Infiltration Equivalency Analysis

The minimum technical requirements as defined by the EPA for Subtitle D Final Cover Systems are contained in 40 CFR 258.60. This regulation allows for an alternative (performance based) cover system. One of the requirements for determining equivalency is infiltration. Typically, this is evaluated using two methodologies – (i) the Hydrologic Evaluation of Landfill Performance (HELP) Model and (ii) the Giroud Method1. Both of these methods have been used to compare the infiltration performance of the ClosureTurf® Final Cover System to the Prescriptive Subtitle D Cover. A comparison of infiltration rates is shown in the Table for both methodologies for a generic site in Texas.

The results demonstrate that the ClosureTurf Final Cover System provides superior protection against infiltration when compared to the Prescriptive Subtitle D Standard landfill final closure systems.

Infiltration Equivalency Analysis

ClosureTurf® Cover System

Prescriptive Subtitle D Cover System

HELP Model for Site in Texas – Average Annual Infiltration (Cubic Feet)



Giroud Method with Silty-Sandy Soil below the ClosureTurf® (Gallons / day)



Giroud Method with Silty-Sandy Soil with Some Clay below the ClosureTurf® (Gallons / day)



Summary of Results for Infiltration Equivalency Analyses for a Generic Site in Texas

1 Rate Of Liquid Migration Through Defects In A Geomembrane Placed On A Semi-Permeable Medium, J.P. Giroud,
T.D. King, T.R. Sanglerat, T. Hadj-Hamou and M.V. Khire, Geosynthetics International 1997, Vol. 4, Nos. 3-4.