Final Second Five-Year Review Report Fort Ord Superfund Site ...

Former Fort Ord boundary (See Section 5.2). Additional investigations are underway by the Army to
assess the extent of contaminated groundwater beyond the northwest boundary of the Former Fort Ord.
The groundwater plume as of July 2006 is shown on Plate 3.
5.2 Remedial Actions
5.2.1 Remedy Selection
The following three remedial alternatives were evaluated in the OU 1 RI/FS (HLA, 1987) are as follows:
• Alternative 1: Air stripping of groundwater with vapor phase carbon treatment of effluent and
biodegradation of soil.
• Alternative 2: Air stripping of groundwater with vapor phase carbon off-gas treatment, aqueous
carbon polishing of effluent and biodegradation of soil.
• Alternative 3: Aqueous carbon effluent treatment of groundwater and biodegradation of soil.
5.2.2 Remedy Implementation
Alternative 3 was selected as the appropriate remedial action for groundwater at OU 1. The OU 1
groundwater GWETS was installed in 1988 and consisted of two EW (EW-OU1-17-A and EW-OU1-18-
A) and an activated carbon treatment system. Treated water from the system was used to bioremediate
contaminated soils at the site. Treated water enhanced with nutrients was sprayed on the soils overlying
the contaminated groundwater. Soils treatment was completed in August 1991. Treated water continued
to be discharged in the same location until 2006.
5.2.3 System Operations and Maintenance
The GWETS operated nearly continuously from the time of initial start-up until the start of the rebound
evaluation in February 2006 except for a five-month shutdown in 1989 to modify the treatment system.
There have been no design changes to the system other than a 33 percent increase in pumping capacity
installed during the 1989 shutdown. The system configuration has been unchanged – two 33-cubic-foot
(1,000 pound) carbon vessels are connected in series with a third off-line unit (available for replacement
of spent carbon). Declining VOC concentrations in the influent have extended the operating cycle of the
system. Before the shut-down for the rebound evaluation, carbon change-outs were needed
approximately every other year. In 2006, groundwater quality in all MWs within the GWETS capture
zone met the remediation cleanup targets and both EW were shut down in February 2006 to conduct a
rebound evaluation study (HGL, 2006c). The rebound evaluation is still underway and both wells remain
off-line.
5.2.3.1 OU 1 Groundwater Monitoring Within Former Fort Ord
Quarterly sampling of groundwater from selected MWs within the long-term monitoring began in 1988
and continued during this second five-year review period. The sampling frequency at some wells was
decreased to a semi-annual or annual cycle in response to improving or stable groundwater quality. Some
new wells installed during the 2004 – 2006 period were added to the long-term monitoring network.
The quarterly groundwater sampling data was presented in annual reports for the years 2002 through 2005
and shows long-term trends of system operation (HGL, 2006a, 2005; AGSC 2003, 2005). Quarterly letter
reports have been prepared through the third quarter of 2006 (HGL, 2006b, 2007a, and 2007b) as of the
Final
5-2
FORMER FT ORD 5YR REVIEW 2007_FINAL United States Department of the Army