Emulsified Zero-Valent Nano-Scale Iron Treatment of Chlorinated Solvent DNAPL, South Carolina

Site Name:

Site 45, Dry Cleaning Facility (Building 193)

Location:

Parris Island Marine Corps Recruit Depot (MCRD), South Carolina

Period of
Operation:

Field activities were conducted at the site from June 2006 until. March 2009. Injections were conducted in October 2006.

Cleanup
Type:

Field Demonstration

Technology:
During this field demonstration, emulsified zero-valent nano-scale iron (EZVI) was used to remediate a chlorinated solvent dense non-aqueous phase liquid (DNAPL) source zone. Details about the demonstration are provided below:

  • The demonstration was designed to include two hydraulically independent pilot test plots in a DNAPL source area. These were injected and designed as follows:
    • The Pneumatic Injection test plot consisted of five fully screened monitoring wells and seven multilevel monitoring wells. The fully screened wells were screened between 4 and 19 feet (ft) below ground surface (bgs), while the multilevel wells each contain seven, 3-inch screened intervals positioned at 2.5-ft intervals from approximately 4 to 19 ft bgs.
    • The Direct Injection test plot consisted of a single fully screened monitoring well, screened from 3.5 to 13.5 ft bgs.
  • The EZVI was manufactured on site and was composed of nanoscale zero-valent iron (nZVI), water, corn oil, and surfactant in the following proportions by weight: 10%, 51%, 38%, and 1%, respectively.
  • EZVI was injected into both the Pneumatic and Direct Injection test plots; however, migration of some of the EZVI to the ground surface was caused by preferential flow paths created by previous soil borings in the area that provided short circuit pathways for the EZVI to surface.
  • 576 gallons of the EZVI were injected between 7 and 18.5 ft bgs at 8 locations in the Pneumatic Injection test plot, and an estimated 32 gallons migrated to the ground surface through former soil borings located on the site.
  • 151 gallons of EZVI were injected between 6 and 12 ft bgs into 4 locations in the Direct Injection test plot and an estimated 5 gallons migrated to the ground surface through former soil borings located on the site.
  • Post-injection, soil cores were collected from 10 locations around the injection points in each test plot. Groundwater sampling was also conducted from select monitoring wells following EZVI injection.

Cleanup Authority:
Department of Defense (DoD)

Contacts:

Principal Investigator
Tom Krug
Geosyntec Consultants, Inc.
130 Research Lane, Suite 2
Guelph, ON N1G 5G3
Phone: 519-822-2230, Ext. 242
Email: tkrug@geosyntec.com

Project Manager
Suzanne O'Hara
Geosyntec Consultants, Inc.
130 Research Lane, Suite 2
Guelph, ON N1G 5G3
Phone: 519-822-2230, Ext. 234
Email: sohara@geosyntec.com

Field Study Leader
Mark Watling
Geosyntec Consultants, Inc.
130 Research Lane, Suite 2
Guelph, ON N1G 5G3
Phone: 519-822-2230, Ext. 316
Email: mwatling@geosyntec.com

Technical Advisor
Jacqueline Quinn
NASA
Mail Stop KT-D-3 (SLSL 308-2)
Kennedy Space Center, FL 32899
Phone: 321-867-8410
Email: Jacqueline.W.Quinn@nasa.gov

Technical Advisor
Robert Puls
USEPA, National Risk Management Research Laboratory
P.O. Box 1198
919 Kerr Research Drive
Ada, OK 74820
Phone: 580-436-8543
Email: puls.robert@epa.gov

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

Contaminants:
Tetrachloroethene (PCE) and Trichloroethene (TCE)

Waste Source:
Uncontained overflow from aboveground storage tanks located alongside a former dry cleaner at the site resulted in chlorinated VOC contamination in the surface and subsurface soil and groundwater.

Type/Quantity of Media Treated:
DNAPL

Purpose/Significance of Application:
The primary purpose of the demonstration was to evaluate EZVI for the treatment of VOCs from a DNAPL source zone and to evaluate the ability of two injection technologies — Pneumatic Injection and Direct Injection — in achieving even distribution of EZVI in the subsurface.

Regulatory Requirements/Cleanup Goals:
The primary performance criteria for the demonstration include:

  • In the Pneumatic Injection test plot, achieve a 75 percent decrease in total VOCs, DNAPL mass, and mass flux of dissolved-phase VOCs over baseline conditions. Degradation of VOCs in the Direct Injection test plot was secondary to the primary goals of decreasing DNAPL mass and mass flux of dissolved-phase VOCs compared to baseline conditions.
  • Achieve a radius of influence (ROI) of greater than 5 feet for the Pneumatic Injection test plot and a ROI of greater than 1 foot in the Direct Injection test plot.
  • Evaluate the ability of the injection technologies to evenly distribute EZVI in a controlled manner.

Results:
Sampling results from the demonstration indicated the following:

  • In the Pneumatic Injection test plot, a 93 percent reduction in the DNAPL mass and an 86 percent in the estimated total mass of target VOC was observed. Mass flux of PCE and TCE was significantly reduced by 85 percent and 86 percent, respectively and there were also reductions in the mass flux of degradation products vinyl chloride (VC) and ethane.
  • The measured ROIs were as much as 7 ft for the Pneumatic Injection and 2.5 ft for the Direct Injection.
  • There were some difficulties evenly distributing EZVI throughout the treatment area due to the shallow nature of the target treatment interval and pre-existing soil boreholes.

Cost Factors:
The cost assessment showed more than 62% cost savings compared to pump-and-treat. The total cost of the EZVI field demonstration (including labor and expenses) was $559,700, including $61,800 for baseline characterization and $279,000 for performance monitoring. Specific capital cost elements are detailed below:

  • Design and Planning: $39,200
  • Well Installation: $41,700
  • EZVI injections (Pneumatic Injection): $105,600
  • EZVI injections (Direct Injection): $32,400
  • Baseline Characterization: $61,800
  • Performance Monitoring: $279,000

Description:
The field demonstration was conducted at the Site 45 Dry Cleaning Facility, located in the Main Post area at Parris Island MCRD in South Carolina. Following the removal of an underground storage system in 1988, four aboveground storage tanks were placed along the northern side the former dry cleaner facility (Building 193) at the site. In March 11, 1994, one of the tanks was overfilled with PCE and an unknown amount flowed into the concrete catch basin. This overflow was washed onto the surrounding soil due to heavy rainfall at the site. Results of previous field investigations indicate that chlorinated VOC contamination in the surface and subsurface soil at the Site has impacted the groundwater from the upper boundaries of the unconfined aquifer to about 19 feet bgs. Results of a 2005 field investigation indicate the presence of a DNAPL source area consisting primarily of PCE. The DNAPL source area (primarily PCE) at the site has been relatively well-characterized and was ideal for this demonstration. The purpose of the demonstration to evaluate the ability of EZVI to remediate the chlorinated solvent DNAPL source zone at the site, achieve pre-established ROI goals, and evaluate the ability of Pneumatic and Direct Injection techniques to evenly distribute the EZVI in a controlled manner. EZVI was injected into the test plots at the site in October 2006. 576 gal of EZVI was injected into 8 locations within the Pneumatic Injection test plot, and a total of 151 gallons of EZVI was injected into 4 locations within the Direct Injection test plot. There were some complications during the demonstration due to the shallow nature of the target injection areas and pre-existing soil borings at the site. As a result, EZVI was not evenly distributed throughout the treatment areas of each test plot. All other performance objectives including the reduction in DNAPL mass and mass flux of PCE and TCE were successfully met.