Description
Historical activity that resulted
in contamination.
| Plaza cleaners operated from 1971 to 2001. The site is located in a commercial area adjacent to residential. The cleaners used PCE as it's solvent. No known discharges or spills were reported. The source of contamination appears to be from the location of the sewer line and "out the back door", either from disposal or storage of PCE containing materials.
Nearby receptors include future commercial (vapor intrusion) on site, as well as downgradient use of groundwater for irrigation and domestic uses.
Before investigation and cleanup activities were initiated, the building had been removed, leaving just a concrete slab. There was a lot of room to work, and no real time constraints on the cleanup work. 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 |
|
|
| Tetrachloroethene (PCE) |
groundwater |
|
|
| Tetrachloroethene (PCE) |
soil |
|
|
| Trichloroethene (TCE) |
groundwater |
|
|
| Trichloroethene (TCE) |
soil |
|
|
Site Hydrology
| Deepest Significant
Groundwater Contamination: |
|
55ft bgs |
| Plume Size: |
|
|
| Average Depth
to Groundwater: |
|
10ft |
Lithology and Subsurface Geology
|
|
silt with sand and gravel layers
Depth: 0-10ft bgs
10ft thick
Conductivity: 1ft/day
|
|
|
clay and silt
Depth: 10-16ft bgs
6ft thick
|
|
|
sand and gravel
Depth: 16-55ft bgs
39ft thick
|
Pathways and DNAPL Presence
 Groundwater
Sediments
Soil
 Presumptive Evidence of DNAPL
|
Vapor Intrusion Pathway
Has the potential for vapor intrusion (VI) been evaluated? |
|
Yes
|
How was the site evaluated? |
|
Groundwater sampling,Compared sample concentration to screening criteria
|
Results of VI evaluation: |
|
Undetermined |
Has a vapor mitigation system been installed? |
|
No |
Additional VI Information: |
|
Further asssessment of the VI pathway is needed before the site can be considered for closure. |
Remediation Scenario
Cleanup
Goals: |
|
To remove the source and treat on-site highly concentrated groundwater over a short term (<5 years)in order to reduce concentrations to below risk based concentrations for vapor intrusion on-site, as well as reduce the threat of continued off-site migration toward downgradient groundwater users.
|
Remedy Level: |
|
Interim Action |
Technologies
In Situ Bioremediation |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Other technologies used:
Carbstrate (dextrose) was used as the primary electron donor. Hydrolized ethyl lactate was later used. Both substrates were added to water extracted from downgradient wells and reinjected in and up gradient of the source area in a recirculating system. Ethyl lactate was later injected into the well network as slug injections.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
In Situ Biostimulation |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Other technologies used:
Carbstrate (dextrose) was used as the primary electron donor. Hydrolized ethyl lactate was later used. Both substrates were added to water extracted from downgradient wells and reinjected in and up gradient of the source area in a recirculating system. Ethyl lactate was later injected into the well network as slug injections.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
In Situ In Situ Flushing |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Other technologies used:
Carbstrate (dextrose) was used as the primary electron donor. Hydrolized ethyl lactate was later used. Both substrates were added to water extracted from downgradient wells and reinjected in and up gradient of the source area in a recirculating system. Ethyl lactate was later injected into the well network as slug injections.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
Ex Situ Carbon Adsorption |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
Ex Situ Soil Vapor Extraction |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
Ex Situ Soil Removal |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
In Situ Other |
|
Why the technology was selected:
Limited excavation of source material was selected because of ease of access (building had been removed and site was very accessible. There was space to treat excavated soil on-site and time was not a significant factor for the soil treatment.
Recirculating groundwater with electron donor amendments was elected as a proven method to greatly reduce contaminated mass in groundwater near the source zone quickly. O&M costs are relatively low.
Date implemented:
8/2006
Final remediation design:
A vapor intrusion assessment (soil gas sampling) is needed, along with a risk screening, to determine if any additinoal cleanup (final remedy) is needed. It is likely that no additional active cleanup will be required at this site.
Results to date:
250 cubic yards of soil contaminated with PCE were excavated and treated.
Groundwater concentrations of PCE and TCE were reduced by approximately 98%, from 2,700 ug/L to 35 ug/L
Next Steps:
A vapor intrusion assessment is needed to determine if any further cleanup (or engineering/institutional controls) may be needed prior to closure.
Cost to Design and Implement:
$197,000 for all technologies
|
Costs
Cost
for Assessment:
|
|
$34,000 |
Cost
for Operation and Maintenance:
|
|
$25,000/year for 2.8 years |
Total
Costs for Cleanup:
|
|
$301,000 |
Lessons Learned
The fact that the building had been removed, there was good site access for excavation and on-site treatment of soil, and there were few time constraints on the work made this project very cost effective, and the source of the contamination could be remediated quickly.
Limited soil removal remains a very cost effecitve technology.
Bioremediation using a recirculating (injection/extraction) approach increases the flow through the contaminated aquifer, helping to desorb and remove more contaminant mass in less time.
|
Contacts
Donald Hanson, RG
Oregon Department of Environmental Quality
165 E. 7th Avenue, Suite 100
Eugene, OR 97401
(541) 687-7349
hanson.don@deq.state.or.us
|
Site Specific References
|
