Description
Historical activity that resulted
in contamination.
| The site is located near the Atlantic Incoastal waterway off the coast of North Carolina in the town of Swansboro. The facility operated as a drycleaner from the 1970's until 2006. The facility was located in a single story, slab-on-grade multi-tenant building that was vacant during assessment and remediation. The solvent plume is comingled with a UST petroleum release adjancent to the facility location. Remediation Status: In groundwater monitoring |
Contaminants
Contaminants present and the highest amount
detected in both soil and groundwater.
| Contaminant |
Media |
Concentration (ppb) |
Nondetect |
| Benzene |
groundwater |
|
|
| cis-1,2-Dichloroethene |
groundwater |
|
|
| ethylbenzene |
groundwater |
|
|
| Tetrachloroethene (PCE) |
groundwater |
|
|
| Tetrachloroethene (PCE) |
soil |
|
|
| naphthalene |
groundwater |
|
|
| Trichloroethene (TCE) |
groundwater |
|
|
| toluene |
groundwater |
|
|
| Vinyl Chloride |
groundwater |
|
|
Site Hydrology
| Deepest Significant
Groundwater Contamination: |
|
37ft bgs |
| Plume Size: |
|
Plume Length: 900ft
Plume Width: 280ft
Plume Thickness: 37ft |
| Average Depth
to Groundwater: |
|
11.2ft |
Lithology and Subsurface Geology
|
|
Coastal fluvial sediments of mostly sand mixed with some silt and clay.
Conductivity: 0.089ft/day
Gradient: 0.02ft/ft
|
Pathways and DNAPL Presence
 Groundwater
Sediments
Soil
 Presumptive Evidence of DNAPL
|
Vapor Intrusion Pathway
Has the potential for vapor intrusion (VI) been evaluated? |
|
Yes
|
How was the site evaluated? |
|
Soil vapor and/or Sub-slab vapor sampling,Indoor air sampling,Groundwater sampling,Compared sample concentration to screening criteria,Used an exposure screening model
|
Results of VI evaluation: |
|
A completed VI pathway has been indentified |
Has a vapor mitigation system been installed? |
|
Yes |
Type of Vapor Mitigation System(s): |
|
Sub-slab Depressurization
Soil Vapor Extraction
|
Additional VI Information: |
|
An SVE system was installed to address VI for on-site building. Additional assessment for off-site buildings indicated no mitigation was needed off-site. The SVE system was removed after confirmation of mitigation achieved cleanup goals for indoor air. |
Remediation Scenario
Cleanup
Goals: |
|
To reduce contaminant concentrations so that the site risks do not exceed a cumulative cancer risk of 1E-05 and a hazard index below 1.0.
|
Remedy Level: |
|
Interim Action |
Technologies
In Situ Bioremediation |
|
Why the technology was selected:
The injection was selected to remediate concentrations of dry cleaning solvents in the groundwater source and surrounding area. The type of injectate selected was based on a favorable record of success at other sites.
Date implemented:
August 2009
Final remediation design:
Full-scale implementation of the The SVE system operated from August 2009 to February 2010. In September 2009, approximately 9,030 gallons of IET's injection mixture was emplaced using four injection wells and 27 direct-push points.
Other technologies used:
Reductive dechlorination by injecting a mixture of Hydrogen Release Compound (HRC), zero valent iron (ZVI), EHC, vitamin stimulants (B2 and B12), yeast extract, sulfite, nutrients, and propionate. The injectate mixture and proposed injection process were designed by Innovative Environmental Technologies (IET).
Results to date:
As of January 2010, the SVE system had removed approximately 11.5 pounds of vapor phase PCE. The system was shutdown in February 2010 and indoor air sampling was performed which confirmed VI concerns had been adequately addressed. Problems encountered during the system operation consisted of water infiltration causing periodic shutdowns. This was an unavoidable problem due to the shallow water table on-site and was rectified by pumping out the moisture seperator serveral times during operation. Data collected from pre and post-injection monitoring activities suggests that the injection activities were successful in reducing contaminant concentrations within the injection area.
Next Steps:
Completion of a groundwater monitoring event is planned to evaluate whether the plume is stable. If it is, closure will be pursued.
Cost to Design and Implement:
$122,346.38
|
In Situ Soil Vapor Extraction |
|
Why the technology was selected:
Soil vapor extraction (SVE) was selected to address impacted soil that could not be removed due to structural considerations while concurrently mitigating vapor intrusion by depressurization.
Date implemented:
August 2009
Final remediation design:
Full-scale implementation of the The SVE system operated from August 2009 to February 2010. In September 2009, approximately 9,030 gallons of IET's injection mixture was emplaced using four injection wells and 27 direct-push points.
Results to date:
As of January 2010, the SVE system had removed approximately 11.5 pounds of vapor phase PCE. The system was shutdown in February 2010 and indoor air sampling was performed which confirmed VI concerns had been adequately addressed. Problems encountered during the system operation consisted of water infiltration causing periodic shutdowns. This was an unavoidable problem due to the shallow water table on-site and was rectified by pumping out the moisture seperator serveral times during operation. Data collected from pre and post-injection monitoring activities suggests that the injection activities were successful in reducing contaminant concentrations within the injection area.
Next Steps:
Completion of a groundwater monitoring event is planned to evaluate whether the plume is stable. If it is, closure will be pursued.
Cost to Design and Implement:
$122,346.38
|
In Situ Vapor Mitigation |
|
Why the technology was selected:
Soil vapor extraction (SVE) was selected to address impacted soil that could not be removed due to structural considerations while concurrently mitigating vapor intrusion by depressurization. The injection was selected to remediate concentrations of dry cleaning solvents in the groundwater source and surrounding area. The type of injectate selected was based on a favorable record of success at other sites.
Date implemented:
August 2009
Final remediation design:
Full-scale implementation of the The SVE system operated from August 2009 to February 2010. In September 2009, approximately 9,030 gallons of IET's injection mixture was emplaced using four injection wells and 27 direct-push points.
Results to date:
As of January 2010, the SVE system had removed approximately 11.5 pounds of vapor phase PCE. The system was shutdown in February 2010 and indoor air sampling was performed which confirmed VI concerns had been adequately addressed. Problems encountered during the system operation consisted of water infiltration causing periodic shutdowns. This was an unavoidable problem due to the shallow water table on-site and was rectified by pumping out the moisture seperator serveral times during operation. Data collected from pre and post-injection monitoring activities suggests that the injection activities were successful in reducing contaminant concentrations within the injection area.
Next Steps:
Completion of a groundwater monitoring event is planned to evaluate whether the plume is stable. If it is, closure will be pursued.
Cost to Design and Implement:
$122,346.38
|
In Situ Zero Valent Iron |
|
Why the technology was selected:
The injection was selected to remediate concentrations of dry cleaning solvents in the groundwater source and surrounding area. The type of injectate selected was based on a favorable record of success at other sites.
Date implemented:
August 2009
Final remediation design:
Full-scale implementation of the The SVE system operated from August 2009 to February 2010. In September 2009, approximately 9,030 gallons of IET's injection mixture was emplaced using four injection wells and 27 direct-push points.
Other technologies used:
Reductive dechlorination by injecting a mixture of Hydrogen Release Compound (HRC), zero valent iron (ZVI), EHC, vitamin stimulants (B2 and B12), yeast extract, sulfite, nutrients, and propionate. The injectate mixture and proposed injection process were designed by Innovative Environmental Technologies (IET).
Results to date:
As of January 2010, the SVE system had removed approximately 11.5 pounds of vapor phase PCE. The system was shutdown in February 2010 and indoor air sampling was performed which confirmed VI concerns had been adequately addressed. Problems encountered during the system operation consisted of water infiltration causing periodic shutdowns. This was an unavoidable problem due to the shallow water table on-site and was rectified by pumping out the moisture seperator serveral times during operation. Data collected from pre and post-injection monitoring activities suggests that the injection activities were successful in reducing contaminant concentrations within the injection area.
Next Steps:
Completion of a groundwater monitoring event is planned to evaluate whether the plume is stable. If it is, closure will be pursued.
Cost to Design and Implement:
$122,346.38
|
Costs
Cost
for Assessment:
|
|
$239,106.99 |
Cost
for Operation and Maintenance:
|
|
Approximately $49,000 |
Total
Costs for Cleanup:
|
|
On-going |
Lessons Learned
|
Installation of an SVE system concurrent with injection activities successfully addressed VI concerns and reduced source area concentrations to stabilize the plume.
|
Contacts
Al Chapman, L.G. Project Manager
DSCA Program
NCDENR - Division of Waste Managment
1646 Mail Service Center
Raleigh, NC 27699-1646
Phone: (919) 707-8368
Fax: (919) 707-8368
Email: Al.Chapman@ncdenr.gov
Website: www.ncdsca.org
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