H.E.L.P. for landfill design in Chile

Abstract

Leachate, the liquid that leaches through solid waste in a landfill, can potentially contaminate groundwater and surface waters. Therefore, leachate management in landfills is crucial to safeguard the environment and public health. Leachate management is a growing concern in developing countries in which environmental protection has traditionally been secondary to economic progress. An example of such a country is Chile, which has recently embarked in the design and construction of several new landfills. Engineers and consent writers in Chile require special tools to address landfill issues, particularly for the control of leachate. The Hydrological Evaluation for Landfill Performance (HELP) model is a special tool that helps to assess the effectiveness of landfill designs in the U.S. To adequately model leachate generation, the HELP model uses a synthetic weather generation model, WGEN. This thesis focuses on adapting the HELP model so that it can be used in Chile. The synthetic weather generation routine (WGEN) of the HELP model is modified to include the parameters necessary to generate synthetic precipitation, temperature, and solar radiation data for Chile. The precipitation parameters that are calculated are the shape and scale parameters (α and β ) of the gamma distribution used to generate precipitation amounts, and the conditional probabilities of precipitation occurrence (P(W/W) and P(W/D)). The temperature and solar radiation parameters that are calculated are the means, amplitudes, and variations of maximum temperature, minimum temperature, and solar radiation for wet and/or dry days. Correlation coefficients between maximum temperature, minimum temperature , and solar radiation are calculated. The weather generation routine is modified to work with specific correlation coefficients for each location instead of using the original values embedded in the original programme. The effectiveness of the weather generation parameters is assessed in relation to other parameters that have been previously calculated, and in relation to historic data and a specific landfill design. In addition, the weather interface, originally in BASIC for DOS, is updated to work in Visual Basic 6.0. As a result, precipitation parameters for 18 locations in Chile have been calculated. These parameters are calculated with as many years as possible (more than 20 in most cases) and for different locations covering the different types of Chilean weather. The temperature and solar radiation parameters are calculated only for 8 locations (due to lack of data). However, these parameters still cover most of the weather spectrum, and it is shown that small variations in temperature and solar radiation do not significantly affect the sensitivity of the final results. The use of specific correlation coefficients to calculate synthetic temperature and solar radiation data contributes to the overall accuracy of the programme. The final programme works well and with good results, but there certainly is room for further improvement. The rest of the programme could be updated to Visual Basic and improvements could be made to the weather generation routine to increase its accuracy.