Drycleaner Site Profiles

Williams/Hangers Cleaners, Wilmington, North Carolina

Description
Historical activity that resulted in contamination.

The property was developed with the present-day building structure in 1983 as a drycleaner. According to historical information (aerial photographs and city directories) the subject property was undeveloped prior to 1983. Tetrachloroethylene (PCE) was reportedly utilized as a drycleaning solvent from 1983 through 1997. In 1997, drycleaning operations on site were discontinued until 2001. During the period 1997 through 2001, the facility was used as a drop-off location only. In 2001 new petroleum-based drycleaning equipment was installed. Since 2001 (through present day) the facility has used Exxon DF-2000 (petroleum-based) drycleaning solvent. The name of the drycleaner changed from Williams Cleaners to Hangers Cleaners at an unknown date.

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
1,2-Dichloroethane groundwater
Tetrachloroethene (PCE) groundwater
Tetrachloroethene (PCE) soil
Trichloroethene (TCE) groundwater
Vinyl Chloride groundwater

Site Hydrology

Deepest Significant Groundwater Contamination:   40ft bgs
Plume Size:   Plume Length: 128ft
Plume Width: 68ft
Plume Thickness: 40ft
Average Depth to Groundwater:   10.73ft

Lithology and Subsurface Geology

 
  Interbedded silty sand, clayey sand, and fine to medium grained sand

Conductivity: 0.016ft/day
Gradient: 0.01ft/ft

Pathways and DNAPL Presence

Groundwater
Sediments
Soil
DNAPL Present

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,Groundwater sampling,Compared sample concentration to screening criteria,Used an exposure screening model
Results of VI evaluation:
  A potential VI pathway has been indentified
Has a vapor mitigation system been installed?
  Yes 
Type of Vapor Mitigation System(s):
  Soil Vapor Extraction
Additional VI Information:
  Indoor air sampling was not performed since drycleaning is actively performed in the on-site building. However, modeling indicated a potential risk of VI. An air sparge/soil vapor extraction system was installed to remediate source area impacts which posed a possible VI risk.

Remediation Scenario

Cleanup Goals:
  The cleanup goals are to reduce source area concentrations sufficient to achieve plume stability and reduce the VI risk.
Remedy Level:
  Full Scale Remedy

Technologies

In Situ Air Sparging
 

Why the technology was selected:
Air sparge (AS) was added to the system to concurrently reduce source area groundwater impacts.

Date implemented:
The AS/SVE system operated from March 2009 to June 2010.

Final remediation design:
The AS/SVE system operated from March 2009 to June 2010.

Results to date:
As of June 2010, the SVE system had removed approximately 7.4 pounds of vapor phase PCE. 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-mitigation monitoring activities suggests that the remediation activities were successful in reducing contaminant concentrations.

Next Steps:
Completion of a risk assessment and pursuit of site closure is planned.

Cost to Design and Implement:
$186,991 for all technologies

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.

Date implemented:
The AS/SVE system operated from March 2009 to June 2010.

Final remediation design:
The AS/SVE system operated from March 2009 to June 2010.

Results to date:
As of June 2010, the SVE system had removed approximately 7.4 pounds of vapor phase PCE. 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-mitigation monitoring activities suggests that the remediation activities were successful in reducing contaminant concentrations.

Next Steps:
Completion of a risk assessment and pursuit of site closure is planned.

Cost to Design and Implement:
$186,991 for all technologies

Costs

Cost for Assessment:
  $155,643
Cost for Operation and Maintenance:
  $70,548
Total Costs for Cleanup:
  On-going

Lessons Learned

Installation of an AS/SVE system successfully reduced source area contaminant concentrations.

Contacts

Delonda Alexander, NC DSCA Program, 1646 Mail Service Center, Raleigh, North Carolina 27699-1646, (919) 707-8365, delonda.alexander@ncdenr.gov

Site Specific References

9/20/10 Soil Gas Sampling Report, 7/16/10 Remediation System Operation & Maintenance Report, and
5/31/10 Annual Groundwater Monitoring Report