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In-Situ Groundwater Remediation/Floating Product Removal
At a Convenience Store Site Northern Indiana
Setting |
- Northern Indiana (Confidential Site)
- Four ISGR systems; two ISGR/FPR systems. Residential
neighborhood.
- BTEX and MTBE contamination. Floating product
(gasoline).
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Hydrogeology |
- Fine/medium sand aquifer:
- Hydraulic conductivity: 55 ft/day
- Plume thickness: 30 ft
- Depth to groundwater: 9 - 14 ft
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Contamination |
- BTEX and MTBE (dissolved); Gasoline (LNAPL)
- BTEX concentrations entering the wells: up
to 8,300 ppb.
MTBE concentrations entering the wells: up to 330
ppb
- Primary Objective: Capture plume and remove
contaminants to non-detect in effluent water from
the treatment wells. Remove any remaining floating
product.
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Inorganic Chemistry |
- Groundwater is in equilibrium with calcite, indicating
potential for calcite scale formation. High
iron levels: 14 to 33 ppm.
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Operation Details |
- One ISGR well operating at 3.5 gpm. Five
other systems operate at 10 to 10.5 gpm.
- Carbon treatment of water for removal of dissolved
contaminants.
- Systems on line: ISGR-4 September 2004. ISGR-3
August 2005. ISGR/FPR 1 December 2005. ISGR/FPR2,
ISGR-5, and ISGR-6 January 2006
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Results
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The carbon was changed out (1,500 lb) at ISGR-4, after
eleven months of operation. The average influent levels
for the eleven-month period (1.7 million gallons of water)
are given below. All effluent samples were non-detect.
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Influent (mg/L) |
Effluent |
| Benzene |
1,928 |
ND |
| Ethylbenzene |
177 |
ND |
| MTBE |
101 |
ND |
| Toluene |
39 |
ND |
| Xylenes |
784 |
ND |
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ISGR/FPR-2: Floating product had been seen at
the site over several years, at thicknesses up to 3 inches. However,
no floating product had been seen at the site in over
two years. Well ISGR/FPR-2 began operation on January
19, 2006. Five weeks later, gasoline was detected
in the skimmer well. Over a four-week period, 13
gallons of gasoline were removed from the well.
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