Technology:
In Situ Bioremediation - HRC®
- In May 2000, approximately 7,000 lbs of HRC® were injected into 45 borings in the vicinity of the source zone covering an area of approximately 3,000 ft2. A second injection was performed in August 2002.
- Former Colony: A single injection event of HRC® occurred in October 2000. The compound was injected at depths of 6 to 12 ft bgs via direct push at 5 locations up gradient of the source zone. Four lbs/ft were injected for a total of 50 lbs/injection point (total of 250 lbs).
- Former Prestonwood: The limestone subsurface was fractured by injecting HRC® at high pressure at depths of 15 to 25 ft bgs. At shallower depths of 5 to 15 ft bgs, slightly less pressure (40-60 psi) was used. A total of 3,400 lbs was injected.
- Ted’s Cleaners: In September 2002, HRC® was injected at nine injection points. The free product from the wells was removed by bailing in May 2003. Groundwater monitoring events were conducted in November 2002; January 2003; May 2003; and June 2004.
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Cleanup Authority:
State
Contacts: Varied by site |
Contaminants:
Chlorinated Solvents: PCE; TCE; DCE; Cis-1,2-DCE; Trans-1,2-DCE; 1,1-DCE; 1,1,1-TCA; Vinyl Chloride; Dichlorobenzenes; Ethylbenzene
- Arlington: (Groundwater) cis-1,2-DCE - 7.3 g/L; PCE - 4.5 g/L; TCE - 7.3 g/L; VC - 0.87 g/L
- Former Colony: (Groundwater) cis-1,2-DCE - 3.85 g/L; trans-1,2-DCE - 0.18 g/L; PCE - 0.63 g/L; TCE - 2.6 g/L; VC - 0.008 g/L; dichlorobenzenes - 0.006 g/L. (Soil) cis-1,2-DCE - 0.4 g/kg; PCE - 7.4 g/kg; TCE - 0.84 g/kg; ethylbenzene - 0.04 g/kg.
- Former Prestonwood (Groundwater) 1,1-DCE - 0.005 g/L; cis-1,2-DCE - 1.08 g/L; trans-1,2-DCE - 0.55 g/L; PCE - 2.35 g/L; TCE - 0.429 g/L; 1,1,1-TCA - 0.012 g/L. (Soil) PCE - 53 g/kg
- Ted’s Cleaners: (Groundwater) cis-1,2-DCE - 2.33 g/L; trans-1,2-DCE - 0.021 g/L; PCE - 22 g/L; TCE - 0.82 g/L; VC - 0.001 g/L. (Soil) cis-1,2-DCE - 0.0410 mg/kg; PCE - 0.0640 mg/kg; TCE - 0.0025 mg/kg |
Waste Source:
- Waste and wastewater from dry cleaning operations.
- At one site (Ted’s Cleaners), prior disposal of PCE wastes, still bottoms, and spent filter cartridges in a dumpster located at the facility, may also have contributed to the contamination. |
Type/Quantity of Media Treated:
Soil, Groundwater
- Arlington: depth to groundwater: 7 ft bgs; subsurface geology: Predominantly medium to dark gray shale
- Former Colony: depth to groundwater: 13 to 15 ft bgs; subsurface geology: Clay at 15 ft bgs, limestone (Austin Chalk) at 15 ft bgs
- Former Prestonwood: depth to groundwater: 5 ft bgs; subsurface geology: Fill material, clay lenses, limestone
- Ted’s Cleaners: depth to groundwater: 3.2 to 10.7 ft bgs; subsurface geology: Limestone bedrock is overlain by sand and gravel alluvium in a matrix of silt and clay. Overburden varies from 5.7 ft to 22.5 ft bgs. |
Purpose/Significance of Application:
Use of in situ bioremediation using HRC® to treat soil and groundwater contaminated with chlorinated solvents at dry cleaner facilities. |
Regulatory Requirements/Cleanup Goals:
- Arlington: (Groundwater) PCE - 500 μg/L; TCE - 500 μg/L; cis-1,2-DCE - 7,000 μg/L; VC - 200 μg/L. (Soil) PCE - 7 mg/kg; TCE - 0.5 mg/kg; cis-1,2-DCE - 0.5 mg/kg; VC - 0.2 mg/kg
- Former Colony: Cleanup goals not specified
- Former Prestonwood: (Groundwater) PCE - 500 μg/L. (Soil): PCE - 50,000 μg/kg
- Ted’s Cleaners: Remove or reduce contaminant source area. No site specific cleanup goals were established. |
Results:
- Arlington: Sampling conducted in January and April 2002 indicated that PCE concentrations exceeded the cleanup goal in one monitoring well, leading to a second HRC® injection event. Following the second injection, the dissolved contaminants remained below cleanup goals. Confirmatory soil samples indicated that cleanup goals for the soil were not exceeded. A certificate of completion was issued for this site.
- Former Colony: Contaminant concentrations in groundwater have decreased since HRC® injection in October 2000. Groundwater monitoring is being continued at the site.
- Former Prestonwood: Two years after HRC® injection, PCE concentration in one monitoring well increased from 15,000 μg/L to 23,500 μg/L. Additional groundwater monitoring has been recommended for the site.
- Ted’s Cleaners: As of the June 2004 monitoring results, no effect of HRC® injection had been observed on down gradient contaminant concentrations approximately 5 ft away. Additional testing is being done at the site, including the polymerase chain reaction test. |
Cost Factors:
- Arlington, Former Colony, and Former Prestonwood: No cost data available
- Ted’s Cleaners: $7,500 (remedy selection report); $ 35,000 (pilot study injection); $110,000 (total project cost to date including monitoring) |
Description:
In situ bioremediation using HRC® was conducted at four dry cleaner sites contaminated with chlorinated solvents. The concentration of contaminants varied by site with levels of cis-1,2-DCE and TCE as high as 7.3 g/L and PCE as high as 22 g/L. Levels of TCE, and PCE in soil were as high as 0.8 g/kg, and 53 g/kg, respectively. At three sites (Arlington, Former Colony, and Former Prestonwood), remediation was carried out at full scale while at Ted’s Cleaners, a pilot scale operation was performed.
At the Arlington site, HRC® was injected in two events. Following these injections, the concentrations of dissolved contaminants were reduced tobelow the cleanup goals and a certificate of completion was issued for the site. An important lesson learned at this site was that contaminant concentrations can rebound with use of HRC®. Monitoring should be continued for at least a year after injection to ensure that cleanup levels for various contaminants are not exceeded. At the Former Colony site, HRC® injection was used to stimulate biodegradation. A single injection was carried out in October 2000, where 250 lbs was injected into the contaminated source area. PCE concentrations have steadily declined since the injection. Monitoring is ongoing at the site. At the Former Prestonwood site, excavation of contaminated soil had been carried out prior to HRC®. Injection in June 2001. At this site, limestone subsurface had to be fractured using a higher pressure injection of HRC® at greater depths and a lower pressure injection at shallower depths. Approximately 136 lbs were injected into 25 boreholes, for a total injection of 3,400 lbs of HRC® at the site. PCE concentration increased from 15,000 μg/L to 23,500 μg/L approximately two years after the first injection. Additional monitoring has been recommended at the site. At the Ted’s Cleaners site, HRC® was selected for a pilot test, where it was injected at 9 points in the target area in a grid-like pattern. As of June 2004, no change in groundwater contaminant concentrations had been observed, and additional monitoring is being carried out at the site for natural attenuation parameters in addition to polymerase chain reaction tests. The total cost of the project including monitoring costs was about $110,000. |
