Crestwood Public Drinking Water Supply Contamination

Fact Sheet
May 2009

Village of Crestwood, Cook County

Area map


This fact sheet has been prepared based on the information that the Illinois Environmental Protection Agency (Illinois EPA) has at this time and on its investigation to date. The Illinois EPA discovered that a contaminated emergency back-up water supply well was being used illegally by supplementing the treated Lake Michigan water that Crestwood provides to its residents. The well has been sealed; Crestwood has been supplying only treated Lake Michigan water to its residents since November 2007.

What Happened?

From 1986 to 2007, the Illinois EPA believes Crestwood was using water from its contaminated groundwater well to supplement the Lake Michigan source water without informing the Illinois EPA or its water customers. Since the Crestwood Public Water Supply (PWS) well was reportedly not in use during this time period, no routine samples of that well were taken; federal Safe Drinking Water Act regulations do not require sampling of PWS wells that are not in use. Consequently, no regularly-collected analytical data are available to determine the levels of contamination over those years. However, in a letter to the Illinois EPA from April 1998, a consultant investigating a nearby drycleaner solvent release reported results from two samples collected from the Crestwood well. This letter also documents conversations with Crestwood officials who told the consultants that the well water was being mixed with the purchased Lake Michigan water at a ratio of 10:90. If this report is accurate, this set of results indicates that the chemical contamination discovered in 1986 had not yet degraded into the more dangerous chemical, vinyl chloride, which was first found in a 2007 well sample.

Based on our investigations of records (including, monthly operational reports), and on-site inspection of the public water supply meters back to 1999, the Illinois EPA has concluded that the volume of water taken from the contaminated well, chlorinated, and presumably then blended with the fully treated Lake Michigan water averaged only about 10 percent of Crestwood’s water distribution per month, with the highest volumes no more than 20 percent of the total public water supply distribution per month. Lake Michigan water is treated at City of Chicago treatment plants, tested frequently and documented to meet regulatory standards.

Contamination of the PWS well, identified in 1985-86, was confirmed in September 2007 when Crestwood sampled the well in response to the Illinois EPA’s statewide initiative to test the water quality of all emergency back-up wells in case they needed to be used in an emergency. Coincidentally, later that fall, during a routine engineering evaluation in November and in response to an anonymous complaint that the Crestwood emergency back-up well was in use, Illinois EPA's inspectors investigated and asked the operator about the use of the well; the operator denied its use. Our inspector advised the operator that the well appeared to be contaminated so it should not be used -- not even for emergency purposes. Within the next few weeks, our inspectors independently verified through a comparison of 2007 Lake Michigan water billing records and 2007 Crestwood water distribution records that the well water was being used illegally in Crestwood’s drinking water supply. However, at that time, the Illinois EPA did not know the extent and duration of Crestwood’s past use of the well.

When the 2007 illegal use of the well was determined in December of 2007, the Illinois EPA began enforcement action by sending a Non-Compliance Advisory letter to Crestwood advising against future use of the emergency back-up well found to be contaminated stating, "the use of Well #1…is a clear violation of the Illinois Environmental Protection Act[.]"

The enforcement action, begun in early December 2007 with issuance of the Non-Compliance Advisory letter, continued. In April 2008, Crestwood provided an unacceptable response to that enforcement letter. Within a month, Illinois EPA responded with a Violation Notice for improper use of the Crestwood well, and for violation of the groundwater quality standard for vinyl chloride in the well. Again, we formally notified Crestwood to not use the well without proper treatment of the water. We initiated this enforcement action to ensure that a long-term solution was reached either to properly treat water produced by the Crestwood PWS well, or to properly abandon the well.

Further, in June 2008 we recommended to the Illinois Department of Public Health that notification should be made to the local press and to well owners in the area because of the potential threat of contamination to private water wells in the vicinity; that notice was made in August 2008. Later in August, the Crestwood PWS operator admitted that the well had been in use when he had told Illinois EPA inspectors during the November 2007 inspection that the well was not being used. This admission initiated further investigation. Illinois EPA staff compared water supplier billing data to Crestwood pumping data and confirmed the well had not been used since November 2007.

In late March 2009, Illinois EPA finally received and reviewed Lake Michigan water supplier billing records dating back to 1999 and was able to compare them to a Crestwood PWS records ledger provided by the Office of the Illinois Attorney General on March 17. These records verified that Crestwood was using the well to supplement the Lake Michigan water from November 2007 at least back to 1999. Following this determination, the Illinois EPA cited the village again, this time for violations of the Safe Drinking Water Act and for knowingly providing false information about the source of its drinking water to the Illinois EPA and to its water consumers. Those and additional enforcement actions are pending. Because of pending litigation, we will not be able to provide further details of enforcement actions we have initiated in concert with the U.S. EPA and the Illinois Attorney General's Office.

Frequently Asked Questions

What were the chemicals found in the well water in the mid 1980's and why was Crestwood allowed to continue to use the well? What were the chemicals found in 2007?

The Illinois EPA sample of the Crestwood well water collected in 1985 indicated a concentration of 2.8 parts per billion (ppb) of 1,1–dichloroethylene (DCE) in the Crestwood Public Water Supply well. One ppb is approximately equivalent to one drop in a swimming pool (one drop in 17,000 gallons). Crestwood was informed of this contamination and was required to conduct quarterly monitoring for volatile organic chemicals (VOCs), the class of chemicals that includes 1,1-DCE and the chemicals discussed below. An August 1986 well water sample collected by Crestwood had a concentration of 4 ppb of trans-1,2 DCE; the confirmation sample taken in November 1986 indicated 5 ppb of trans-1,2 DCE. (The Safe Drinking Water Act establishes Maximum Contaminant Levels (MCLs) allowable in public drinking water supplies; these 1985 and 1986 concentrations of 1,1-DCE and trans-1,2 DCE are below the now allowable limit of 7 ppb for 1,1-DCE and 100 ppb for trans-1,2 DCE; these MCLs did not exist in 1985-86 but only became effective several years later.)

In 1986, Crestwood officials told the Illinois EPA that they were purchasing Lake Michigan water as their drinking water supply. The routine sampling schedule for the PWS well was stopped because Crestwood officials indicated that the well was to be used only for emergency back-up. Under state regulations, use of an emergency back-up well requires immediate Illinois EPA notification; no such notice was ever received by the Illinois EPA. Results from the September 2007 sample collected by Crestwood found vinyl chloride at a concentration of 1.5 ppb (MCL is 2 ppb) and cis-1,2-DCE at 2.6 ppb (MCL is 70 ppb). Illinois EPA's confirmation sample results collected in October 2007 found 5.4 ppb of vinyl chloride and 1.61 ppb of cis-1,2-DCE. (The difference between the vinyl chloride concentrations found by Crestwood and the Illinois EPA could be due to a number of potentially interacting factors including variations in sample collection and sample analysis techniques as well as variations in groundwater composition and flow.)

Did these concentrations of contaminants violate the public drinking water standards that are supposed to protect the public?

Based on our calculations, no violations would have occurred. The maximum federally-allowable contaminant level, MCL, is the enforceable standard that is not to be exceeded for contaminants in public drinking water supplies. The MCL standard is determined by U.S. EPA under the authority of the federal Safe Drinking Water Act (SDWA). Violation of the standard is measured by either a running annual quarterly average exceeding the numeric standard or a one-time concentration exceeding more than 4 times the standard. The MCL for vinyl chloride is 2 ppb; the MCL for cis-1,2-DCE is 70 ppb. By our calculations, even at the 20 percent maximum contribution from the well, the vinyl chloride and cis-1,2-DCE concentrations would not have exceeded their respective MCLs and would have been allowable in the drinking water supply.

The SDWA also establishes non-enforceable recommendations for drinking water called Maximum Contaminant Level Goals (MCLGs); the MCLG for vinyl chloride is zero. Establishing an MCLG at zero does not imply that actual harm would occur to people at a level somewhat above zero, but rather zero is the desired goal, which includes a margin of safety. The MCLG is set at zero for all chemicals that are thought to cause cancer. The enforceable MCLs for cancer-causing chemicals, including vinyl chloride, are set as close to zero as is feasible and are considered safe levels that are protective of public health.

Where are the VOCs vinyl chloride, 1,1-dichloroethylene (1,1-DCE) and the cis- and trans- forms of 1,2-DCE coming from?

Vinyl chloride is often found in the environment as a breakdown product of other solvents and is most likely coming from a release of the drycleaner solvent known as tetrachloroethylene (PCE; also known as either perchloroethylene or "perc") that has leached into the groundwater. PCE biologically breaks down over time into other solvents including cis-1,2-DCE and trans-1,2-DCE, 1,1-DCE, and finally, into the much more stable chemical, vinyl chloride. This breakdown process can take decades once the contaminants have leached from soil into the groundwater. Illinois EPA is actively researching potential sources of the Crestwood well contamination.

In 1998, Crestwood allowed the sampling of their PWS well twice by a consultant investigating one of the suspect source sites. Sample results conveyed to the Illinois EPA’s voluntary Site Remediation Program staff in our Bureau of Land in an April 1, 1998 letter indicated cis-1,2-DCE at 3 ppb in both samples and noted that the two samples were also "analyzed for selected chlorinated VOCs and degradation products of the specific VOCs that have been found at the site. …Importantly, other site-related VOCs were not detected[.]" The Illinois EPA infers from this information that the chemical contamination of the well had not yet broken down to vinyl chloride, since no vinyl chloride was found at this time. Therefore we surmise that vinyl chloride first appeared in the well between 1998 and 2007.

What concentrations of these chemicals were people exposed to if they drank the Crestwood water all those years? What are the health effects of that exposure?

The Illinois EPA evaluated the potential concentration of the chemical of most concern to human health, vinyl chloride, which people could have been exposed to. Illinois EPA considered the following to conduct the evaluation: 1) we assumed a starting concentration of vinyl chloride at the highest concentration we found in the well in October of 2007, 5.4 ppb; 2) we used monthly operational reports; and 3) we considered the spot checks of the meters at the public water supply that we documented in on-site inspection reports. The monthly operational reports and the spot checked meter data at the public water supply showed 10 and 20 percent water volume contributions from the well. Thus, our calculations were based on these percentages. If 20 percent of Crestwood’s drinking water was obtained from the well, we calculated that the concentration of vinyl chloride in finished drinking water could be 1.1 ppb. If a 10 percent well water volume is used in the calculation, the concentration of vinyl chloride in drinking water could be 0.5 ppb.

The Illinois EPA has consulted with the Illinois Department of Public Health to help us characterize the health risks to Crestwood residents exposed over the long-term to these concentrations. The set of conservative (protective) assumptions used to calculate the vinyl chloride concentration and to estimate human health risk -- assuming exposure to vinyl chloride in drinking water at the highest concentration found, with a 20 percent contribution to the water supply and drinking two liters of that water per day over a seventy-year life span, -- tends to overestimate the risks to which Crestwood residents were exposed during the potential 10 year period during which vinyl chloride could have been present in the well and during which we suspect well water was being used (from early 1998 to late 2007). Yet even this conservative exposure calculation indicates an exposure with a potential increased cancer risk of about two to four additional cancers per 100,000 people. To put this potential increased risk into perspective, one out of every third person is at risk of developing some type of cancer in the U.S. (a risk of 1 in 3).

Where can I find more information about the health effects of vinyl chloride?

To review the vinyl chloride fact sheet from the Illinois Department of Public Health, please go to:
To review the vinyl chloride fact sheet from the ATSDR, please go to:
To review the vinyl chloride fact sheet from the U.S. EPA, please go to:

Please note: Exposure concentrations discussed in mg/L (milligrams per liter) is the same as parts per million (ppm). The concentrations found in the well water in Crestwood are in µg/L (micrograms per liter) or parts per billion (ppb), a thousand times smaller. The health effects described in these fact sheets are due to very high exposures in thousands of parts per million, which is 10,000 to 100,000 times higher than the chemical concentrations discovered in the Crestwood PWS Well water.

Is my private well safe?

Because groundwater flows to the northeast in this region, presumably discharging to the Calumet-Sag Channel, private wells to the south and west are not endangered by this contamination. While the Crestwood public drinking water supply is safe, anyone in the area who gets their drinking water from a private well should consider that there is always the potential for their well to become contaminated. If you are a private well owner, you may want to periodically sample and test your well water for various contaminants, including volatile organic chemicals. For more discussion of private well testing and lists of local laboratories that test for VOCs, please go to:

The Illinois Department of Public Health can also provide lists of private laboratories approved for bacteriological, radiological, and inorganic chemical and VOC testing. To get a copy of any of those lists, call 630-293-6800. Once well water samples have been analyzed, residents can also call the health department for an explanation of the test results.

Is the vinyl chloride (or any of the other chemicals) found at concentrations high enough to cause vapor intrusion into area homes or businesses?

Once in the groundwater, these volatile organic chemicals can volatilize (evaporate) and migrate up through soils and building foundations into structures where they can be inhaled by building occupants. This phenomenon is called vapor intrusion. Vinyl chloride is the chemical of most concern among the contaminants found in the Crestwood well. However, vinyl chloride concentrations must be considerably higher, by a factor of 10, than those found in the Crestwood well to cause a potential vapor intrusion risk.

What happens next?

Legislation supported by Governor Pat Quinn, Attorney General Lisa Madigan and the Illinois EPA has been proposed in the Illinois General Assembly to prevent another drinking water contamination concern like the Crestwood situation. Specifically, the legislation would mandate that PWS records of the source of drinking water be maintained for 10 years and be available for inspection. The legislation would also enhance penalties for anyone who knowingly falsifies such records and requires that all customers using a community's drinking water be notified within 10 days (the Agency would have 7 days to notify the public water supply, and the water supply would have 3 business days to notify all of its customers) of any groundwater contamination that poses a threat to human health, of any enforcement action referred to the Attorney General’s office for prosecution, or any violation notice or seal order issued by the Agency.

In addition, the Illinois EPA will continue its investigation into the origins of the Crestwood PWS well contamination. As the results of the investigation become available, the Illinois EPA will provide updates to the community.

If I have any questions, where can I find more information?

Residents with questions for Illinois EPA, the regulator of the Crestwood PWS, should contact:

Mara McGinnis
Carol Fuller
Office of Community Relations, Illinois EPA

This fact sheet update, along with the original May 8, 2009 Crestwood fact sheet, can be found (see Crestwood) or at the Crestwood Public Library District. Any further updates from the Illinois EPA concerning Crestwood, including the environmental investigation results, will be posted on this web page.

Residents with specific health-related questions or concerns about private wells should contact:

Tom Baughman
Toxicology Section, IDPH West Chicago Regional Office