Drycleaner Site Profiles

Washington Square Mall Dry Cleaners, Germantown, Wisconsin

Description
Historical activity that resulted in contamination.

The Washington Square Mall Dry Cleaners operated in mixed commercial and residential setting from the 1970s until 1998. The drycleaners relied on perchloroethylene (PCE) solvent as a cleaning agent in the operations. The drycleaner operations likely contributed to the chlorinated compound contamination in the soil and groundwater through releases into the floor drains. The underlying statutory authority for the cleanup was Chapter 292 of the Wisconsin Statutes, also known as the "Spill Law." The investigation and remediation activity at the site qualified for financial reimbursement through the Wisconsin Drycleaner Environmental Response Program. Contractors completed remediation activities, and Wisconsin Department of Natural Resources (DNR) granted closure to the site in January 2001.

Contaminants
Contaminants present and the highest amount detected in both soil and groundwater.


Contaminant Media Concentration (ppb) Nondetect
Tetrachloroethene (PCE) groundwater 2,000 ppb
Tetrachloroethene (PCE) soil 80,000 ppb
Trichloroethene (TCE) groundwater 94.9 ppb
Trichloroethene (TCE) soil 110 ppb
1,2-Dichloroethene soil 870 ppb

Site Hydrology

Deepest Significant Groundwater Contamination:   20ft bgs
Plume Size:   Plume Length: 200ft
Plume Width: 100ft
Average Depth to Groundwater:   12.5ft

Lithology and Subsurface Geology

Uppermost Unit
  Surficial top soil and small-medium-sized gravel or concrete
Depth: 0-2ft bgs
2ft thick
Conductivity: 2.83ft/day
Gradient: 0.015ft/ft
 
  medium, well sorted gravel
Depth: 2-2.75ft bgs
0.75ft thick
Silty Clay unit
  Light brown to dark brown to gray sandy clays to clayey silts, clays, and silty clays with trace amounts of small-to-medium gravel
Depth: 10-17ft bgs
7ft thick

Pathways and DNAPL Presence

checkGroundwater
Sediments
checkSoil
DNAPL Present

Remediation Scenario

Cleanup Goals:
  The remedial goals include the removal of as much of the source as possible and restore groundwater quality according to the enforcement standards established NR 140 Wis. Adm. Code. A site-specific residual contaminant level (RCL) of 25 mg/kg was established for soil.

Technologies

In Situ Bioremediation
 

Why the technology was selected:
Most effective, feasible methods to remove the source, and to inhibit further migration of chlorinated compounds in groundwater. Access limitations and the low permeability of the silty clay unit influenced this decision. The carbon amendment technology requires little maintenance, and can be readily implemented. Carbon injection can be initiated at a slow rate, and the effects can be monitored to assess the adequacy of the injection rates utilized.

Final remediation design:
PCE-impact soil, to a depth of 14 ft. bgs., was excavated and transported to a landfill. Contactors encountered groundwater, from precipitation and surface run-in during excavation or from the sand-seam that was penetrated, during the soil removal activity and pumped and discharged it to the sanitary sewer. Contractors used carbon injections (molasses) to promote enhanced reductive dechlorination of PCE. 182 Geoprobe injection points were used in a grid-like pattern across the estimated area of impact, sited to intersect the sand seam (12-17 ft. bgs.). A Geoprobe rod was initially used as a well screen and riser for injection of the dilute molasses solution. After 15 Geoprobe borings had been completed, the rod was replaced with a 1-inch temporary PVC pipe. Bentonite pellets were then used to seal the temporary wells. 15-25 gal. of molasses and 25 gal. of water/gal. of molasses were injected during the first event. 10 wells were installed after the first event to facilitate performance monitoring within limits of the plume. 5 follow-up injections of the same size were completed over a six-month period.

Results to date:
Soil removal: Contractors removed 3,125 tons of soil, and disposed of it in an off-site landfill. PCE concentrations were below the soil RCL of 25 mg/kg following the excavation. Groundwater Remediation: Sampling results taken from a 20-month period following completion of soil remediation activities and the initial carbon injection event reveal PCE concentrations at non-detectable levels. An expected increase in PCE breakdown products, such as cis-1,2-DCE and vinyl chloride (VC), occurred. VC concentrations ranged from 0.37 µg/L to 88 µg/L, TCE concentrations occurred at 15 µg/L, and cis-1,2-DCE occurred at 300 µg/L. Observed concentrations of these PCE breakdown products over time suggested that residual contaminant levels would steadily decrease as the reductive dechlorination process continued. Concentrations of the non-toxic, innocuous end-products of dechlorination, ethane and ethene, were detected in four monitoring wells at approximately 1-2 orders of magnitude higher than the ethane and ethene concentrations in wells on the fringe of the plume. This was viewed as evidence that the reductive dechlorination process was going to completion. Site is now closed.

Next Steps:
Site was closed Oct. 4, 2001 without the need for institutional controls. This site did NOT qualify for reimbursement under the WI Dry Cleaner Environmental Response Program (DERP).

Cost to Design and Implement:
$1,150,000 for all technologies

In Situ Monitored Natural Attenuation
 

Why the technology was selected:
Most effective, feasible methods to remove the source, and to inhibit further migration of chlorinated compounds in groundwater. Access limitations and the low permeability of the silty clay unit influenced this decision. The carbon amendment technology requires little maintenance, and can be readily implemented. Carbon injection can be initiated at a slow rate, and the effects can be monitored to assess the adequacy of the injection rates utilized.

Final remediation design:
PCE-impact soil, to a depth of 14 ft. bgs., was excavated and transported to a landfill. Contactors encountered groundwater, from precipitation and surface run-in during excavation or from the sand-seam that was penetrated, during the soil removal activity and pumped and discharged it to the sanitary sewer. Contractors used carbon injections (molasses) to promote enhanced reductive dechlorination of PCE. 182 Geoprobe injection points were used in a grid-like pattern across the estimated area of impact, sited to intersect the sand seam (12-17 ft. bgs.). A Geoprobe rod was initially used as a well screen and riser for injection of the dilute molasses solution. After 15 Geoprobe borings had been completed, the rod was replaced with a 1-inch temporary PVC pipe. Bentonite pellets were then used to seal the temporary wells. 15-25 gal. of molasses and 25 gal. of water/gal. of molasses were injected during the first event. 10 wells were installed after the first event to facilitate performance monitoring within limits of the plume. 5 follow-up injections of the same size were completed over a six-month period.

Results to date:
Soil removal: Contractors removed 3,125 tons of soil, and disposed of it in an off-site landfill. PCE concentrations were below the soil RCL of 25 mg/kg following the excavation. Groundwater Remediation: Sampling results taken from a 20-month period following completion of soil remediation activities and the initial carbon injection event reveal PCE concentrations at non-detectable levels. An expected increase in PCE breakdown products, such as cis-1,2-DCE and vinyl chloride (VC), occurred. VC concentrations ranged from 0.37 µg/L to 88 µg/L, TCE concentrations occurred at 15 µg/L, and cis-1,2-DCE occurred at 300 µg/L. Observed concentrations of these PCE breakdown products over time suggested that residual contaminant levels would steadily decrease as the reductive dechlorination process continued. Concentrations of the non-toxic, innocuous end-products of dechlorination, ethane and ethene, were detected in four monitoring wells at approximately 1-2 orders of magnitude higher than the ethane and ethene concentrations in wells on the fringe of the plume. This was viewed as evidence that the reductive dechlorination process was going to completion. Site is now closed.

Next Steps:
Site was closed Oct. 4, 2001 without the need for institutional controls. This site did NOT qualify for reimbursement under the WI Dry Cleaner Environmental Response Program (DERP).

Cost to Design and Implement:
$1,150,000 for all technologies

Ex Situ Soil Removal
 

Why the technology was selected:
Most effective, feasible methods to remove the source, and to inhibit further migration of chlorinated compounds in groundwater. Access limitations and the low permeability of the silty clay unit influenced this decision. The carbon amendment technology requires little maintenance, and can be readily implemented. Carbon injection can be initiated at a slow rate, and the effects can be monitored to assess the adequacy of the injection rates utilized.

Final remediation design:
PCE-impact soil, to a depth of 14 ft. bgs., was excavated and transported to a landfill. Contactors encountered groundwater, from precipitation and surface run-in during excavation or from the sand-seam that was penetrated, during the soil removal activity and pumped and discharged it to the sanitary sewer. Contractors used carbon injections (molasses) to promote enhanced reductive dechlorination of PCE. 182 Geoprobe injection points were used in a grid-like pattern across the estimated area of impact, sited to intersect the sand seam (12-17 ft. bgs.). A Geoprobe rod was initially used as a well screen and riser for injection of the dilute molasses solution. After 15 Geoprobe borings had been completed, the rod was replaced with a 1-inch temporary PVC pipe. Bentonite pellets were then used to seal the temporary wells. 15-25 gal. of molasses and 25 gal. of water/gal. of molasses were injected during the first event. 10 wells were installed after the first event to facilitate performance monitoring within limits of the plume. 5 follow-up injections of the same size were completed over a six-month period.

Results to date:
Soil removal: Contractors removed 3,125 tons of soil, and disposed of it in an off-site landfill. PCE concentrations were below the soil RCL of 25 mg/kg following the excavation. Groundwater Remediation: Sampling results taken from a 20-month period following completion of soil remediation activities and the initial carbon injection event reveal PCE concentrations at non-detectable levels. An expected increase in PCE breakdown products, such as cis-1,2-DCE and vinyl chloride (VC), occurred. VC concentrations ranged from 0.37 µg/L to 88 µg/L, TCE concentrations occurred at 15 µg/L, and cis-1,2-DCE occurred at 300 µg/L. Observed concentrations of these PCE breakdown products over time suggested that residual contaminant levels would steadily decrease as the reductive dechlorination process continued. Concentrations of the non-toxic, innocuous end-products of dechlorination, ethane and ethene, were detected in four monitoring wells at approximately 1-2 orders of magnitude higher than the ethane and ethene concentrations in wells on the fringe of the plume. This was viewed as evidence that the reductive dechlorination process was going to completion. Site is now closed.

Next Steps:
Site was closed Oct. 4, 2001 without the need for institutional controls. This site did NOT qualify for reimbursement under the WI Dry Cleaner Environmental Response Program (DERP).

Cost to Design and Implement:
$1,150,000 for all technologies

Costs

Cost for Assessment:
  $120,000
Cost for Operation and Maintenance:
 
Total Costs for Cleanup:
  $1,270,000

Lessons Learned

1. The thorough site investigation made it easier to approve the remediation technologies. The knowledge of the plume dynamics increased the efficiency of the decision making process.
2.The source removal (soil) and active groundwater treatment facilitated a timely closure. This avoided years of groundwater monitoring.

Contacts

Margaret Brunette, Hydrogeologist
Remediation and Redevelopment
Milwaukee Service Center
WI Department of Natural Resources
2300 N. Martin Luther King Jr. Dr.
PO Box 12436
Milwaukee, WI 53212
414-263-8557
brunem@dnr.state.wi.us

Contractors:
Jim Drought
ARCADIS Geraghty & Miller, Inc.
126 North Jefferson Street, Suite 400
Milwaukee, WI 53202
414-276-7742
jdrought@ARCADIS-us.com