Diagram of the original “Option D” WIPP Panel Closure System, also known as the panel plug. Despite DOE's description of this system as a 'Panel Seal' these plugs are not true seals since air and gases will still be able to pass through these closures. Particles, however, will not. DRZ stands for the Disturbed Rock Zone which is an area of the salt radiating out from the WIPP excavation that has been fractured as a result of that excavation. In this design, the DRZ will be removed up to and down to the interbeds above and below the panels to increase the stability of the panel plugs. The new WIPP Panel Closure design does not excavate to the interbeds. DOE has been unable to create and pour a concrete mixture which will meet required specifications for this system.(USDOE)