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

Confirmation Report and Post-Remediation Health Risk Assessment, Site 12 Remedial Action, Basewide
Remediation Sites, Fort Ord, California (IT, 1999c). The soil remediation resulted in the site being
available for unrestricted reuse.
Groundwater Remedy
A groundwater pump and treat system was constructed in 1999 to remediate the plume of COCs in
groundwater. During the operation of the treatment system, sampling and analysis are conducted to
verify that the treatment system is operating effectively. Since 1999, water samples and water levels from
groundwater MWs have been collected every three months. This information has been compiled into
quarterly and annual reports to show the long-term trends resulting from system operation.
The groundwater treatment system originally consisted of carbon adsorption, accomplished using two
13,000-pound carbon vessels connected in series. The original system extracted water from eight wells
located at Site 12 and discharged into five Upper 180-Foot Aquifer recharge structures (2 injection wells
and 3 infiltration galleries). After startup, system modifications were immediately implemented due to
the presence of vinyl chloride concentrations greater than anticipated. System modification included
construction of a pipeline to transport and combine treated water from OU 2 with treated water from Site
12 prior to conveyance to the aquifer recharge structures. Most recently, an air stripper has been added
for treatment of vinyl chloride (Section 7.1.2.4).
7.1.2.3 System Operations and Maintenance
The Sites 2/12 groundwater treatment system has been in operation since April 1999.
The Sites 2/12 groundwater remedy is operated in accordance with the Operation and Maintenance,
Groundwater Treatment Systems, Former Fort Ord, California (Harding ESE/IT, 2001a) and Sampling
and Analysis Plan, Operable Unit 2, and Sites 2 and 12 Groundwater Treatment Systems, Former
Fort Ord, California (AGSC, 2004). O&M activities are summarized annually in treatment system data
summary reports. The most recent annual report describing Sites 2/12 O&M is the Annual Groundwater
Treatment Systems Operation Data Summary Report, January through December 2005, Operable Unit 2
and Sites 2/12, Former Fort Ord, California (AGSC, 2007). To date, the system has processed over 884
million gallons of water and removed over 334 pounds of contaminants, of which approximately 75.8
percent is TCE, cis-1,2-DCE, 1,1-DCA, PCE, and chloroform. The system operates continuously except
for periods of routine maintenance, carbon servicing, and replacement of worn equipment, and has been
operational approximately 95.5 percent of the time. Carbon replacement in the system has occurred
approximately every 4 to 6 months since operation began.
7.1.2.4 Progress Since the last Five-Year Review
In February 2002, the Army received Regulatory Agency approval to temporarily increase the maximum
discharge level for vinyl chloride to the State of California MCL of 0.5 μg/L. The RI Sites ROD
(Army, 1997b) lists the discharge limit and aquifer cleanup level for vinyl chloride as 0.1 μg/L. In
February 2003, the discharge level was revised to 0.3 μg/L and was effective until June 2006. The
elevated discharge limit for vinyl chloride allowed the groundwater treatment system to be operated
closer to the initial individual well design flow capacity.
The pilot study evaluating the effectiveness of in-situ chemical oxidation of vinyl chloride using
potassium permanganate was completed in 2002. In addition to the pilot study, an evaluation of various
remediation alternatives and approaches was also conducted. The treatment augmentation recommended
in the Engineering Design and Analysis Report (Shaw, 2005b) consists of a modified low profile air
stripper, with vapor treatment by a substrate impregnated with potassium permanganate. Since the
Final
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FORMER FT ORD 5YR REVIEW 2007_FINAL United States Department of the Army