As a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priority List site, Fort Wainwright, Alaska, has undergone extensive remedial investigation and subsequent treatment to restore contaminated soil and groundwater to safe levels. Treatment systems were installed at various contaminated areas beginning in the mid-1990’s and now, several years later, an approach must be developed to bring these systems off- line. The purpose of this paper is to develop a methodology for shutting down treatment systems, including determining the optimal time to shutdown a treatment system and the steps to take following the shutdown. Shutting down a treatment system at the most appropriate time is the critical factor, as demonstrated below. If contaminants rebound, the system was shut down prematurely; however, if contaminants do not rebound, the system may have been run longer than necessary. To develop a methodology for shutting down treatment systems, including the optimal time to shutdown a treatment system.

Four factors examined in development of a shutdown process:

Two representative treatment systems studied for this paper - Eight-Car Header and Valve Pit C

Keywords: Remediation; Shutdown; Soil contamination; Soil vapor extraction; Rebound