Slug test analysis in vertical cutoff walls. I: Analysis methods

Analysis of a slug test to estimate hydraulic conductivity of a vertical cutoff wall is complicated by the high compressibility of the backfill materials and by the proximity of the well intake section to the edge of the cutoff wall. The writers developed two methods to evaluate hydraulic conductivity of the vertical cutoff wall with the aid of a numerical program, Slug_3D. The first method, named the type curve method, expands the general type curve concept frequently used by hydrogeologists to take into account the complex boundary conditions of the vertical cutoff wall. The other method, named the modified linear curve fitting method and modified from the Hvorslev and the Bouwer and Rice methods, provides an easy and practical way of evaluating hydraulic conductivity of the vertical cutoff wall. To illustrate the use of the type curve and the modified linear curve fitting methods in practice, a case study involving two slug tests at a landfill site is presented. The methods are shown to be useful and practical.