Technology:
Pump and Treat
- Original extraction well network, installed in 1995, included seven wells; an eighth well was added in 1998; as of May 1999, five wells are active, including three located within the plume
- Extraction wells constructed of 6-inch diameter stainless steel, screened at varying depths ranging from 9 to 101 feet below ground surface (bgs); design pumping rate - 20 gpm per well (total system of 110 gpm)
- Monitoring well network includes three groups of wells - 13 interior plume wells; nine perimeter wells located at the edge of the plume; and 12 sentinel wells located downgradient of the plume
- Aboveground treatment - ultraviolet oxidation; metals precipitation followed by clarification and filtration (not currently in use); from May 1996 to April 1999 - average flow rate was 76 gpm, plant was operational 94-97% of the time; effluent discharged to a sanitary sewer
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Cleanup Authority:
CERCLA
- ROD signed in February 1998
Contact:
Naval Facilities Engineering Command
1100 23rd Avenue
Port Hueneme, CA 93043 |
Contaminants:
Chlorinated Volatile Organic Compounds (VOCs)
- 1,1-dichloroethene (1,1-DCE), 1,1-dichloroethane (DCA), cis-1,2-dichloroethene (cis-1,2-DCE), trichloroethane (TCA), tetratchloroethene (PCE), trichloroethene (TCE) |
Waste Source:
Disposal of liquid wastes in the acid/caustic pit disposal area; disposal of waste fuels, oils, and degreasing solvents |
Type/Quantity of Media Treated:
Groundwater
- Two layers: Layer 1 - unconfined groundwater occurring within the upper stratified sand/silt unit; Layer 2 - semi-confined groundwater occurring within a lower coarse sand unit
- Hydraulic conductivity - 1x10-8 cm/sec |
Purpose/Significance of Application:
Use of pump and treat to treat groundwater contaminated with chlorinated VOCs |
Regulatory Requirements/Cleanup Goals:
The ROD specified cleanup levels for nine contaminants: 1,1-DCE (7 ug/L), 1,1-DCA (5 ug/L), 1,2-DCA (5 ug/L), cis-1,2-DCE (70 ug/L), trans-1,2-DCE (70 ug/L), 1,1,1-TCA (200 ug/L), 1,1,2-TCA (3 ug/L), TCE (5 ug/L), PCE (5 ug/L)
- Hydraulic containment of the plume
- Effluent must meet the Brunswick Sewer District discharge limits for 19 parameters, including metals, organics, pH, and turbidity |
Results:
As of May 1999, 536 pounds of VOCs have been removed
- In 1998, mass removal had begun to decrease; following installation of the eighth extraction well, VOC mass removal has remained steady
- Actual average annual pumping rates of individual wells ranged from 8 to 18.6 gpm, below the design rate of 20 gpm
- Treatment plant - since 1996 - two slight exceedances of discharge limits for VOCs; one exceedance of pH; consistently exceeded manganese concentrations
- Monitoring data indicate that the extent and position of the plume has not changed since the system began operating |
Cost Factors:
- Total capital costs - $4,246,319 (including mobilization, groundwater extraction system, treatment plant, and demobilization)
- Annual O&M costs - $1,144,031(including replacement parts, labor, and chemicals)
- Average cost per pound of mass removed over time - downward trend from a high of $11,000 per pound in September 1996 to $6,200 per pound for the most recent eight months of operation (through May 1999); decrease in unit cost attributed to installation of the eighth well in a hot spot, which improved system performance |
Description:
The Naval Air Station in Brunswick Maine is used to support the operation and maintenance of the P-3 Orion aircraft. The Eastern Plume of groundwater contamination is located at the eastern edge of the installation. The plume originated from three sites - the Acid/Caustic Pit (Site 4) where acid and caustic liquid wastes were disposed of in a pit; the former Fire Training Area (Site 11) where liquid wastes (oils, fuels, degreasing solvents) were used in training exercises; and the DRMO area (Site 13) where fuels and wastes were stored in USTs - resulted in groundwater contamination. A ROD for the eastern plume was signed in February 1998 and specified pump and treat as the remedy.
A groundwater pump and treat system for the Eastern Plume began operating in May 1995. The system initially included seven extraction wells, with an eighth well added in 1998 when VOC mass removal began to decrease. The treatment plant included ultraviolet oxidation. An effectiveness evaluation for the pump and treat system at this site was performed as part of a study by the Remedial Action Operation/Long Term Monitoring working group led by the Naval Facilities Engineering Service Center. As of May 1999, the system had removed 536 pounds of VOCs and the mass removal rate has been steady. According to the Navy, while the system had not experienced a significant decrease in mass removal efficiency, the price of operation has been high with an average cost per pound of mass removed of more than $7,000. The treatment plant was originally designed to handle extracted water from the Eastern Plume and water from a landfill at the installation. However, the plant was only used to treat the Eastern Plume. As a result, the capital costs significantly skewed the average cost per pound of contaminant removed, since the system had been overbuilt. Recommendations for the system include enhancing mass removal; beginning a formal evaluation of MNA; and identifying and evaluating alternatives for the discharge from the treatment plant. |
