Oil recovery at a former wood‐treating facility

Abstract

Pools of mobile dense nonaqueous phase liquids (DNAPL) are often found perched above capillary boundaries at sites where DNAPLs have been managed. An approach to partially address risks posed by pools of mobile DNAPLs is to recover the mobile fraction of the DNAPL and, thereby, limit the potential for future DNAPL migration. During the last 8 yrs, development and implementation of an effective mobile DNAPL recovery technique has been ongoing at a former wood‐treating plant located in Laramie, Wy. The technology relies on dual horizontal water and DNAPL recovery drainlines, installed in a single trench, coupled with parallel single water delivery drainlines. By cycling water between the upper recovery and parallel delivery drainlines, DNAPL is hydraulically driven to the lower recovery drainlines. Presently, full‐scale DNAPL recovery operations at the site are in their fourth year of an approximate 8‐yr program. An area of ∼24 ha is being addressed. To date, ∼4.9 million L of DNAPL has been recovered and an endpoint of 95% recovery of mobile DNAPL is being achieved. Review of this technology's development and implementation provides insight into a unique approach to mobile DNAPL recovery which is likely applicable at other sites.