PlainWater

Williamson County, Illinois

SDWIS compliance plate

Sheet IL199 · Williamson County 26 sys · 1,069 viol · #697/3254

VIOL-SEVERE · HEALTH-LOW · RANK-UPPER · PHOTO-FINISH · PFAS-HIGH · SRC-SW · SYS-SMALL · BOOK-FULL

  • VIOL-SEVERE 96.2% flagged
  • HEALTH-LOW 17.4% health
  • RANK-UPPER #697/3254
  • PHOTO-FINISH ±0.0 pp
  • PFAS-HIGH 71.4% detect
  • SRC-SW SW lead 96%
  • SYS-SMALL 26 systems
  • BOOK-FULL 7/7 fields

Nearest flagged-rate peer: Mason County (+ 0 pp flagged-rate)

According to EPA SDWIS county population served used on /counties, Williamson County ranks #697 of 3,254 counties by people served, and #21 of 102 counties in Illinois. See methodology · corpus placement.

Williamson County standing, mid-flagged corpus third

Flagged-system rate 96.2% is in the corpus middle third (≤ 100.0% flagged) across 2,973 counties with ≥3 SDWIS systems . Health-based share 17.4% is health-based share in the middle third (≤ 24.5%) . UCMR5 detect rate 71.4% is UCMR5 detect rate above the tested-pool upper third (> 33.3%) . Population served ranks #697 of 3,254 · #21 of 102 in Illinois.

Flagged-rate neighbourhood around Williamson County

Lowest/highest poles plus in-state counties nearest Williamson County on % of SDWIS systems with ≥1 violation. Full ladder: /counties.

0% 20% 40% 60% 80% 100% Sangamon · lowest Putnam · near Williamson · this county Pulaski · highest 58.8% 95.1% 95.5% 96% 96.2% 96.2% 100%

Source: EPA SDWIS (county aggregates) As of 2026-05-15

Water Systems

System Name Population Violations PFAS
Marion 16,855 136 Detected
Herrin 12,747 19 Detected
Lake of Egypt Pwd 11,368 172 Clean
Carterville 6,484 29 Detected
Coal Valley Pwd 3,960 23 Clean
Corinth Pwd 3,927 16 Detected
Johnston City 3,509 20 Detected
Pittsburg 2,948 45 -
Cambria 1,727 18 -
Crainville 1,711 57 -
Fci-Marion 1,544 57 -
Devils Kitchen Water District 1,428 52 -
Ferges Water District 1,185 15 -
Highway 37 North Pwd 1,065 34 -
Energy 984 5 -
Blairsville Pwd 807 31 -
Hurst 782 68 -
Creal Springs 683 26 -
Colp 506 54 -
Freeman Spur 373 39 -
Bush 285 35 -
The Orchards Mhc 253 10 -
Marion Mobile Home Village 220 0 -
Crab Orchard Refuge 25 99 -
Walmart Supercenter #0216 25 4 -
Lj Ice Company 25 5 -

Compare beyond Illinois

Mid-flagged peers for Williamson County

Cross-state counties nearest Williamson County on flagged-system share (96.2%) and cumulative violation count (1,069). In-state neighbours stay on the compliance plate above.

Similar flagged-system rate

Nearest cross-state counties by % of SDWIS systems with at least one violation on record.

4 peers

Similar violation load

Nearest cross-state counties by cumulative SDWIS violation count (all systems in the county).

4 peers
Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.