Post date: Sep 01, 2014 4:31:34 AM
June 22, 2001
More 1,4-Dioxane Found in Deepest Aquifer
A new monitoring well (MW-64) installed by Pall-Gelman showed 844 to 866 ppb of 1,4-dioxane when it was first sampled on May 30, 2001. A later sample on June 13, 2001 showed 1328 ppb.
This new well is installed in the deepest aquifer above bedrock in the Pall-Gelman contamination area. This deeper "E" aquifer is some 200 feet below the surface at an elevation of about 720 feet +/- 10 feet and was thought to be protected from contamination from above by extensive clay layers.
The impetus to install this new well was the prior discovery of moderate levels of 1,4-dioxane in the E aquifer in other monitoring wells beyond the edge of Pall-Gelman-supplied plume maps.
The high levels of dioxane at MW-64 still 1500 feet from the original source means that the lateral and vertical extent of the contamination is not yet defined. Many more deeper monitoring wells will need to be installed in and around the main part of the contamination.
MW-64 is south of Aprill Drive midway between MW-32 and MW-33 and is about 1/3 mile from the next nearest E aquifer monitoring well.
A few existing monitoring wells that are screened in the E aquifer have been sampled by Pall-Gelman, one for the first time since 1993! That one showed a level of 67 ppb, up from 9 ppb in 1993.
There are no other E aquifer monitoring wells in the "core area" where the contamination first happened.
There are no purge wells operating in the E aquifer.
The City of Ann Arbor supply well that was shut down because of 1,4-dioxane contamination is screened at a elevation lower than MW-64.