has farranging effects on water quality

and, therefore, on fish and wildlife.

Drainage from closed mines is particularly acidic in streams in Pennsylvania,

Ohio, northern West Virginia, and Maryland. In contrast, drainage from abandoned mines in southern West Virginia,

Virginia, and eastern Kentucky is rarely

acidic, but in these areas other contaminants such as manganese and selenium

to improve mine-permitting procedures, and may thus enhance the

recovery of coal reserves that might

otherwise not be permitted under

current conditions.

• Secondly, the kinetics of pyrite

(FeS2) oxidation and the formation

of acid drainage from coal mines are

being studied in the laboratory to

through oxidation and the leac

minerals in the remanent coal. 

use the USGS coal-quality dat

(COALQUAL) to interpret geo

parameters that control the am

composition of mineral matter 

Coal, however, is not the only 

tor of contaminants, and so the 

conducting a systematic geolo

geochemical study of strata as

with coal. This study will defin

logic parameters that control th

distribution of minerals in rock

contribute to contaminated coa

drainage.

Presently, the permitting o

mines, as related to potential m

drainage water quality, is base

ical data from analyses of core 

from coal overburden. These d

collected without regard to geo

information other than litholog

coring study (fig. 1) will provid

geologic information on coal-b

strata and quantify the spatial v

of minerals such as pyrite (FeS

siderite (Fe2CO3), which contr

contaminated mine drainage.

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact She

Figure 1. Distribution of

coal-bearing strata in the

Appalachian region study

area. Dots indicate corehole locations. Green,

areas having a low potential for acid mine drainage

(AMD) from surface mining; red, areas having

high AMD potential; yellow, areas having intermediate AMD potential.
Kinetics of Pyrite Oxidation

The acidity of coal-mine drainage is

caused primarily by the oxidation of the

mineral pyrite (FeS2), which is found in

coal, coal overburden, and mine waste

piles. Pyrite oxidation and the consequent

generation of sulfuric acid have long been

recognized as major contributors to acid

rock drainage, yet pyrite reactivity remains

poorly understood. Some studies have suggested that pyrite reactivity is inversely

related to particle size; other studies suggest that this relation is not always valid.

For example, some varieties of megascopic pyrite are stable for years once exposed

to the atmosphere, while other varieties

begin to oxidize almost instantaneously.

Empirical results show that some coalmine sites that appear to have similar sulfide contents and geologic settings have

very different acid mine drainage (AMD)

susceptibilities. These differences may be

related to trace element occurrences in the

pyrite crystal structure rather than to pyrite

particle size and surface area. Arsenic is

generally the most abundant minor constituent in pyrite, and its presence is thought

to destabilize the pyrite structure, thereby

making the pyrite more reactive. The USGS

is further evaluating pyrite structure and

composition to improve predictions of

surface recharge. These mines may act as

a single hydrologic unit (“pool”) if coal

barrier pillars fail between mines. Water

quality in the mines varies from nearly

potable in southern West Virginia and eastern Kentucky to acidic water having high

metal concentrations in the northern part

of the Appalachian coal region. Mine

pools in the Pittsburgh coal bed are of particular concern because of the vast areas of

past and present mining (fig. 2). Water

from abandoned mines along the eastern

side of the Pittsburgh coal bed is being

pumped and treated to prevent direct

mine-water discharge into the Monongahela River drainage basin. In contrast,

abandoned mines along the west side of

the Pittsburgh coal bed (in the vicinity of

the Ohio River) have had slower surface

recharge, and their current surface discharge is minimal.

Because the impact of drainage from

future mining is largely unknown, the

USGS is developing a three-dimensional

geologic model where scenarios can be

tested to determine the size of barrier pillars necessary to prevent hydrologic connection between the eastern and western

mined areas of the Pittsburgh coal bed. A

“worst-case” scenario, in which barrier pillars fail and mine pools connect across the

• the factors that control the 

of pyrite—the primary cau

mine drainage

• the potential for drainage 

doned underground coal m

• improved methodologies f

treatment of waters discha

coal mines

The goal of these activities is to 

the technologies underlying the 

(prevention), mitigation, and re

of contaminated mine drainage 

with coal extraction. As these g

achieved, the recovery of coal r

will be enhanced.

For more information, please 

C. Blaine Cecil

U.S. Geological Survey

956 National Center

Reston, VA 20192

Telephone: 703–648–6415

Fax: 703–648–6419

E-mail: bcecil@usgs.gov

Susan J. Tewalt

U.S. Geological Survey

956 National Center

Reston, VA 20192

Telephone: 703–648–6437

Fax: 703–648–6419

E-mail: stewalt@usgs.gov