Slug Test Analysis in Vertical Cutoff Walls. II: Applications

This paper addresses practical applications of the type curve method and modified linear curve fitting method described in a companion paper for evaluating the hydraulic conductivity of a vertical cutoff wall. Sensitivity analyses were performed for factors that might influence results from a slug test in a vertical cutoff wall. The factors considered are (1) width of the vertical cutoff wall, (2) eccentricity of a well location, (3) well aspect ratio, and (4) distance from the upper and lower boundaries of the wall to a well intake and discharge section. In addition, the effects of variable hydraulic properties-hydraulic conductivity (k) and specific storage (Ss)-on the results of a slug test are evaluated. Also, the effect of initial slug size and difference between a rising and falling head slug test are investigated in connection with the variability of the hydraulic properties. Analyses show that the compressibility of the porous medium has a dominant effect. Various errors can arise from the simplifying assumptions used in slug test analysis, but these errors often tend to offset one another. Performing sequential slug tests can yield progressively lower hydraulic conductivity as a result of consolidation of the barrier wall material.