Drycleaner Site Profiles

Brock's Cleaners, Tryon, North Carolina

Description
Historical activity that resulted in contamination.

From approximately 1948 to 1984 petroleum based dry-cleaning solvents were used during cleaning operations. From approximately 1984 to present, Brock's Cleaners has utilized tetrachloroethene (PCE) as the dry-cleaning solvent. There was a significant release from the machine in the mid 90's. Soil impacts appear to be localized beneath the dry cleaner. Depth to bedrock ranges from 0-8' at the site. Grondwater is contaminated at concentrations indicative of DNAPL presence and the plume has caused significant surface water impacts approximately 500' from teh site. Also Vapor Intrusion occurring at moderate levels in two off property residences.

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
cis-1,2-Dichloroethene soil
1,1-Dichloroethene groundwater
Tetrachloroethene (PCE) groundwater
Tetrachloroethene (PCE) soil
naphthalene groundwater
naphthalene soil
Trichloroethene (TCE) groundwater
Trichloroethene (TCE) soil
trans-1,2-Dichloroethene groundwater

Site Hydrology

Deepest Significant Groundwater Contamination:   80ft bgs
Plume Size:   Plume Length: 700ft
Plume Width: 600ft
Plume Thickness: 80ft
Average Depth to Groundwater:   10.73ft

Lithology and Subsurface Geology

 
  yellowish-orange, coarse to medium micaceous sandy silt saprolite and partially weathered rock (PWR) regolith
Depth: 0-8ft bgs
8ft thick
Conductivity: 0.000286299ft/day
Gradient: 0.11ft/ft

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
Results of VI evaluation:
  A completed VI pathway has been indentified
Has a vapor mitigation system been installed?
  No 

Remediation Scenario

Cleanup Goals:
  To stabilize the plume in order to decrease concentrations leaving the site thereby reducing VI potential and impacts to the surface water body 500 feet away. Furhtermore, decrease the overall advancement of a large plume.
Remedy Level:
  Interim Action

Technologies

In Situ Bioremediation
 

Why the technology was selected:
Bench scale studies indicated that activated persulfate did not perform well and permanganate daylighting issues were a concern. With the presence of daughter products, the measured presence of dehalococcoides, and absence of electron competitors, reductive dechlorination and in situ chemical reduction vial ZVI were selected. Also the viscosity of the mixture was important because much the top of bedrock was very shallow and we were aiming for maximal contaminant/reagent contact.

Date implemented:
April 11, 2011

Final remediation design:
Prior to the injection, four monitoring wells (PZ-4 through PZ-7) were installed and seven injection wells (IW-14 through IW-20) and a baseline groundwater sampling event was conducted between April 1 and 15, 2011. The injection activities were conducted between April 11 and 16, 2011. The solution (consisting of ABC+, ZVI, and water) was injected into the subsurface through 26 temporary injection points (IP-1 through IP-26) and 20 injection wells (IW-1 through IW-20). Injection depths ranged from approximately 3.5 ft below ground surface (bgs) to 8 ft bgs. A total of approximately 1,768 gallons of ABC+ solution was injected into the subsurface.

Results to date:
Groundwater elevation data indicate that groundwater flow in the shallow aquifer is to the northeast towards an unnamed tributary of Vaughn Creek. The ABC+ injection effectively reduced PCE and TCE concentrations in the vicinity and downgradient of the injection area with reductions up to 93% in MW-1 and 99% in MW-10s between April 2011 and October 2011. Similarly, TCE concentrations decreased significantly in the performance monitoring wells with reductions up to 69% in MW-1 and 62% in PZ-6. Increased concentrations of cis-1,2-DCE, trans-1,2-DCE, and VC (PCE and TCE breakdown products) were generally observed in the performance monitoring wells within the first two months after the April 2011 injection. Subsequently, cis-1,2-DCE,trans-1,2-DCE, and VC concentrations were varied during the August and October 2011 sampling events. These results indicate the ABC+ injection is effectively stimulating reductive dechlorination of PCE and TCE in the injection area.The ABC+ injection successfully created anaerobic conditions conducive to reductive dechlorination as indicated by reductions in DO and ORP and increases in methane.Increased concentrations of chloride (a by-product) and ethene and ethane (end products) provide further evidence that the ABC+ injection has successfully stimulated reductive dechlorination.The ABC+ solution was effectively distributed within the injection area and remains present to continue stimulating reductive dechlorination as evidenced by increases in TOC, VFAs, and iron. Microorganisms and functional genes responsible for reductive dechlorination are present within the injection area at the site.

Next Steps:
Monitor the site for performance of the injection, the aquifer's return to preinjection geochemical status, and evaluate a second injection.

Cost to Design and Implement:
~$98,105.00

In Situ Zero Valent Iron
 

Why the technology was selected:
Bench scale studies indicated that activated persulfate did not perform well and permanganate daylighting issues were a concern. With the presence of daughter products, the measured presence of dehalococcoides, and absence of electron competitors, reductive dechlorination and in situ chemical reduction vial ZVI were selected. Also the viscosity of the mixture was important because much the top of bedrock was very shallow and we were aiming for maximal contaminant/reagent contact.

Date implemented:
April 11, 2011

Final remediation design:
Prior to the injection, four monitoring wells (PZ-4 through PZ-7) were installed and seven injection wells (IW-14 through IW-20) and a baseline groundwater sampling event was conducted between April 1 and 15, 2011. The injection activities were conducted between April 11 and 16, 2011. The solution (consisting of ABC+, ZVI, and water) was injected into the subsurface through 26 temporary injection points (IP-1 through IP-26) and 20 injection wells (IW-1 through IW-20). Injection depths ranged from approximately 3.5 ft below ground surface (bgs) to 8 ft bgs. A total of approximately 1,768 gallons of ABC+ solution was injected into the subsurface.

Results to date:
Groundwater elevation data indicate that groundwater flow in the shallow aquifer is to the northeast towards an unnamed tributary of Vaughn Creek. The ABC+ injection effectively reduced PCE and TCE concentrations in the vicinity and downgradient of the injection area with reductions up to 93% in MW-1 and 99% in MW-10s between April 2011 and October 2011. Similarly, TCE concentrations decreased significantly in the performance monitoring wells with reductions up to 69% in MW-1 and 62% in PZ-6. Increased concentrations of cis-1,2-DCE, trans-1,2-DCE, and VC (PCE and TCE breakdown products) were generally observed in the performance monitoring wells within the first two months after the April 2011 injection. Subsequently, cis-1,2-DCE,trans-1,2-DCE, and VC concentrations were varied during the August and October 2011 sampling events. These results indicate the ABC+ injection is effectively stimulating reductive dechlorination of PCE and TCE in the injection area.The ABC+ injection successfully created anaerobic conditions conducive to reductive dechlorination as indicated by reductions in DO and ORP and increases in methane.Increased concentrations of chloride (a by-product) and ethene and ethane (end products) provide further evidence that the ABC+ injection has successfully stimulated reductive dechlorination.The ABC+ solution was effectively distributed within the injection area and remains present to continue stimulating reductive dechlorination as evidenced by increases in TOC, VFAs, and iron. Microorganisms and functional genes responsible for reductive dechlorination are present within the injection area at the site.

Next Steps:
Monitor the site for performance of the injection, the aquifer's return to preinjection geochemical status, and evaluate a second injection.

Cost to Design and Implement:
~$98,105.00

Costs

Cost for Assessment:
  ~$304,911.92
Cost for Operation and Maintenance:
  ~$50,000
Total Costs for Cleanup:
 

Lessons Learned

In this case a bench scale study completely changed the reagent to be used in the remediation. Had we used activated persulfate, the remediation would likely have been a failure.

Contacts

Billy Meyer
919-707-8366
217 W. Jones Street, Raleigh, NC 27603
Contractors:
AECOM
Hart and Hickman

Site Specific References

ABC+ Injection
Final Project Evaluation Report
April 17, 2012