Overview
Highway 96 Site History
The Highway 96 Site ("Site") is located in White Bear Township, Minnesota. The Site operated as a local disposal area from the 1920s until 1973. Primarily residential wastes were received and burned at the Site. Some drummed wastes were disposed at the Site in the late 1960s and early 1970s.
In 1986, a study was conducted at the Site by the United States Environmental Protection Agency (USEPA), which identified groundwater contamination by volatile organic compounds (VOCs). The Minnesota Pollution Control Agency (MPCA) subsequently issued a Request for Response Action to three potentially responsible parties (PRPs): Whirlpool Corporation, Reynolds Metals Company and Red Arrow Waste Disposal Services. The PRPs retained an environmental consultant, GHD Services Inc. (GHD) [known as Conestoga-Rovers and Associates (CRA) prior to July 1, 2015], to assist with implementation of the response actions.
The response actions associated with the Highway 96 Superfund Site are stipulated by a 1993 Minnesota Decision Document (MDD), 1995 Consent Order, and subsequent amendments. The response actions are divided into four operable units:
- Operable Unit 1 - Source Control [drum removal, waste consolidation, and capping; remedial actions completed in 1995.]
- Operable Unit 2 - Groundwater Remediation [on-site groundwater extraction (hydraulic containment) and on/off-site groundwater monitoring; remedial actions are ongoing.]
- Operable Unit 3 - Residential Drinking Water East of Gilfillan Lake [municipal water connection for 60 homes; remedial actions completed in 1994.]
- Operable Unit 4 - Residential Drinking Water West of Gilfillan Lake [remedial actions are ongoing; detailed information provided below.]
Residential Drinking Water West of Gilfillan Lake
In October 2004, during routine sampling of residential wells in North Oaks as part of the off-Site monitoring program associated with Operable Unit 2, low levels of vinyl chloride were detected in groundwater water samples collected from two residential wells located along West Shore Road. Since October 2004, the PRPs have conducted extensive studies, under the supervision of the MPCA, to investigate the nature and extent of VOC contamination in residential wells located west of Gilfillan Lake.
In June 2007, the MPCA requested that the PRPs complete a Feasibility Study (FS) to evaluate potential response actions for vinyl chloride-contaminated groundwater on the west side of Gilfillan Lake (Operable Unit 4). The MPCA approved the FS Report, with modifications, in November 2007. The MPCA used the FS Report to develop a Proposed Plan for an amendment to the MDD for the Highway 96 Site. The Proposed Plan was issued by MPCA on February 15, 2008. MPCA held a public meeting on February 26, 2008 and public comments on the Proposed Plan were accepted until March 21, 2008. The MPCA reviewed the public comments on the Proposed Plan and finalized an amendment to the MDD (MDD Amendment #1) and a Responsiveness Summary Document. MDD Amendment #1, which includes the Responsiveness Summary, was signed by MPCA on August 26, 2008. MDD Amendment #1 and other Site-related documents issued during the remedy selection process for Operable Unit 4 are posted on the City of North Oaks website (Highway 96 Superfund Site - MDD Amendment #1).
As outlined in the MDD Amendment #1, the final MPCA-selected response actions for homes located within Operable Unit 4 include:
- Provision of a new/deeper residential well in the Prairie du Chien aquifer for homes that are issued a well advisory by the Minnesota Department of Health (MDH) due to an exceedance of MDH-established health risk limits (HRLs) for Listed VOCs (as identified on Table 1 of the 2008 MDD Amendment)
- Long-term groundwater monitoring
- Conditional installation and operation of a pump out system in the Ski Lane Ravine (in the event that vinyl chloride or another Listed VOC exceeds its respective MDH-established HRL in any of the Ski Lane Ravine monitoring wells)
Since October 2004, residential well sampling of over 80 homes located in Operable Unit 4 has shown that the number of locations that have ever had a detectable concentration of vinyl chloride is limited to ten homes. To date, only three of these homes have had detectable levels of vinyl chloride at or above the associated HRL and have subsequently received well advisories issued by the MDH. The PRPs provided new/deeper replacement wells to each of these homes in accordance with MDD Amendment #1. No MDH well advisories have been issued to homes located within Operable Unit 4 since 2012.
In accordance with MDD Amendment #1, residential well sampling in Operable Unit 4 is conducted on a routine basis. Information related to residential well sampling frequencies, upcoming sampling events, and residential well sampling results are posted on the City of North Oaks website (Highway 96 Superfund Site - Residential Well Sampling).
Ongoing activities associated with Operable Unit 2 and Operable Unit 4 are summarized in Annual Monitoring Reports, which are prepared by GHD, on behalf of the PRPs, and submitted to the MPCA in March of each year. These reports are also posted on the City of North Oaks website (Highway 96 Superfund Site - Annual Site Reports).
The City of North Oaks has hired an environmental consultant, Wenck Associates, Inc., to review Site-related documents and keep the City informed of ongoing activities. Updates provided to the City Council are posted on the City of North Oaks website (Highway 96 Site - Updates to City Council).