MAXIMUM SATURATED DEPTH OVER LANDFILL LINER

Explicit formulas for the steady-state maximum saturated depth over a landfill liner are derived analytically from basic principles of unconfined seepage. The lateral drainage over the liner is described by an extended form of the Dupuit discharge formula. The liner is modeled as an impervious sloping plane. The factors that determine the maximum saturated depth over the liner are the rate of vertical inflow to the drainage layer, the hydraulic conductivity of the drainage layer, the slope of the liner, the maximum distance of flow, and the hydraulic condition at the downstream end of the drainage layer. Practical applications of these formulas include the analysis and design of drainage systems for landfill covers and bottom liners. An example illustrates the use of these formulas in the design of a cover drain for a hazardous-waste landfill. A formula that appears in several technical guidance documents of the U.S. Environmental Protection Agency is shown to overestimate the maximum saturated depth over a landfill liner.