Is OAK BROOK required to publish a Consumer Confidence Report?

Yes. OAK BROOK is a community water system, and federal rules (40 CFR 141 Subpart O) require every community water system to publish a Consumer Confidence Report each year.

When is OAK BROOK’s next Consumer Confidence Report due?

OAK BROOK’s next Consumer Confidence Report is due by July 1, 2027. The report covers calendar year 2026.

What is a Consumer Confidence Report?

A Consumer Confidence Report (CCR) is the annual drinking water quality report that community water systems must provide to the people they serve. It lists the contaminants detected in the system’s water during the year, where the water comes from, and how the results compare with federal limits. EPA’s revised CCR rule takes effect January 1, 2027, and the first reports in the new format are due July 1, 2027.

OAK BROOK, IL · DuPage County

OAK BROOK Water System

Consumer Confidence Report status

OAK BROOK must publish a Consumer Confidence Report — the annual drinking water quality report covering calendar year 2026 — by July 1, 2027.

As of August 1, 2026, EPA's federal records show no open violations for OAK BROOK.

Data sourced from the EPA ECHO database (SDWA bulk download), last refreshed August 1, 2026. This is a record-keeping and public-information tool — it does not replace Illinois’s official records. Always confirm current status with Illinois before making decisions based on this information.

System facts

System ID (PWSID): IL0430700
System type: Community Water System
Population served: 9,400
Service connections: 3,295
Ownership: local government
Water source: surface water (rivers, lakes, or reservoirs)

OAK BROOK is one of 248 community water systems in Illinois in the 3,301 to 10,000 people size category, serving 9,400 people from surface water.

As of August 1, 2026, its federal record holds 4 entries between 1977 and 1989, all of which EPA lists as closed. Nothing has been added since 1989.

Of the 4, 1 are monitoring and reporting requirements — the category that accounts for about four in five of all violations in EPA's national dataset — rather than findings about the water itself. The record involves the Radionuclides and Revised Rad Rule.

Violation history

Maximum Contaminant Level Violation, Average
Health-based
Combined Radium (-226 and -228)
October 1, 1989 – March 9, 1992
Resolved
Maximum Contaminant Level Violation, Average
Health-based
Gross Alpha, Excl. Radon and U
December 1, 1985 – June 11, 1986
Resolved
Maximum Contaminant Level Violation, Average
Health-based
Combined Radium (-226 and -228)
October 4, 1985 – October 3, 1989
Resolved
Monitoring, Regular
—
Gross Alpha, Excl. Radon and U
June 30, 1977 – June 29, 1981
Archived

Resolved addressed and confirmed by the stateArchived closed in EPA's records (typically due to age or a data correction)

Period	Violation	Contaminant / rule	Health-based	Status
October 1, 1989 – March 9, 1992	Maximum Contaminant Level Violation, Average	Combined Radium (-226 and -228)	Health-based	Resolved
December 1, 1985 – June 11, 1986	Maximum Contaminant Level Violation, Average	Gross Alpha, Excl. Radon and U	Health-based	Resolved
October 4, 1985 – October 3, 1989	Maximum Contaminant Level Violation, Average	Combined Radium (-226 and -228)	Health-based	Resolved
June 30, 1977 – June 29, 1981	Monitoring, Regular	Gross Alpha, Excl. Radon and U	—	Archived

Resolved addressed and confirmed by the stateArchived closed in EPA's records (typically due to age or a data correction)

Enforcement actions

June 23, 2025State Public Notification received1 linked violation
June 11, 2025State Compliance achieved1 linked violation
November 13, 2024State Compliance achieved1 linked violation
November 1, 2024State Violation/Reminder Notice1 linked violation
October 15, 2024State Public Notification requested1 linked violation
October 15, 2024State Violation/Reminder Notice1 linked violation
October 2, 2024State Public Notification received3 linked violations
February 27, 2024State Compliance achieved2 linked violations
October 11, 2023State Violation/Reminder Notice3 linked violations
April 12, 2005State Public Notification requested2 linked violations
March 9, 1992State Compliance achieved2 linked violations
October 25, 1991State Public Notification received1 linked violation
July 26, 1991State Public Notification received1 linked violation
April 29, 1991State Public Notification received1 linked violation
January 29, 1991State Public Notification received1 linked violation
January 28, 1991State Public Notification received1 linked violation
October 29, 1990State Public Notification received2 linked violations
July 27, 1990State Public Notification received1 linked violation
April 27, 1990State Public Notification received1 linked violation
January 29, 1990State Public Notification received1 linked violation
October 11, 1989State Public Notification received1 linked violation
July 28, 1989State Public Notification received2 linked violations
October 12, 1988State Public Notification received2 linked violations
June 11, 1986State Compliance achieved1 linked violation

Common questions

Is OAK BROOK required to publish a Consumer Confidence Report?: Yes. OAK BROOK is a community water system, and federal rules (40 CFR 141 Subpart O) require every community water system to publish a Consumer Confidence Report each year.
When is OAK BROOK’s next Consumer Confidence Report due?: OAK BROOK’s next Consumer Confidence Report is due by July 1, 2027. The report covers calendar year 2026.
Does OAK BROOK have any open drinking water violations on record?: As of August 1, 2026, EPA's federal records show no open violations for OAK BROOK.
What is a Consumer Confidence Report?: A Consumer Confidence Report (CCR) is the annual drinking water quality report that community water systems must provide to the people they serve. It lists the contaminants detected in the system’s water during the year, where the water comes from, and how the results compare with federal limits. EPA’s revised CCR rule takes effect January 1, 2027, and the first reports in the new format are due July 1, 2027.

Contact

O'MALLEY, TIM

630-368-5276

OAK BROOK, IL 60523