Evaluation of Slurry Wall Construction Using Paper Clay for Containment of Contaminated Groundwater

Abstract

Slurry walls have been used widely as passive vertical barriers to control the horizontal flow of groundwater and contaminants and therefore limit the migration of contaminants through the subsurface. The material used as slurry to reduce contaminant transport is expected to form a filter cake with low permeability along the sides of the trench wall/excavation face. In this article, paper mill sludge (hereafter referred to as paper clay) is investigated as a possible slurry. Previous research by Moo Young et al. (2000) has shown that paper clay has several properties that make its use in vertical barriers very promising. It can be compacted to low permeability values (10−7 cm/s to 10−9 cm/s) and has a high organic content that may act as a potential carbon source for microbial growth and sorption sites for heavy metal attenuation. To determine the feasibility of paper clay in a slurry, column testing to determine the dispersion coefficient for transport modeling, slump testing, and filter cake formation tests were performed. It is shown that the coefficient of hydrodynamic dispersion within paper clay is in the order of 10−7 cm2/ s. It is also shown that paper clay can achieve the required slump of between 5.08 and 15.24 cm (2 and 6 in) similar to that of a workable soil-bentonite backfill. Furthermore, it is shown that the filter cakes that are formed have permeability values similar to those of soil-bentonite filter cakes.