Technology Status Report: In Situ Flushing - CLU-IN

In Situ Flushing Project Summaries
GWRTAC Case Study Database
GWRTAC ID: FLSH0043
Project Name: Umatilla Army Depot (Lagoons), Hermiston, OR
City: Hermiston State/Province: OR
Primary GWRTAC Personal
Communication Source
(Name/Organization):
Project Summary:
Harry Craig
U.S. EPA
Report(s)/Publication(s) (GWRTAC Source):
Internet URL http://www.epa.gov/superfund/index.htm
Internet URL http://www.epa.gov/superfund/oerr/impm/products/nplsites
U.S. EPA, Nov 1996: Innovative Treatment Technologies: Annual Status Report (8th Ed.), EPA
542-R-96-010, No. 8, U.S. EPA OSWER (5102G), TIO, Washington DC
The following text is from notes from May 1997 and August 1998 conversations with the EPA RPM:
Residual explosives (TNT, RDX, TNB, HMX) contamination was present from the surface to a
depth of 53 feet below the ground surface (bgs), beneath an old lagoon area approximately onehalf
acre in areal extent. The original lagoon was approximately five feet deep, and the area was
excavated to a depth of 20 feet bgs. Consequently, the current contaminated zone being flushed is
from approximately 20 to 53 feet bgs. (Excavated soils were treated via bioremediation
(composting)). The contaminated zone consists of sandy alluvium with low organic content. The
average hydraulic conductivity of the treatment zone is 10-5 cm/sec. The contaminated soil
volume is approximately 48,400 yd3.
The water table is present at an approximate 53 foot depth bgs. The groundwater contamination
plume covers a 350 acre area. A confining layer is present at 80 to 90 feet bgs, and consists of a
20 to 30 foot thick solid basalt layer. Ground-water is extracted via three pumping wells at depths
of 100 to 150 feet bgs, at a rate of approximately 1,600 gpm. Extracted ground-water is treated
with carbon, and 400 gpm are re-injected via infiltration galleries. Containment is via hydraulic
control. It is estimated that the in situ flushing project will continue for one to two years, and that
groundwater treatment will continue for 27 years.
The specific groundwater cleanup goals for each of the four main constituents are:
TNT (2.8 ppb), RDX (2.1 ppb), TNB (1.8 ppb), and HMX (350 ppb). As of August 1998, monitoring
wells adjacent to the flushing operation have exhibited a 90% reduction in leachable explosives in
groundwater in the first year of operation. A slug of the four target contaminants (spike of 9,000
ppb in a monitoring well) had also moved through between the lagoon flushing zone and the
closest extraction well. The spikes had not yet been seen in the extraction wells.
Report(s)/Publication(s) (Additional Information Sources):
Ground-Water Remediation Technologies Analysis Center
Operated by Concurrent Technologies Corporation
Appendix - Page 88 of 164
Copyright GWRTAC 1998
Revision 1
Tuesday, November 17, 1998