Electrical Resistive Heating at Hunter Army Airfield, Former Pumphouse #2, Savannah, Georgia

Site Name:

Hunter Army Airfield (Hunter AAF), Former Pumphouse #2

Location:

Savannah, Georgia

Period of
Operation:

April 5, 2002 to August 5, 2002

Cleanup
Type:

Full scale

Technology:
Electrical Resistive Heating - Six-Phase HeatingTM (SPH)

- A total of 111 ERH electrodes were installed at a spacing of 18 feet (ft), and to a depth of 16 ft bgs. The steel conductive interval ranged from 8 to 16 ft bgs, with the actual steel electrode extending from 9 to 16 ft bgs.
- In the area where free product (LNAPL) was located, 18 of the electrodes were installed as a combination of electrode and dual vapor extraction (DVE) wells. The conductive interval was 9 to 16 ft bgs for the DVE wells. The electrode/DVE wells served as heating elements and as contingency product-extraction points.
- A total of 23 vapor recovery wells (VRWs) were installed at a spacing of 40 ft, for a radius of influence of 25 ft. Two types of VRWs were installed in 8-inch diameter boreholes; DVE and soil vapor extraction (SVE) wells.
- To monitor the internal temperature of the treatment area, 15 temperature monitoring points (TMPs), were installed with thermocouples located at 8, 12, and 16 ft bgs.
- The average subsurface temperature was greater than 90°C

Cleanup Authority:
State (Georgia Environmental Protection Division)

Contacts:

State Regulator
Mr. William Logan
Georgia Environmental Protection Division
Underground Storage Tank Management Program
4224 International Parkway, Suite 104
Atlanta, Georgia 30354
Telephone: (404) 362-4529
E-mail: William_Logan@dnr.state.ga.us

Potentially Responsible Party (PRP) Oversight
Ms. Ana Vergara
U.S. Army Corps of Engineers (USACE)
Savannah District
100 W. Oglethorpe Avenue
Savannah, Georgia 31401
Telephone: (912) 652-5835
E-mail: Anadel.R.Vergara@sas02.usace.army.mil

Ms. Tressa Rutland
Department of the Army Headquarters, Fort Stewart
Directorate of Public Works, Environmental Branch
1550 Frank Cochran Drive, Bldg. 1137
Fort Stewart, Georgia 31314-4927
Telephone: (912) 767-2010
E-mail: Tressa.Rutland@stewart.army.mil

Consultant/Contractor
Ms. Patricia A. Stoll, P.E.
Science Applications International Corporation
151 Lafayette Drive
Oak Ridge, Tennessee 37831
Telephone: (865) 481-8792
E-mail: Patricia.A.Stoll@saic.com

Contaminants:
Petroleum constituents - BTEX and PAHs

Dissolved groundwater plume covered an area of approximately 85,800 ft2. Initial area of benzene contamination in groundwater was approximately 55,500 ft2 observed in January 2002. A 1997 investigation discovered Light nonaqueous-phase liquid (LNAPL) in one of the wells which covered an area of approximately 3,825 ft2. In May 2002, LNAPL covered an area of 11,500 ft2.

Waste Source:
Leaks from underground storage tanks (USTs)

Type/Quantity of Media Treated:
Soil, groundwater, and LNAPL

Approximately 35,000 cubic yards of media were treated.

Purpose/Significance of Application:
Use of ERH to remediate PAHs in soil, groundwater, and LNAPL form

Regulatory Requirements/Cleanup Goals:
The objectives of the corrective action were to remove free product (LNAPL) from the site, reduce concentrations of benzene in groundwater to less than the alternate concentration limit (ACL) of 469 micrograms per liter (µg/L), and to reduce concentrations of benzene and indeno(1,2,3-cd)pyrene in soil to below their alternate threshold levels (ATLs) of 0.44 milligram per kilogram (mg/kg) and 0.66 mg/kg, respectively.

Results:
- From April to August 2002, an estimated 44,000 pounds of volatile organic compounds (VOCs) were removed. The amount of free product was reduced from a maximum of 11,500 ft2 measured in May 2002 to no free product measured beginning in June 2002.
- Confirmatory soil samples were collected in February 2003. These samples indicated that none of the BTEX or PAH compounds exceeded their applicable ATLs.
- As of March 2004, post-treatment concentrations of benzene and other PAHs in groundwater were all below their respective ACLs.
- The site remains in a semiannual monitoring only program. If the concentrations of the constituents are below their ACLs following a year of semiannual sampling, then a no-further-action-required status will be requested for the site.

Cost Factors:
The total cost for the ERH application at Hunter AAF was approximately $1,300,000, consisting of:
- $ 1,042,129 for design, mobilization/demobilization, installation, and operation and maintenance of the system for four months;
- $ 259,000 for electrical service connection.

This total cost does not include costs for the generator (PCU), which was provided on loan from DOE.

Description:
Hunter AAF contains a former aviation-gas fuel island (Former Pumphouse #2), which was used from approximately 1953 to the early 1970s. It consisted of ten 25,000-gal USTs. The pumphouse was inactive from the early 1970s to 1995. In 1995, eight of the ten 25,000-gal USTs were removed from the ground. Leakage from USTs resulted in the contaminant plume. The site is being remediated under Georgia Environmental Protection Division, Underground Storage Tank Management Program.

Site investigations carried out in 1996 and 1997 identified petroleum contaminants in soil and groundwater, including BTEX and PAHs. The investigation identified the dissolved groundwater plume as covering an area of approximately 85,800 ft2. The 1997 investigation also discovered LNAPL in one of the wells which covered an area of approximately 3,825 ft2. The ERH implementation was initiated in April 2002 and continued for four months. Approximately 35,000 cubic yards of media were treated.

Site-specific ACLs for groundwater and ATLs for soil were developed for contaminants at the site. The objectives of the treatment were to remove LNAPL from the site, reduce concentrations of benzene in groundwater to less than the ACL of 469 µg/L, and reduce concentrations of benzene and indeno(1,2,3-cd)pyrene in soil to below their ATLs of 0.44 mg/kg and 0.66 mg/kg, respectively. From April to August 2002, an estimated 44,000 pounds of volatile organic compounds (VOCs) were removed. The amount of free product was reduced from a maximum of 11,500 ft2 measured in May 2002 to no free product measured beginning in June 2002. Confirmatory soil samples collected in February 2003 indicated that none of the BTEX or PAH compounds exceeded their applicable ATLs. As of March 2004, post-treatment concentrations of benzene and other PAHs in groundwater were all below their respective ACLs.

The total cost for the ERH application at Hunter AAF was approximately $1,300,000, consisting of $1,042,129 for design, mobilization/demobilization, installation, and operation and maintenance of the system for four months; and $259,000 for electrical service connection. This total cost does not include costs for the generator (PCU), which was provided on loan from DOE