State Coalition for Remediation of Drycleaners Site Profiles
Sno-White Cleners, Charlotte, North Carolina
Description
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| Prior assessment activities indicated that a release at the former drycleaning facility resulted in impacted soil and groundwater. The PCE plume in groundwater extends appproximately 1,500 feet to the northwest and off-site in the downgradient direction. Soil excavation was performed in 2008 and an AS/SVE system was installed in
May 2009 and to remediate the source area. The remediation efforts were successful in significantly reducing
source area concentrations. The AS/SVE system was shutdown in May 2010 and four groundwater monitoring
events were conducted to evaluate plume stability. Based on the results of the monitoring events, the plume associated with the site appears adequately defined, generally stable, and concentrations are reducing. A TIER II risk assessment has been performed using the RAM RBCA toolkit and, additionally a site-wide TIER III risk assessment was performed using GSI's RBCA toolkit to specifcally address groundwater concentrations marginally exceeding the GW>IA screening levels. The site passed the risk asssessement and a Risk Management Plan has been written with on-site land use restrictions for: groundwater, vapor intrusion, and residential use. Off-site contamination is being controlled through notices placed on the survey plat that the property is impacted by tetrachloroethylene, and a "NOTICE OF DRY CLEANING SOLVENT REMEDIATION" documented with the county register of deeds which prohibits the use of groundwater on the property in accordance with 15A North Carolina Administrative Code 02C .0107(b)(1), (t)he source of water for any water supply well shall not be from a water bearing zone or aquifer that is contaminated. Remediation Status: Site closed |
Contaminants
Contaminants present and the highest amount
detected in both soil and groundwater.
| Contaminant | Media | Concentration (ppb) | Nondetect |
|---|---|---|---|
| Tetrachloroethene (PCE) | groundwater | ||
| Tetrachloroethene (PCE) | soil | ||
| Trichloroethene (TCE) | groundwater | ||
| Trichloroethene (TCE) | soil |
Site Hydrology
| Deepest Significant Groundwater Contamination: | 50ft bgs | |
| Plume Size: | Plume Length: 1,500ft Plume Width: 300ft Plume Thickness: 50ft |
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| Average Depth to Groundwater: | 13.5ft |
Lithology and Subsurface Geology
| Silty clay to fine sandy silt coarsening with depth to saprolite Conductivity: 1.66ft/day Gradient: 0.02ft/ft |
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Metagabbro of the Charlotte Belt |
bedrock |
Pathways and DNAPL Presence
 GroundwaterSedimentsSoil Presumptive Evidence of DNAPL |
Vapor Intrusion Pathway
Has the potential for vapor intrusion (VI) been evaluated? |
Yes |
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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 |
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Results of VI evaluation: |
A completed VI pathway has been indentified,A potential VI pathway has been indentified | |
Has a vapor mitigation system been installed? |
Yes | |
Type of Vapor Mitigation System(s): |
Soil Vapor Extraction |
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Additional VI Information: |
Environmental media exceeding VI screening levels were primarily contained to a small soil and groundwater source beneath the building. An excavation within the footprint of the former cleaner, followed by installation of an SVE/Air Sparge system in the source area, reduced Indoor Air concentrations below a Target Risk Level of 1.0 E -05 and HI of 1.0. Off property grounwater concentrations slightly exceeded NCDSCA GW>IA screening levels, therefore the GSI RBCA toolkit was used to perform a site wide ris assessment, and specifically evaluate off-property VI potential. The site wide risk assessment met closure criteria. |
Remediation Scenario
Cleanup
Goals: |
Achieve overall sitewide cumulative risk level of less than 1.0E-05 for all exposure pathways (combined) for each exposure unit evaluated through a risk assessment. Pathways evaluated were: Non-Residential Worker - Surficial SoilCombined Pathway; Non-Residential Worke Subsurface Soil - Vapor Emissions to Indoor Air; Non-Residential Worker Groundwater - Vapor Emissions to Indoor Air; and Protection of Groundwater (assuming point of exposure at the downgradient property boundary). |
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Remedy Level: |
Interim Action |
Technologies
In Situ Air Sparging |
Why the technology was selected: Date implemented: Final remediation design: Results to date: Next Steps: Cost to Design and Implement: |
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In Situ Soil Vapor Extraction |
Why the technology was selected: Date implemented: Final remediation design: Results to date: Next Steps: Cost to Design and Implement: |
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Ex Situ Soil Removal |
Why the technology was selected: Date implemented: Final remediation design: Results to date: Next Steps: Cost to Design and Implement: |
Costs
Cost
for Assessment: |
$166,187.13 (including risk assessment) $170,204.13 | |
Cost
for Operation and Maintenance: |
~$7,000.00 over approx 3 years | |
Total
Costs for Cleanup: |
$420,019.16 |
Lessons Learned
| Source removal was very effective at reducing indoor air concentrations. It appears that soil and groundwater must be addressed simultaneously in order to adequately reduce vapor intursion and reduce indoor air concentrations. This strategy is being used at an almost identical site. The only problems were O&M of the SVE/Air sparge blower. This remedial approach was optimal for these specific conditions and in hind site the same remedial approach would likely be used again with little modification. |
Contacts
| Billy Meyer, NCDSCA Project Manager 217 W. Jones Street, Raleigh, NC 919-707-8366 billy.meyer@ncdenr.gov |
Site Specific References
| 2/26/10: "Interim Building Assessment and Remediation" 4/28/10: "Assessment Report" 3/9/11: "Remediation System Operation and Maintenance adn POst-Remediation Air Sampling Report" 7/27/11: Groundwater Montoring (Plume Stability Documentation) Report 10/12/11: TIER 3 Risk Assessment 2/14/12: Risk Management Plan |
