Remediation Status: In groundwater monitoring

Why the technology was selected:
Although groundwater concentrations were not highly elevated, it was thought that the shallow water table (~2 feet at times) and basement seeps were the source of elevated indoor air levels.

Date implemented:
2013

Date completed:
2013

Final remediation design:
Groundwater treatment pilot injections were performed on January 28 and 29, 2013. The injections included using push-probe equipment to deliver the selected remediation material (EHC-L, developed by FMC) into the subsurface at several depths (some material was also introduced into the vapor pit screen within the dry cleaners space). A total of 495 gallons of the EHC-L material was injected between four separate locations at a dilution of about 25 to 1. The four injection locations included:
" One angled direct-push boring completed outside on the west side of the building (this point was added to the injection scope to allow injection to depths below 15 feet bgs the maximum depth attainable with the limited-access drilling equipment used for the interior probes). To minimize the distance between the injection point and the target treatment area, the exterior probe was angled toward MW-9, at 20 degrees from vertical. The deep probe was completed to a depth of about 22 feet bgs.
" Two direct-push borings completed within a 5-foot radius of MW-9. The attainable probe depths were 13 and 16 feet bgs.
" The previously installed screen of the Valet Cleaners vapor collection pit (a depth of 5 feet bgs).

For each of the drilled injections, the process included pushing to the maximum depth and retracting the rod four feet to expose the injection screen. The diluted material was injected using a progressive cavity pump and injection pressures for the deep (angled) probe averaged 80 psi while injection pressures for the interior probes were kept low (averaging 25 psi) in order to prevent rapid surfacing of the reagent. A total of
9,400 gallons of solution (376 gallons of EHC-L) were injected at the 18- to 22-foot bgs interval. The tighter soils encountered in the 12- to 15-foot interval resulted in a lower injection volume, with a total of about
2,700 gallons of solution (108 gallons of EHC-L). To prevent the surfacing of the material during application into the vapor-pit screen, the shallow injection was only gravity fed (unpressurized) and only 275 gallons of solution (11 gallons of EHC-L) were applied at the 5-foot depth over the two-day injection period.

Results to date:
Minimal changes have been observed in groundwater concentrations in the year since the pilot test.

Next Steps:
Bi-annual monitoring

Cost to Design and Implement:
$15,000

Why the technology was selected:
Source area has not been identified.

Date implemented:
2011

Date completed:
2013

Final remediation design:
The scope of work of the IRAM included:
" Installation of sub-slab vapor collection pits and associated system components (piping and fan) to create a relatively low pressure condition beneath the floor slab in the area of the highest sub-slab vapor concentrations to reduce the potential for migration through the floor into the ambient air space above;
" Modification of the existing HVAC systems to increase fresh air intake and interior air pressure to induce positive pressure conditions in the building relative to the sub-slab (to further reduce the potential for vapor intrusion);
" Sealing of the basement sumps and wall seeps to reduce volatilization into the basement airspace, and connection of the sealed air spaces to the vapor collection system (using a historical ventilation duct as a conduit) to further reduce the potential for vapor migration into the basement;

Results to date:
Highly elevated soil gas concentrations remain, but indoor air levels, with the exception of TCE in one tenant space, meet cleanup goals.

Next Steps:
bi-annual monitoring

Cost to Design and Implement:
$40,000

Why the technology was selected:
Although groundwater concentrations were not highly elevated, it was thought that the shallow water table (~2 feet at times) and basement seeps were the source of elevated indoor air levels.

Date implemented:
2013

Date completed:
2013

Final remediation design:
Groundwater treatment pilot injections were performed on January 28 and 29, 2013. The injections included using push-probe equipment to deliver the selected remediation material (EHC-L, developed by FMC) into the subsurface at several depths (some material was also introduced into the vapor pit screen within the dry cleaners space). A total of 495 gallons of the EHC-L material was injected between four separate locations at a dilution of about 25 to 1. The four injection locations included:
" One angled direct-push boring completed outside on the west side of the building (this point was added to the injection scope to allow injection to depths below 15 feet bgs the maximum depth attainable with the limited-access drilling equipment used for the interior probes). To minimize the distance between the injection point and the target treatment area, the exterior probe was angled toward MW-9, at 20 degrees from vertical. The deep probe was completed to a depth of about 22 feet bgs.
" Two direct-push borings completed within a 5-foot radius of MW-9. The attainable probe depths were 13 and 16 feet bgs.
" The previously installed screen of the Valet Cleaners vapor collection pit (a depth of 5 feet bgs).

For each of the drilled injections, the process included pushing to the maximum depth and retracting the rod four feet to expose the injection screen. The diluted material was injected using a progressive cavity pump and injection pressures for the deep (angled) probe averaged 80 psi while injection pressures for the interior probes were kept low (averaging 25 psi) in order to prevent rapid surfacing of the reagent. A total of
9,400 gallons of solution (376 gallons of EHC-L) were injected at the 18- to 22-foot bgs interval. The tighter soils encountered in the 12- to 15-foot interval resulted in a lower injection volume, with a total of about
2,700 gallons of solution (108 gallons of EHC-L). To prevent the surfacing of the material during application into the vapor-pit screen, the shallow injection was only gravity fed (unpressurized) and only 275 gallons of solution (11 gallons of EHC-L) were applied at the 5-foot depth over the two-day injection period.

Results to date:
Minimal changes have been observed in groundwater concentrations in the year since the pilot test.

Next Steps:
Bi-annual monitoring

Cost to Design and Implement:
$15,000

Why the technology was selected:
Source area has not been identified.

Date implemented:
2011

Date completed:
2013

Final remediation design:
The scope of work of the IRAM included:
" Installation of sub-slab vapor collection pits and associated system components (piping and fan) to create a relatively low pressure condition beneath the floor slab in the area of the highest sub-slab vapor concentrations to reduce the potential for migration through the floor into the ambient air space above;
" Modification of the existing HVAC systems to increase fresh air intake and interior air pressure to induce positive pressure conditions in the building relative to the sub-slab (to further reduce the potential for vapor intrusion);
" Sealing of the basement sumps and wall seeps to reduce volatilization into the basement airspace, and connection of the sealed air spaces to the vapor collection system (using a historical ventilation duct as a conduit) to further reduce the potential for vapor migration into the basement;

Results to date:
Highly elevated soil gas concentrations remain, but indoor air levels, with the exception of TCE in one tenant space, meet cleanup goals.

Next Steps:
bi-annual monitoring

Cost to Design and Implement:
$40,000