Industry paper

Dewatering and containment of coal ash using geotextile tubes for ash pond closure

Authors: Meena Viswanath, Ming Zhu, Tom Stephens and Kirk Foley

This paper presents a case history of the construction of a geotextile tube wall in an ash pond at a confidential site for a large mid-Atlantic utility. The geotextile tubes were stacked in two layers and formed an approximately 3.4-m (11-ft) high, 730-m (2,400-ft) long wall with most of the wall constructed in a 3-2 pyramid structure (i.e., 3 tubes in the bottom layer and 2 tubes in the top layer). The wall separated the ash pond into two areas – a pool area, which continued to serve as an operations area to receive sluiced coal ash, and a construction area where preparation work for final closure grading was to be started. Coal ash from the pool area was dredged and pumped into the geotextile tubes, reducing the amount of coal ash that would otherwise have needed to be stabilized in place during the final closure. The wall also serves as a buttress to improve slope stability during interim construction. At the end of the closure, the entire pond will be filled to final closure grades and the geotextile tubes will be buried in place.