Air Sparging at Four Sites

Site Name:

Four Service Stations (specific site names not identified)

Location:

- Service station, Pensacola, Florida
- Fuel station, Albuquerque, New Mexico
- Service station, Sebato, Maine
- Service station, Massachusetts (city not provided)

Period of
Operation:

1993 to 1995
- Florida site (3/94 to 7/94)
- New Mexico site (6/93 to 1/95)
- Maine site (4/94 to 10/95)
- Massachusetts site (operated for 21 months; dates not provided)

Cleanup
Type:

Full scale

Vendor:

Nick Hastings/David Bass
IT Corporation
431-F Hayden Station Road
Windsor, CT 06095
Telephone: (860) 688-1151
Fax: (860) 688-8239
E-mail: nhastings@theitgroup.com

Technology:
Air Sparging
- Number of air sparging wells at the four sites ranged from 4 to 9, with well spacings ranging from 25 to 50 feet (ft) and flow rates of wells ranging from 5 to 10 scfm
- One of the systems was pulsed on a daily cycle; the others sparged on a continuous basis
- For three sites, the air sparging wells were located over the source area; for one site, the air sparging wells were arrayed at points located downgradient from the source

Cleanup Authority:
Not provided

Contaminants:
MTBE, BTEX
- MTBE concentrations at the sites ranged from 215 ug/L to 62,000 ug/L in groundwater
- BTEX concentrations at the sites ranged from 64 ug/L to 198,000 ug/L in groundwater

Waste Source:
Leaks from gasoline storage tanks

Type/Quantity of Media Treated:
Groundwater
- Sand to fine sand aquifers at three of the sites (Florida, New Mexico, Maine); not reported for Massachusetts site
- Depth to groundwater about 40 feet below ground surface at New Mexico site; not reported for other sites

Purpose/Significance of Application:
Air sparging used to treat MTBE in groundwater

Regulatory Requirements/Cleanup Goals:
Information about specific cleanup goals for each site was not provided

Results:
- For four sites, the reduction in MTBE concentrations at shutdown ranged from greater than 99% to 46.5%
- Post-closure monitoring for MTBE, performed at three sites, showed reductions that ranged from greater than 97.8% to 99.97% ug/L
- At the Florida site, air sparging reduced the concentration of MTBE in the groundwater to <5 ug/L, with no rebound after 6 months of post-closure monitoring
- At the New Mexico site, MTBE concentrations were reduced to 27 ug/L, with the concentration further reduced to 8 ug/L after 13 months of post-closure monitoring
- At the Maine site, MTBE concentrations were reduced to between 16 and 980 ug/L, and the concentration was further reduced to ND - 115 ug/L after 6.5 months of post-closure monitoring
- At the Massachusetts site, MTBE was reduced to 115 ug/L (a 46.5% reduction); no rebound was reported for this site

Cost Factors:
No cost data were provided for these sites

Description:
Air sparging was used to treat groundwater contaminated with gasoline from leaking storage tanks at the following four sites - a service station in Pensacola, Florida, a fuel station in Albuquerque, New Mexico, a service station in Sebato, Maine, and a service station in Massachusetts. Contaminants found in the groundwater included MTBE and benzene, toluene, ethylbenzene, and xylenes (BTEX) at two sites, MTBE, BTEX, and gasoline at one site, and MTBE and benzene at one site. The number of air sparging wells at the four sites ranged from 4 to 9, with well spacings ranging from 25 - 50 feet (ft) and flow rates of wells ranging from 5 - 10 scfm. One of the systems was pulsed on a daily cycle and the others sparged on a continuous basis. The duration of the projects ranged from 4 to 21 months.

Information on specific cleanup goals for each site was not provided. Air sparging reduced the concentration of MTBE in the groundwater to <5 ug/L, with no rebound after 6 months of post-closure monitoring at the Florida site; to 27 ug/L at the New Mexico site, with the concentration further reduced to 8 ug/L after 13 months of post-closure monitoring; to between 16 and 980 ug/L at the Maine site, with the concentration further reduced to ND - 115 ug/L after 6.5 months of post-closure monitoring; and to 115 ug/L at the Massachusetts site, with no rebound reported. According to the vendor, in situ air sparging also can be applied in combination with bioaugmentation for rapid initial mass removal by volatilization followed by removal via aerobic biodegradation (where air sparging becomes the oxygen delivery vehicle).