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  1. The Site is a former municipal landfill facility that operated from the 1930s through 1986 and is owned by the City of Windom. The groundwater and soil on the site have been contaminated as a result of disposal activities.

  2. Currently this site poses no known public health hazard. It is uncertain whether or not this site posed a health hazard in the past.

  3. The Site is capped, in accordance with the ROD, thereby limiting potentially significant exposures to contaminated soils or air emissions from the site. Also, surface water is not currently impacted by the site. Therefore, the main contaminated media of concern at this site is groundwater.

  4. A recovery well and spray system was installed in 1990 which effectively captures and treats groundwater from the site.

  5. The wells in the recovery well system continue to create a combined capture area that includes virtually the entire former landfill. The sprayer system appears to continue to effectively remove contaminants from the groundwater. However, regular chlorination of the wells is necessary to remove iron bacteria slime.

  6. The City of Windom expects an increase in water usage of 150% over the next 20 years. City well #7, which was part of the recovery well system, is being reconnected to the municipal supply and a new city supply well is being drilled in response to the demands on the system. Vinyl chloride was last detected in CW7 in 1993.

  7. The vinyl chloride concentrations most recently noted in City well #8 (0.09 g/l in 1994) are currently below detection limits and health based guidelines. After treatment in the city municipal water system no vinyl chloride contamination is detected.

  8. Groundwater monitoring wells located on-site indicate that vinyl chloride, cis-1,2-dichloroethene, and arsenic have been present in identifiable concentrations since the last MDH SRU (1995). Previously detected compounds include: vinyl chloride, cis-1,2-dichloroethene, arsenic, nitrates, 1,1,2-trichloroethene, and dichlorofluoromethane. Only vinyl chloride and arsenic have been identified above levels of concern.

  9. Some of the historic arsenic data for Windom monitoring and recovery wells appears to be flawed. However, there is still evidence that arsenic is present in groundwater in the vicinity of the Windom city wells.

  10. DCPA metabolites and p-nitrophenol have been detected in the municipal water system at levels below known health concern.

  11. Maintenance of contaminant concentrations (specifically; vinyl chloride, arsenic, and nitrates) below the HRLs should be protective of a sensitive population including children.



MDH recommends that monitoring of groundwater, the spray treatment area, and the Windom City municipal system be continued. These recommendations are consistent with an approach that will contain and reduce the contaminants at the Site. This will, in turn, reduce the possibility of exposure to hazardous levels of Site contaminants and protect public health.

Special attention should be paid to City Wells #6, #7, and #8.

  • The detection of vinyl chloride in MW1 since 1995 may be an indication that contamination from the site is moving towards CW6.

  • Historically, CW7 was the most contaminated well in the municipal supply. Even though samples from CW7 since 1994 have not detected the presence of vinyl chloride in this well, it should be monitored closely for any reappearance of contamination.

  • CW8 is the last city well to show vinyl chloride contamination and should also be monitored closely.

Since municipal supply water is treated before it is delivered to residents for consumption, and results have indicated that the treatment has been successful in removing low level contamination, there is not currently a complete exposure pathway. However, the potential contamination of these three wells, and the system as a whole, needs to be vigilantly monitored in order to provide a high degree of protection of the public water supply for the City.

Results from monitoring well MW11 should also be carefully checked since this well monitors the movement of groundwater towards the south and away from the spray area. While there are no city wells in this area, there may be private wells south of the groundwater capture area. MW11 is in an area that should be the first zone to indicate a reduction in treatment efficiency. It should be noted that there has been no contamination identified at this well to date, indicating that the system is working.

MDH recommends regular monitoring for arsenic, p-nitrophenol, DCPA, and DCPA metabolites in the city wells as well as monitoring wells, and pumpout wells in Windom. MDH is concerned about the anticipated increased demands on the unconfined aquifer. Additional pumping will reduce the travel time from the site or other sources of contamination, to the municipal supply or other potable water supplies. This concern is also the basis of our recommendation that any contamination of wells in the vicinity of Windom be monitored closely and potential sources of contamination be identified. Therefore, MDH recommends that possible sources of p-nitrophenol and DCPA should be investigated.

Since contamination remains under the site, and the remedial action is ongoing, MDH should continue to periodically review site conditions and other factors which could impact the public water supply in Windom. This could help to insure that the contamination does not migrate and create a completed exposure pathway. A periodic review will also help insure that all pertinent data regarding public health issues are being collected and included in the decision-making process.

This consultation was prepared by:

Carl Herbrandson, Ph. D.
Rich Soule, M. S.
Site Assessment and Consultation Unit
Environmental Surveillance and Assessment Section
Minnesota Department of Health

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