Role of waste hydraulic properties on landfill engineered systems

Hydraulic design and operation of liquid injection systems and retrofitted vertical extraction wells were analyzed in this study. A two-dimensional unsaturated fluid flow model was used to simulate the hydraulic interactions that occur during liquid injection and drainage from a liquid injection system into refuse. Results from the numerical model analysis suggested that the rate of pressure increase and subsequent decrease in flow rate within a perforated injection pipe is inversely proportional to the refuse hydraulic conductivity. An injection trench positioned within refuse with a low hydraulic conductivity resulted in rapid saturation and decrease in the injected volume when compared to a high hydraulic conductivity. A set of empirical equations were present to predict the pressure development within a trench and injection volume for a range of refuse hydraulic properties and pipe hydraulic configurations were presented.;Field scale pump and recovery tests and slug injection tests were conducted at the Brady Road Landfill located in Winnipeg Manitoba to provide insight into the movement of liquid and pressure responses in a landfill and to assess refuse hydraulic properties. The well extraction rate and well specific capacity were measured and pressure responses during pumping and recovery were monitored in an array of piezometers. Pressure responses from the pump tests suggest that low permeability layers within a landfill may limit vertical liquid movement. Drawdown pressure responses were simulated using analytical methods for an unconfined aquifer and a double aquifer analytical model, recovery response data and slug test data were analyzed with analytical methods for an unconfined aquifer. Deduced refuse transmissivity from all the selected analytical methods rangedfrom 0.16 to 9.65 m2/day and the storativity ranged from 10-1 to 10-3, an unconfined aquifer analytical model deduced a specific yield that ranged from 0.13 to 0.14.