EM’s Waste Isolation Pilot Plant (WIPP) celebrated its 20th anniversary this past month. WIPP is a U.S. Department of Energy facility licensed and constructed as a repository for the disposal of defense-generated transuranic (TRU) radioactive wastes in a bedded salt formation. It was in 1979 that Congress authorized WIPP as a research and development facility to demonstrate the safe disposal of radioactive waste. The facility faced opposition from various external organizations causing site testing to be delayed. Final legislation mandated that the Environmental Protection Agency (EPA) issue revised safety standards for the facility. To ensure that the facility would provide a safe repository in perpetuity, Congress ordered Sandia National Laboratories to begin an extensive evaluation of the facility against the standards set forth by the EPA. Beginning in 1985, INTERA was contracted by Sandia National Laboratories to conduct field hydrogeological characterization, data documentation, data interpretation, and modeling in support of site characterization. INTERA staff were responsible for performing much of the field characterization and groundwater modeling used to support the original license application for the facility to be approved as a repository. The information collected in the various site characterization programs was incorporated into the WIPP parameter database for inclusion in the safety assessment modeling for site compliance. INTERA provided a full-time, on-site field team from 1985 to 1997 to perform hydrogeologic testing and characterization of the various geologic units and has maintained a local presence since that time. In May 1998, the EPA certified that WIPP met all applicable federal radioactive waste disposal regulations, and on March 26, 1999, the first nuclear waste shipment arrived at the facility. INTERA has continued to provide hydrogeological characterization services, including planning and management, test design and implementation, test equipment design and fabrication, data interpretation and documentation, and sampling and monitoring services through the re-licensing cycles. INTERA is proud to have been a part of the successful licensing and continued operations of the WIPP Facility.