Vertical Barriers/Slurry Walls Bio-Polymer Trenches Permeable Reactive Barriers Soil Mixing Jet Grouting Wetlands Site Remediation Dam Grouting MGP Sites Levee/Dam Reinforcement & Repair

Funnel and Gate Systems

Andrews, AFB, MD: Soil-Bentonite Barriers With Permeable Reactive Barrier Gates And Gate Groundwater Control


This site is located on Andrews AFB (AAFB) in Northern Maryland, just outside Washington, DC. AAFB is home to the 89th Airlift Wing as well as the 79th Medical Wing of the United States Air Force (USAF).

The funnel and gate system at Andrews Air Force Base (AAFB) was designed to be installed to an invert elevation of 224 feet above mean sea level, approximately 37 feet below most of the prepared work platform. The three funnel portions of the application were designed to be installed as low permeability soil-bentonite (SB) slurry walls. Two gate sections were installed as permeable reactive barriers (PRBs) utilizing the bio-polymer slurry wall method. Excavation depths of up to 41 feet below the ground surface (bgs) account for deviations in the final elevation of the work pad. Geo-Con executed excavation of both the funnel and gate portions of the project to the designed depths using a long-reach hydraulic excavator.

Project Objectives

  • Provide the means by which to contain groundwater and leachate collecting and flowing in and around the landfill perimeter
  • Provide the ability to control the contained groundwater through two PRB gates
  • Install the means to remediate the controlled groundwater via ten injection wells
  • Complete 57,000 vertical square feet of Soil Bentonite slurry wall
  • Complete 6,000 vertical square feet of permeable reactive barrier slurry wall installed by the bio-polymer slurry method
  • Excavate 7,000 cubic yards of material, over 10,000 tons of earth and debris
  • Install of a modified gravel and sand mixture exhibiting the exact standard to allow the injected reagents to remain in contact with groundwater for the optimal time of remediation
  • Soil bentonite slurry wall specified permeability of 1x10-7
  • Perform a mix design and compatibility testing
  • Provide design support


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