State Coalition for Remediation of Drycleaners Site Profiles
Long Prairie, Long Prairie, Minnesota
Description
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| This site originated from a drycleaner operation located in the downtown area. Contamination spread over a 10-block area and impacted two municipal wells before it was detected. Remedies included pumpouts along the heart of the mile-long plume and GAC treatment of contaminated water, SVE at the source, and alternative water supply. Also, most affected private wells were abandoned, and residences were put on city water. This site was remediated under the state and federal Superfund programs. |
Contaminants
Contaminants present and the highest amount
detected in both soil and groundwater.
| Contaminant | Media | Concentration (ppb) | Nondetect |
|---|---|---|---|
| cis-1,2-Dichloroethene | groundwater | 85 ppb | |
| cis-1,2-Dichloroethene | soil | 10 ppb | |
| 1,1-Dichloroethene | groundwater | 1 ppb | ND |
| Tetrachloroethene (PCE) | groundwater | 140 ppb | |
| Tetrachloroethene (PCE) | soil | 1,200 ppb | |
| Trichloroethene (TCE) | groundwater | 80 ppb | |
| Vinyl Chloride | groundwater | 1 ppb | ND |
Site Hydrology
| Deepest Significant Groundwater Contamination: | 75ft bgs | |
| Plume Size: | Plume Length: 5,280ft |
|
| Average Depth to Groundwater: | 30ft |
Lithology and Subsurface Geology
| interbedded glacial till and sand and gravel outwash deposits Depth: 0-200ft bgs 200ft thick |
Pathways and DNAPL Presence
 Groundwater SedimentsSoilDNAPL Present |
Remediation Scenario
Cleanup
Goals: |
Groundwater: The targets for groundwater are MCLs (5 ppb for PCE and TCE and 70 ppb for DCE). Surface Water: Discharge of treated water at MCLs also meets the chronic surface water quality standards. Soil: PCE 1,200 ppb |
Technologies
In Situ Soil Vapor Extraction |
Why the technology was selected: Date implemented: Results to date: Next Steps: Cost to Design and Implement: |
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Ex Situ Carbon Adsorption |
Why the technology was selected: Date implemented: Results to date: Next Steps: Cost to Design and Implement: |
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Ex Situ Pump and Treat |
Why the technology was selected: Date implemented: Results to date: Next Steps: Cost to Design and Implement: |
Costs
Cost
for Assessment: |
$363,998 | |
Cost
for Operation and Maintenance: |
$300,000 annually | |
Total
Costs for Cleanup: |
Lessons Learned
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1. Source removal/extraction is key to plume concentrations reduction and should be the first response action. Lateral spread is hard to control. I agree. Findings from this site clearly show the importance of finding the source (highly contaminated soil and groundwater including DNAPL directly beneath the area of release) and removing it as soon as possible. The magnitude of dissolved contamination in the groundwater began to decrease dramatically as soon as source removal was implemented. It appears that the plume is now beginning to shrink and natural attenuation is now taking affect. At present, natural attenuation data is being collected so that the rate of natural attenuation and an estimate of when remediation will be completed are currently being calculated. 2. This is a good example of how far and fast a chlorinated solvent plume can spread under the right hydrogeologic conditions. Before the site was discovered in the mid 1980s, the length of the plume was captured and contained by municipal wells located about one-third of a mile downgradient. After these wells were shut down, the plume rapidly (in less than ten years) migrated another two-thirds of a mile downgradient to the Long Prairie River. 3. Conducting periodic and updated water supply well surveys and keeping area land owners and residents informed over the life of a long-term remediation project is very important. Due to the shallow groundwater at this site, it is not unusual for the area residents to install their own shallow sand point wells for secondary use. There has been a number of instances at this site where new residence or land owner have installed wells in the plume, and where new residents used old secondary wells without knowing about potential groundwater contamination. |
Contacts
| Groundwater Atlas https://www.pca.state.mn.us/data/minnesota-groundwater-contamination-atl What's in My Neighborhood https://www.pca.state.mn.us/data/whats-my-neighborhood Current Consultant (O&M): Dave Wolfgram Terracon 33535 Hoffman Road East White Bear Lake, MN 55110 651-770-1500 ext 126 djwolfgram@terracon.com Former Consultant (Design, Construction, early O&M): Dale Finnesgaard, Barr Engineering 8300 Norman Center Drive Minneapolis, MN 55437-1026 (952) 832-2667Dfinnesgaard@Barr.com |
Site Specific References
| 1. Long Prairie ROD & 2 ESDs, June 1988, June 1991, May 1994 2. Long Prairie Ground Water Contamination Five-Year Review, MPCA and EPA, 9/30/02 |
