A 2008 isoconcentration map of Pall-Gelman’s 1,4-dioxane contamination was superimposed in Google Earth. Then dioxane isoconcentration lines were extruded to show magnitude of 1,4-dioxane contamination above 85, 1000, 2000, and 3000 ppb. The Prohibition Zone outline was extruded up to 85 ppb (blue) to show the level at which the dioxane levels would have to be reduced had Michigan’s cleanup standard of 85 ppb been applied in the Prohibition Zone as it has been outside of the zone. The red outline is the well Prohibition Zone where no water wells can be used because of the high levels of 1,4-dioxane projected to move through the aquifers in that area. |
Since no one is allowed to use the groundwater within the Prohibition Zone, the dioxane levels within the zone now only have to be cleaned up to 2800 ppb, Michigan’s groundwater/surface water interface standard. In contrast to using the 85 ppb cleanup standard, this allows a huge amount of dioxane to escape cleanup and possibly migrate to other areas where groundwater is used. |
The actual readings for 2008 are superimposed on the 3D map to show that some are much higher than the extruded isoconcentration levels. |
For states that have 1,4-dioxane groundwater cleanup standards, each state was extruded out in proportion to its dioxane cleanup standard. Until 1995, dioxane in Michigan groundwater had to be cleaned up to 3 ppb. In 1995, the dioxane cleanup standard for Michigan was changed to 77 ppb and later to the current 85 ppb… much higher than any other state standard. This is unfortunate since Michigan is steward to 20% of the world’s fresh water. |