Effects of Hydration of GCLs with Groundwater on their Hydraulic Performance

Project Duration: September 1st, 2019 – August 31st, 2020

Investigators:     Prof: Tarek Abichou, Ph.D. P.E. and Youneng Tang, Ph.D.

                             FAMU – FSU Dept. of Civil and Env. Eng.

Motivation and Objectives:

The FDEP regulations states: "The hydraulic conductivity of GCLs shall be tested with method ASTM D5887, hereby adopted and incorporated by reference, or ASTM D6766, .... First, the GCL test specimen shall be hydrated with the fluid which is expected to cause hydration in the field, or a similar fluid, for a minimum of 48 hours using sufficient backpressure to achieve a minimum B coefficient of 0.9….. Then, the hydraulic conductivity test on the GCL specimen shall be conducted, using the appropriate permeant fluid, at a confined effective consolidation stress not exceeding five pounds per square inch. The hydraulic conductivity test shall continue until steady state conditions are reached or a minimum of two pore volumes of permeant fluid have passed through the test specimen. The permeant fluid shall be either leachate from the landfill (or a similar landfill) if the GCL is used in a liner system, or water if the GCL is used as a barrier layer in a final cover." Based on our recent experience with GCLs and FL leachates, we propose to investigate the appropriateness of using this methodology to assess the compatibility of conventional and polymer modified GCLs to FL groundwater and leachates. We also suggest that two pore volumes might not be enough or appropriate when testing polymer modified GCLs.

The objectives of the project are to:

Methodology: The proposed research project consists of collecting groundwater quality and geochemistry data and soil leaching characteristics at various locations around the state. Synthetic groundwater and soil water samples will then be prepared in the laboratory. The synthetic groundwater and soil water will be used to pre-hydrate conventional and polymer modified GCLs in accordance to current FDEP requirements. Once hydrated, hydraulic conductivity tests will be conducted on the GCLs with leachates representative of MSW, MSWI ash, and Co-Disposal. Index properties of the bentonite from each GCL will be determined using DI water, actual groundwater, and synthetic groundwater. These index properties will then be correlated to hydraulic properties of the GCL. All hydraulic conductivity testing of polymer modified GCLs will be continued for more than 5-10 pore volumes to investigate emulsion and its effects on long term hydraulic behavior of these products.

TAG 1 Meeting PPT Slides

Quarterly Progress Report 1