Technology:
In Situ Bioremediation Using HRC®
- HRC® is a proprietary, food quality, polylactate ester that slowly degrades to lactic acid upon hydration; the lactic acid is metabolized to a series of organic acids and hydrogen, which serve as electron donors for reductive dechlorination of chlorinated VOCs
- Two applications - first in May 2000 with1,329 gal injected in 103 injection points from 8 to 28 ft bgs using a bottom-up injection method; second in November 2001 in 105 injection points with 575 gal injected from 10 to 30 ft bgs using a top-down injection method
- HRC® applied on a 5 ft by 10 ft grid within the 1,000 μg/L TCE in groundwater contour (about two-thirds of the injection points), and on a 5 ft by 5 ft grid within the 5,000 μg/L TCE contour (about one third of the injection points)
|
Cleanup Authority:
State
Contacts:
State Contact:
Michelle Rembaum-Fox
The California Regional Water Quality Control Board, San Francisco Bay Region
1515 Clay Street, Suite 1400
Oakland, CA 94612
Telephone: (510) 622-2387
Prime Contractor:
Catherine McDonald
GeoTrans Inc.
3035 Prospect Park Drive, Suite 40
Rancho Cordova, CA 95670
Telephone: (916) 853-1800 |
Contaminants:
Volatiles-Halogenated; Trichloroethene (TCE)
- Volatile organic contaminants (VOCs) , primarily TCE
- TCE concentrations as high as 10,000 μg/L in groundwater and 10,000 μg/kg in soil |
Waste Source:
Released from manufacturing operations |
Type/Quantity of Media Treated:
Groundwater
- Depth to groundwater - 7 to 10 ft bgs |
Purpose/Significance of Application:
Use of enhanced in situ bioremediation using HRC® to treat VOC-contaminated groundwater at a site with an active business |
Regulatory Requirements/Cleanup Goals:
- Groundwater cleanup goals based on state and EPA MCLs, including TCE - 5 μg/L; cis-1,2-DCE - 6 μg/L; trans-1,2-DCE-10 μg/L; vinyl chloride - 0.5 μg/L
- No soil cleanup goals established as initial concentrations were below EPA Region 9 Preliminary Remediation Goals for residential soils |
Results:
- Data are available for May 1999 to July 2003, with analytical data presented for four wells, including wells upgradient, in the center of the plume, and along the perimeter of the plume
- After the first injection of HRC® in May 2000, concentrations of TCE decreased, with corresponding increase in degradation products cis-1,2-DCE and vinyl chloride
- After the second injection in November 2001, TCE concentrations continued to decrease, concentrations of cis-1,2-DCE and vinyl chloride decreased, and concentrations of degradation product ethene increased
- As of July 2003, TCE concentrations were below cleanup goals in selected wells; while concentrations of cis-1,2-DCE and vinyl chloride continued to decrease, they remained above the cleanup goals in most of the selected wells
- Currently, groundwater monitoring and natural attenuation monitoring are being performed on a semiannual basis at the site |
Cost Factors:
- Costs for two applications of HRC® were $107,000
- Direct push injection costs totaled approximately $30,000 including the two HRC® applications and soil sampling
- Groundwater monitoring costs averaged approximately $8,000 per monitoring round for nine wells, including field costs (low-flow purging) and laboratory costs for the full suite of in-situ bioremediation monitoring parameters
- Estimated budget for the in-situ monitoring and analyses conducted from May 2000 through July 2003 totaled approximately $130,000 |
Description:
The site is a 4.1 acre property, located in San Jose, California, that is occupied by a 76,000 square foot building that is currently being used for light industrial retail. From the 1960s to the 1980s, the site was used for various manufacturing. Site investigations, conducted in the late 1980s, showed the presence of volatile organic compounds (VOCs) in the subsurface, with TCE concentrations detected as high as 5,000 μg/L in groundwater and 10,000 μg/kg in soil. Cleanup activities at the site are being conducted under a State of California Regional Water Quality Control Board, San Francisco Bay Region order. In late March 1997, the site was proposed for a pilot under a state research and development project to develop methods for setting site cleanup objectives. In March 1999, the Board approved the “In-Situ Remedial Alternatives Evaluation Report” for the site where the proposed remedy was to stimulate anaerobic degradation activities. Results of bench-scale testing during the Spring of 1999 showed that the use of an electron donor could stimulate microbial activity and biodegradation. HRC® and a benzoate-lactate mixture were considered. HRC® was selected because it offered a one-time application process with no ongoing operations and maintenance (O&M) activities, while the benzoate-lactate application used a continuous feed system that would require daily O&M activities. Therefore, it was concluded that HRC® could stimulate the microbial community and the biodegradation process without disrupting the business activities being conducted at the site.
Two applications of HRC® were performed. HRC® was applied on a 5 ft by 10 ft grid within the 1,000 μg/L TCE in groundwater contour(about two-thirds of the injection points), and on a 5 ft by 5 ft grid within the 5,000 μg/L TCE contour (about one third of the injection points). The first application in May 2000 involved injecting 1,329 gal injected in 103 injection points. TCE concentrations decreased, with a corresponding increase in degradation products cis-1,2-DCE and vinyl chloride. A second application of HRC® was performed in November 2001 to complete the degradation process and involved injecting 575 gal into 105 injection points. As of July 2003, TCE concentrations had decreased to below cleanup goals in selected wells. Concentrations of cis-1,2-DCE and vinyl chloride decreased, with a corresponding increase in ethene concentrations; however, these contaminants remain above the cleanup goals in selected wells. Currently, groundwater monitoring and natural attenuation monitoring are being performed on a semiannual basis at the site. |
