Soil Vapor Extraction at the Sand Creek Industrial Superfund Site, Operable Unit No. 1, Commerce City, Colorado

Site Name:

Sand Creek Industrial Superfund Site

Location:

Commerce City, Colorado

Period of
Operation:

September 24, 1993 - April 27, 1994

Cleanup
Type:

Full-scale cleanup

Vendor:

Christopher Strzempka
Project Technical Mgr. for OU-1
OHM Remediation Services Corp.
16406 U.S. Route 224
East Findlay, OH 45840
(800) 537-9540

Technology:
Soil Vapor Extraction

- System was OHM's patented Fluid Injection-Vacuum Extraction (FIVE) technology
- Included 31 vertical wells and 1 horizontal well, and catalytic oxidizer
- Wells screened 3-32.5 ft below ground surface (bgs)
- Some wells operated as injection wells and others as extraction wells

Cleanup Authority:
CERCLA
- Action Memorandum Date 9/29/89
- Federal Lead/Fund Financed

SIC Code:
2879 (Pesticides and Agricultural
Chemicals, NEC)
2911 (Petroleum Refining)
Point of Contact:
Erna Waterman, 8 EPR-SR
USEPA Region VIII
999 18th Street, Suite 500
Denver, CO 80202-2466
(303) 312-6762

Contaminants:
Volatiles - Halogenated: chloroform, methylene chloride, tetrachloroethene (PCE), and trichloroethene (TCE); Volatiles - Nonhalogenated: TPH

- Maximum soil concentrations: chloroform - 0.820 mg/kg; methylene chloride - 5.8 mg/kg; TCE - 0.087 mg/kg; and PCE - 9.34 mg/kg

Waste Source:
Manufacturing Process

Type/Quantity of Media Treated:
Soil
- Estimates of quantity treated ranged from 31,440 -52,920 yd3
- Sandy loams, loamy sands
- Silt and clay - 19.99-24.71%
- LNAPL plume also identified at site

Purpose/Significance of Application:
Full-scale application combining fluid injection and vacuum extraction wells to treat VOC-contaminated soil.

Regulatory Requirements/Cleanup Goals:
- Soil cleanup goals specified for 4 VOCs as follows: chloroform - 0.165 mg/kg; methylene chloride - 0.075 mg/kg; TCE - 0.285 mg/kg; and PCE - 1.095 mg/kg

Results:
- Soil cleanup goals met within 6 months of system operation
- Maximum concentrations in treated soil were: chloroform - 0.0099 mg/kg; methylene chloride - ND; TCE - 0.10 mg/kg; and PCE - 0.28 mg/kg
- Approximately 3,250 lbs of chloroform, methylene chloride, TCE, and PCE extracted (primarily PCE) -
- Approximately 176,500 lbs of total VOCs extracted

Cost Factors:
- Approximately $2,140,000 were expended for this application, including $81,231 for before-treatment activities, and $2,058,564 for activities directly attributed to treatment
- The unit cost for activities directly attributed to treatment was $39-65/yd3 of soil treated, and $11.70/lb of VOC removed
- EPA's decision to revise air emissions control equipment from activated carbon with off-site regeneration to catalytic oxidation resulted in a significant cost savings to the government

Description:
The Sand Creek O.U. 1 site was the location of pesticide manufacturing companies in the 1960s and 1970s, and prior to that, by a petroleum refinery. The pesticide manufacturing companies had two fires in the period from 1968-1977, and were reported to have unsatisfactory waste management practices. Remedial investigations conducted from 1984 to 1988 showed three subareas of soil contamination at Sand Creek O.U. 1 with the following maximum soil concentrations of halogenated VOCs: chloroform - 0.820 mg/kg, methylene chloride - 5.8 mg/kg, TCE - 0.087 mg/kg, and PCE - 9.34 mg/kg. Based on these concentrations, EPA estimated the total mass of the four target contaminants in the operable unit as 684 pounds.

A Record of Decision (ROD) addressing Sand Creek O.U. 1 was signed in September 1989 and an Explanation of Significant Differences (ESD) modifying the 1989 ROD was issued in September 1993. OHM's patented fluid injection/vapor extraction (FIVE) system was used to remediate O.U. 1. In the FIVE technology, pressurized air is injected into vadose zone soils to produce relatively larger subsurface pressure gradients and higher flow rates of extracted vapors than would be achieved solely with using vapor extraction technology. The FIVE system used at O.U. 1 consisted of 32 extraction/injection wells (31 vertical, 1 horizontal), three positive displacement blowers (for extraction), one liquid/vapor separator, one catalytic oxidizer, and two blowers (for injection). The wells were screened up to 32.5 feet below ground surface.

Confirmatory soil borings showed that the concentrations for all four target contaminants were less than the cleanup standards set in the ROD. The maximum concentration of target contaminants measured in the confirmation soil borings was: chloroform - 0.0099 mg/kg, methylene chloride - not detected, TCE - 0.10 mg/kg, and PCE - 0.28 mg/kg. Approximately 176,500 pounds of total VOCs were extracted during this application, including 3,250 pounds of the four target contaminants. The mass of target compounds removed was almost 5 times greater than the original estimate. According to the RPM, possible reasons for this discrepancy include VOC losses during pre-remediation sampling and analysis, which can cause the results to be biased low; and results not representative of the zone of influence of the SVE wells.