TRANSPORT AND DEPOSITION OF COAL FLY ASH IN THE WATTS BARR RESERVOIR SYSTEM FROM THE KINGSTON, TENNESSEE ASH STORAGE CELL FAILURE IN 2008
During the first year following the spill, thick ash beds were mapped in the Emory River channel within 1.5 km of the release. At the distal end of the spill, stratified, graded ash beds from the initial failure were recorded in cores. These ash deposits thinned downstream to an ash/sediment mixture and discontinuous ash lenses were recorded in the lower Emory River during the 2009 fieldwork. Adjacent to the channel, on submerged terraces, ash beds are buried below mats of organic detritus.
Seismic profiles collected in 2011 show thick ash deposits in the river channel downstream of the dredged area. However, vibra-cores record beds of alluvial sand and gravel capping these deposits. The Emory River has a hummocky, scoured riverbed 1.6 km downstream of the spill. This is an area of sediment transport with thin (30 cm) ash beds interbedded with organic mats and alluvium. A depositional sedimentary environment occurs at the mouth of the Emory River as indicated by the smooth riverbed and thick (1.3 m) ash beds recovered in the 2011 cores. These ash deposits are represented on seismic profiles by a transparent channel fill facies. The high discharge of the Clinch River has mixed the ash deposits with native sediment and buried isolated ash lenses.
Ash in the channel near the spill area is now buried beneath beds of sand and gravel that will restrict resuspension to high flow velocities. Cohesive organic mats deposited on submerged terraces during periods of slack water will limit erosion of the broad but thin ash beds in this sedimentary environment. Along channel slopes, ash is exposed and susceptible to erosion and transport. Ash from the spill has been transported through the Emory River and is temporarily deposited just above its confluence with the Clinch River. This ash will eventually reach the Tennessee River and its ultimate depocenter, the Watts Bar Reservoir.