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03/01/2019 - First Detectable (almost undetectable) Dioxane in Ann Arbor's Drinking Water

An email today hearlds an important milestone in the Gelman/Pall/Danaher dioxane groundwater contamination site:To City of Ann Arbor partners and Stakeholders :

date:Mar 1, 2019, 12:50 PM
subject:City of Ann Arbor Water Quality Testing Results - 1,4-Dioxane

To City of Ann Arbor partners and Stakeholders:

I am sending this email to update you on some recent water quality results associated with the City’s drinking water.  This information was shared with Ann Arbor City Council this afternoon and will be shared with the media later today.


In February, one of the water treatment plant lab tests, sampled on Feb. 6, indicated an almost undetectable amount of 1,4-dioxane in the city’s surface water supply (Huron River) and in the finished drinking water. The results estimated concentrations of 0.061 parts per billion (ppb) of 1,4-dioxane at the city’s intake in Barton Pond and 0.030 ppb in the finished drinking water.  These levels were lower than the lab quantification limit of 0.2 ppb. In March, we will test for 1,4-dioxane, using two independent water-quality labs to corroborate the results.


Enclosed is a 1,4-dioxane fact sheet and frequently asked questions that will be shared on the city’s website and via our communication channels today. In addition, analytical testing results will be posted on the city’s website at www.a2gov.org/A2H2O. This is a complex issue, but we hope that these materials will give customers a better understanding of steps staff are taking to protect the city’s drinking water and proactively test for contaminants.


Please feel free to contact me should you want to discuss this matter further.


Brian Steglitz, P.E. | Manager, Water Treatment Services | bsteglitz@a2gov.org | City of Ann Arbor 
 919 Sunset Rd. | Ann Arbor, MI  48103 | 734.794.6000 ext. 43905

In summary, this is not all that surprising given that the Gelman site is still discharging dioxane into a Honey Creek tributary upstream from Barton Pond.

Tracing the dioxane from source to faucet...
 Sample locations
 Dioxane levels Dates Sampled
 highest 2018 reading on Gelman site
 18,000 ppb
 purge wells levels 140-1100 ppb 01/07/2019-01/14/2019
 pre-treatment purge influent levels 370-420 ppb
 post-treatment discharge levels to Honey Creek tributary
 5.3-6.4 ppb
 natural venting from groundwater through Artesian #3 to Honey Creek tributary
 9.8 ppb
 Honey Creek at Dexter Rd 2.1 ppb
 Huron River downstream from Honey Creek < 1.0 ppb 01/01/2019-01/31/2019
 Current DEQ cleanup standard
(not yet in Gelman permit or
Consent Judgment)

 7.2 ppb
(old 85 ppb still in effect until permit & CJ change)
 EPA 1-in-1,000,000 risk guideline 0.350 ppb --
 lab quantification limit 0.200 ppb --
 city’s intake in Barton Pond 0.061 ppb  02/06/2019
 finished drinking water 0.030 ppb 02/06/2019

For one thing, we don't know how long the city has been using this analysis method that can detect levels that low.
Those levels are below the State's 7.2 ppb cleanup standard for dioxane (1-in-100,000 risk, 32-year exposure) and the EPA's 3.5 ppb (1-in-100,000 risk level, 70-year lifetime exposure) or EPA's 0.35 ppb (1-in-1,000,000 risk level, 70-year lifetime exposure). Still, it's a wake-up call for all stakeholders to do more due diligence to find and remediate all dioxane pathways.

03/02/2019 update:
0.061 ppb of dioxane in Ann Arbor's daily water intake of ~14Mgal/day amounts to about 1/2 to 2/3 a teaspoon of dioxane entering with the 14Mgal. [calcs]