Soil Vapor Extraction at Fort Richardson, Building 908 South, Anchorage, Alaska

Site Name:

Fort Richardson


Anchorage, Alaska

Period of

Status: Ongoing
Report covers: 2/95 through 3/96 (closure planned for Spring of 1999)


Indefinite Delivery Type Remedial Action;
voluntary cleanup


Linder Construction
8220 Petersburg Street
Anchorage, AK 99507
(907) 349-6222

AGRA Earth & Environmental
711 H Street, Suite 450
Anchorage, AK 99501
(907) 276-6480

Soil vapor extraction

- Two SVE wells screened from 7 to 50 ft bgs were installed to a total depth of 55 ft bgs.
- Soil gas extracted by a rotary blower was discharged to the ambient air after passing through a knockout drum and a particulate filter.
- The system was operated at an air flow rate of 205-220 scfm, with a vacuum at the wells of 2-7.5 inches water.

Cleanup Authority:
Alaska Department of Environmental Conservation UST Regulations (18 AAC 78)

Regulatory Point of Contact:
Information not provided
USACE Contact:
Deirdre M. Ginter
USACE - Alaska District
P.O. Box 898
Anchorage, AK 99506-0898
(907) 753-2805

Volatile - nonhalogenated: BTEX; volatile - halogenated: chlorobenzenes; and Petroleum Hydrocarbons: GRO and DRO. Maximum contaminant concentrations were DRO (17,000 mg/kg), total BTEX (2.28 mg/kg), and total chlorobenzenes (11.93 mg/kg).

Waste Source:
Leaking underground storage tank

Type/Quantity of Media Treated:
- Estimated as 4,600 yd3.
- Primarily consisted of gravel with either sand or clay.
- Geology consists of surface deposits of glacial till, outwash, and silt

Purpose/Significance of Application:
Application of SVE to treat gravelly-soil contaminated with diesel fuel.

Regulatory Requirements/Cleanup Goals:
- ADEC Matrix Level B cleanup levels were identified for this application. These levels are as follows: DRO (200 mg/kg), GRO (100 mg/kg), Benzene (0.5 mg/kg), Total BTEX (15 mg/kg).
- No performance objectives were established for air emissions from the blower for the application.

- In a soil boring collected in March 1996 (after approximately one year of operation), the concentrations of DRO, GRO, benzene, and total BTEX were lower than their respective cleanup goals at all depths sampled.
- Analytical data from March 1995 to February 1996 indicate that DRO emissions from the blower were reduced by approximately 90 percent, and that GRO emissions were reduced by approximately 95 percent, over that time period.
- The system is planned for shutdown in the Spring of 1999, after evaluation of analytical results from confirmation samples.

Cost Factors:
- The award cost for this application was $305,053, with $252,200 being directly attributed to construction and operation of the treatment system. This corresponds to $55 per yd3 of soil treated.
- Since the application has not yet been completed, information about actual costs were not available, and it was not known how the actual costs will compare with the award costs.

Ft. Richardson, constructed in 1950, is located adjacent to Elmendorf Air Force Base and is eight miles from Anchorage, Alaska. Four USTs were removed in 1989 and 1990. One of these tanks, a 1,000-gallon fuel oil tank removed in September 1989 from an area adjacent to Building 908 South, was found to be leaking. Contaminated soil was excavated to 26 ft bgs, but remained at the bottom of the excavation. ADEC allowed the backfilling of the excavation with the understanding that the contamination would be remediated at a later date.

In the initial remedy selection process, low-impact bioventing was selected over aggressive bioventing and natural attenuation with or without the installation of a protective cap. However, SVE was eventually selected for implementation at Ft. Richardson because it did not require the nutrient addition or monitoring of biological activity parameters that would have been needed for bioventing. The SVE system was installed in February 1995.

An interim soil boring was drilled between the two SVE wells in March 1996, and samples from the boring showed that cleanup goals were being met in that area. The system was operating as of July 1998 and is currently slated for shutdown in the Spring of 1999 if additional sampling confirms that cleanup goals have been met throughout the area.