Drycleaner Site Profiles

Decorah Shopping Center Drycleaners, Decorah, Wisconsin

Description
Historical activity that resulted in contamination.

The Decorah Shopping Center drycleaners is an active facility that has operated in a commercial setting since 1974. A different drycleaner operated on the site between 1965 and 1969. Investigations revealed the presence of chlorinated compounds in the soil and groundwater. The contamination has migrated off-site, but has not been known to impact any drinking water wells. Although the source of contamination has not been definitely identified, investigations suggest that perchloroethylene (PCE) was released through the floor drains and sewer system. PCE was likely released over 15 years ago. The underlying statutory authority for the cleanup is Chapter 292 of the Wisconsin Statutes, also known as the "Spill Law." The investigation and remediation activity at the site have qualified for financial reimbursement through the Wisconsin Drycleaner Environmental Response Program.

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


Contaminant Media Concentration (ppb) Nondetect
Tetrachloroethene (PCE) groundwater 99 ppb
Tetrachloroethene (PCE) soil 1,500 ppb
Trichloroethene (TCE) groundwater 0.39 ppb
1,2-Dichloroethene groundwater 1 ppb ND

Site Hydrology

Deepest Significant Groundwater Contamination:  
Plume Size:   Plume Length: 1,600ft
Plume Width: 500ft
Plume Thickness: 20ft
Average Depth to Groundwater:   8ft

Lithology and Subsurface Geology

 
  Light brown to black sandy silt and silty sand with varying amounts of clay
Depth: 0-5ft bgs
5ft thick
Conductivity: 3.7ft/day
Gradient: 0.028ft/ft
 
  Brown to gray fine to medium grained sand
Depth: 5-11ft bgs
6ft thick
 
  Brown to gray fine silty sand and sandy silt with a little silty clay
Depth: 11-24ft bgs
13ft thick
 
  Gray silty clay
Depth: 24-28ft bgs
4ft thick

Pathways and DNAPL Presence

checkGroundwater
Sediments
checkSoil
DNAPL Present

Remediation Scenario

Cleanup Goals:
  Remediation activities should remove the contaminant source, stabilize plume migration, and minimize long-term threats posed to human health and the environment. The ultimate cleanup goal is to reduce contaminant concentrations to the groundwater quality standards established in the Wisconsin Administrative Code, NR140. The enforcement standard for PCE in groundwater is 5 µg/L. A site-specific residual contaminant level (SSRCL) has been established for PCE concentrations in soil. The SSRCL for PCE based on the protection of groundwater is 2,864 µg/kg. (This assumes a reduction in infiltration due to the presence of an asphalt cap.) The most conservative SSRCL for PCE to minimize excess risk associated with the direct contact exposure pathway is 8,300 µg/kg.

Technologies

In Situ Cap
 

Why the technology was selected:
Contaminant concentrations offer little indication of naturally occuring reductive dechlorination. The plume is relatively wide-spread, relatively low-concentration. Access restrictions associated with off-site residential properties make addressing the source contamination the most cost effective approach. MNA will be relied on to address the bulk of the plume that has moved beneath a residential area.

Final remediation design:
Contractors expect to install an asphalt-surface soil cap to reduce infiltration of PCE into the groundwater. This cap should, if properly maintained, minimize potential direct contact risk of PCE exposure.

Results to date:
Natural Attenuation: Six rounds of quarterly sampling data indicate that PCE concentrations have been generally stable, ranging from 2.5-18 µg/L in groundwater and from less than 25-1,400 µg/kg in soil. The upward hydraulic gradient and relatively high horizontal gradient likely minimize the potential vertical migration of PCE. The plume has migrated to other properties, however.

Cost to Design and Implement:
$250,000 (for all technologies, as of 2012)

In Situ Chemical Oxidation
 

Why the technology was selected:
Contaminant concentrations offer little indication of naturally occuring reductive dechlorination. The plume is relatively wide-spread, relatively low-concentration. Access restrictions associated with off-site residential properties make addressing the source contamination the most cost effective approach. MNA will be relied on to address the bulk of the plume that has moved beneath a residential area.

Date implemented:
Chemical oxidation pilot test began in early 2005. That work has been completed and is being evaluated as of 11/2005. Full-scale remediation will begin in 2006.

Final remediation design:
Full scale injection, using 7 - 9 permanent injection wells, is anticipated to begin in 2006. It is expected that 200 to 500 gallons of 3 - 4% KMnO4 solution will be injected in each well once per year for 2 years. This work will be followed by 2 years of post-remediation monitoring.

Results to date:
The effectiveness of the pilot KMnO4 injection is currently being evaluated.

Next Steps:
Full scale KMNO4 inj. started in 2006. Additional MnO4 injection approved 12/11 involved $49,800 for 3rd round of injection. Contractors expect to continue remediation activities for two more years.

Cost to Design and Implement:
$250,000 (for all technologies, as of 2012)

In Situ Soil Vapor Extraction
 

Why the technology was selected:
Contaminant concentrations offer little indication of naturally occuring reductive dechlorination. The plume is relatively wide-spread, relatively low-concentration. Access restrictions associated with off-site residential properties make addressing the source contamination the most cost effective approach. MNA will be relied on to address the bulk of the plume that has moved beneath a residential area.

Final remediation design:
A passive SVE will be installed beneath the asphalt cap to limit PCE vapor migration.

Cost to Design and Implement:
$250,000 (for all technologies, as of 2012)

Costs

Cost for Assessment:
  $154,000
Cost for Operation and Maintenance:
 
Total Costs for Cleanup:
 

Lessons Learned

Monitored natural attenuation with the possibility of HRC injection was the originally proposed remedy for the site. There is little evidence of naturally occuring reductive dechlorination at the site and the State project manager determined that MNA alone was an inappropriate remedy, especially given that the plume has migrated beneath a residential housing area.

Because there was a lack of evidence for reductive dechlorination, chemical oxidation was chosen by the owner as the remedial methodology.

Contacts

Binyoti F. Amungwafor, Hydrogeologist
Bureau for Remediation and Redevelopment, Southeast Region
WI Department of Natural Resources
2300 N. M.L. King Jr. Dr.
PO Box 12436
Milwaukee, WI 53212
414-263-8607
amungb@dnr.state.wi.us

Contractors:
Curtis M. Hoffart
W66 N215 Commerce Court
Cedarburg, WI 53012
414-375-4750
choffart@keyengineering.com