Andover | Red Oaks neighborhood groundwater contamination

In 2021, the Minnesota Pollution Control Agency (MPCA) began sampling private wells in the Red Oaks neighborhood for 1,4-dioxane and per- and polyfluoroalkyl substances (PFAS) as these contaminants can be associated with former landfills.

The MPCA discovered contamination from the chemical 1,4-dioxane while conducting water sampling near the Waste Disposal Engineering (WDE) Closed Landfill in Andover. The chemical was initially found by MPCA in private residential wells located near Bunker Lake Boulevard and Crosstown Boulevard in the Red Oaks neighborhood in 2021. MPCA is currently providing bottled water to residential homes where 1,4-dioxane has been detected above health-based values established by the Minnesota Department of Health (MDH). The MDH develops health-based values to evaluate potential human health risks from exposures to chemicals in groundwater.

Samples collected from private wells were also analyzed for PFAS compounds. PFAS concentrations exceed the MDH’s health-based values in six wells. These residents are currently receiving bottled water and are included in the mitigation area that will be connected to the City of Andover municipal water supply.

The source(s) of the 1,4-dioxane and PFAS in groundwater have not been determined at this time; however, two potential sources in the immediate vicinity of these neighborhoods include the WDE Closed Landfill and the South Andover Superfund site. The map below illustrates the location of the Red Oaks neighborhood where MPCA has conducted private residential well testing for 1,4-dioxane and PFAS, and the locations of the WDE Closed Landfill and South Andover Superfund sites. MPCA investigation work to date has not identified a direct link to the WDE Closed Landfill as the source of 1,4-dioxane in the Red Oaks neighborhood.  Investigation work related to the South Andover Superfund site as a potential source of 1,4-dioxane in the Red Oaks neighborhood is being directed by the United States Environmental Protection Agency (U.S. EPA).

The MPCA has completed multiple rounds of private residential well sampling in the Red Oaks neighborhood, beginning in 2021. Fifty-eight homes in the Red Oaks neighborhood had 1,4-dioxane levels in their private residential wells at or above the MDH health-based value and six homes in the mitigation area (see map below) had PFAS levels above MDH health-based values. MPCA is providing bottled water as an interim mitigation measure to these homes.

Long term solution for clean drinking water

MPCA received $6.1 million from the Minnesota Legislature to extend municipal water to all homes in the Red Oaks mitigation area, outlined in red in Figure 2. Residents with wells at or above the health-based values will continue to receive bottled water, free of charge, until the permanent municipal water supply connection is implemented.  MPCA is currently working with the City of Andover to administer the legislative funding and begin the design and implementation of municipal supply connections in the Red Oaks neighborhood for homes that have 1,4-dioxane and/or PFAS at or above the MDH health-based values.

Ongoing investigations to determine contamination source(s) in Red Oaks

The Red Oaks neighborhood is located between the WDE Closed Landfill site and the South Andover EPA Superfund Site (see Figure 1). In summer 2022, the MPCA drilled five temporary monitoring wells to investigate if contamination may be coming into Red Oaks from the nearby South Andover Superfund site. Also, three new permanent monitoring wells were installed between the WDE Closed Landfill and Red Oaks to evaluate if groundwater contamination is moving into Red Oaks from the WDE Closed Landfill.

The permanent monitoring wells installed between the WDE Closed Landfill and Red Oaks are showing very little 1,4-dioxane. Only five of the fifteen wells had detections of 1,4-dioxane, and those detections are below health-based values. Groundwater data from these monitoring wells shows a northerly groundwater flow direction for the shallow groundwater near the WDE Closed Landfill.  The northerly groundwater flow direction from the site and the limited detections of 1,4-dioxane directly southwest of the WDE Closed Landfill suggests contamination from the landfill would migrate north away from the Red Oaks neighborhood. 

Four of the groundwater samples collected from the five temporary monitoring wells along Bunker Lake Boulevard directly north of the South Andover Superfund site exceeded health-based values for 1,4-dioxane.  The U.S. Environmental Protection Agency (EPA) is the regulatory lead for the South Andover Superfund site which is located directly southeast of the Red Oaks neighborhood.   EPA is currently requiring the responsible parties for the site to submit a work plan to sample for 1,4-dioxane and conduct studies on groundwater flow at the Site.  This information will assist in determining the potential source(s) of 1,4-dioxane in the private residential wells in the Red Oaks neighborhood.