Drycleaner Site Profiles

Dryclean Express #53-0001, Sanford, North Carolina

Description
Historical activity that resulted in contamination.

An active facility using Perc Dry-to-Dry machine with base tank located in a tenant space of a single-story strip shopping center built slab on grade with multiple adjacent commercial tenants since 1984. No previous incidents were reported at the site prior to discovery date. Site was discovered in March 2007 by property owner during Phase II assessment for a property transaction. Probable source of contamination is unknown but is most likely related to historical daily operations and use in solvent storage, handling, and waste management practices prior to establishment of state release prevention regulations implemented in 1997. The targeted source area is the subsurface soils and groundwater immediately underneath the shopping center tenant spaces below the dry cleaning facility and adjacent tenant spaces.

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
Tetrachloroethene (PCE) groundwater
Tetrachloroethene (PCE) soil
Trichloroethene (TCE) groundwater
Trichloroethene (TCE) soil
Vinyl Chloride groundwater
Vinyl Chloride soil

Site Hydrology

Deepest Significant Groundwater Contamination:   40ft bgs
Plume Size:   Plume Length: 720ft
Plume Width: 200ft
Plume Thickness: 40ft
Average Depth to Groundwater:   13ft

Lithology and Subsurface Geology

 
  interbedded sandy silts and clays
Depth: 0-20ft bgs
20ft thick
Gradient: 0.0241ft/ft
 
  fluvial deposits of conglomerate, fanglomerate sandstone, and mudstone
Depth: 20-75ft bgs
55ft thick

Pathways and DNAPL Presence

Groundwater
Sediments
Soil
checkDNAPL 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,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
Additional VI Information:
  A subfloor depressurization system was deployed prior to the installation of the soil SVE system but could not achieve the indoor air concentration mitigation goals within the affected tenant spaces. Therefore, a more aggressive SVE system was evaluated. However, based on simultaneous indoor air sampling within the dry-cleaning facility and the adjacent tenant spaces during times of active and inactive dry-cleaning operations at the facility, it was determined that emissions from the active dry-cleaner operations caused an increase in the indoor air concentrations in the adjacent tenant units above what is being contributed by vapor intrusion from the sub-floor and subsurface soils and groundwater.

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:
Indoor air concentrations in adjacent tenant spaces was considered an imminent hazard to receptors, so needed to reduce indoor air concentrations from vapor intrusion pathway and reduce soil concentrations in source areas beneath the building to reduce VI risks in future. SVE offered greatest radius of influence beneath the building than other technologies and could be implemented quicker than acquiring state permits for substrate injections.

Date implemented:
May 16, 2011

Final remediation design:
5 SVE Wells installed in the highest concentrations in soil beneath the building footprint connected to one blower.

Results to date:
Removed 64 lbs of contaminant mass based on effluent air concentrations within first two months of operation. Air flow rates were lower than expected, but good vacuum is being observed. Thus, the system should address the soil contamination over the long term.

Next Steps:
When SVE effluent concentrations have decreased and stabilized, the system will be shutdown to test indoor air levels during periods when the dry-cleaner is not operating to determine if the levels warrant continued operation of the SVE system. The SVE system will be kept in place and reactivated if groundwater treatment becomes necessary if SVE remediation of soils is not sufficient to decrease indoor air concentrations. Once equilibrium has been reached with effluent concentrations, pulsing the SVE blower has shown to effectively increase effluent concentrations if remediation goals have not been met before expenditure of additional capital costs to expand the system.

Cost to Design and Implement:
$171,095.53

Costs

Cost for Assessment:
  $226,003.88
Cost for Operation and Maintenance:
  $22,649.04
Total Costs for Cleanup:
  Not completed.

Lessons Learned

Emissions from dry cleaners in multi-tenant buildings are a source of indoor air impacts in adjacent tenant spaces. SVE systems can be installed and implemented faster than in-situ technologies depending on time to ascertain injection permits for a site which can be an asset if time to implementation is an issue.

We will know once system life and expenditures have been completed to determine if a different technology may have had a higher capital cost but less operational time to complete goals compared to longevity of O&M costs due to time required to reach remediation goals using current system.

Contacts

Al Chapman, L.G. - Project Manager
North Carolina Dry Cleaning Solvent Cleanup Act Program
NCDENR - Division of Waste Management
1646 Mail Service Center
Raleigh, NC 27699-1646
Phone: (919) 707-8368
Email: Al.Chapman@ncdenr.gov

Site Specific References

The site reports are available on the NCDENR document portal system at https://edm.nc.gov/DENR-Portal/. For a list of the site reports, type the site ID 530001 in the ID Value field under Property criteria, then click the Search button below the fields window. Afterwhich, a list of site reports are shown in the Content window. Right-click on the Adobe Acrobat symbol for download, preview, and other options.