Remediation Status: In groundwater monitoring

Why the technology was selected:
Since reductive dechlorination is actively occurring in groundwater at the site, the introduction of nutrients (enhanced biosparging or EBS) should enhance contaminant degradation.

Date implemented:
enhanced biosparging - January 11, 2002.

Final remediation design:
Biosparging System - Four biosparing wells were installed utilizing a direct push rig - one slant well (installed beneath the drycleaning facility) and three vertical wells. Well screens are constructed of stainless steel and risers are black iron pipe. At the completion of the triethylphosphate/nitrous oxide treatment regime, propane may be added approximately 6 hours biweekly to improve the microbe concentration.

Biosparge wells: screened 33-35 ft bgs
System design radius of influence: 25-30 ft
Design injection flow rate: 3-5 scf/m per well (12-20 scf/m total flow rate)
Actual injection rate: 1 scf/m per well, sparging from two wells at a time in one-hour intervals twice per day to allow aquifer stabilization between injections.
Injection concentrations/mass (for project life): nitrous oxide, 0.07% - 0.1% by volume in air (1060 lbs total mass); triehtylphosphate, 0.007% by volume in air (106 lab total mass); oxygen (as air), 3-5 scf/m per well at 15 psig (1,060,000 lbs total mass); propane, 50% of lower explosive limit in air, 6 hours biweekly at end of treatment regime (10 lbs total mass)

Water from the air/water separator is discharged to an infiltration trench located in the radius of influence of both the SVE and EBS systems so that any water extracted will be retreated by the biosparge system.

Other technologies used:
Enhanced Biosparging (PHOSters/Magnus)

Results to date:
The biosparge system was operated from January-November 2002; July 2003-March 2004 and then from April 2005-March 2006. Contaminant rebound occurred after each shut down period. The SVE system was shut down on July 13, 2006. Confirmatory soil sampling showed that contaminated soil has been effectively remediated.

Vinyl chloride is the only contaminant in groundwater in concentrations exceeding MCLs. During the most recent monitoring event, vinyl chloride concentraitons were as high as 38 ug/l. Contamination is limited to the very top (upper 5 feet) of the water table.

Next Steps:
Monitored natural attenuation

Cost to Design and Implement:
Design $32,000
Implementation: $118,000 for for all technologies together

Why the technology was selected:
Since reductive dechlorination is actively occurring in groundwater at the site, the introduction of nutrients (enhanced biosparging or EBS) should enhance contaminant degradation.

Date implemented:
enhanced biosparging - January 11, 2002.

Final remediation design:
Biosparging System - Four biosparing wells were installed utilizing a direct push rig - one slant well (installed beneath the drycleaning facility) and three vertical wells. Well screens are constructed of stainless steel and risers are black iron pipe. At the completion of the triethylphosphate/nitrous oxide treatment regime, propane may be added approximately 6 hours biweekly to improve the microbe concentration.

Biosparge wells: screened 33-35 ft bgs
System design radius of influence: 25-30 ft
Design injection flow rate: 3-5 scf/m per well (12-20 scf/m total flow rate)
Actual injection rate: 1 scf/m per well, sparging from two wells at a time in one-hour intervals twice per day to allow aquifer stabilization between injections.
Injection concentrations/mass (for project life): nitrous oxide, 0.07% - 0.1% by volume in air (1060 lbs total mass); triehtylphosphate, 0.007% by volume in air (106 lab total mass); oxygen (as air), 3-5 scf/m per well at 15 psig (1,060,000 lbs total mass); propane, 50% of lower explosive limit in air, 6 hours biweekly at end of treatment regime (10 lbs total mass)

Water from the air/water separator is discharged to an infiltration trench located in the radius of influence of both the SVE and EBS systems so that any water extracted will be retreated by the biosparge system.

Results to date:
The biosparge system was operated from January-November 2002; July 2003-March 2004 and then from April 2005-March 2006. Contaminant rebound occurred after each shut down period. The SVE system was shut down on July 13, 2006. Confirmatory soil sampling showed that contaminated soil has been effectively remediated.

Vinyl chloride is the only contaminant in groundwater in concentrations exceeding MCLs. During the most recent monitoring event, vinyl chloride concentraitons were as high as 38 ug/l. Contamination is limited to the very top (upper 5 feet) of the water table.

Next Steps:
Monitored natural attenuation

Cost to Design and Implement:
Design $32,000
Implementation: $118,000 for for all technologies together

Why the technology was selected:
SVE is a cost-effective technology for removing VOCs from permeable unsaturated soils.

Date implemented:
SVE - January 9, 2002

Final remediation design:
A horizontal vapor extraction well was installed because of the shallow depth of groundwater at the site. The SVE lateral was installed just outside the service door of the facility. The SVE lateral is piped to a portable trailer-mounted treatment system.

Extraction well: 1- 20 ft. screened section of 4-inch PVC
Depth: 2 ft bgs
SVE motor size: 5 hp Rotron 707F72MXL blower.
Design flowrate: 34 scf/m at design vacuum of 49 in. w.c.
Operational flowrate: 50.5 to 103 scf/m
Design radius of influence: 16 ft
Emissions treatment: 2-200 lb GAC canisters in series.

Results to date:
The SVE system was modified to include the addition of a large diameter vapor extraction well installed beneath the facility floor slab. Soil was excated beneath the faciliyt floor slab (an area 3 ft x 3 ft x 2 1/2 feet deep). A 55-gallon polyethylene drum with 0.06 to 0.010 inch slots was placed in an excavation and the annulus was lined with 1/4 to 1/2-inch diameter river rock. Operational flow rate for the large diameter well was 20.7 scfm with 30 inches w.c. The calcuated radius of influence for this well was 27.4 feet. The modified SVE system including the large diameter well and the original lateral vapor extraction well went online on April 25, 2003.

Vinyl chloride is the only contaminant in groundwater in concentrations exceeding MCLs. During the most recent monitoring event, vinyl chloride concentraitons were as high as 38 ug/l. Contamination is limited to the very top (upper 5 feet) of the water table.

Next Steps:
Monitored natural attenuation

Cost to Design and Implement:
Design $32,000
Implementation: $118,000 for for all technologies together