Field Demonstration/Validation of Electrolytic Reactive Barriers for Energetic Compounds at Pueblo Chemical Depot

Site Name:

Pueblo Chemical Depot (PCD)

Location:

Pueblo, Colorado

Period of
Operation:

A 35-foot electrolytic reactive barrier was installed in January 2006 and energized in March 2006. The energized electrolytic reactive barrier was operated for 770 days. Due to a DC-DC voltage controller failure in late 2007, barrier operation was interrupted for three weeks.

Cleanup
Type:

Field Demonstration

Technology:
This demonstration used an electrolytic reactive barrier to remediate contaminated groundwater at the site. The electrolytic reactive barrier used electric potential to reduce energized compounds in groundwater. Details regarding the demonstration are provided below:

  • 11 temporary monitoring wells and 10 piezometers were installed across the site to characterize the site and obtain baseline water quality data. These wells were sampled in July and September 2005.
  • The 35-foot long electrolytic reactive barrier was installed on January 30 through February 2, 2006. The electrolytic barrier was comprised of fifteen active electrode panels.
  • In February and early March 2006, the electrical supply control system was installed. The start of the demonstration was on March 15, 2006, when the electrolytic reactive barrier was energized at 1.4 volts.
  • During the demonstration period, data loggers were used to record reduction/oxidation (redox) conditions upgradient and downgradient of the electrolytic reactive barrier.

Cleanup Authority:
Department of Defense (DoD)

Contacts:

Principal Investigator
Tom Sale
Engineering Research Center
Colorado State University
Fort Collins, CO 80523
Phone: 970-491-8413
E-mail: tsale@engr.colostate.edu

Project Researcher
Mitch Olson
Engineering Research Center
Colorado State University
Fort Collins, CO 80523
Phone: 970-491-8224
E-mail: mitchell.olson@colostate.edu

Graduate Research Assistant
Matt Petersen
GE Global Research Center
1 Research Circle
Niskayuna, NY 12309
Phone: 518-387-7054
E-mail: matthew.petersen@research.ge.com

Health and Safety Hazardous Materials
Dominic Leffler
Environmental Health Services
Colorado State University
149E General Services Building
Fort Collins, CO 80523
Phone: 970-491-4830
E-mail: dleffler@lamar.colostate.edu

Site Contact Coordination of On-Site Activities
Christopher Pulskamp
Pueblo Chemical Depot
104 W.B. Street
Pueblo, CO 81003
Phone: 719-549-4252
E-mail: Christopher.Pulskamp@us.army.mil

Environmental Restoration Program Manager
Andrea Leeson
ESTCP Program Office
901 Stuart Street, Suite 303
Arlington, VA 22203
Phone: 703-696-2118
Email: andrea.leeson@osd.mil

Contracting Officer's Representative
Erica Becvar
AFCEE/TDV
2261 Hughes Avenue, Suite 155
Lackland, AFB, TX 78236-9853

Contaminants:
RDX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT), and 1,3,5-trinitrobenzene (1,3,5-TNB)

Waste Source:
Historical use at PCD produced contaminated wastewater from munitions washout operations. This wastewater was discharged to washout ponds onsite; contaminants then leached into the soil and groundwater creating groundwater plumes.

Type/Quantity of Media Treated:
Groundwater (quantity not documented)

Purpose/Significance of Application:
This demonstration evaluated the viability of using electrolytic reactive barriers as an alternative in controlling energized compounds in groundwater at the site.

Regulatory Requirements/Cleanup Goals:
For the PCD demonstration, the performance objectives are detailed below:

  • Document the installation of the electrolytic reactive barrier
  • Evaluate the removal of contaminant concentrations in groundwater downgradient of the electrolytic reactive barrier
  • Evaluate long-term performance by taking into account contaminant levels, physical performance, and electrical performance
Quantitative performance goals include the following:
  • Reduce RDX concentrations below the Colorado Department of Public Health and Environment Level (0.55 microgram/liter (µg/L)).
  • Reduce groundwater concentration below the following levels:
    • 0.0885 µg/L for 2,4-DNT
    • 2.01 µg/L for TNT
    • 361 µg/L for 1,3,5-TNB
    • 602 µg/L for HMX

Results:
Data logging equipment recorded information during the demonstration. This information included applied voltages, amperages, and reduction/oxidation (redox) conditions upgradient and downgradient of the barrier.

RDX was the primary contaminant monitored during the study. Concentrations of RDX ranged from <0.02 µg/L at 6.5 volts to 2.4 µg/L at 0 volts. It was noted in the study that the RDX concentrations were variable which made it difficult to assess the performance of the electrolytic reactive barrier. Percent removal data of RDX suggests a 20-40% removal regardless of voltage applied.

Cost Factors:
Primary cost elements are described below:

  • Baseline Characterization Cost: $45,000
  • Materials and Panel Fabrication Cost: $60,326
  • Installation Cost: $56,367
  • Operations Cost: $30,000/year
  • Maintenance Cost: $31,920/year

Description:
The PCD was constructed during World War II and had a variety of uses from the 1940’s through the 1980’s. These uses include ammunition and material storage, shipping, missile repair, and maintenance. Munitions washout activities at the site utilized holding ponds from 1948 through 1974, causing releases of hazardous constituents to groundwater. Release plumes several miles long have been identified from these ponds. Excavation of contaminated sediments from the holding ponds was conducted in 1998, but contamination remains in soil and groundwater.

Site investigation results indicated that contaminant plumes several miles long originated from these ponds and had migrated offsite into the Arkansas River alluvium. A baseline groundwater characterization study was conducted in July and September 2005 prior to barrier installation.

In this demonstration, an electrolytic reactive barrier was installed at the head of an RDX plume and was used to remediate energized compound contamination in groundwater. The demonstration was conducted between two former washout ponds at the PCD. The purpose of the demonstration was to evaluate the use of electrolytic reactive barriers as an effective remedy for managing energized compounds in groundwater. On January 30 through February 2, 2006, the 35-foot long electrolytic reactive barrier comprised of fifteen active electrode panels was installed at the site. In February and early March 2006, the electrical supply control system was installed. The start of the demonstration was on March 15, 2006, when the electrolytic reactive barrier was energized at 1.4 volts. Over the course of the demonstration, the voltage was increased gradually to a maximum of 6.3 volts. Data loggers were used to record upgradient and downgradient voltages, amperages, and redox conditions.

RDX was the primary contaminant monitored during the study. Concentrations of RDX ranged from <0.02 µg/L at 6.5 volts to 2.4 µg/L at 0 volts. It was noted in the study that the RDX concentrations were variable, which made it difficult to assess the performance of the electrolytic barrier. Percent removal data of RDX suggests a 20-40% removal regardless of voltage applied. Factors that may have attributed to the varying RDX concentrations include variable flow patterns from significant rain events during the course of the demonstration, contaminant degradation by biological processes, matrix diffusion controls, and the tendency of the compound to sorb to solids.

Overall, the field demonstration indicated that electrolytic reactive barriers can be used to reduce concentrations of energized compounds in groundwater. However, their use does not provide a significant advantage over alternative technologies in terms of cost and performance. Other technologies such as iron and bark mulch barriers are less expensive and more effective than the electrolytic reactive barrier.