In Situ Bioremediation of Perchlorate and Nitrate in Vadose Zone Soil using Gaseous Electron Donor Injection Technology in Sediment at Hunters Point Shipyard Parcel F, San Francisco Bay, California

Site Name:

Boeing Inactive Rancho Cordova Test Site (IRCTS) Propellant Burn Area (PBA)

Location:

Rancho Cordova, CA

Period of
Operation:

Field Demonstration: December 12, 2007 to December 1, 2008, including:

  • System Checkout: December 12, 2007 to January 2, 2008
  • Phase II — Tracer Tests: January 17, 2008 to February 8, 2008
  • Phase II — Optimization: February 20, 2008 to April 16, 2008
  • Phase II — Steady State Mixed Gas — April 10, 2008 to August 12, 2008
  • Phase IV — Steady State LPG — September 8, 2008 to December 1, 2008

Cleanup
Type:

Field Demonstration

Technology:
Enhanced In Situ Bioremediation

Gaseous electron donor injection technology (GEDIT) involves injection of gaseous electron donors (GED) into the soil with the purpose of promoting anaerobic biodegradation of perchlorate to water and chloride ions.

The demonstration at IRCTS was conducted in four phases.

  • Phase I — Treatability studies conducted in the laboratory and at the site.
  • Phase II — Characterization of gas transport in the vadose zone using tracer tests. To determine the most cost-effective method for gas delivery into the vadose zone and minimize oxygen interference, optimization tests were conducted using a gas mixture of N2, H2, liquefied petroleum gas (LPG), and carbon dioxide (CO2).
  • Phase III — A five month period when the gas mixture composed of 79% N2, 10% H2, 10% LPG, and 1% CO2 was continuously injected into the vadose zone to create anaerobic conditions that would support perchlorate biodegradation. A total of 100 cubic feet per hour (cfh) of the gas mixture was injected into the 18- and 28-feet below ground surface (bgs) screens of piezometer P4. The flow was divided equally into each screen (i.e., 50 cfh each).
  • Phase IV — A three month period when only pure LPG was continuously injected to evaluate its potential use as an electron donor. LPG was injected at a flow rate of 100 cfh divided evenly across the 18- and 28-feet bgs screens of piezometer P4.


The demonstration was conducted to a depth of 50 feet bgs. A total of three long-screen injection wells and 10 short-screen (6-inches)/multi-depth piezometers were installed for the demonstration. The gas injection system was designed to be operated without any electrical requirements because of the remoteness of the site. The liquid N2 and LPG systems were vaporized using vendor-supplied equipment prior to injection. Each gas flow was controlled using manual pressure regulators and flow control valves along with rotameters to measure flow and gauges to monitor pressure.

Cleanup Authority:
Department of Defense (DoD)

Contacts:

Principal Investigator
Patrick Evans
CDM
14432 S.E. Eastgate Way, Suite 100
Bellevue, WA 98007
Phone: 425-519-8300
Email: evanspj@cdm.com

Co-Principal Investigator
Rachel Brennan
The Pennsylvania State University
Department of Civil and Environmental Engineering
University Park, PA 16802
Phone: 814 -865-9428
Email: rbrennan@engr.psu.edu

Site Owner
Rodney Fricke
Aerojet-General Corp. P.O. Box 13222, MS-5519
Sacramento, CA 95813
Phone: (916) 355-5161
Email: rodney.fricke@aerojet.com

Site Regulator
Alexander MacDonald
California Regional Water Quality Control Board
11020 Sun Center Drive
Suite 200 Rancho Cordova, CA 95670
Phone: 916-464-4625
Email: amacdonald@waterboards.ca.gov

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

Contaminants:
Perchlorate and Nitrate/Nitrites

Waste Source:
From about 1957 to 1963, the site was used for the incineration of waste rocket propellant and/or laboratory chemicals resulting in widespread soil perchlorate contamination within the PBA.

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

Purpose/Significance of Application:
The objective of this project was to demonstrate and validate GEDIT for the treatment of perchlorate and nitrate in vadose zone soil. Project objectives included identifying valuable engineering design information on GEDIT implementation and the development of an engineering guidance document was another objective of the project.

Regulatory Requirements/Cleanup Goals:
Quantitative Performance Objectives for the demonstration include the following:

  • Achieve an average 90% reduction in perchlorate concentration within the radius of influence (ROI) for electron donor transport
  • Achieve an average 90% reduction in nitrate/nitrate concentration within the ROI for electron donor transport
  • Achieve an average 90% perchlorate reduction within 12 months
  • Achieve an average 90% nitrate/nitrite reduction within 12 months
  • Achieve a ROI for electron donor transport of greater than 10 feet in the permeable zones

Results:
Technology performance was evaluated by comparing final samples the soil borings installed immediately adjacent to piezometers and injection wells to the baseline data from 2006. All performance objectives were met or exceeded. A summary of the results is presented below:

  • The performance objective of 90% for perchlorate destruction was exceeded. A 93 ± 9 percent reduction in perchlorate concentrations was observed within the targeted 10-foot ROI around the injection point at a depth of 10 to 40 feet bgs. Perchlorate reduction was not significant at 50 feet bgs and at distances greater than 15 feet from the point of injection.
  • The performance objective of 90% for nitrate destruction was exceeded. A 94 ± 9 percent reduction in nitrate/nitrite concentration was observed within the 10-foot ROI around the injection point at depth of 10 to 50 feet bgs. 90 ± 14 percent reduction in nitrate/nitrite concentrations was observed within 56 feet from injection point at depth of 10 to 50 feet bgs. Nitrate reduction was relatively constant, suggesting that LPG supported nitrate reduction.
  • A 88 ± 11 percent perchlorate reduction was observed in 3 months, based on comparison of confirmation boring CB3 concentrations to baseline concentrations. A 93 ± 9% perchlorate reduction was observed in 5 months or less.
  • A 93 ± 5% nitrate/nitrite reduction was observed in 3 months.
  • An ROI for electron donor transport of greater than 10 feet in the permeable zones was achieved. The ROI for consistent H2 distribution and oxygen depletion was at least 10 feet and likely as much as 15 feet. With respect to conditions for nitrate destruction, the ROI was at least 56 feet. H2 and propane were observed up to 56 feet away from the injection point; oxygen depletion occurred up to 56 feet away from injection point; and significant perchlorate destruction was observed at distances up to 15 feet from the injection point.


The results also indicated that continuous injection of pure LPG was less effective than the gas mixture with respect to oxygen depletion and electron donor distribution. However, injection of pure LPG did have a distinct advantage with respect to oxygen depletion and electron donor distribution at depths greater than the point of injection.

Cost Factors:
Based on the IRCTS-PBA demonstration, the following cost estimate was developed for a full-scale design.

Treatability Study and Gas Permeability Test: $160,000
Engineering Design: $ 67,000
Installation: $9,566,000
Operation and Maintenance: $ 7,728,000
Final Report and Demobilization: $ 575,000
Project Management: $ 85,000
Total - $ 20,868,000
Cost per cubic yard: $68

The cost estimate assumes a ROI of 10 feet, 79% N2 composition, 10% H2 composition, a 10% LPG composition, a total soil volume of 310,000 cy, and a treatment objective of achieving 90% mass reduction of perchlorate.

Description:
The demonstration was conducted at the PBA within the IRCTS, which is located approximately 15 miles east of Sacramento. The PBA comprises approximately 8 acres of undeveloped land in the northwestern quadrant of the IRCTS. From about 1957 to 1963, the site was used for the incineration of waste rocket propellant and laboratory chemicals. Starting in 1992 and continuing into 1998, several investigations assessed the depth and breadth of contamination associated with various chemicals that were released to the soil and groundwater at the PBA. Site investigation data indicated that perchlorate contamination in soil is widespread within the PBA. The perchlorate concentrations ranged up to 250 milligram/kilogram (mg/kg), with an average of 35mg/kg.

In the one-year field demonstration, GEDIT was used for the treatment of perchlorate and nitrate in vadose zone soil. In the demonstration area, perchlorate concentrations in excess of 100 mg/kg were observed near the surface and decreased with depth. The demonstration was conducted to a depth of 50 feet bgs. The demonstration was conducted in four phases. Phase I consisted of treatability studies conducted in the laboratory and at the site. Phase II involved tracer tests and optimization tests using a H2/N2 mixture. During Phase III, a gas mixture composed of 79% N2, 10% H2, 10% LPG, and 1% CO2 was continuously injected from April 10, 2008 to August 12, 2008. Phase IV involved continuous injection of pure LPG to evaluate its potential use as an electron donor. LPG was injected continuously from September 8, 2008 to December 1, 2008. Gas and soil samples were collected during both Phase III and Phase IV to verify system operation and quantify perchlorate and nitrate degradation. Results indicated that all performance objectives were met. Significant perchlorate and nitrate concentration reductions were observed within the 10-foot target ROI. Perchlorate reductions were especially pronounced in the shallower vadose zone horizons, while nitrate concentration reductions were observed at all depths. The results also indicated that continuous injection of pure LPG was less effective than the gas mixture with respect to oxygen depletion and electron donor distribution. However, injection of pure LPG did have a distinct advantage with respect to oxygen depletion and electron donor distribution at depths greater than the point of injection.