Drycleaner Site Profiles

Coastal Dry Cleaners #650007, Swansboro, North Carolina

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
checkPresumptive 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