Pump and Treat, In Situ Bioremediation, and In Situ Air Sparging of Contaminated Groundwater at Site A, Long Island, New York

Site Name:

Site A

Location:

Long Island, New York

Period of
Operation:

Status: Ongoing
Report covers: 7/95 - 10/96

Cleanup
Type:

Full-scale cleanup (interim results)

Vendor:

Treatment System Vendor: RETEC Associates
Site Management: RETEC Associates (1993-1997)
Land Tech Remedial, Inc. (1997-present)

Technology:
Pump and Treat; In Situ Bioremediation; Air Sparging, Soil Vapor Extraction

- Groundwater was extracted using 5 wells, located on site, at an average total pumping rate of 18 gpm
- Extracted groundwater was treated with air stripping and gravity separation
- Nutrients were added to the treated water to adjust nitrogen and phosphorus levels, and then the water is reinjected into the aquifer through a reinjection trench located upgradient of the plume
- Air was injected through 44 sparging wells at points approximately 10 ft below the water table, in a pulsed system operation, and effluent vapors are collected with 20 SVE wells (16 vertical and 4 horizontal)

Cleanup Authority:
CERCLA Remedial
- ROD Date: 6/24/91

EPA Point of Contact:
Maria Jon, RPM
U.S. EPA Region 2
290 Broadway, 19th Floor
New York, NY 10007-1866
(212) 637-3967

Site Contact:
Stephen Hoelsher
Phillips Bldg
Bartville, OK 74004
(918) 661-3769
State Point of Contact:
Carl Hoffman
New York State DEC
Bureau of Hazardous Site Control
50 Wolf Road
Albany, NY 13323-7010

Contaminants:
Volatiles - nonhalogenated (BTEX)

- Maximum initial concentrations were benzene (430 µg/L), toluene (350,000 µg/L), ethylbenzene (5,600 µg/L), and xylenes (45,000 µg/L)

Waste Source:
Leaking drums and spills of petroleum and solvent materials

Type/Quantity of Media Treated:
Groundwater

- 8.4 million gallons treated as of October 1996
- LNAPL observed in several monitoring wells on site
- Groundwater is found at 15-18 ft bgs
- Extraction wells are located in 1 aquifer, which is influenced by a nearby surface water
- Hydraulic conductivity reported as 53.5 ft/day

Purpose/Significance of Application:
Relatively high unit cost; system included groundwater extraction, air sparging, and SVE wells.

Regulatory Requirements/Cleanup Goals:
- Remediate the groundwater to meet maximum contaminant levels (MCLs) established by the NYSDEC, which are the primary drinking water standards.
- Cleanup goals were established for benzene (0.0007 mg/L), toluene (0.005 mg/L), ethylbenzene (0.005 mg/L), and xylene (0.005 mg/L).
- A primary goal of the extraction system is to contain the contaminant plume and prevent it from discharging to the harbor; the goal is for both horizontal and vertical containment.
- A primary performance goal for in situ bioremediation is to maintain specified levels for pH, nitrogen, phosphorus, and DO.

Results:
- Maximum BTEX levels have declined from 153 to 27 mg/L; however, cleanup goals have not been met. Monitoring data from 1997 indicate that elevated BTEX levels persist in wells along the western portion of the site.
- Plume containment appears to have been achieved, and performance standards were generally met for nitrogen, phosphorus, and DO; there were several exceptions where nitrogen, phosphorus, and DO were outside the specified ranges.
- From July 1995 to July 1996, the system removed approximately 5,314 pounds of BTEX from the groundwater (air sparging removed approximately 85% of the BTEX and P&T the remaining 15%).

Cost Factors:
Actual costs for the treatment system were approximately $1,941,560 ($1,503,133 in capital and $358,427 in O&M), which correspond to $200 per 1,000 gallons of groundwater extracted and $365 per pound of contaminant removed.

Description:
Site A operated as a petroleum bulking facility from 1939 until 1980, and it operated as a petroleum bulking and chemical mixing facility from 1980 to 1984. In 1984, in response to a toluene spill, EPA and the NYSDEC investigated the site, and discovered contamination by organics and metals in the soil, and organics in the groundwater, surface water, and air. The site was placed on the NPL in June 1986 and a ROD was signed in June 1991.

The groundwater extraction system consists of five wells installed in the areas of highest contamination within the plume, all screened at depths of approximately 10 ft below the water table. One well was placed in an area where free-phase BTEX product was observed in the western portion of the site. Extracted groundwater is treated with air stripping. After stripping, water is treated through pH adjustment and addition of nutrients, and then re-injected into the aquifer. In addition, oxygen is injected into the aquifer through 44 air sparging points. Effluent vapors from the sparging points are collected by 20 SVE wells.

Groundwater cleanup goals for this site have not been met after two years and three months of operation. However, the remedy has contained the plume, reduced average BTEX concentrations, and recovered free-phase product.