The Biological Recovery of the Clinch River
Following a Fly Ash Pond Spill
JOHN CAIRNS, JR., Professor
KENNETH L. DICKSON, Research Assistant
JOHN S. CROSSMAN, Research Assistant
Department of Biology
Virginia Polytechnic Institute
Blacksburg, Virginia
INTRODUCTION
A dike surrounding a fly ash settling lagoon collapsed, dumping highly caustic
water into the Clinch River killing over 200,000 fish in 90 miles of river in Virginia
and Tennessee. This caustic water was produced at Appalachian Power Company's
700 megawatt steam powered generating plant on the Clinch River at Carbo,
Virginia. Native coal is utilized to produce steam which is subsequently used in the
production of electric power. The native coal has a high ash content resulting in the
production of approximately 960 tons of fly ash daily. To efficiently remove the ash
from the furnace hoppers, Clinch River water is mixed with the ash to form a slurry
which is pumped to large fly ash settling lagoons. A closed system incorporating
recirculation of the supernatant is used to conserve water. Recycling allows free lime
(CaO) in the fly ash to react with water forming Ca(OH)2- This eventually raises the
pH of the recirculating water and the water in the fly ash lagoons to extremely high
pH values ranging from 12.0 to 12.7 (1).
Dike Failure
On June 10, 1967, a 50-75 ft section of a dike surrounding a fly ash settling
lagoon collapsed. Within less than an hour 400 acre-ft (approximately 130 ml gal) of
highly caustic water (pH 12.0) poured into Dump's Creek which joins the Clinch
River one half mile downstream. This slug of caustic water equalled 40 per cent of
the daily flow of the Clinch at that time and blocked the normal flow of the river for
several min while raising the water level several ft forcing some waste upstream
approximately 0.5 miles. Thus an essentially undiluted slug of highly caustic water
entered the Clinch River. For the next four and one half days the highly basic slug
traveled downstream at a rate of approximately 0.85 miles/hr (1).
The exact cause of the dike failure was never determined. One possible reason
given by Appalachian Power Company was that a leak developed in a recirculation
pipe buried in the dike. Another possible cause was that erosion of foundation
material due to the flow of Dump's Creek might have caused part of the dike to
settle and collapse (2).
Fish-Kill
As the highly basic mass of water moved down the Clinch River, it killed
essentially all the fish in its path (2). During this period, 162,000 sport and rough
fish were killed in 66 miles of the Clinch River in Virginia. An additional 54,600
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