State environmental officials say 35 private wells on or near Rose Drive in Ann Arbor had no detectable level of 1,4 dioxane after testing water samples.
It's a little bit of good news in the ongoing saga of Ann Arbor's dioxane-contaminated groundwater.
A plume of water contaminated with the dangerous chemical is slowly moving under the city towards the Huron River.
The wells for the recent group of homes tested were on the northern edge of the plume; many homes closer to the contamination have had to be connected to Ann Arbor's water system after high levels of dioxane were detected in the residents' private wells.
Ann Arbor draws most of its water from Barton Pond, which lies well north of the plume.
Dan Hamel of the Michigan Department of Environmental Quality says there will also be samples drawn this week from surface water in West Park.
"We will take a sample there with the idea that will give us – could give us – an indication if shallow ground water is venting to the surface that's contaminated," says Hamel.
Hamel says dioxane tends to stay closely bound with water, but there's still a chance that dioxane could be released into the air at the park, or into basements near the park if the basements are not dry.
The state has proposed a new cleanup standard for 1,4 dioxane (7.4 ppb) that is much stricter than the old standard (85 ppb).
Hamel says if the standard is adopted, Pall Corporation (which bought Gelman Sciences, the source of the contamination) will almost certainly have to do more to clean up the water.