Nashville's LP Responsible Party for Arsenic, Lead, & Copper Leach in Tacoma

Building industry giant, Louisiana Pacific, is one of the parties responsible for toxic levels of chemicals including arsenic leaching from a Washington state woodwaste landfill into surrounding soil and ground water. The next step in clean up is to build a slurry wall around contaminated soil and water as a barrier. A slurry wall is a trench backfilled with bentonite clay. That may be the acceptable way to control leaching, but after TVA's coal ash spill defied an acceptable way to pond fly ash, this layperson wonders whether a trench filled with clay is enough to protect the watershed. Should we trust it?