GROUNDWATER QUALITY OF AN AREA IMPACTED BY ACID MINE DRAINAGE, STARK CO. OHIO
MILLER, Steve and A. FOOS, Geology Department, University of Akron, Akron Ohio 44325-4101
Presented at the North Central Geological Society of America 33rd Annual Meeting, 4/22/99. GSA Abs. & Prog. V. 31, no. 5, p. A61.
ABSTRACT
Throughout this century coal has been and continues to be mined in southern Stark
County, Ohio resulting in Acid Mine Drainage (AMD). This has effected both the local
surface and the ground water quality. Local geology includes interbedded coals,
shales, and limestone including the Brookville Underclay which acts as a major regional aquiclude,
and occurs at the contact between the Pottsville and the Allegheny Formations.
Seven samples were collected in early spring from domestic wells and analyzed for
temperature, pH, conductivity, dissolved oxygen, total dissolved solids, alkalinity,
HCO3-, Cl-, SO4-2, PO4-3, Na, K, Mg, Ca, Mn, Fe, Si, and Al. Results showed a relationship between
water chemistry and elevation of well depth, which reveled the presence of three
aquifers. One sample with a well depth of 1160 feet in elevation is classified as
a SO4-2/Ca rich water showing evidence of AMD influence, with elevated levels of SO4-2, Mg, Mn, Fe, Al, and TDS at 2067, 223, 46, 47, 5.40 and 2899 mg/l respectively,
and an acidic pH of 4.89. Five samples collected at intermediate well depths classify
as alkaline/carbonate rich waters with a TDS average of 811 mg/l, and showed little
to no influence of AMD. The deepest well (720 fsl) classifies as a Na/Cl rich water
with a TDS of 2996 mg/l. It has a Br/Cl ratio of 1/110 which could be indicative
of a deep basinal brine. Owner and well log indicate original Cl concentration was
slight and has increased with time in this 2 year old well.
Results suggest three aquifers, the upper most which is isolated by the impermeable
Brookville Underclay, shows contamination by AMD. The 2nd or mid elevation aquifer
produces high quality water and the lowest which is contaminated by deep basinal
brines. Results show contamination of upper aquifer by AMD, and an isolation of the
lower aquifers from AMD influence. Contamination of middle wells by brine from the
lowest aquifer is time and depth related.
STUDY AREA
The study area is located in rural southern Stark County Ohio in the Bear Creek Run Watershed. This area is an unglaciated part of Ohio with relief of up to 200 feet per 0.5 miles.
Three Pennsylvanian aged units are present in the area; the Conemaugh, Allegheny,
and Pottsville Formations. These units consist of interbedded shales, sandstones,
coal, underclay and limestone. the area has been strip mined for coal and limestones
for most of this century and abandoned mine spoils occupy approximately 40% of the
drainage basin.
Geology of the study area showing the distribution of Pennsylvanian aged units
.
Areas occupied by strip mine spoils (red).
METHODS
Domestic water well logs were obtained from the Ohio Department of Natural Resources.
The elevation of the wells was determined with a pocket altimeter, corrected for
drift. Water samples were collected for chemical analysis from seven domestic water
wells. Temperature, dissolved oxygen, conductivity and pH measured on site. The samples
were filtered and split in the laboratory with concentrated nitric acid added to
one split as a preservative. The unacidified split was used to determine sulfate
and chlorine by ion chromatography. Metal concentrations were measured on acidified samples
using inductively coupled plasma spectroscopy (Al, Ca, Fe, Mg, Mn, P, and Si) and
atomic absorption (K and Na). Hach methods were used for the determination of PO4-3, and NO3-. Specific ion electrodes were used for F- and Br- analyses.
WATER WELLS
Seven wells were selected for detailed chemical analysis. The two shallowest wells
(2167 and 5900) are extracting water from the Allegheny Formation. The remaining
five wells (8200, 8250, 7925, 8004, 7049) were drilled down to the Pottsville Formation.
Each of these five wells were cased to below 1000 feet, the approximate elevation
of the Brookville Underclay, which separates the Allegheny Formation from the Pottsville
Formation.
RESULTS
PIPER DIAGRAM
The piper diagram was used to classify the water samples. Three distinct water types
were observed. The shallowest well (2167) contained water which was classified as
a sulfate-calcium rich water. The wells of intermediate depth (5900, 8200, 8250,
7925, 8004) were classified as alkaline-carbonate rich waters. The deepest well (7049)
was classified as a sodium-chloride rich water.
TDS vs DEPTH
With the exception of sample 2167, there was an increase in total dissolved solids
with increasing well depth.
EPA DRINKING WATER STANDARDS
None of the water samples met the EPA Total Dissolved Solids Drinking water Standard.
Sample 2167, from the shallowest well did not meet the EPA standards for pH, SO4-2,
Mn, Fe, and Al. The sample from the deepest well din not meet the EPA Cl- standard.
Three samples (7925, 5900, 2167) slightly exceeded the standard for F-.
CONCLUSIONS
Sample 2167 which has a low pH, high TDS and elevated levels of SO4-2, Ca, Mg, Mn,
Fe and Al, was contaminated by acid mine drainage. This sample was collected from
a shallow well that was located on top of an abandoned mine spoil.
Groundwater from the Allegheny Formation is represented by sample 5900. This well
produced good drinking water, however the level of sulfate was elevated relative
to ground water from deeper wells.
Wells of intermediate depth (8004, 7925, 8250, and 8200) produced quality drinking
water, however the TDS values were high. These wells all extracted water from the
Pottsville Formation. The impermeable Brookville Underclay, has isolated this aquifer
from the overlying AMD contaminated aquifer.
The deepest well (7049) produced ground water with a high TDS, and elevated Na and
Cl concentrations. The Br/Cl ratio of 1/110 suggest contamination by a deep basinal
brine. The owner and well log indicate the original Cl concentration was slight
and has increased with time in this 2 year old well, suggesting that pumping of the well
is drawing brines up from below.
Questions and comments on this page should be addressed to Dr. Annabelle Foos
last updated 4-26-99
All original material copyright (c) 1999 by Annabelle Foos. All rights reserved.
