Description
Historical activity that resulted
in contamination.
| PCE drycleaning operations were conducted at the facility from 1970 until 1985. The site is located in a strip mall in a mixed retail commercial/residential setting. The bay of the strip mall formerly occupied by the drycleaning operation is currently utililzed by a laundromat. Two contaminant source areas were found during the site assessment, the soil beneath the floor slab at the former location of the drycleaning machine and the area outside the back door of the facility where wastewater was reportedly discharged. 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 |
|
|
| Benzene |
soil |
|
|
| cis-1,2-Dichloroethene |
groundwater |
|
|
| cis-1,2-Dichloroethene |
soil |
|
|
| 1,1-Dichloroethene |
groundwater |
|
|
| Tetrachloroethene (PCE) |
groundwater |
|
|
| Tetrachloroethene (PCE) |
soil |
|
|
| Trichloroethene (TCE) |
groundwater |
|
|
| Trichloroethene (TCE) |
soil |
|
|
| toluene |
soil |
|
|
| trans-1,2-Dichloroethene |
groundwater |
|
|
| trans-1,2-Dichloroethene |
soil |
|
|
| Vinyl Chloride |
groundwater |
|
|
Site Hydrology
| Deepest Significant
Groundwater Contamination: |
|
60ft bgs |
| Plume Size: |
|
Plume Length: 580ft
Plume Width: 280ft
Plume Thickness: 56ft |
| Average Depth
to Groundwater: |
|
2.74ft |
Lithology and Subsurface Geology
|
|
silty, fine-grained sand with organic matter grading to silt with lenses of peat and clay
Depth: 0-3.5ft bgs
3.5ft thick
Conductivity: 8.89ft/day
Gradient: 0.0029ft/ft
|
|
|
fine to medium-grained sand interbedded with silty, fine-grained sand
Depth: 3.5-94ft bgs
90.5ft thick
|
Pathways and DNAPL Presence
 Groundwater
 Sediments
Soil
Presumptive Evidence of DNAPL
|
Vapor Intrusion Pathway
Has the potential for vapor intrusion (VI) been evaluated? |
|
No
|
Has a vapor mitigation system been installed? |
|
Yes |
Type of Vapor Mitigation System(s): |
|
Other
|
Additional VI Information: |
|
Performed excavation of contaminated soil behind building and under building floor slab. Installed piping for soil vapor extraction system. |
Remediation Scenario
Cleanup
Goals: |
|
Soil: PCE = 30 ug/kg, TCE = 30 ug/kg
Groundwater: PCE = 3 ug/L, TCE = 3 ug/L, cis 1,2-DCE = 70 ug/L, trans 1,2-DCE = 100 ug/L, 1,1-DCE = 7 ug/L, vinyl chloride = 1 ug/L
|
Remedy Level: |
|
Interim Action |
Technologies
In Situ Biostimulation |
|
Why the technology was selected:
Biostimulation was utilized because conditions are favorable for reductive dechlorination in groundwater and the excavation was into the top of the water table, which facilitated the introduction of the carbon amendment.
Date implemented:
First excavation: November 2 - December 1, 2009.
Second excavation: February 15 - April 15, 2010.
Final remediation design:
The first excavation was conducted under the facility floor slab where the drycleaning machine was formerly lcoated and in the parking lot immediately adjacent to the building. Depth of excavation was 3.5 to 4 ft BLS. The excavation was stablized with wooden shoring. Approximately 140 tons of soil was removed and shipped off site. Four hundred pounds of lime (powdered limestone and dolomite) was placed in the excavation for pH adjustment. Ninety-three (93) gallons of HRC-X mixed with 93 gallons of water was emplaced in the excavation under the former facility.
Two-inch diameter horizontal vapor extraction PVC screens were installed three feet below grade in the area within the bay that formerly housed the drycleaning operation and outside the bay in the parking lot. Piping was routed outside the building. Additionally, a one-inch diameter injection well (screened 5-25 ft BLS) to be utilized for future injection of carbon amendments and two monitor wells (screened 3-13 and 16-26 ft BLS) were installed in the excavated area within the former drycleaning facility to serve as performance monitoring wells. The area was backfilled and restored.
The second source removal area was located behind the facility. Approximately 496 tons of soil was excavated from this area to a depth of from 3.5 to 9 ft BLS. Sheet piling was used to stablize the deeper (9 ft BLS) portion of the excavation. Four hundred pounds of lime (powdered limestone and dolomite) was placed in the excavation for pH adjustment. Approximately 420 pounds of EOS 595 and 80 ounces of vitamin B12 was emplaced in this excavation. The area was then backfilled and restored.
Results to date:
Groundwater monitoring conducted on March 16, 2011. Little contamination remains in the upper surficial aquifer (Zone A - water table to 20 ft BLS). PCE (35 ug/l) was detected in only one well and the highest concentraitons of TCE and cis 1,2-DCE were 51 and 190 ug/l, respectively. Virtually no vinyl chloride has been detected in groundwater at the site.
No PCE is present in groundwater samples collected from Zone B (20-35 ft BLS)monitor wells. The highest remaining contaminant concentrations are in Zone B (1,200 ug/l TCE & 460 ug/l cis 1,2-DCE). The highest contaminant concentrations detected in Zone C (35-50 ft BLS) monitor wells were 460 ug/l TCE and 380 ug/l cis 1,2-DCE. No contaminants were detected in Zone D monitor wells (screened > 50 ft BLS).
Next Steps:
When available, a soil vapor extraction remedial system will be moved to the site and hooked up to the in-place piping for further remediaiton of the unsaturated zone under the strip mall. Two days of Membrane Interface Probe logging was conducted in and near the contaminant source area to aid in developing a remedial action plan for biostimulation of contaminated groundwater at the site.
Cost to Design and Implement:
All technologies: Design: 41,700
Implementation: $383,000
|
In Situ Soil Vapor Extraction |
|
Why the technology was selected:
Soil vapor extraction was selected to remove contaminants from the soil beneath the building floor slab that could not be excavated.
Next Steps:
When available, a soil vapor extraction remedial system will be moved to the site and hooked up to the in-place piping for further remediaiton of the unsaturated zone under the strip mall. Two days of Membrane Interface Probe logging was conducted in and near the contaminant source area to aid in developing a remedial action plan for biostimulation of contaminated groundwater at the site.
|
Ex Situ Soil Removal |
|
Why the technology was selected:
Excavation was chosen because most of the contaminated soil was accessible (outside the back of the building), and because PCE was sorbed to the peat in the soil and if not removed, would continue to desorb into the groundwater.
Date implemented:
First excavation: November 2 - December 1, 2009.
Second excavation: February 15 - April 15, 2010.
Final remediation design:
The first excavation was conducted under the facility floor slab where the drycleaning machine was formerly lcoated and in the parking lot immediately adjacent to the building. Depth of excavation was 3.5 to 4 ft BLS. The excavation was stablized with wooden shoring. Approximately 140 tons of soil was removed and shipped off site. Four hundred pounds of lime (powdered limestone and dolomite) was placed in the excavation for pH adjustment. Ninety-three (93) gallons of HRC-X mixed with 93 gallons of water was emplaced in the excavation under the former facility.
Two-inch diameter horizontal vapor extraction PVC screens were installed three feet below grade in the area within the bay that formerly housed the drycleaning operation and outside the bay in the parking lot. Piping was routed outside the building. Additionally, a one-inch diameter injection well (screened 5-25 ft BLS) to be utilized for future injection of carbon amendments and two monitor wells (screened 3-13 and 16-26 ft BLS) were installed in the excavated area within the former drycleaning facility to serve as performance monitoring wells. The area was backfilled and restored.
The second source removal area was located behind the facility. Approximately 496 tons of soil was excavated from this area to a depth of from 3.5 to 9 ft BLS. Sheet piling was used to stablize the deeper (9 ft BLS) portion of the excavation. Four hundred pounds of lime (powdered limestone and dolomite) was placed in the excavation for pH adjustment. Approximately 420 pounds of EOS 595 and 80 ounces of vitamin B12 was emplaced in this excavation. The area was then backfilled and restored.
Results to date:
Groundwater monitoring conducted on March 16, 2011. Little contamination remains in the upper surficial aquifer (Zone A - water table to 20 ft BLS). PCE (35 ug/l) was detected in only one well and the highest concentraitons of TCE and cis 1,2-DCE were 51 and 190 ug/l, respectively. Virtually no vinyl chloride has been detected in groundwater at the site.
No PCE is present in groundwater samples collected from Zone B (20-35 ft BLS)monitor wells. The highest remaining contaminant concentrations are in Zone B (1,200 ug/l TCE & 460 ug/l cis 1,2-DCE). The highest contaminant concentrations detected in Zone C (35-50 ft BLS) monitor wells were 460 ug/l TCE and 380 ug/l cis 1,2-DCE. No contaminants were detected in Zone D monitor wells (screened > 50 ft BLS).
Next Steps:
When available, a soil vapor extraction remedial system will be moved to the site and hooked up to the in-place piping for further remediaiton of the unsaturated zone under the strip mall. Two days of Membrane Interface Probe logging was conducted in and near the contaminant source area to aid in developing a remedial action plan for biostimulation of contaminated groundwater at the site.
Cost to Design and Implement:
All technologies: Design: 41,700
Implementation: $383,000
|
Costs
Cost
for Assessment:
|
|
$244,000 |
Cost
for Operation and Maintenance:
|
|
|
Total
Costs for Cleanup:
|
|
|
Lessons Learned
If peat is present in the the contaminant source area and is accessible, it should be excavated. Remove as much of the peat as possible, including excavating well below the water table if feasible. If not removed, contaminats will continue to desorb from the peat and it will be difficult to achieve reductions in contaminant concentrations in groundwater.
MIP is a good tool for determining contaminant mass distribution in contaminant source areas. MIP data should be used to determine screen intervals for injection and performance monitoring wells.
|
Contacts
Aaron Cohen
Florida Dept. of Environmental Protection
Bureau of Waste Cleanup, MS 4500
2600 Blair Stone Road
Tallahassee, Florida 32399
850-245-8974
Aaron.Cohen@dep.state.fl.us
|
Site Specific References
Site Assessment Report: 2005
Remedial Action Plan: 2008
Construction Completion Report: 2010
Groundwater Monitoring Reports: 2006 - present
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|
