Back to calendar
Permitting an Evapotranspiration Landfill Cap in El Paso, Texas
Permitting an Evapotranspiration Landfill Cap in El Paso, Texas
Cami Van Abel, Environmental Engineer, SAIC
This eSession will cover the design, modeling and permitting efforts required of the McCombs Landfill in El Paso, Texas, to use an all soil (evapotranspiration, or “ET”) final cap. It also will include a brief discussion of ideas to consider when evaluating the feasibility of ET caps in other regions of the United States. ET caps typically consist of fine graded soils designed to store water and sustain vegetation. Water eventually is removed through natural evapotranspiration cycles. These caps minimize the construction costs included with installing geosynthetics.
The speaker will explain how the landfill operators came to decide upon an ET cap, and how they then proceeded to demonstrate that the proposed ET cap design provided reduction and protection from wind and water erosion equivalent to a conventional landfill cap. This demonstration was required according to the published guidance procedures of the Texas Commission on Environmental Quality (TCEQ), the state regulator.
Because the landfill is located in an arid region of Texas, the implementation of a test plot area was not required to demonstrate equal performance of an ET cap to a conventional cap. Instead, the landfill was required to perform hydrogeologic modeling of the cap design using the Unsaturated Soil Water and Heat Flow Model (UNSAT-H). The speaker will describe the process by which soil samples were collected from onsite landfill stockpiles, submitted to an offsite laboratory for a multitude of sampling parameters to represent cap conditions during construction and during a 30-year post-closure period, and the sampling results input into the UNSAT-H software to model site specific conditions. Other site specific parameters included in the modeling input efforts included climate, vegetation design for the ET cap and precipitation.
The ET cap evaluation was performed in conjunction with a major permit modification for the site to adjust waste filling slope and vertical height of the landfill, which will also be discussed.
For registrations or more information, please click here.