In Situ Bioremediation of Chlorinated Solvents Source Areas with Enhanced Mass Transfer at the Fort Lewis, Pierce County, Washington

Site Name:

Fort Lewis East Gate Disposal Yard (EGDY)

Location:

Pierce County, Washington

Period of
Operation:

Injections began in July 2005 and ended in February 2006. Injections were performed over a period of several hours on the following dates:

Injection Strategy 1

  • Treatment Cell 1- July 19, 2005; September 13, 2005; and October 4, 2005
  • Treatment Cell 2 - November 8, 2005; December 13, 2005; January 15, 2006; and February 22, 2006.


Injection Strategy 2
  • Treatment Cell 2 - July 19, 2005; August 16, 2005; September 13, 2005; and October 4, 2005
  • Treatment Cell 1- November 8, 2005; December 13, 2005; January 15, 2006; and February 22, 2006

Cleanup
Type:

Field-scale

Technology:
In Situ Bioremediation (Bioavailability Enhancement Technology {B.E.T.™})

Two hydraulically isolated treatment cells, each consisting of a network of monitoring wells, an injection well, and an extraction well, were installed at the site.

  • Treatment Cell 1 was located on the fringe of the DNAPL source area
  • Treatment Cell 2 was located within the DNAPL source area


Two injection strategies were applied to each treatment cell.
  • For Treatment Cell 1, the first injection strategy was high concentration (10%) whey powder injections, and the second strategy was low concentration (1%) whey powder injections.
  • For Treatment Cell 2, the first injection strategy was the low concentration (1%) injections, and the second strategy was the high concentration (10%) injections.
  • The composition of whey powder used for injections was 70 to 75% w/w lactose and 10 to 13% protein.
  • Injection flow rates were maintained between 5 and 12 gallons per minute (gpm), and injections were performed over a period of several hours. The total target volume injected was approximately 1,800 gallons


Monitoring wells
  • Each treatment area was configured with four monitoring wells, which were completed using a continuous multichannel tubing (CMT) system to provide multilevel sampling capability.
  • Each CMT well was completed with four sampling ports at discrete depths: Port 1 from 13-14 ft bgs, Port 2 from 17-18 ft bgs, Port 3 from 22-23 ft bgs, and Port 4 from 27-28 ft bgs.
  • Two CMT wells were aligned along the groundwater flow axis between the injection and extraction wells, and two CMT wells were aligned cross gradient from the injection and extraction well axis.

Cleanup Authority:
Contacts:

Principal Investigator
Kent Sorenson, Jr.
CDM
555 17th Street, Suite 1100
Denver, CO 80202
Phone: 303-383-2300
Email: sorensonks@cdm.com

Project Engineer
Tamzen W. Macbeth
CDM
50 West 14th Street, 2nd Floor
Helena, MT 59601
Phone: 208-569-5147
Email: macbethtw@cdm.com

Environmental Restoration Program Manager
Andrea Leeson
ESTCP Office
901 North Stuart Street, Suite 300
Arlington, VA 22203
Phone: 703-696-2118
Email: andrea.leeson@osd.mil

Contaminants:
Chlorinated Solvents (trichloroethene [TCE], dichloroethene [DCE])

Waste Source:
Historical site activities including landfill trenching and disposal activities associated with the Fort Lewis East Gate Disposal Yard.

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

Purpose/Significance of Application:
The primary performance objective was to demonstrate that the high-concentration whey injection strategies resulted in greater mass transfer and higher treatment efficiency compared to ambient and low-concentration whey injections. The ESTCP demonstration was specifically designed for quantifying enhanced mass transfer during bioremediation in a real source zone during whey powder amendment under two injection strategies.

Regulatory Requirements/Cleanup Goals:
Key performance measures included increase in total volatile organic compound (VOC) and/or ethene mass flux within source area during treatment with high concentration whey powder; and the reduction of majority of TCE (>99%) contaminant mass flux within and downgradient from treatment areas.

Results:
Comparison of the demonstration results in each treatment cell during injection of low and high whey concentrations facilitated quantification of the relative difference of the enhanced mass transfer mechanisms both within and downgradient of the DNAPL source area. Samples were collected from multilevel sampling wells both during and after the injection. Sampling results indicated the following:

  • Increase in total average VOC and ethene concentrations by a factor of three and two during 10% whey injections compared to 1% whey injections within source area.
  • Increase in total average VOC and ethene concentrations by a factor of three to 16 during 10% whey injections compared to 1% whey injections downgradient of the source area.
  • 99.96% reduction in TCE mass and a 33 to 52% decrease in total VOC mass within treatment areas. Post-treatment samples indicate the conversion to cis-DCE (52-59% of total mass), VC (33-36% of total mass), and ethene (4-10% of total mass) within treatment cells.
  • Seven of eight downgradient monitoring wells observed a 94-98% reduction in total VOC concentrations post bioremediation.


The results demonstrated that the high-concentration whey injection strategy substantially accelerated mass removal rates from the source area and the downgradient plumes compared to ambient and low-concentration whey injection strategy.

Cost Factors:
The total cost for the in situ bioremediation system over a three-year period followed by long-term monitoring is estimated to be approximately $1,976,390. A breakdown of these costs is provided below:

  • Start-Up (field preparation, preliminary site characterization): $289,700
  • Capital (equipment and installation): $26,000
  • Injection (Based on 3 wells and 4 injections per year for 3 years): $180,000
  • Operation and Maintenance (Equipment Rental, Sampling and Analysis): $453,200
  • Demobilization: $26,000
  • Long-term Monitoring: $1,001,498

Description:
The Fort Lewis Logistics Center is located in Pierce County, Washington, approximately 11 miles south of Tacoma and 17 miles northeast of Olympia. The Logistics Center occupies approximately 650 acres of the Fort Lewis Military Reservation. The East Gate Disposal Yard (EDGY) is located southeast of the Logistics Center in an otherwise undeveloped portion of Fort Lewis. At the EGDY, landfill trenching and disposal activities historically occurred over an area of approximately 35 acres resulting in the release of chlorinated solvents to the groundwater at the site.

Site characterization performed as part of the EGDY Phase II Remedial Investigation (RI) indicated high concentrations of dissolved phase TCE (up to 125 mg/L) and DCE (up to 140 mg/L) from 3-14 ft below ground surface. High chlorinated contaminant concentrations were limited to the upper 10 feet of the aquifer. In situ bioremediation with enhanced transfer was used to address the chlorinated solvent source zones located at the site. Two hydraulically isolated treatment cells, each consisting of a network of monitoring wells, an injection well, and an extraction well, were installed at the site. One treatment cell was located on the fringe of the DNAPL source area, and the other was located within the DNAPL source area. Within these two treatment cells, whey powder was injected using two different injection strategies utilizing both high concentration (10%) and low concentration (1%) whey powder injections. The demonstration was implemented in three phases. The objective of Phase 1 and Phase II were to characterize groundwater hydraulic characteristics and determine baseline contaminant concentrations and flux. During Phase III of the demonstration, a series of injections were conducted from July 2005 to February 2006. Samples were collected from multilevel sampling wells both during and after the injection to quantify the relative difference of the enhanced mass transfer mechanisms both within and downgradient of the DNAPL source area. The results demonstrated that the high-concentration whey injection strategy substantially accelerated mass removal rates from the source area and the downgradient plumes compared to the low-concentration whey injection strategy.