Prediction of runoff and infiltration related to landfill final cover

Predictive landfill flow modeling requires an understanding of moisture movement through final surface covers. The experimental study evaluated a bench-scale, geomembrane lined surface cover system for short-duration, high-intensity storm events. The study analyzed storm intensity, slope, and hydraulic conductivity parameters. Project objectives included: identification of current liner regulations, landfill flow models, geomembrane infiltration mechanisms, presentation of experimental test data for runoff and infiltration in a simulated landfill cell, development of a runoff model, and statistical evaluation of the experimental results.;A test plan was developed to assess total runoff and infiltration for constant flow storm events. Experimental regression models developed provided accurate estimates of total runoff and were found to be an attractive alternative in predicting total runoff for short-term, high-intensity storm events for solid-waste landfills. Consequently, the prediction of total runoff for the design of surface runoff systems were simplified within the range of the variables presented. A linear relation was clearly indicated by the experimental data with the correlation coefficient for the total runoff regression model equal to 0.984. Infiltration through the geomembrane liner in the cover system decreased as the slope of the liner was increased.;The experimental runoff data were compared with chosen default HELP model runoff predictions. The HELP model tended to underpredict runoff for all simulations run on the experimental cell, ranging from 8% to 24%. The HELP model's predictive runoff output proved to be highly dependent on the represented field parameters. Specifically, the recompacted soil matrix material that is typical of most solid waste landfills may not be comparable with native soil material used as the basis for the SCS curve numbers. The SCS method also suffers from the omission of the actual storm duration time, which may have an effect on runoff projections. The experimental results confirm previous suggestions of the HELP model's underprediction of surface runoff from landfills.;The development of the regression models introduce a new, more realistic technique to predict the formation of total runoff for landfills with geomembrane liners.