## Hydrologic and Design Factors Affecing the Production of Landfill Leachate

### by Karen E. Schmitt

The objectives of this project are the following:

• Gain a deeper understanding of the numerous variables that affect infiltration and the methods used to predict it.
• Use the hydrologic water balance to determine the effect of design parameters on the production of landfill leachate.

To accomplish my objectives I am going to use the U.S. Environmental Protection Agency's software model HELP - Hydrologic Evaluation of Landfill Performance. Once I have gathered the requisite input information, I will complete an independent water balance exercise to "calibrate" the model. The HELP model uses Soil Conservation Service curve numbers to predict runoff and models infiltration as I = P- E- Runoff- dS. I would like to compare that method with other methods learned in class this semester (Green-Ampt, if applicable, etc.). I would further like to compare calculations made by the HELP model, which uses daily precipitation values, to calculations made by considering the duration and intensity of individual rainfall events.

As input to the HELP model and the separate calibration procedure, I will need the following data for Austin (from as yet unknown sources):

• daily precipitation values for the previous 5-20 years.
• precipitation information for a period of 2 years relating to the intensity and duration of individual storm events.
• mean monthly temperature for 1 year.
• mean monthly solar radiation for the same year.
• soil characteristics for Austin, including SCS curve numbers and properties of typical surface soils

Other input parameters will be based on suggested data given in the HELP model and in the Applied Hydrology textbook. Design data will be based on my own experience with soils and landfills.

Once the model is up an running, I hope to do a small parametric study to evaluate the effects of hydrologic factors such as evapotranspiration, runoff, and soil moisture on the infiltration and subsequent leachate generation in landfills. Furthermore, I would like to study the effects of design variables such as cover slope angle, liner type, and liner thickness on the amount of leachate generated.

At the end of the project, I hope to have accomplished the following:

• understand the many non-waste-related factors which affect the production of landfill leachate.
• gain familiarity with a useful tool, the HELP model, frequently used in practice in my field.
• learn whether geosynthetic clay liners can really be hydraulically equivalent to compacted clay liners.

I can be reached at k.schmitt@mail.utexas.edu