Drycleaner Site Profiles

Hangers Cleaners #68-0007, Carrboro, North Carolina

Description
Historical activity that resulted in contamination.

The site is located in the central piedmont region of NC. The drycleaner operated from 1981 to 2006 and the building is a standalone single story slab on grade. A doctor's office now occupies the building.

Remediation Status: In active remediation


Contaminants
Contaminants present and the highest amount detected in both soil and groundwater.


Contaminant Media Concentration (ppb) Nondetect
cis-1,2-Dichloroethene groundwater
cis-1,2-Dichloroethene soil
methylene chloride groundwater
Tetrachloroethene (PCE) groundwater
Tetrachloroethene (PCE) soil
Trichloroethene (TCE) groundwater
Trichloroethene (TCE) soil
trans-1,2-Dichloroethene groundwater
Vinyl Chloride groundwater
Vinyl Chloride soil

Site Hydrology

Deepest Significant Groundwater Contamination:   200ft bgs
Plume Size:   Plume Length: 735ft
Plume Width: 400ft
Plume Thickness: 200ft
Average Depth to Groundwater:   13.18ft

Lithology and Subsurface Geology

 
  Partially weathered parent rock of sand, silty sand, and clayey sands
Depth: 0-25.5ft bgs
25.5ft thick
Conductivity: 0.2834ft/day
Gradient: 0.02ft/ft
 
  metamorphosed granitic bedrock
Depth: 25.5ft bgs

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:
  Soil excavation and an SVE system were installed to address VI for on-site building prior to building used as a doctor's office. Additional assessment for off-site buildings indicated pathway complete, but levels indicated that no mitigation was required.

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 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:
The SVE system began operation in June 2009.

Final remediation design:
SVE is expected to continue as an interim action to address VI concerns. Groundwater remediation will also be needed to achieve cleanup goals. However, groundwater remediation has been postponed to date pending funding availability.

Results to date:
As of May 2011, the SVE system had removed approximately 17.7 pounds of vapor phase PCE. Problems encountered during the system operation consisted of water infiltration causing periodic shutdowns. This was addressed by installing moisture barrier at the ground surface to impede water infiltration. Additional contaminant mass was also removed during excavation of 210 tons of impacted soil.

Next Steps:
Continue to run the SVE system while sampling indoor air on a semi-annual basis.

Cost to Design and Implement:
$303,967.66 Dig and haul and SVE design, installation, and startup.

Ex Situ Soil Removal
 

Why the technology was selected:
Removal of accessible impacted soil was determined to be most effective method of source removal and was conducted concurrent with site redevelopment.

Date implemented:
The soil excavation was completed in July 2007 and consisted of removing 210 tons.

Final remediation design:
SVE is expected to continue as an interim action to address VI concerns. Groundwater remediation will also be needed to achieve cleanup goals. However, groundwater remediation has been postponed to date pending funding availability.

Results to date:
As of May 2011, the SVE system had removed approximately 17.7 pounds of vapor phase PCE. Problems encountered during the system operation consisted of water infiltration causing periodic shutdowns. This was addressed by installing moisture barrier at the ground surface to impede water infiltration. Additional contaminant mass was also removed during excavation of 210 tons of impacted soil.

Next Steps:
Continue to run the SVE system while sampling indoor air on a semi-annual basis.

Cost to Design and Implement:
$303,967.66 Dig and haul and SVE design, installation, and startup.

Costs

Cost for Assessment:
  $431,128.63
Cost for Operation and Maintenance:
  Approximately $25,000.00
Total Costs for Cleanup:
  On-going

Lessons Learned

Excavation of impacted soil and installation of SVE piping concurrent with site redevelopment successfully addressed VI concerns for the new occupant (including a sensitive pediatrician's office) and helped further remediation efforts.

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

Site Specific References

The site reports are available on the NCDENR document portal system located at https://edm.nc.gov/DENR-Portal/. To access the site reports, enter the DSCA site ID# 680007 in the ID Value field under Property criteria fields window, then click the Search button above the Content window. The list of reports for the site will appear in the Content window below the criteria search fields window. Right-clicking on the Adobe Acrobat symbol next to a report in the list will allow downloading, preview, and other options for that report.