Kingston Ash Slide
Temporary Ash Storage
Updated March 23, 2009
TVA is preparing a temporary ash storage area to safely hold material dredged from the Emory River. The preparation includes installing a large number of special drains to help remove water from the temporary storage area.
The dredged ash material that TVA is removing from the Emory River will be dried to approximately a 20% moisture level and placed in the temporary ash storage area (formerly known the ball fields) on the Kingston site, as identified in the TDEC and EPA approved dredging plan.
The temporary ash storage area was prepared by first clearing the area, then placing a porous fabric material (similar to the fabric used in residential flower beds) on the soil foundation and covering this material with a layer of crushed rock. This material will serve to provide stabilization to the existing soil, filtration for water passing through and separation from the existing soil to the rock on top.
The storage area is then being prepared to drain water through a system called wick drains. Wick drains are a prefabricated vertical drain system composed of an inner corrugated plastic core wrapped with a porous fabric materials similar to the one explained above.
The purpose of the wick drains is to allow water in the ash to drain as more wet ash is piled on top of it. This wicking of the water in the ash below the surface, also aids the drying process.
The wick drains are installed to a depth of 50 to 60 feet below grade with a machine especially designed to install this type of drainage system.
TVA will install approximately 17,500 wick drains in the temporary ash storage area.
Once the wick drains are installed, a second layer of crushed rock is placed on top of the wick drains, and a second layer of the porous fabric material is placed on top of the crushed rock.
The second layer of porous fabric material acts as a separation barrier from the ash that will be stored on top from mixing with the crushed rock layer below. As the ash is continually stacked on top at the temporary ash storage area, the weight of the ash will push water out of the wet ash below it, up through the wick drains, and into the crushed rock material.
After the water has entered the crushed rock through the wick drains, it will move laterally through the crushed rock layer and flow by gravity to a drainage ditch installed along the perimeter of the temporary ash storage area, and finally to the Kingston Plant ash pond system.