In Situ Chemical Oxidation (ISCO); In Situ Heat Soil Vapor Extraction (HSVE)
- At the Former Market Place site: ISCO with ozone was implemented; followed by monitored natural attenuation (MNA); technology included ozone air sparge and C-sparging with ozone injection
- At the Denver Colorado site: ISCO using ISOTEC's Modified Fenton's Reagent was implemented; two phases - two injection events for the area inside the former dry cleaner building to treat contaminant source; three injection events to treat the entire groundwater plume; a total of 26,987 gallons of ISOTEC reagents were injected through 244 temporary injection locations; 1st phase: direct push locations (nine points per event) inside former dry cleaner building; direct push locations were on 15-ft centers and shifted laterally between events; 2nd phase: direct push injection points were spaced on 30-ft centers based on a conservative radius of influence of 15 ft determined from a pilot test; direct push locations for second and third injection events shifted laterally from first event locations to ensure complete reagent coverage across the site
- At the United Cleaners #1973 site, in situ HSVE was implemented; system used a series of in-ground coils to transfer heat, increase volatility of organic contaminants, and facilitate removal of volatile solvents from the soil using a vapor extraction system; after operation for 120 days, the system was modified slightly, including adding heat points and an extraction well
Varied by site
Tetrachloroethene (PCE); Trichloroethene (TCE); Dichloroethene (DCE); Volatiles-Halogenated
- Former Market Place: PCE - 27,000 g/L; Plume size: 28,600 ft2
- Denver Colorado - PCE - 18,200 g/L; TCE - 12,600 g/L
- United Cleaners #1973 - PCE - 4,300,000 g/kg; TCE - 170,000 g/kg; cis-1,2-DCE - 144,000 g/kg; trans-1,2-DCE - 865 g/kg; 1,1,1-trichloroethane - 5,610 g/kg; 1,1-Dichloroethene - 306 g/kg
Waste and wastewater from drycleaning operations
Type/Quantity of Media Treated:
Groundwater; Soil; DNAPL
Former Market Place:
- Depth to groundwater: 10 ft bgs
- Subsurface geology: fine silty sands, clay and shellhash
- Groundwater gradient: 0.006 ft/ft
- Depth to groundwater: 9 ft bgs
- Subsurface geology: sands, silts, and clay overlying siltstone bedrock. Clay, 0-9 ft bgs; permeable sand and gravel, 9-12 ft bgs; siltstone, 12+ ft bgs; subsurface conditions appear to be relatively uniform throughout the plume area; groundwater at the site appears to be confined to the permeable zone overlying the siltstone;
- Groundwater gradient: 0.121 ft/ft to the east
United Cleaners #1973
- Native soils in the vicinity are Wadsworth and Haeger Members of the Wedron Formation; Silty and pebbly drifts containing local areas of sandy to gravely till in outer moraines. Bedrock in the site consists of Silurian-aged dolomite
Purpose/Significance of Application:
Use of in situ treatment technologies to treat chlorinated solvents in groundwater at dry cleaner facilities
Regulatory Requirements/Cleanup Goals:
- Former Market Place - Groundwater: <5 g/L of PCE; <5 g/L of TCE; <70 g/L of cis-1,2-DCE, <100 g/L of trans-1,2-DCE, <2 g/L of vinyl chloride
- Denver Colorado - None available
- United Cleaners #1973 - site-specific cleanup goals: 1,1-DCA - 1,830,000 g/kg; cis-1,2-DCE - 1,900,000 g/kg; PCE - 100,000 g/kg; TCE - 440,000 g/kg; vinyl chloride - 250 g/kg
Former Market Place:
- MW-2I (an intermediate well with the highest initial concentration on site) showed a reduction of PCE from 26,800 g/L to 704 g/L
- Following final injection event, PCE concentrations ranged from 70 g/L to non-detect (ND); average PCE concentration across the site was reduced from 3,267 g/L to 39.6 g/L, a reduction of 99%. PCE concentration in MW-5 was reduced from 925 g/L to 51 g/L, a reduction of 94%.
- TCE concentrations ranged from 170 g/L to ND; average TCE concentration across the site was reduced from 1,387.8 g/L to 64.9 g/L, a reduction of 95%. TCE concentration in MW-5 was reduced from 550 g/L to 52 g/L, a reduction of 90%.
- Average TCE concentrations in all wells (including source area wells) was reduced by 98%.
- PCE soil concentrations reduced from 4,300,000 g/kg to 2,400,000 g/kg. Additionally, one of the two areas where the remediation system was installed was completely cleaned up. The vapor extraction system was turned off in this area. Extraction has continued only at those areas where the objectives have not yet been met.
- Former Market Place - Cost for operation and maintenance (O&M) - $50,000
- Denver Colorado - $39/cubic yard of saturated soil treated. Costs include pilot scale tests, full-scale treatment, and direct push injection equipment and labor.
- United Cleaners #1973 - Not available
In situ treatment was conducted at three dry cleaner sites contaminated with chlorinated solvents from dry cleaning operations, with PCE and TCE as the primary contaminants in groundwater. The technologies implemented included ISCO and HSVE. The concentrations of PCE and TCE contamination varied by site with levels of PCE in groundwater as high as 27,000 µg/L and TCE in groundwater as high as 12,600 µg/L. Levels of PCE and TCE in soil were as high as 4,300,000 µg/kg and 170,000 µg/kg, respectively. The remediations, including full-scale and demonstration-scale projects, involved the subsurface injection of ozone and ISOTECs Modified Fentons Reagent, and the use of in-ground coils to transfer heat and remove volatile contaminants.
At the Former Market Place site, PCE concentrations were reduced substantially, but still remained above the cleanup goal of 5 µg/L. At the Denver Colorado site, PCE concentrations across the site were reduced by 99%, and TCE concentrations were reduced by 90%. At the #1973 site, PCE soil concentrations were reduced by approximately 50%. Additionally, one of the two areas where the remediation system was installed was completely cleaned up. At the Denver Colorado site, the cost of implementing ISCO was approximately $39/cubic yard of saturated soil treated. At the United Cleaners #1973 site, it was useful to have remote access capability to check the system during operation.