Compton

Rules violated and the list above come from EPA's SDWIS violation records, one row per violation and contaminant, grouped by the rule each row belongs to. A violation counts when its non-compliance period ended on or after Jul 1, 2023, the start of the thirteen quarters ECHO's three-year figures cover, or is still open; it is unresolved when it was still open at EPA's data refresh on Oct 7, 2026. EPA's rule code 500, "Not Regulated", is left out, as in ECHO's counts. Each rule's violation count is EPA's, and one rule can carry several: a missed monitoring round for a group of contaminants is one violation per contaminant and period. Category names are EPA's violation categories.

ECHO's own summary count of rules violated agrees with this grouping for 98.8% of active systems nationally, and its count of rules being violated for 98.7%; where they differ, the figures here follow the rows listed.

A measured value shown with a rule is the sample result EPA recorded with that violation (SDWIS viol_measure), against the limit EPA recorded on the same row (state_mcl), both in EPA's unit as written; violations without a recorded value, such as missed monitoring, show none. Other measured contaminant levels are not part of this record; each system publishes them in its annual Consumer Confidence Report.

Lead and copper are the newest 90th-percentile results in EPA's SDWA data download (LCR_SAMPLES, codes PB90 and CU90), retrieved on Oct 12, 2026: for each monitoring period a system reports the 90th-percentile value of its tap samples, which EPA compares with its action level of 0.015 mg/L for lead and 1.3 mg/L for copper (40 CFR 141.80). A result is not a measurement of any one tap.

Service area from EPA's Public Water System Service Area Boundaries dataset: Random Forest method, Federal agency. The system's location is the centre of the service area EPA publishes for the system.

Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Illinois records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.