The Minnesota Department of Agriculture (MDA) Incident Response Unit (IRU) is the state lead agency for the investigation and remediation of incidents involving agricultural chemicals (pesticides and fertilizer). Generally, MDA IRU programs use a site specific risk based approach for investigation and remediation decisions. Decisions about where to investigate, what the cleanup goals for a site should be and where remediation is necessary are made using information available to MDA IRU about the site. The information used to make these decisions includes but is not limited to the location of the site, hydro-geologic information, depth to groundwater, the practicability and cost of remediation, labeled application rate of the contaminants and the potential for site
contamination to adversely affect human health or the environment.
For most sites, when the IRU closes a case file, application of the factors above has resulted in an investigation or a cleanup which is believed to be complete and protective of human health and the environment. However, sometimes it is necessary to close a site that has contaminated soil or groundwater remaining at or near the site above the cleanup goals established for the site. The majority of these situations involve small amounts of soil. Examples of this include soil that is left in place next to a building foundation or below a buried utility line. In these cases, the IRU evaluation of the site indicates that the level of contamination, volume and location are not considered to be a threat to human health or the environment.
Similarly, there may be a groundwater contaminant plume with contaminant levels that exceed established health based or environmental standards. In these cases, if the extent of the contaminant plume has been fully defined, if the plume is not increasing in size and if there is limited potential for exposure to the contaminant plume by humans or the environment at levels of concern, the contaminant plume is not considered to be a threat to human health or the environment.
Both of these types of case files are closed noting in the ”closure letter” that soil and/or groundwater contaminated above health or environmentally based standards remains at the site, where it is and why it was not remediated. There are no additional actions required for the responsible parties and there is no follow-up required by the MDA. As always, the MDA reserves the right to investigate and remediate these sites if further information is received that provides a basis for such action.
Occasionally, sites are closed that still have the potential for adverse affects to human health or the environment but there is little or no current risk of exposure because the sites are closed with an institutional control in place to mitigate the risk. These sites may require action on the part of the responsible party, the landowner, a city, county and/or the MDA to maintain the institutional control and to implement corrective actions if needed in the future. The types of contingent closures used at these sites and the types of follow-up required are described below. All contingencies include a GIS polygon to identify the area that the contingency applies to. These may be found by searching for your area of interest in the MDA “What’s In My Neighborhood – Agricultural” interactive mapping webpage. This information also includes a link to a PDF file for each site, describing the type of restrictions and/or contingencies associated with the site.
Contingent Closures: Contingent Closures are the most common type of contingency used. The largest number of contingent closures is for abandoned agricultural chemical facilities which are closed without investigation. After these sites were evaluated, it was determined that the risks associated with the site were too low to warrant investigation. These sites are referenced in the MDA database as not investigated and no IRU follow-up is conducted.
The remaining contingent closures involve situations where contamination has been left in place due to the presence of structures such as buildings or concrete slabs. Typically, the contingency involves a requirement that the site owner notify the MDA if the structure is to be removed so that the area beneath it can be investigated and if necessary remediated. MDA follow-up on these sites is typically an annual site visit or letter to the responsible party and/or landowner to ensure that conditions have not changed and to ensure that the current landowner and/or facility manager is aware of the contingencies.
Deed Affidavits and Restrictive Covenants: In some cases, the contingencies involve land use requirements and/or restrictions. In these cases, an affidavit or restrictive covenant is attached to the deed to ensure that property owners are aware of the residual contamination and the land use requirements and restrictions. MDA staff inspect these sites annually to ensure that site conditions have not changed and to ensure that the current landowner and/or facility manager is aware of the restrictions.
Local Ordinances: In some cases, local ordinances exist or are put in place, which restrict land use within the area of concern. The most common use of this is to prevent installation of wells in shallow groundwater. MDA staff follow-up on these sites involves contacting the local unit of government responsible for the ordinance every year to make sure that the ordinance is still in place and being enforced.
Special Well Construction Areas: Special Well Construction Areas (SWCA) are put in place by the Minnesota Department of Health (MDH) for areas where groundwater contamination exists at levels of concern for any consumptive or other uses of the impacted groundwater. The MDH SWCA remains in effect until removed by the MDH.
Well location, depth and construction method restrictions are used in these areas to ensure that contaminated groundwater is not used and to ensure that a well does not become a conduit for contamination into adjacent aquifers. Groundwater monitoring data for the contaminant plume will be re-evaluated by MDA staff until the SWCA is removed by the MDH.
Locating Sites With Contingencies: For each site and each contingency type, a GIS polygon was created to identify the area that the contingency applies to. These may be found by searching in your area of interest using the MDA “What’s In My Neighborhood – Agricultural” interactive mapping webpage. The information available also includes a link to a PDF file for each site describing the type of restrictions and/or contingencies associated with the site.