Effects of Underground Mining and Mine Collapse on the Hydrology of Selected Basins in West Virginia United States Geological Survey Water-Supply Paper 2384 Prepared in cooperation with the West Virginia Geological and Economic Survey METRIC CONVERSION FACTORS AND VERTICAL DATUM Multiply By To obtain Length inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) Area square mile (mi2) 2.590 square kilometer (km2) acre 0.4047 hectare (ha) Volume gallon (gal) 3.785 liter (L) 3.785xlO~3 cubic meter (m3) million gallons (106 gal) 3,785 cubic meters (m3) 3.785xlO~3 cubic hectometers (hm3) cubic foot (ft3) 0.02832 cubic meter (m3) Flow cubic foot per second (ft3/s) 28.32 liter per second (L/s) 0.02832 cubic meters per second (m3/s) gallon per minute (gal/min) 0.06309 liter per second (L/s) 6.309xlO~5 cubic meters per second (m3/s) million gallons per day (Mgal/d) .04381 cubic meters per second (m3/s) Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929. Effects of Underground Mining and Mine Collapse on the Hydrology of Selected Basins in West Virginia By W.A. HOBBA, Jr. Prepared in cooperation with the West Virginia Geological and Economic Survey U.S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 2384 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government UNITED STATES GOVERNMENT PRINTING OFFICE: 1993 For sale by U.S. Geological Survey, Map Distribution Box 25425, Bldg. 810, Federal Center Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Hobba, W. A. (William A.) Effects of underground mining and mine collapse on the hydrology of selected basins in West Virginia / by W.A. Hobba, Jr. p. cm. (U.S. Geological Survey water-supply paper : 2384) "Prepared in cooperation with the West Virginia Geological and Economic Survey." Includes bibliographical references (p. ). 119.13: 2384 1. Mineral industries Environmental aspects West Virginia. 2. Mine subsidences Environmental aspects West Virginia. 3. Water, Underground Pollution West Virginia. I. West Virginia Geological and Economic Survey. II. Title. IN. Series. TD428.M56H631992 91-31953 551.49-dc20 CIP CONTENTS Glossary IV Abstract 1 Acknowledgments 1 1.0 Introduction 2 1.1 Purpose and Scope 2 1.2 Surface Expression of Underground Mine Collapse 4 1.3 Source and Movement of Ground Water 6 2.0 Mined Bed Above Major Streams or Rivers 10 2.1 Mining and Subsidence Norton, W. Va., Area 10 2.1.1 Mining History and Methods 10 2.1.2 Subsidence and Reclamation 12 2.2 Streamflow 16 2.2.1 Base Flow 16 2.2.2 Flow Duration 18 2.2.3 Stream Seepage Measurements 20 2.3 Stream Quality 22 2.3.1 Specific Conductance at Low Flow 24 2.3.2 pH at Low Flow 26 2.4 Ground Water 28 2.4.1 Areal Water Levels 28 2.4.2 Fluctuations 30 2.5 Aquifer Characteristics of Subsided Area 34 2.6 Water Budget 36 3.0 Mined Bed Below Major Streams or Rivers 38 3.1 Mining and Subsidence Farmington, W. Va., Area 38 3.1.1 Mining History and Methods 38 3.1.2 Subsidence History and Effects 40 3.1.3 Orientation of Subsidence Fractures 42 3.2 Streamflow 44 3.2.1 Base Flow 44 3.2.2 Flow Duration 48 3.2.3 Stream Seepage Measurements 50 3.3 Stream Quality 52 3.3.1 Specific Conductance at Low Flow 52 3.3.2 pH at Low Flow 54 3.3.3 Natural Water Quality Compared to That Affected by Mining 56 3.4 Ground Water 60 3.4.1 Areal Water Levels 60 3.4.2 Fluctuations 62 3.4.3 Seepage Points 66 3.5 Aquifer Characteristics of Mined and Unmined Areas 68 3.5.1 Tests Using Streamflow Methods 68 3.5.2 Tests Using Well Methods 70 3.6 Water Budget 74 4.0 How Mine Subsidence Factors Relate to Well, Spring, or Stream Development 76 5.0 Summary 78 6.0 References 79 Contents III GLOSSARY The hydrologic and mining terms pertinent to this report are defined as Microsiemens the unit used in reporting specific conductance of water follows: per centimeter at 25 °C. Anticline an upward fold in the rocks. Overburden rock and soil overlying a minable coal bed. Aquifer rock formation that contains sufficient saturated permeable Perched water table a saturated zone of rock separated from an material to yield significant amounts of water to wells or springs. underlying unconfined aquifer by unsaturated zone. Perched water Aquifer, confined (or artesian) the water level in a well tapping a tables sometimes are associated with a zone of relatively low confined aquifer will rise above the top of the aquifer because of hydraulic conductivity inside the unsaturated zone overlying an hydrostatic pressure. unconfined aquifer. Aquifer, unconfined the water level in a well tapping an unconfined Permeability, intrinsic a measure of the relative ease with which a aquifer will not rise above the water table. porous medium can transmit a liquid under a hydraulic gradient. Base flow a stream is at base flow when all of its flow is derived from pH the negative logarithm of the hydrogen-ion concentration in the ground-water inflow. water. Bedding plane any plane in sedimentary rock, along which sediment Porosity, primary interstices that were created at the time the rocks was deposited simultaneously. were formed. Coefficient of storage the volume of water an aquifer releases, or takes Potentiometric surface an imaginary surface that everywhere coincides into storage, per unit surface area of the aquifer, per unit change in with the static level of water in an aquifer. head. Precipitation, atmospheric water in the form of hail, mist, rain, sleet, Depression, cone of the depression in the water table or other potenti- or snow that falls to the Earth's surface. ometric surface caused by the withdrawal of water from a well. Recovery of pumped well when pumping from a well ceases, the water Dip of rock strata the angle between the horizontal and the bedding level rises (or recovers) toward the level existing (static level) before plane; dip is measured in a vertical plane at right angles to the strike pumping. of the bedding. (See strike of rock strata.) Seepage measurements flow measurements made at various points Drawdown in a well the vertical drop in water level caused by pumping. along a stream to determine if the stream is losing or gaining water. Drift mine a horizontal or nearly horizontal mine passage underground Slug test a well-testing method whereby a known volume or "slug" of that follows a mineral deposit (such as a coal bed) and is entered from water is suddenly injected into or removed from a well, and the the surface. decline or recovery of the water level is repeatedly measured at Evapotranspiration evaporation from water surfaces, plus transpiration closely spaced intervals to determine hydraulic characteristics of the from plants. rocks penetrated by the well. Fault a fracture in the Earth's crust accompanied by displacement of one Specific capacity the rate of discharge of a well, divided by the side of the fracture with respect to the other. drawdown of the water level in the well. Fracture a break in rock that may be caused by compressional or Specific conductance the measured electrical conductance of a unit tensional forces. length and cross section of water, reported in microsiemens (|j,S/cm) Gaming stream a stream, or segment of a stream, that receives water per centimeter at 25 °C. Often referred to as "conductivity." from an aquifer. (See losing stream.) Storage coefficient the volume of water an aquifer releases or takes into Gob or spoil the refuse or waste rock material displaced by mining. storage per unit surface area of the aquifer, per unit change in head. Gradient, hydraulic the change of head per unit distance from one point Strike of rock strata the direction of a line formed by the intersection of to another in an aquifer. the bedding and a horizontal plane. (See dip of rock strata.) Ground water water contained in the zone of saturation in the rock. (See Strip mining removal of mineral from beneath the Earth's surface by surface water.) excavation of surface soil and rock, generally in a "strip" parallel to Head the height above a datum plane of a column of water. the mineral outcrop. High wall the exposed vertical or near-vertical rock wall associated with Subsidence a sinking of part of the Earth's surface, such as may result a strip mine or surface mine. from soil compaction, collapse of underground mines, or removal of Hydraulic conductivity a medium has a hydraulic conductivity of unit ground water, oil, or gas. length per unit time, if it will transmit in unit time a unit volume of Subsidence crack a crack or joint in the rock formed or widened as a water at the prevailing viscosity through a cross section of unit area, result of subsidence. measured at right angles to the direction of flow, under a hydraulic Surface water water on the surface of the Earth, including snow and ice.