How the plumes were identified

Last update: September 15, 2007 - 4:22 PM

The maps reproduced in this report were created for regulatory or public health purposes by engineers who inferred broad areas of potential pollution using well test data. Not every point between two sampled wells is necessarily contaminated. Therefore, it can't be assumed that every property within a mapped plume has pollution beneath it. When state agencies test private and municipal wells, owners are notified of the results.

The Star Tribune examined maps and other public records, analyzed a Superfund database and interviewed regulators, engineers, public health officials and water supply managers to identify 20 areas of significant groundwater contamination in the seven-county metro region. The list includes large areas of contamination and smaller ones with notable risks.

Some plumes are excluded, especially if pollution remains on site. Not all areas of chemical contamination had maps or sufficient data for inclusion.

Other information, including affected aquifers and data sources, appears with an interactive map at StarTribune.com/groundwater.

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