heavy, medium and light soils, respectively. Table 3.6-12 Year 1979 1979 1979 1981 1981 1981 1983 1983 1983 Erosion Rates for Natural and Reclaimed Heavy, Medium, and Light Soils Soil Type Heavy Medium Slight Heavy Medium Slight Heavy Medium Slight Natural Soil Erosion Rate (tons/mi2) 133 21 31 62 17 25 30 6 4 Reclaimed Soil Erosion Rate (tons/mi2) 497 400 359 132 98 85 100 78 22

21 22 23 24 25 Selenium levels for the eastern Powder River Basin study area generally did not exceed 10 ppb except for samples that had iron and manganese concentrations greater than U.S. EPA secondary public water supply standards (Larson, 1987).

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3.6.6

Northwest
3.6.6.1 Climate

The currently producing coal region of concern in the Northwest Region includes only the State of Alaska, particularly interior Alaska. The continental climate of interior Alaska has a wide range of air temperature between summer and winter and large fluctuations around the seasonal means. Mean annual temperatures in the Tanana Valley average 26.4˚F at the Fairbanks International Airport, with the warmest month, July, averaging 61.3°F, and the coldest (January) averaging -10.3˚F (1917 to 2000 averages). However, these averages do not present a good picture of either the summer or winter air temperatures. For example, in the Tanana Valley, periods of extreme cold ranging in the vicinity of -40°F to -49˚F are not uncommon at any time from late November through February. In contrast, daily maximum temperatures occasionally reach 90˚F to 98.6˚F in June and July, often with only modest night cooling because of persistent daylight. (Bonanza Creek Long-Term Ecological Research website, http://www.lter.uaf.edu/bnz_climate.cfm, accessed 10-19-2010). Records show that Alaska has warmed substantially over the 20th century, particularly over the past few decades (Overpeck, et al., 1997). Since the 1950s, average warming has been 4°F (2°C) across the state. The greatest warming, about 7°F (4°C), has occurred in the state’s interior in winter (Chapman and Walsh 1993; Weller et al., 1998). The growing season has lengthened by more than 14 days since the 1950s (Keyser et al., 2000). In 2004, Denali National Park and Preserve headquarters recorded the warmest mean monthly temperatures for May, June, and August based on an 80-year National Weather Service record… Elevations range from sea level to 20,320 feet. Latitudes span from 55 degrees north to more than 65 degrees north. Climate in this vast area is extremely variable, ranging from strongly maritime to strongly continental, with large differences in temperature and precipitation. (Natural Resource Year in Review, 2004, accessed at http://www.nature.nps.gov/YearInReview/yir2004/01_E_lit.html, date 10-19-2010) Annual precipitation in interior Alaska is low and decreases from west to east, with a 50-year average for Fairbanks of 11.3 inches and a range from 5.6 inches in 1957 to 18.8 inches in 1990. Most summer and winter precipitation is generated from major frontal systems that cross the State, but convective storms add significantly to the summer precipitation. Precipitation events in early summer (May, June, and early July) are typically light and showery, with high spatial variability. The relatively dry summer conditions are replaced by the fall rain events, which can be heavy and sustained. On average, precipitation increases through the summer. There is considerable variability in annual precipitation in Alaska with low precipitation years, such as 1957, generating frequent wildfires, while high-precipitation years, such as 1967, often result in flooding. Although precipitation during the growing season may be low, evaporation rates are also low because of the relative short growing season and cool temperatures. Nonetheless, as much as 76 to 100 percent of the summer precipitation may be lost as evapotranspiration (Dingman 1966). Thus much of the summer precipitation probably derives from recycling of water that evaporated from land (Serreze and Etringer 2003). Based on precipitation data from the Fairbanks Airport (1948-2000), snowfall accounts for about 35% of the yearly total precipitation (range 13-77%, standard deviation = 13%). Little winter snowmelt occurs due to
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typically below-freezing temperature throughout the winter. (Bonanza Creek Long-Term Ecological Research website, http://www.lter.uaf.edu/bnz_climate.cfm, accessed 10-19-2010). 3.6.6.2 Hydrology The Yukon River is composed of many streams and rivers. Utilizing the Alaska Hydrologic Unit Classification system (U.S. Geological Survey, 1987) and a somewhat similar classification system for Canada, the Yukon River Basin can be divided into 13 major basins. These basins represent the eight major tributaries to the Yukon River and the major lowland areas that drain directly into the Yukon River. (Brabets, et al., 2000). The Tanana River Basin encompasses the Alaskan coal mining area within the overall Yukon River Basin. The Tanana River Basin is approximately 44,300 square miles in area, and primarily drains the north side of the Alaska Mountain Range, including glaciers. Three basic patterns of runoff are exhibited throughout the Yukon River Basin: lake runoff, snowmelt runoff, and glacier runoff. Generally, beginning in October and ending in late April to mid-May, runoff is minimal and streamflow gradually decreases. Most runoff occurs from May to September; however, the timing of runoff in the rivers is different, depending on the particular basin characteristics. (Brabets, et al., 2000). During the snowmelt period, (generally late April) snow is released as stream-flow over a relatively short period, making snowmelt the major hydrological event of the year. (Bonanza Creek Long-Term Ecological Research website, http://www.lter.uaf.edu/bnz_climate.cfm, accessed 10-19-2010). The overall average discharge of the Yukon River Basin is 227,000 cubic feet per second, with the Tanana River Basin providing approximately 44,600 cubic feet per second of that amount (Brabets, et al., 2000). Due to glacial activity within the Tanana River Basin, that basins percentage of flow contribution is greater than its percentage of drainage area to the overall Yukon River Basin. In the Yukon River Basin, annual high flows for most of the major rivers occur during the summer rainy season. However, on the main stem of the Yukon, flooding commonly occurs from ice jams in the spring. Although levees have been built at Dawson to prevent flooding from ice jams, villages located along the lower part of the Yukon River are still subject to flooding each spring. Since 1949, three major floods have occurred in the Yukon River Basin: in 1964, 1967, and 1994. These floods covered large areas of the basin and caused considerable property damage. The 1967 flood involved a 10-inch rainfall in the middle and lower Tanana River Basin near Fairbanks, which was nearly the average annual precipitation for the area. Flood discharge on the Salcha River at Fairbanks was almost twice that of a 100-year recurrence interval. 3.6.6.3 Water Quality The chemistry of the Yukon River reflects the chemical inputs from its major tributaries. The waters of the tributaries to the Yukon are predominantly calcium magnesium bicarbonate waters with specific conductance ranging from 54 to 373 S/cm. Specific conductance values in the Tanana River at Nenana have a mean value of 243 S/cm. Data show that nitrate concentrations are highest in the Tanana and Porcupine Rivers, and the Tanana River also has the highest totalphosphorus concentrations with a median concentration of 0.17 mg/L phosphorous.
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Concentrations of both total iron and total manganese, with median concentrations of 7,000 and 200 g/L respectively, are highest in the Tanana River, perhaps reflecting the presence of glaciers. Mining activity has, and continues to be, an important economic industry in the Yukon River Basin. Probably the biggest concern of mining is the possible harm to fish-spawning areas. Although today’s mining practices are highly regulated to prevent damage to fish habitat, many old abandoned mine areas remain. One example is Coal Creek, located in Yukon-Charley Rivers National Preserve. This particular watershed was mined extensively in the early 1900’s and the mining practices used at the time had a severe impact on the watershed. The site was declared a Superfund site by the U.S. Environmental Protection Agency and cleanup was completed in 1998. (Brabets, et al., 2000).

3.6.7

Other Western Interior
3.6.7.1 Climate

The general climate of this region is continental affected primarily by alternative masses of warm moist air from the Gulf of Mexico and cold, comparatively dry air from the northern polar regions. Hence, there are large variations in precipitation and temperature. Average annual precipitation ranges from approximately 34 inches, in the western area increasing to greater than 40 inches towards the east (see Figure 3.6-26). About 70 percent of precipitation occurs in the growing season from April through October. Rainfall occurs either in intense thunderstorms of short duration or longer storms that cover greater areal extent. The 10-year 24-hour storm is approximately 5 inches. Evaporation increases from east to west, varying from approximately 46 to 40 inches, thereby generally exceeding rainfall from May through October (see Figure 3.627). Average temperature averages about 56 °F with July usually the warmest month with an average daily maximum of 91°F and an average daily temperature of 69°F. January is the coldest month with the average daily maximum and minimum of 40°F and 21°F, respectively (see Figure 3.6-28). Winds are generally out of the west (see Figure 3.6-29).

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Figure 3.6-26

Other Western Interior Region 7 Mean Total Precipitation (Annual)

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Figure 3.6-27

Other Western Interior Region 7 Mean Evapotranspiration (Annual)

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Figure 3.6-28 Other Western Interior Region 7 Mean Daily Average Temperature (Annual)

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Figure 3.6-29

Other Western Interior Region 7 Mean Wind Speed (Annual)

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3.6.7.2 Hydrology Daily and seasonal variations in precipitation cause considerable differences in monthly and yearly flow patterns and volumes. Lowest flows occur during period of little or no precipitation, usually in the late summer when evapotranspiration rates are high, or in the late winter. The highest flows of the year occur in spring and early summer. Average annual flows can be estimated by using the equation, Qa = 0.08 A0.95 where average annual streamflow (Qa) is in cubic feet per second and drainage area (A) is in square miles. Most unregulated streams with drainage areas less than 50 square miles will cease to flow for 7 or more consecutive days in 50 percent of the years. Low flows of most streams are not sustained during droughts because there are few aquifers capable of providing substantial quantities of ground-water inflow. Few unregulated streams continue to flow during droughts. Frequency of flooding is expressed as a probability of occurrence, or recurrence interval. Flood frequency equations (see Table 3.6-13) were developed by Jordan and Irza (1975) for Kansas streams and by Hauth (1974) for Missouri streams. The equations, which are applicable to unregulated streams only, may be applied to all areas of 0.4 square mile or greater. Table 3.6-13 Recurrence interval, t, in years Flood Frequency Equations for Kansas and Missouri Streams C X Y Standard error, in percent

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Kansas streams: Qt = Ct Axt P2yt (from Jordan and Irza, 1975) 2 0.707 0.548 4.752 42.5 5 3.98 .530 4.021 41.5 10 9.92 .525 3.591 43.0 25 25.6 .524 3.127 48.0 50 7.6 .523 2.821 53.0 100 83.8 .524 2.529 58.0 x A-0.02 y Missouri streams: Qt = Ct A t St (from Hauth, 1974) 2 53.5 0.851 0.356 38.6 5 64.0 .886 .450 34.7 10 67.6 .905 .500 34.5 25 73.7 .924 .542 35.0 50 79.8 .926 .560 33.3 100 85.1 .934 .576 33.3 Q = flood peak, in cubic feet per second for t-year recurrence interval A = drainage area, in square miles S = slope, in feet per mile between points 10 and 85 percent of the distance along the main stream channel from the site to the basin divide
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P2 = 24-hour rainfall amount, in inches, for 2-year recurrence interval (Hershfield, 1961), determined at the centroid of the basin. *Equations only apply to unregulated natural streams. Steep slopes of flow-duration curves for unregulated streams indicate highly variable flows. The flow-duration curve is a cumulative frequency curve that shows the percentage of time that a flow rate was exceeded (Searcy, 1959). A steep slope indicates highly variable flow, whereas a flat slope indicates more uniform flow, which can be a result of ground- or surface-water storage contributions. Typical flow-duration curves indicate similar flow characteristics for unregulated streams in this area. The slopes are steep, indicating most streamflow is from direct surface runoff. The flow of these streams is not well sustained during dry weather because there are few aquifers capable of providing substantial quantities of ground-water inflow. Annual surface runoff volume for a mining site in western Missouri was analyzed from 1984 to 1986. Surface runoff, 31.5 in, accounted for 32 percent of the 2-year precipitation of 99 in with the remaining 68 percent being lost to evapotranspiration (Blevins and Ziegler, 1992). Runoff was reduced due to increased ponding behind spoil ridges. After reclamation, which consisted of flattening spoil ridges and vegetation there was reported a slight decrease in runoff volume to 28 percent of the precipitation of 50.4 in occurring between Nov. 1988 and May 1990. The slight decrease may simply be reflective of the lower precipitation and evaporative demand during the monitoring period. 3.6.7.3 Water Quality Groundwater discharge from coal-mined areas causes large concentrations of dissolved solids in receiving streams during low-flow periods. The streams that have the largest mean concentrations of dissolved solids are small streams that drain extensively coal-mined areas. Several of the streams that drain mined areas have mean concentrations of dissolved solids less than 375 mg/L because most of their flow is from unmined areas. Streams impacted by coalmine drainage have the largest in-stream concentrations of dissolved-solids during low-flow periods when ground-water discharge from the mined areas is a significant part of the streamflow. The regression equations (see Figure 3.6-30) are valid for the range of dissolved solids concentrations and specific conductance values used to compute them.

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Figure 3.6-30

Mean Specific Conductance

2 3 4 5 Sulfate derived from oxidation of sulfide minerals is the primary chemical constituent indicating coal-mine drainage. Mean concentrations of sulfate are directly related to the percentage of the drainage area that has been strip mined (see Figure 3.6-31).

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Figure 3.6-31

Percentage of Drainage Area Strip Mined

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Maximum total recoverable-iron concentrations for 16 of the streams draining coal-mined in Kansas and Missouri and three of the streams draining unmined areas exceeded the maximum permissible limit established by the Surface Mining Control and Reclamation Act of 1977. A significant correlation usually existed between total recoverable-iron and suspended-sediment concentrations. The regression equation describing the relationship for streams draining unmined areas is: TFe = 86.6 SSC0.80 where TFe is the total recoverable-iron concentration, in micrograms per liter; and SSC is the suspended-sediment concentration, in milligrams per liter. The regression equation for streams draining coal-mined areas is: TFe = 84.4 SSC0.78. The relationship between coal-mined and unmined areas is presented in Figure 3.6-32. As indicated by the slope of the line, the total recoverable iron concentration increases with increasing suspended sediment concentration.

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Figure 3.6-32

Suspended Sediment Concentration

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Mean concentrations of total recoverable manganese range from 50 to 1,600 micrograms per liter on streams draining unmined areas and range from 12 to 5,900 micrograms per liter on streams draining coal-mined areas. Three types of mine lakes were designated for a study conducted in western Missouri: 1) shallow perched lakes, < 8 ft in depth and receiving runoff from spoil ridges, 2) shallow groundwater supplied lakes, and 3) deep lakes, > 9 ft in depth and predominately supplied by groundwater. The specific conductance of shallow perch lakes, shallow groundwater-supplied lakes and deep lakes ranged from 1,620 (single value), 1,180 to 4,600 and 2,110 to 3,550 µmho/cm, respectively. Sulfate was a large component of specific conductance ranging from 960 for shallow perched lakes, 640 to 3,100 for shallow groundwater-supplied lakes, and 1,200 to 2,300 mg/L for deep lakes, respectively (Blevins and Ziegler, 1992). The specific conductance of surface runoff from unmined lands ranged from 280 to 1,100 µS/cm and after mining values ranged from 500 to 3,470 µS/cm. Similar to the lake studies, sulfate was the primary constituent of surface runoff from spoil, ranging from 250 to 2,400 mg/L (Blevins and Ziegler, 1992).

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3.6.8

Surface Effects of Underground Mining

Underground mining, over time, usually results in some level of subsidence, which damages the land above and adjacent to the mine. Two categories of underground mining are typically implemented: room and pillar (or low extraction) and planned subsidence (high extraction). Planned subsidence methods can include longwall, shortwall, pillar extraction and retreat mining. These planned subsidence methods all plan for and allow the roof of the mined area to collapse as the mining is moved forward. With respect to surface hydrology, the major concern with subsidence is how streams and other surface water features are affected by this lowering and fracturing of the land surface. Existing streams and ponds can be dewatered due to flow diversion into the fractured underlying rock strata created by the subsidence and into the mine voids below. However, despite the prevalence, the effects of underground coal-mining-related land subsidence on overlying hydrologic systems generally are complex and poorly understood, particularly when the depth of overburden is shallow (less than 500 ft). (USGS Scientific Investigations Report 2007-5026). The effect from underground coal mining on hydrologic systems can range from minimum to severe depending upon mining method, depth to mining, overburden depth, and mined seam overburden stratigraphy and structure. (Gayla, Thomas A., 2008). Gayla further writes that subsidence theory indicates a subsidence profile develops where mining impacts can extend upwards 30 to 60 times the mining height (Kendorski, 1993). In addition to the subsidence fracturing, natural stress relief fracturing can extend downwards to depths of 80 feet (Kipp and Dinger, 1991). In overburden strata less than 60 times mined thickness, it is possible that stress relief and subsidence-induced fracturing can intersect, resulting in a direct hydraulic connection between the surface and fractured strata overlying the mines. There are 5 zones that have been identified by Kendorsky (1993) for high extraction mining impacts on the mined roof overburden (descending stratigraphically). Figure 3.6-33 illustrates these 5 zones: 1. Surface Fractured zone-zone of potentially vertically transmissive surface cracks 2. Constrained Zone- Zone no significant effect on transmissivity or storativity. 3. Dilated Zone- Zone of increased storativity with little or no vertical transmissivity (24-60 x Mine Height) 4. Fractured Zone- Zone of vertically transmissive fractures (6-10 x Mine Height) 5. Caved Zone- Zone of complete disruption to the roof rock (6-10 x Mine Height) Aquifer dewatering is enhanced by enlargement of existing fractures or opening of new fractures above the zone of caving during a subsidence event. Both represent an increase in permeability and porosity that could result in dewatering aquifers or streams. Dewatering of the aquifer is usually limited to active mining areas. As the strata settles and becomes re-compressed, groundwater levels may rebound as flow paths to the mine become more restricted and less direct. These fractures may heal themselves with time if sufficient amount of clay and shale
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material are in the strata. On the other hand, if the strata are friable sandstone units with little silts and clays, the ability of the fractures to heal is diminished. (Borch, 2009) Figure 3.6-33 Five Zones for High Extraction Mining Impacts on Mined Roof Overburden

5 6 7 8 9 10 11 12 13 14 The various underground mining techniques have different impacts on hydrology. Room and pillar method effects are generally more localized, irregular in shape, and often long-delayed in occurrence. Longwall subsidence effects are more immediate, pervasive, systematic and predictable (Booth, 1997) 3.6.8.1 Potential Impacts on Streams and Surface Waters Rauch (1985) describes dewatering impacts of room-and-pillar mining in the north central Appalachians as follows: Typically the greatest groundwater inflow rates occur near the working face of the mine where groundwater is being drained from storage, especially from fractures
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in mine roof rocks. In older mine sections, long term groundwater recharge to the mine is under more or less steady state conditions, originating ultimately from infiltration of precipitation or surface water .… This water typically enters the mine along rock fractures that intersect the mine ceiling, especially along vertical fracture zones …. Groundwater inflow is especially great in areas of mine ceiling collapse due to the leaving of too little roof rock support or to weak ceiling rock where fracture zones intersect the mine. This drainage to room-and-pillar mines dewaters some overlying aquifers. The extent of this drainage is best determined from studies of water wells and springs overlying the mines. In general, significant dewatering extends to 20 to 100 feet vertically above drained room-and-pillar mines, but is usually restricted to within about 40 feet vertically of these mines. Localized, significant hydraulic impacts of deep headings and uncollapsed roomand-pillar mines will be seen in shallow aquifers only in areas (such as fracture zones) where vertical hydraulic connections are naturally high or where the mine itself is very shallow (Booth, 1986). Shallow room-and-pillar mining (within 200 feet (61 m) and particularly within 100 feet (30.5 m) of the surface) drastically increases the likelihood of significant impacts to surface waters. High extraction mining can result in profound changes to surface water resources above or nearby a mine site. Carver and Rauch (1994) drew the following conclusions regarding impacts to streamflow based on their study of a longwall mine in West Virginia: Subsidence from longwall mining typically reduced stream discharge for two to three years. Panels positioned beneath upland catchment areas and not under streams caused no apparent stream dewatering …. Monitored stream reaches within the angle of draw zone of an adjacent panel did not normally become dewatered for panels older than 2.3 years. However, stream reaches in basins less than 200 acres in size often experienced dewatering for up to 3.1 years after undermining …. After two to three years since mine subsidence occurred recovered streams display lower high base flow and higher low base-flow discharge, or more uniform base-flow discharge, compared to unsubsided streams …. Water diverted from affected streams and supplies remained in the shallow groundwater flow system and probably did not penetrate deeper than local base level, as shown by the reported low groundwater inflow rate to the mine and by the most impacted streams having returned to "normal" flows down-gradient. The lost waters probably moved down-gradient as underflow through shallow aquifers and then returned to streamflow in unsubsided or recovered areas.

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