Drycleaner Site Profiles

Thorne's Dry Cleaners, Rocky Mount, North Carolina

Description
Historical activity that resulted in contamination.

North Carolina Drycleaning Solvent Cleanup Act (DSCA) Site 33-0002. Located at 502 Rose Street, Rocky Mount, NC. An abandoned perc cleaner on a property planned for commercial re-development

Remediation Status: In groundwater monitoring


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

Site Hydrology

Deepest Significant Groundwater Contamination:  
Plume Size:  
Average Depth to Groundwater:   5.82ft

Lithology and Subsurface Geology

 
  clay
Depth: 0-9ft bgs
9ft thick
Gradient: 0.014ft/ft
 
  sand & gravel with some clay
Depth: 9-12ft bgs
3ft thick
Yorktown Formation
  fossilferous marine clay
Depth: 12-35ft bgs
23ft thick
 
  unknown cemented sand
Depth: 35ft 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,Groundwater sampling,Compared sample concentration to screening criteria
Results of VI evaluation:
  A potential VI pathway has been indentified
Has a vapor mitigation system been installed?
  No 
Additional VI Information:
  Soil gas samples were collected on each side of the newly constructed store. One sample contained a concentration which exceeded the indoor air screening level for Vinyl Chloride. Indoor air samples are to be collected from the store to verify if vapor intrusion is an issue.

Remediation Scenario

Cleanup Goals:
  Tier 1 RBSLs for subsurface soils and vapor intrusion 0.18 mg/kg
Remedy Level:
  Interim Action

Technologies

In Situ Chemical Oxidation
 

Why the technology was selected:
The quantity of impacted souce area soil was too great for traditional dig and haul. The soils would have to be disposed of as hazardous (F-002) and the cost was too high. The site was under development and the impacted area was to be utilized as a parking lot. Since long term active remediation was not an option, this technology was cost effective and would do the most for the down-gradient groundwater quality. To ensure surface stability for the proposed parking lot, dry portland cement was intrduced into the blended area.

Date implemented:
December 3, 2010

Final remediation design:
December 16, 2010

Other technologies used:
Excavation of the top four (4) feet of soil and containerization in roll off boxes. Subsequent characterization of the soils using the "Contained In Policy" determined that 352 tons was listed hazardous and 49 tons was listed as non-hazardous. In-situ Soil Blending of the remaing area to a depth of 4-12 feet using Potassium Permanganate as the chemical oxidant.

Results to date:
99% reduction in source area soils 98% reduction in source area gw

Next Steps:
Monitor the down-gradient wells for groundwater quality and plume stability.

Cost to Design and Implement:
$522,437 for all technologies

Ex Situ Soil Removal
 

Why the technology was selected:
The quantity of impacted souce area soil was too great for traditional dig and haul. The soils would have to be disposed of as hazardous (F-002) and the cost was too high. The site was under development and the impacted area was to be utilized as a parking lot. Since long term active remediation was not an option, this technology was cost effective and would do the most for the down-gradient groundwater quality. To ensure surface stability for the proposed parking lot, dry portland cement was intrduced into the blended area.

Date implemented:
December 3, 2010

Final remediation design:
December 16, 2010

Other technologies used:
Excavation of the top four (4) feet of soil and containerization in roll off boxes. Subsequent characterization of the soils using the "Contained In Policy" determined that 352 tons was listed hazardous and 49 tons was listed as non-hazardous. In-situ Soil Blending of the remaing area to a depth of 4-12 feet using Potassium Permanganate as the chemical oxidant.

Results to date:
99% reduction in source area soils 98% reduction in source area gw

Next Steps:
Monitor the down-gradient wells for groundwater quality and plume stability.

Cost to Design and Implement:
$522,437 for all technologies

Costs

Cost for Assessment:
  $30.876
Cost for Operation and Maintenance:
 
Total Costs for Cleanup:
  $553,313

Lessons Learned

In-situ chemical oxidation was very successful with reduction in the source area. Since the source area of impact was so large, it was also very cost effective. Based on the results and the costs incurred, I would consider this approach with a similar site.

Contacts

Jay W. King
Project Manager DSCA Program
NCDENR Div. of Waste Management
Superfund Section

Site Specific References

Interim Action Completion Report
Hart & Hickman Project No. DSO-60D
February 28, 2011

Post-Interim Action Sampling Report
Hart & Hickman Job No. DS0-60
April 28, 2011