Environmental Engineering Reference
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time 1,4-dioxane was detected and has not been used since. This well provided less than 5% of the
City of Ann Arbor's water. P/GSI noted that the city voluntarily stopped using the well, which had
1,4-dioxane concentrations of 2-4 ppb, whereas the drinking water action level was 85 ppb. Other
sources of 1,4-dioxane could have caused the contamination, according to P/GSI, and the well had
other water quality problems unrelated to P/GSI's release (Shelton, 2004; Kellogg, 2005). Among
the other possible sources, P/GSI noted that three landi lls, including the city's closed landi ll and
the University of Michigan landi ll, had detections of 1,4-dioxane in leachate. The city allows
untreated groundwater from those landi lls to be pumped into the sanitary sewer and discharged
into the Huron River because the small contaminant mass is diluted in the voluminous l ow of the
receiving water (Kellogg, 2005). Leachate from the city's closed landi ll contains 1,4-dioxane in
excess of 100 ppb (Davis, 2002).
Prior to the litigation over the detection of 1,4-dioxane concentrations of 2-4 ppb in the
Montgomery well, the city appealed a decision by MDEQ to allow an increase in the 1,4-dioxane
concentration limit to a daily maximum of 60 ppb and a monthly average of 10 ppb for discharge of
P/GSI's treated groundwater into Honey Creek, a tributary to the Huron River upstream of the city's
water intake. The city also prohibited P/GSI's discharge of treated groundwater into its storm sewer
system owing to volume limitations. P/GSI contrasted the city's practice of allowing the discharge
of leachate containing 1,4-dioxane at concentrations up to 100 ppb into its sewers, while P/GSI
discharges treated groundwater with less than 5 ppb into the same receiving water at a high cost
(Davis, 2002). The founder of GSI, Charles Gelman, argued vehemently for consistent application
of regulatory standards, and regulation of all sources of 1,4-dioxane, including antifreeze, aircraft
deicing l uid, and other sources (Bodwin, 1989).
The delineation of the PZ was also the subject of litigation between the city and P/GSI. P/GSI
objected to the city well being included in the PZ. The court agreed to exclude the well, pending
resolution of the separate lawsuit the city i led against P/GSI regarding the contamination of the
city's Montgomery well (MDEQ, 2005).
The City of Ann Arbor and P/GSI crafted an agreement that settled three related state and federal
lawsuits regarding well contamination and the PZ. Under the terms of the agreement, the city was
to receive a $285,000 payment, and P/GSI was required to conduct more groundwater monitoring
to safeguard the city water supply against 1,4-dioxane contamination. The agreement provides for
P/GSI to pay the city more than $4 million if 1,4-dioxane concentrations exceed the state's 85 ppb
drinking water limit (Davis, 2006a).
The longest running lawsuit—lasting 16 years—related to the P/GSI case was between P/GSI
and the State of Michigan over cleanup requirements. In addition to the existing 1300 gpm ozone-
peroxide treatment system that P/GSI installed at its main facility, the MDEQ required that P/GSI
install a treatment system large enough to accommodate 1150 gpm in a commercial area. P/GSI
argued that such a facility would not be safe because of the large volumes of hazardous chemicals
required to treat that volume of contaminated water. The court questioned the feasibility and safety
of MDEQ's proposal, because of the challenges of acquiring and rezoning enough land to site both
the treatment facility and the required treatment ponds in a congested commercial area (Shelton,
2004). The court also noted that MDEQ's requirements would involve piping millions of gallons of
water contaminated with 1,4-dioxane beneath the city to the proposed treatment facility and would
require miles of pipelines including at least 1.5 miles of pipelines in residential Ann Arbor neigh-
borhoods. The judge noted that the City of Ann Arbor concurred with MDEQ's requirements, but
did not offer a commitment to facilitate the installation of pipelines for contaminated groundwater
through Ann Arbor's residential streets (Shelton, 2004).
Judge Shelton determined that MDEQ's requirement that P/GSI comprehensively treat and elimi-
nate 1,4-dioxane was not feasible, was unwarranted, and was not supported by competent, material,
and substantial evidence. However, P/GSI designed and positioned a 200-gpm mobile ozone-peroxide
system to intercept 1,4-dioxane contamination to the State of Michigan Groundwater Surface Water
Interface criteria of 2800 μg/L. The court did not offer a different remedial solution to remove
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