Opinion ID: 6498785
Heading Depth: 3
Heading Rank: 1

Heading: History of the Site

Text: The Site covers two Minnesota cities, St. Louis Park and Edina, both cities with a history of groundwater contamination. In 1983, the EPA added the previously mentioned Reilly Tar Site in St. Louis Park to the NPL because it was a documented source of a hazardous chemical, namely, polynuclear aromatic hydrocarbon (PAH). J.A. 94. Through well samples, the Minnesota Department of Health later detected other hazardous chemicals, chlorinated volatile organic compounds (CVOCs), in Edina’s groundwater as early as 1993 and St. Louis Park’s groundwater as early as 1994. See HRS Revised 11 Documentation Record, Highway 100 and County Road 3 Groundwater Plume, at 13-14 (Sept. 2020) (Revised Documentation Record), reprinted in J.A. 296-356. The relevant CVOCs are 1,1-dichloroethene (DCE); cis-1,2-DCE; trans-1,2-DCE; trichloroethene (TCE); and vinyl chloride—all of which are breakdown products of tetrachloroethene (PCE), a chemical used in certain industrial and cleaning processes. Revised Documentation Record at 14, 33. The Minnesota Pollution Control Agency (MPCA) became involved in 2004 when Edina requested assistance to determine the source of CVOCs in one of its municipal drinking water wells, E7. Jd. As the investigation expanded farther north, CVOCs were detected in four aquifers: the Quaternary Drift Aquifer (Drift Aquifer), which is generally 0 to 90 feet below ground surface (bgs); the Platteville-Glenwood Aquifer, which is generally 90 to 122 feet bgs; the St. Peter Aquifer, which is generally 135 to 290 feet bgs; and the Prairie du Chien-Jordan Aquifer, which is generally 290 to 417 feet bgs. Revised Documentation Record at 15; see also J.A. 361 (cross-section and geological descriptions), 368-69 (cross-sectional maps). In 2007, the MPCA sought the EPA’s assistance in testing soil in the area for CVOCs. Revised Documentation Record at 15. In 2016, the MPCA prepared a preliminary assessment of the Site. Jd. Subsequently, under a cooperation agreement with the EPA, the MPCA conducted a site inspection, which included extensive data from groundwater samples collected from monitoring and municipal wells intersecting the four aquifers at varying depths. Jd. at 15, 18. The data showed CVOC contamination in all of the aquifers. /d. at 15. The inspection focused on evaluating contamination of the Prairie du Chien-Jordan Aquifer because Edina and St. Louis Park 12 municipal drinking water wells draw from that aquifer.® Jd. at 16. The site inspection recommended further investigation to establish whether a contaminant pathway interconnected the aquifers. Id. at 18. Accordingly, the MPCA conducted an Expanded Site Inspection Report (ESI), which included a hydrogeologic investigation. /d.; see generally J.A. 357-97 (relevant portions of the ESI). The ESI concluded that the four aquifers were “laterally continuous and... hydraulically interconnected between St. Louis Park and Edina” based on “aquifer pump tests that showed drawdown in the test wells, and analytical results that document[ed] the migration of [CVOCs] from the Quaternary Drift, Platteville-Glenwood, St. Peter, and Prairie du Chien-Jordan aquifers.” Revised Documentation Record at 18.