The DEQ criteria change for dioxane was discussed at the 1/5/2016 CARD meeting. Here is a DEQ link and some relevant links therein:
The bottom line is that the 1,4-dioxane cleanup criteria change recommendation will likely be accepted this month or next but the rest of the DEQ process to implement it may take another 9 months, or 6 years after the EPA 2010 guidelines that tightened dioxane standards. And then the dioxane standard will likely be reduced from 85 ppb to ~8 ppb because of Michigan's 1-in-100,000 cancer risk criteria (loosened from 1-in-1,000,000 during the Engler administration). If this were an EPA Superfund site, the standard would be 3.5 ppb and real cleanup would continue to completion with stricter oversight.
Here is a screenshot from a recent Google Earth mashup of the dioxane plumes showing the Scio Township parcels without access to city water (red placemarks) in the path of the northward migration of the plumes: