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Frequently Asked Questions

1) Where is the groundwater contamination?

The contaminated groundwater exists in several aquifers beneath the west side of Ann Arbor and Scio Township. For a map of the groundwater contamination, see

2) What is the extent of the groundwater contamination?

Several aquifers have been contaminated. The unit E aquifer represents the largest local water body known to be contaminated with 1,4 dioxane. The contamination of this aquifer is known to extend east and north from the PLS Wagner Road facility, beneath the city of Ann Arbor. As of Jan 2004, the leading edge of the plume is thought to extend just to the east of the municipal drinking water well [closed] on Montgomery Street. The approximate dimensions of the 'plume', or contaminated area, are: 8500 feet long, 2000 feet wide.

3) Is it moving?

Yes. The plume has migrated approximately 8500 feet from the boundary of the PLS Facility. Dioxane is quite soluble in water, and thus moves with the groundwater, which, in the Unit E aquifer, is moving toward the Huron River. PLS estimates that the plume is moving at 1.7 feet per day. (PLS Limited Feasibility Study 1/04)

4) How did dioxane get into the groundwater?

The groundwater contamination began in 1976, when dioxane was used as a solvent by Pall Life Sciences' predecessor, Gelman Sciences, Inc., as part of its process of manufacturing medical filters. The waste stream from this process included wastewater contaminated with dioxane. This wastewater was stored in open lagoons and began to enter the soil below and around the lagoons.

5) Will it get into the Huron River & the Ann Arbor Water Supply?

No one knows for sure. PLS projections show the plume continuing on an eastward pathway toward the Huron River, which is approximately 8,000 feet from the current leading edge of the plume. If projections are correct, the point of entry into the Huron River would be downstream of the city's water supply intake at Barton Dam. PLS has projected that the 85 ppb contour of the leading edge will reach the Huron River in 12 years, and domestic wells in 24 years. (PLS Limited Feasibility Study 1/04)

6) Is there 1,4 dioxane in the City of Ann Arbor's drinking water?

No detectable level of 1,4 dioxane is, or ever has been detected to-date in Ann Arbor's municipal drinking water supply. Tests are frequently applied to the source water brought into the Water Treatment Plant as well as the water supplied to our customers. (Ann Arbor Water Utility 'Water Quality Update', Feb. 21, 2003)

During a routine test in 2001, a trace level of 1,4 Dioxane (1-2 ppb/parts per billion) was detected in water from Ann Arbor's Montgomery well, which was used by the city as a water source during the winter months. The Montgomery well water was not being used at the time of the positive test and was immediately closed and remains closed. The Montgomery well provided less than 5% of Ann Arbor's total source water. (Ann Arbor Water Utility 'Water Quality Update', Feb. 21, 2003)

7) Is the City of Ann Arbor looking for alternative sources of water?

Yes. Identifying adequate sources of safe water to meet long-term needs is a normal part of water system planning. Master planning assures that we will have a safe and sufficient supply of water to serve our community today and into the future. Our master plan for the water system is generally updated every five years. We are updating our plan this year and will be including an analysis of options for source water as part of this update. While there is no lack of safe water for current needs, we are working to assure that there is no lack in the future. (Ann Arbor Water Utility 'Water Quality Update', Feb. 21, 2003)

8) Is the City of Ann Arbor concerned about the future potential for 1,4 dioxane to be detected in Ann Arbor drinking water?

Yes. Our primary concern is to protect the Huron River, which represents 80% of Ann Arbor's source water. City officials and staff have expressed their concern to the Michigan Department of Environmental Quality (MDEQ) that the remediation of contaminated groundwater by Pall Life Sciences (PLS) and subsequent discharge of that treated ground water to Honey Creek is not the most conservative approach to protect the City's main drinking water source. The Michigan Department of Environmental Quality recently granted PLS a permit to significantly increase the discharge of treated groundwater to Honey Creek. The City has appealed this decision. (Ann Arbor Water Utility 'Water Quality Update', Feb. 21, 2003)

9) How can I learn more about Ann Arbor's drinking water quality?

The Ann Arbor Water Utility provides an Annual Water Quality Report to municipal customers, including test results that demonstrate our drinking water consistently meets or exceeds all Federal water quality standards. The most recent report, and more water quality information, is available on the web at

(Ann Arbor Water Utility 'Water Quality Update', Feb. 21, 2003)

10) What is 1,4 dioxane, how is it used, and how might one be exposed to it?

1,4 dioxane (also called dioxane) is produced in large amounts (between 10 million and 18 million pounds in 1990) by three companies in the United States. Companies use dioxane as a solvent for paper, cotton, and textile processing and for various organic products. It is also used in automotive coolant liquid, and in shampoos and other cosmetics. Exposure to dioxane can occur in the workplace or in the environment following releases to air, water, land, or groundwater. It enters the body when people breathe air or consume water or food contaminated with dioxane. It can also be absorbed through skin contact. It does not remain in the body due to its breakdown and removal.

11) What happens to 1,4 dioxane in the environment?

1,4 dioxane mixes easily with water. Most references of 1,4 dioxane to the U.S. environment are to air and surface water. Because it is a liquid that does not bind well to soil, dioxane that makes its way into the ground can move through the ground and enter groundwater. Plants and animals are not likely to store 1,4 dioxane.

12) How does 1,4 dioxane affect human health and the environment?

Effects of 1,4 dioxane on human health and the environment depend on how much 1,4 dioxane is present and the length and frequency of exposure. Effects also depend on the health of a person or the condition of the environment when exposure occurs.

Laboratory studies show that exposure to 1,4 dioxane over a lifetime causes cancer in animals. 1,4 dioxane may likewise cause cancer in humans. Laboratory studies show that repeat exposure to large amounts of 1,4 dioxane in drinking water, in air, or on the skin causes liver and kidney damage in animals.
1,4 dioxane has low toxicity to aquatic life. It is not likely to cause environmental harm at levels normally found in the U.S. environment.


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