Systems with a yearly average at or above an EPA-based study benchmark
3.0%13 of 436 active community water systems
All 436 systems had enough required samples to calculate a yearly average. 13 had at least one yearly average at or above a study benchmark; 423 did not.
EPA-based study benchmark: the unrounded cutoff this research uses to reproduce EPA’s January 2026 technical-assistance classification around the April 2024 federal levels. It is not a current standard or compliance finding and cannot determine household exposure or health risk.
Check your area
Find your water system
ZIP codes are used only to route visitors to public water systems that reported serving them. Confirm the actual provider using a water bill or utility record.
Compound summary
System counts in Illinois
Each count shows how many included water systems had a yearly average at or above the named study benchmark.
| Study benchmark | Systems at or above benchmark | Water systems included | Percent |
|---|---|---|---|
| PFOA: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 9 | 436 | 2.1% |
| PFOS: 4.05 ppt study benchmark (reproduces EPA classification around 4 ppt) | 7 | 436 | 1.6% |
| PFHxS: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 1 | 436 | 0.2% |
| PFNA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 436 | 0.0% |
| HFPO-DA: 15 ppt study benchmark (reproduces EPA classification around 10 ppt) | 0 | 436 | 0.0% |
| Hazard Index: 1.5 study benchmark with at least two detected components (reproduces EPA classification around 1) | 1 | 436 | 0.2% |
System directory
Community water systems with complete monitoring
“Complete monitoring” means at least one sampling location had all required samples needed for a yearly average. Each PWSID appears once, preventing double counting across ZIP associations.
| Public water system | PWSID | Population served | Primary source | Sampling locations | Study benchmark result |
|---|---|---|---|---|---|
| ABINGDON | IL0950050 | 3,275 | Ground water purchased | 1 | At or above a study benchmark |
| ABS WATER COOP | IL0015350 | 6,858 | Ground water purchased | 5 | Below all study benchmarks |
| ADDISON | IL0430050 | 38,017 | Surface water purchased | 1 | Below all study benchmarks |
| ALEXANDER WATER DISTRICT | IL1370020 | 442 | Surface water purchased | 1 | Below all study benchmarks |
| ALGONQUIN | IL1110050 | 30,700 | Ground water | 4 | Below all study benchmarks |
| ALSIP | IL0310030 | 19,063 | Surface water purchased | 1 | Below all study benchmarks |
| ALTONA | IL0950100 | 483 | Ground water | 1 | Below all study benchmarks |
| AMERICAN WATER OPER AND MAINTENANCE, LLC | IL1635237 | 6,779 | Surface water purchased | 1 | Below all study benchmarks |
| ANNA | IL1810050 | 4,910 | Ground water purchased | 1 | Below all study benchmarks |
| ANTIOCH | IL0970050 | 14,175 | Ground water | 7 | Below all study benchmarks |
| AQUA ILLINOIS-CANDLEWICK DVN | IL0075050 | 6,426 | Ground water | 1 | Below all study benchmarks |
| AQUA ILLINOIS-KANKAKEE | IL0915030 | 80,000 | Surface water | 1 | Below all study benchmarks |
| AQUA ILLINOIS-NORTH MAINE UTILITIES | IL0315350 | 30,043 | Surface water purchased | 2 | Below all study benchmarks |
| AQUA ILLINOIS-PEOTONE | IL1970750 | 4,182 | Surface water purchased | 2 | Below all study benchmarks |
| AQUA ILLINOIS-UNIVERSITY PARK | IL1975030 | 7,002 | Surface water purchased | 1 | Below all study benchmarks |
| AQUA ILLINOIS-VERMILION COUNTY | IL1835120 | 30,106 | Surface water | 1 | Below all study benchmarks |
| AQUA ILLINOIS-WILLOWBROOK | IL1977870 | 5,100 | Ground water | 3 | Below all study benchmarks |
| ARLINGTON HEIGHTS | IL0314030 | 73,320 | Surface water purchased | 1 | Below all study benchmarks |
| ASHKUM | IL0750050 | 724 | Ground water | 2 | Below all study benchmarks |
| ATHENS | IL1290050 | 4,575 | Ground water | 1 | Below all study benchmarks |
| AUBURN, IL | IL1670050 | 4,574 | Surface water purchased | 1 | Below all study benchmarks |
| AURORA | IL0894070 | 183,000 | Surface water | 1 | Below all study benchmarks |
| BARRINGTON | IL0974080 | 10,327 | Ground water | 2 | Below all study benchmarks |
| BARTLETT | IL0314120 | 41,500 | Surface water purchased | 1 | Below all study benchmarks |
| BATAVIA | IL0894130 | 26,098 | Ground water | 1 | Below all study benchmarks |
| BEARDSTOWN | IL0170150 | 5,951 | Ground water | 1 | Below all study benchmarks |
| BEECHER | IL1970050 | 4,713 | Ground water | 3 | Below all study benchmarks |
| BELVIDERE | IL0070050 | 25,339 | Ground water | 5 | Below all study benchmarks |
| BENSENVILLE | IL0434140 | 18,537 | Surface water purchased | 1 | Below all study benchmarks |
| BERKELEY | IL0310180 | 5,214 | Surface water purchased | 1 | Below all study benchmarks |
| BETHALTO | IL1190150 | 15,210 | Ground water | 1 | Below all study benchmarks |
| BLANDINSVILLE | IL1090100 | 569 | Surface water | 1 | Below all study benchmarks |
| BLOOMINGDALE | IL0430100 | 22,018 | Surface water purchased | 1 | Below all study benchmarks |
| BLOOMINGTON, IL | IL1130200 | 77,610 | Surface water | 1 | Below all study benchmarks |
| BLUE ISLAND | IL0310240 | 21,494 | Surface water purchased | 1 | Below all study benchmarks |
| BLUFFS | IL1710100 | 748 | Ground water | 1 | Below all study benchmarks |
| BOND/MADISON WATER COMPANY | IL0050020 | 6,645 | Surface water purchased | 1 | Below all study benchmarks |
| BOOKWALTER WOODS MHP | IL0635125 | 389 | Ground water | 1 | Below all study benchmarks |
| BRAIDWOOD | IL1970150 | 6,194 | Ground water | 1 | Below all study benchmarks |
| BREESE | IL0270250 | 4,772 | Surface water | 1 | Below all study benchmarks |
| BRIDGEVIEW | IL0310270 | 16,467 | Surface water purchased | 1 | Below all study benchmarks |
| BRIGHTON | IL1174160 | 5,041 | Surface water purchased | 1 | Below all study benchmarks |
| BROADVIEW | IL0310300 | 7,847 | Surface water purchased | 1 | Below all study benchmarks |
| BROOKFIELD | IL0310330 | 18,776 | Surface water purchased | 1 | Below all study benchmarks |
| BUCKLEY | IL0750150 | 500 | Ground water | 1 | Below all study benchmarks |
| BUDA | IL0110100 | 482 | Ground water | 1 | Below all study benchmarks |
| BUFFALO GROVE | IL0314180 | 43,212 | Surface water purchased | 1 | Below all study benchmarks |
| BURNHAM | IL0310360 | 3,989 | Surface water purchased | 2 | Below all study benchmarks |
| BURR RIDGE | IL0434190 | 11,192 | Surface water purchased | 1 | Below all study benchmarks |
| BUSHNELL | IL1090150 | 2,972 | Ground water | 1 | Below all study benchmarks |
| BYRON, IL | IL1410100 | 3,784 | Ground water | 3 | Below all study benchmarks |
| CAHOKIA HEIGHTS | IL1635000 | 12,528 | Surface water purchased | 1 | Below all study benchmarks |
| CALHOUN COUNTY RWD | IL0130010 | 4,675 | Ground water | 1 | Below all study benchmarks |
| CALUMET CITY | IL0310390 | 37,000 | Surface water purchased | 2 | Below all study benchmarks |
| CALUMET PARK | IL0310420 | 8,442 | Surface water purchased | 1 | Below all study benchmarks |
| CANTON, IL | IL0570250 | 16,748 | Groundwater under influence of surface water | 1 | Below all study benchmarks |
| CARBONDALE | IL0770150 | 22,107 | Surface water | 1 | Below all study benchmarks |
| CARLINVILLE | IL1170150 | 6,598 | Surface water | 1 | Below all study benchmarks |
| CARLYLE | IL0270300 | 3,373 | Surface water | 1 | Below all study benchmarks |
| CARMI | IL1930100 | 6,307 | Ground water | 1 | Below all study benchmarks |
| CAROL STREAM | IL0430200 | 39,854 | Surface water purchased | 2 | Below all study benchmarks |
| CARPENTERSVILLE | IL0890200 | 37,983 | Ground water | 1 | Below all study benchmarks |
| CARROLLTON, IL | IL0610050 | 2,513 | Ground water | 1 | Below all study benchmarks |
| CARY | IL1110100 | 17,826 | Ground water | 6 | Below all study benchmarks |
| CASEY | IL0230050 | 3,274 | Ground water purchased | 1 | Below all study benchmarks |
| CASEYVILLE | IL1630250 | 13,798 | Surface water purchased | 1 | Below all study benchmarks |
| CENTRALIA | IL1214220 | 12,182 | Surface water | 1 | Below all study benchmarks |
| CHANNAHON | IL1970200 | 13,380 | Ground water | 3 | At or above a study benchmark |
| CHARLESTON | IL0290100 | 17,286 | Surface water | 1 | Below all study benchmarks |
| CHATHAM | IL1670300 | 16,423 | Ground water purchased | 1 | Below all study benchmarks |
| CHERRY VALLEY | IL2010050 | 4,731 | Ground water | 4 | Below all study benchmarks |
| CHESTER | IL1570100 | 8,407 | Surface water | 1 | Below all study benchmarks |
| CHICAGO | IL0316000 | 2,721,308 | Surface water | 2 | Below all study benchmarks |
| CHICAGO HEIGHTS | IL0310450 | 26,184 | Surface water purchased | 1 | Below all study benchmarks |
| CHICAGO RIDGE | IL0310480 | 14,130 | Surface water purchased | 1 | Below all study benchmarks |
| CHILLICOTHE | IL1430200 | 6,660 | Ground water | 7 | Below all study benchmarks |
| CICERO | IL0310510 | 83,000 | Surface water purchased | 1 | Below all study benchmarks |
| CLARK-EDGAR RWD | IL0230010 | 9,657 | Ground water | 1 | Below all study benchmarks |
| CLEAR WATER SERVICE CORP | IL0295100 | 8,900 | Ground water | 2 | Below all study benchmarks |
| CLINTON | IL0390050 | 7,200 | Ground water | 1 | Below all study benchmarks |
| COAL CITY | IL0630200 | 5,749 | Ground water | 1 | Below all study benchmarks |
| COAL VALLEY | IL1614260 | 3,873 | Ground water | 3 | Below all study benchmarks |
| COAL VALLEY PWD | IL1995250 | 4,023 | Surface water purchased | 1 | Below all study benchmarks |
| COLLINSVILLE, IL | IL1194280 | 29,500 | Ground water | 1 | At or above a study benchmark |
| COLUMBIA | IL1330050 | 11,129 | Surface water purchased | 1 | Below all study benchmarks |
| CORINTH PWD | IL1995120 | 3,927 | Surface water purchased | 1 | Below all study benchmarks |
| CORTLAND | IL0370051 | 4,398 | Ground water | 4 | Below all study benchmarks |
| COUNTRY CLUB HILLS | IL0310540 | 16,500 | Surface water purchased | 1 | Below all study benchmarks |
| COUNTRYSIDE | IL0310570 | 6,420 | Surface water purchased | 1 | Below all study benchmarks |
| CREST HILL | IL1970250 | 21,169 | Ground water | 7 | At or above a study benchmark |
| CRETE | IL1970300 | 8,275 | Ground water | 5 | Below all study benchmarks |
| CREVE COEUR | IL1790100 | 4,934 | Ground water | 1 | Below all study benchmarks |
| CRYSTAL LAKE | IL1110150 | 40,661 | Ground water | 5 | Below all study benchmarks |
| CURRAN-GARDNER TOWNSHIP PWD | IL1675350 | 6,651 | Ground water | 1 | Below all study benchmarks |
| DALLAS RURAL WATER DISTRICT | IL0710010 | 6,370 | Ground water | 2 | Below all study benchmarks |
| DARIEN | IL0430270 | 21,751 | Surface water purchased | 1 | Below all study benchmarks |
| DE KALB | IL0370100 | 40,290 | Ground water | 5 | Below all study benchmarks |
| DECATUR | IL1150150 | 76,122 | Surface water | 1 | Below all study benchmarks |
| DEERFIELD | IL0974340 | 19,196 | Surface water purchased | 1 | Below all study benchmarks |
| DES PLAINES | IL0310630 | 60,675 | Surface water purchased | 2 | Below all study benchmarks |
| DIXMOOR | IL0310660 | 2,973 | Surface water purchased | 1 | Below all study benchmarks |
| DIXON | IL1030200 | 15,096 | Ground water | 6 | Below all study benchmarks |
| DOVER | IL0110350 | 200 | Ground water | 1 | Below all study benchmarks |
| DUPO | IL1630350 | 4,684 | Ground water | 1 | At or above a study benchmark |
| DUQUOIN | IL1450100 | 7,169 | Surface water purchased | 1 | Below all study benchmarks |
| DWIGHT | IL1050250 | 4,400 | Ground water | 1 | Below all study benchmarks |
| E J WATER COOP | IL0790010 | 29,720 | Surface water | 6 | Below all study benchmarks |
| EAST ALTON | IL1190200 | 5,786 | Ground water | 1 | At or above a study benchmark |
| EAST MOLINE | IL1610250 | 21,374 | Surface water | 1 | Below all study benchmarks |
| EAST PEORIA | IL1790200 | 22,284 | Ground water | 6 | Below all study benchmarks |
| EASTERN ILLINOIS UNIVERSITY | IL0295500 | 5,500 | Surface water purchased | 1 | Below all study benchmarks |
| EDWARDSVILLE | IL1190250 | 26,808 | Ground water | 1 | Below all study benchmarks |
| EFFINGHAM | IL0490250 | 12,252 | Surface water | 1 | Below all study benchmarks |
| ELDORADO | IL1655030 | 4,715 | Ground water purchased | 1 | Below all study benchmarks |
| ELK GROVE VILLAGE | IL0314400 | 31,802 | Surface water purchased | 1 | Below all study benchmarks |
| ELMHURST | IL0430350 | 45,000 | Surface water purchased | 1 | Below all study benchmarks |
| EMBARRAS AREA WATER DISTRICT | IL0290020 | 3,750 | Ground water purchased | 1 | Below all study benchmarks |
| EUREKA | IL2030200 | 5,216 | Ground water | 1 | Below all study benchmarks |
| EVANSTON | IL0310810 | 74,486 | Surface water | 1 | Below all study benchmarks |
| EVERGREEN PARK | IL0310840 | 19,943 | Surface water purchased | 1 | Below all study benchmarks |
| FAIRBURY | IL1050350 | 3,633 | Ground water | 1 | Below all study benchmarks |
| FAIRFIELD | IL1910100 | 6,202 | Surface water | 1 | Below all study benchmarks |
| FAYETTE WATER COMPANY | IL0510010 | 5,608 | Surface water purchased | 3 | Below all study benchmarks |
| FLORA | IL0250100 | 5,233 | Surface water purchased | 1 | Below all study benchmarks |
| FLOSSMOOR | IL0310870 | 9,371 | Surface water purchased | 1 | Below all study benchmarks |
| FOREST PARK | IL0310900 | 14,340 | Surface water purchased | 1 | Below all study benchmarks |
| FORSYTH, IL | IL1150200 | 3,490 | Ground water | 1 | Below all study benchmarks |
| FORT MASSAC PWD | IL1275050 | 6,290 | Ground water purchased | 1 | Below all study benchmarks |
| FOUNTAIN WATER DISTRICT | IL1330020 | 3,650 | Ground water | 1 | Below all study benchmarks |
| FOX LAKE | IL0970200 | 11,780 | Ground water | 4 | Below all study benchmarks |
| FOX RIVER GROVE | IL1110200 | 4,702 | Ground water | 2 | Below all study benchmarks |
| FRANKFORT | IL1970400 | 24,000 | Ground water | 6 | Below all study benchmarks |
| FRANKLIN PARK | IL0310960 | 18,467 | Surface water purchased | 1 | Below all study benchmarks |
| FREEBURG | IL1630600 | 4,707 | Surface water purchased | 2 | Below all study benchmarks |
| FREEPORT | IL1770200 | 23,930 | Ground water | 4 | At or above a study benchmark |
| FULTON | IL1950250 | 3,346 | Ground water | 2 | Below all study benchmarks |
| GALENA | IL0850200 | 3,308 | Ground water | 3 | Below all study benchmarks |
| GALESBURG | IL0950200 | 31,620 | Ground water | 1 | At or above a study benchmark |
| GENESEO | IL0730500 | 6,539 | Ground water | 1 | Below all study benchmarks |
| GENEVA | IL0890350 | 21,247 | Ground water | 1 | Below all study benchmarks |
| GENOA | IL0370150 | 5,298 | Ground water | 3 | Below all study benchmarks |
| GEORGETOWN | IL1830350 | 4,200 | Ground water | 1 | Below all study benchmarks |
| GIBSON CITY | IL0530100 | 3,500 | Ground water | 1 | Below all study benchmarks |
| GILBERTS | IL0890400 | 8,366 | Ground water | 1 | Below all study benchmarks |
| GILLESPIE | IL1170400 | 3,737 | Surface water | 1 | Below all study benchmarks |
| GLEN CARBON | IL1190300 | 12,618 | Surface water purchased | 1 | Below all study benchmarks |
| GLEN ELLYN | IL0430450 | 28,850 | Surface water purchased | 1 | Below all study benchmarks |
| GLENCOE | IL0310990 | 8,849 | Surface water | 1 | Below all study benchmarks |
| GLENDALE HEIGHTS | IL0430400 | 33,176 | Surface water purchased | 1 | Below all study benchmarks |
| GLENVIEW | IL0311020 | 47,856 | Surface water purchased | 1 | Below all study benchmarks |
| GLENWOOD | IL0311050 | 8,956 | Surface water purchased | 1 | Below all study benchmarks |
| GRANDWOOD PARK SUBDIVISION - LAKE CO PW | IL0975600 | 5,751 | Surface water purchased | 1 | Below all study benchmarks |
| GRAYSLAKE | IL0970250 | 21,248 | Surface water purchased | 1 | Below all study benchmarks |
| GREAT LAKES NAVAL TRAINING STATION | IL0975227 | 23,000 | Surface water | 1 | Below all study benchmarks |
| GREENVILLE | IL0050050 | 8,310 | Surface water | 1 | Below all study benchmarks |
| GURNEE | IL0970350 | 30,193 | Surface water purchased | 1 | Below all study benchmarks |
| HAINESVILLE | IL0970400 | 3,528 | Ground water | 2 | Below all study benchmarks |
| HAMILTON COUNTY WATER DISTRICT | IL0651000 | 3,958 | Surface water purchased | 1 | Below all study benchmarks |
| HAMPSHIRE | IL0890450 | 7,758 | Ground water | 2 | Below all study benchmarks |
| HANOVER | IL0850250 | 863 | Ground water | 2 | Below all study benchmarks |
| HANOVER PARK | IL0314480 | 37,470 | Surface water purchased | 1 | Below all study benchmarks |
| HARRISBURG | IL1650200 | 8,524 | Ground water purchased | 1 | Below all study benchmarks |
| HARVARD | IL1110250 | 9,469 | Ground water | 3 | Below all study benchmarks |
| HARVEY | IL0311110 | 25,000 | Surface water purchased | 1 | Below all study benchmarks |
| HARWOOD HEIGHTS | IL0311140 | 9,065 | Surface water purchased | 1 | Below all study benchmarks |
| HAVANA | IL1250200 | 2,963 | Ground water | 1 | Below all study benchmarks |
| HAZEL CREST | IL0311170 | 13,792 | Surface water purchased | 1 | Below all study benchmarks |
| HERRIN | IL1990400 | 12,747 | Surface water purchased | 1 | Below all study benchmarks |
| HICKORY HILLS | IL0311200 | 14,505 | Surface water purchased | 1 | Below all study benchmarks |
| HIGHLAND | IL1190550 | 10,674 | Surface water | 1 | Below all study benchmarks |
| HIGHLAND PARK, IL | IL0970500 | 30,176 | Surface water | 1 | Below all study benchmarks |
| HIGHWOOD | IL0970550 | 5,335 | Surface water | 1 | Below all study benchmarks |
| HILLSBORO | IL1350300 | 4,402 | Surface water | 1 | Below all study benchmarks |
| HILLSIDE | IL0311230 | 8,200 | Surface water purchased | 1 | Below all study benchmarks |
| HINSDALE | IL0434520 | 17,900 | Surface water purchased | 1 | Below all study benchmarks |
| HOFFMAN ESTATES | IL0311290 | 50,179 | Surface water purchased | 1 | Below all study benchmarks |
| HOMETOWN | IL0311320 | 4,240 | Surface water purchased | 1 | Below all study benchmarks |
| HOMEWOOD | IL0311350 | 19,463 | Surface water purchased | 1 | Below all study benchmarks |
| HOOPESTON | IL1830450 | 5,802 | Ground water | 1 | Below all study benchmarks |
| HUNTLEY | IL1110350 | 28,495 | Ground water | 5 | Below all study benchmarks |
| IL AMERICAN-ALTON | IL1195150 | 46,127 | Surface water | 1 | Below all study benchmarks |
| IL AMERICAN-ANDALUSIA | IL1610050 | 1,184 | Ground water | 1 | Below all study benchmarks |
| IL AMERICAN-CHAMPAIGN | IL0195300 | 150,000 | Ground water | 2 | Below all study benchmarks |
| IL AMERICAN-CHICAGO SUBURBAN | IL0315150 | 11,187 | Surface water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-COUNTRY CLUB | IL0435350 | 1,014 | Surface water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-EAST ST LOUIS | IL1635040 | 131,368 | Surface water | 1 | Below all study benchmarks |
| IL AMERICAN-FERNWAY | IL0315030 | 5,521 | Surface water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-GRANITE CITY | IL1195030 | 33,572 | Surface water | 1 | Below all study benchmarks |
| IL AMERICAN-HOMER TOWNSHIP | IL1970100 | 24,543 | Surface water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-LIBERTY RIDGE WEST | IL0435650 | 3,307 | Surface water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-PEKIN | IL1795040 | 31,731 | Ground water | 7 | Below all study benchmarks |
| IL AMERICAN-PEORIA | IL1435030 | 137,575 | Surface water | 4 | At or above a study benchmark |
| IL AMERICAN-PONTIAC | IL1055030 | 11,864 | Surface water | 1 | Below all study benchmarks |
| IL AMERICAN-SOUTH BELOIT | IL2010450 | 7,893 | Ground water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-STERLING | IL1955040 | 14,782 | Ground water | 2 | Below all study benchmarks |
| IL AMERICAN-STREATOR | IL0995030 | 19,000 | Surface water | 1 | Below all study benchmarks |
| IL AMERICAN-VALLEY VIEW | IL0437350 | 6,721 | Surface water purchased | 1 | Below all study benchmarks |
| IL AMERICAN-WEST SUBURBAN | IL1974151 | 73,978 | Surface water purchased | 1 | Below all study benchmarks |
| IL American - Lincoln | IL1075030 | 15,200 | Groundwater under influence of surface water | 3 | At or above a study benchmark |
| ILLINOIS STATE UNIVERSITY-NORMAL | IL1135510 | 6,600 | Ground water purchased | 1 | Below all study benchmarks |
| ISLAND LAKE | IL0974540 | 8,066 | Ground water | 2 | Below all study benchmarks |
| ITASCA | IL0430500 | 9,506 | Surface water purchased | 3 | Below all study benchmarks |
| JACKSONVILLE | IL1370200 | 19,903 | Surface water | 1 | Below all study benchmarks |
| JERSEY RWC | IL0835300 | 12,750 | Surface water purchased | 1 | Below all study benchmarks |
| JERSEYVILLE | IL0830250 | 8,412 | Ground water | 1 | Below all study benchmarks |
| JOHNSTON CITY | IL1990500 | 3,509 | Surface water purchased | 1 | Below all study benchmarks |
| JOLIET | IL1970450 | 160,000 | Ground water | 11 | Below all study benchmarks |
| JUSTICE-WILLOW SPRINGS WATER COMMISSION | IL0315820 | 18,450 | Surface water purchased | 1 | Below all study benchmarks |
| KENILWORTH | IL0311500 | 2,514 | Surface water purchased | 1 | Below all study benchmarks |
| KINMUNDY | IL1210300 | 940 | Surface water purchased | 1 | Below all study benchmarks |
| LA GRANGE HIGHLANDS SANITARY DISTRICT | IL0315860 | 6,600 | Surface water purchased | 1 | Below all study benchmarks |
| LA GRANGE PARK | IL0311560 | 13,011 | Surface water purchased | 1 | Below all study benchmarks |
| LA SALLE | IL0990300 | 9,700 | Ground water | 1 | Below all study benchmarks |
| LAKE BLUFF | IL0970750 | 5,600 | Surface water purchased | 1 | Below all study benchmarks |
| LAKE FOREST | IL0970800 | 19,642 | Surface water | 1 | Below all study benchmarks |
| LAKE IN THE HILLS | IL1110400 | 28,661 | Ground water | 8 | Below all study benchmarks |
| LAKE OF EGYPT PWD | IL1995200 | 11,368 | Surface water | 1 | Below all study benchmarks |
| LAKE VILLA | IL0970840 | 8,829 | Surface water purchased | 1 | Below all study benchmarks |
| LAKE WINDERMERE ESTATES SUBDIVISION | IL1795730 | 300 | Ground water | 2 | Below all study benchmarks |
| LAKE ZURICH | IL0970850 | 19,759 | Ground water | 5 | Below all study benchmarks |
| LAWRENCEVILLE | IL1010150 | 4,524 | Ground water | 1 | Below all study benchmarks |
| LCPW - PEKARA SUBDIVISION | IL0975900 | 3,711 | Surface water purchased | 5 | Below all study benchmarks |
| LE ROY | IL1130750 | 3,498 | Ground water | 1 | Below all study benchmarks |
| LEBANON | IL1630650 | 4,714 | Surface water purchased | 1 | Below all study benchmarks |
| LEMONT | IL0311620 | 17,500 | Ground water | 4 | Below all study benchmarks |
| LEYDEN TWSP WATER DISTRICT | IL0315880 | 10,000 | Surface water purchased | 1 | Below all study benchmarks |
| LIBERTYVILLE | IL0970900 | 20,500 | Surface water purchased | 1 | Below all study benchmarks |
| LINCOLNSHIRE | IL0970950 | 7,940 | Surface water purchased | 1 | Below all study benchmarks |
| LINCOLNWOOD | IL0311650 | 13,463 | Surface water purchased | 1 | Below all study benchmarks |
| LINDENHURST | IL0971000 | 14,500 | Surface water purchased | 1 | Below all study benchmarks |
| LISLE | IL0430551 | 24,223 | Surface water purchased | 1 | Below all study benchmarks |
| LITCHFIELD | IL1350400 | 6,648 | Surface water | 1 | Below all study benchmarks |
| LOCKPORT | IL1970500 | 23,100 | Ground water | 7 | Below all study benchmarks |
| LOMBARD | IL0430600 | 44,476 | Surface water purchased | 1 | Below all study benchmarks |
| LONG CREEK TOWNSHIP PWS | IL1155150 | 7,850 | Ground water | 1 | Below all study benchmarks |
| LOVES PARK | IL2010150 | 23,335 | Ground water | 4 | Below all study benchmarks |
| LOW POINT WATER DISTRICT | IL2035100 | 200 | Ground water | 1 | Below all study benchmarks |
| LYNWOOD | IL0311680 | 9,149 | Surface water purchased | 1 | Below all study benchmarks |
| LYONS, IL | IL0311710 | 10,304 | Surface water purchased | 1 | Below all study benchmarks |
| MACOMB | IL1090350 | 15,051 | Surface water | 1 | Below all study benchmarks |
| MAHOMET | IL0190450 | 6,580 | Ground water | 1 | Below all study benchmarks |
| MARENGO | IL1110650 | 7,572 | Ground water | 2 | Below all study benchmarks |
| MARION | IL1990550 | 16,855 | Surface water purchased | 1 | Below all study benchmarks |
| MARKHAM | IL0311770 | 12,500 | Surface water purchased | 1 | Below all study benchmarks |
| MARSEILLES | IL0990500 | 5,061 | Ground water | 2 | Below all study benchmarks |
| MARSHALL | IL0230100 | 3,947 | Ground water | 1 | Below all study benchmarks |
| MARYVILLE | IL1190750 | 10,150 | Ground water | 1 | Below all study benchmarks |
| MASCOUTAH | IL1630800 | 8,759 | Surface water purchased | 1 | Below all study benchmarks |
| MATTESON | IL0311800 | 18,293 | Surface water purchased | 1 | Below all study benchmarks |
| MATTOON | IL0290250 | 19,500 | Surface water | 1 | Below all study benchmarks |
| MAYWOOD | IL0311830 | 24,090 | Surface water purchased | 1 | Below all study benchmarks |
| MCHENRY | IL1110600 | 22,335 | Ground water | 4 | Below all study benchmarks |
| MELROSE PARK | IL0311860 | 24,206 | Surface water purchased | 1 | Below all study benchmarks |
| MENDON | IL0010500 | 953 | Ground water purchased | 1 | Below all study benchmarks |
| MENDOTA | IL0990550 | 7,100 | Ground water | 3 | Below all study benchmarks |
| METAMORA | IL2030350 | 3,895 | Ground water | 1 | Below all study benchmarks |
| METROPOLIS | IL1270150 | 6,309 | Ground water | 1 | Below all study benchmarks |
| MIDLOTHIAN | IL0311920 | 14,819 | Surface water purchased | 1 | Below all study benchmarks |
| MILAN | IL1610400 | 4,945 | Ground water | 2 | Below all study benchmarks |
| MILL CREEK PWD | IL0015300 | 5,755 | Ground water | 1 | Below all study benchmarks |
| MILL CREEK WATER RECLAMATION DISTRICT | IL0890120 | 8,000 | Ground water | 1 | Below all study benchmarks |
| MILLSTADT | IL1630850 | 4,071 | Surface water purchased | 1 | Below all study benchmarks |
| MILLSTONE PWD | IL1515050 | 5,565 | Ground water | 1 | Below all study benchmarks |
| MINOOKA | IL0630550 | 12,800 | Ground water | 3 | Below all study benchmarks |
| MITCHELL PWD | IL1195210 | 5,253 | Surface water purchased | 1 | Below all study benchmarks |
| MOKENA | IL1970600 | 19,887 | Surface water purchased | 1 | Below all study benchmarks |
| MOLINE | IL1610450 | 44,500 | Surface water | 1 | Below all study benchmarks |
| MONEE | IL1970650 | 5,148 | Ground water | 3 | Below all study benchmarks |
| MONMOUTH | IL1870150 | 8,902 | Ground water | 2 | Below all study benchmarks |
| MONTGOMERY | IL0894690 | 28,956 | Ground water | 3 | Below all study benchmarks |
| MONTICELLO | IL1470350 | 5,548 | Ground water | 1 | Below all study benchmarks |
| MORO PWD | IL1195250 | 723 | Ground water purchased | 1 | Below all study benchmarks |
| MORRIS, IL | IL0630600 | 14,775 | Ground water | 1 | Below all study benchmarks |
| MORRISON | IL1950350 | 4,188 | Ground water | 2 | Below all study benchmarks |
| MORTON | IL1790500 | 17,111 | Ground water | 3 | Below all study benchmarks |
| MORTON GROVE | IL0311950 | 25,297 | Surface water purchased | 1 | Below all study benchmarks |
| MOUNT CARMEL | IL1850200 | 7,015 | Groundwater under influence of surface water | 1 | Below all study benchmarks |
| MOUNT OLIVE | IL1170700 | 2,193 | Surface water purchased | 1 | Below all study benchmarks |
| MOUNT PROSPECT | IL0311980 | 41,000 | Surface water purchased | 1 | Below all study benchmarks |
| MOUNT VERNON | IL0810300 | 15,793 | Surface water purchased | 1 | Below all study benchmarks |
| MOUNT ZION | IL1150350 | 5,833 | Surface water purchased | 1 | Below all study benchmarks |
| MUNDELEIN | IL0971150 | 31,500 | Surface water purchased | 1 | Below all study benchmarks |
| MURDALE PWD | IL0775200 | 4,963 | Surface water purchased | 1 | Below all study benchmarks |
| NAPERVILLE | IL0434670 | 156,406 | Surface water purchased | 1 | Below all study benchmarks |
| NASHVILLE | IL1890300 | 3,230 | Surface water | 1 | Below all study benchmarks |
| NEW BADEN | IL0274700 | 4,178 | Surface water purchased | 1 | Below all study benchmarks |
| NEW LENOX | IL1970700 | 27,690 | Surface water purchased | 1 | Below all study benchmarks |
| NILES, IL | IL0312010 | 29,350 | Surface water purchased | 1 | Below all study benchmarks |
| NORMAL | IL1130900 | 52,736 | Ground water | 1 | Below all study benchmarks |
| NORRIDGE | IL0312040 | 15,251 | Surface water purchased | 1 | Below all study benchmarks |
| NORTH AURORA | IL0890600 | 18,261 | Ground water | 2 | Below all study benchmarks |
| NORTH CHICAGO | IL0971250 | 16,813 | Surface water | 1 | Below all study benchmarks |
| NORTH EAST CENTRAL PWD | IL1195280 | 3,975 | Ground water purchased | 1 | Below all study benchmarks |
| NORTH EAST MARION COUNTY WATER CMPNY | IL1210030 | 3,220 | Surface water purchased | 1 | Below all study benchmarks |
| NORTH PARK PWD | IL2015500 | 35,580 | Ground water | 3 | At or above a study benchmark |
| NORTH RIVERSIDE | IL0312160 | 7,071 | Surface water purchased | 1 | Below all study benchmarks |
| NORTHBROOK | IL0312070 | 34,407 | Surface water | 1 | Below all study benchmarks |
| NORTHEAST MOUNT VERNON WATER COMPANY | IL0810010 | 5,483 | Surface water purchased | 1 | Below all study benchmarks |
| NORTHERN ILLINOIS UNIVERSITY-DEKALB | IL0375500 | 6,500 | Ground water purchased | 3 | Below all study benchmarks |
| NORTHFIELD, IL | IL0312100 | 5,470 | Surface water purchased | 1 | Below all study benchmarks |
| NORTHLAKE | IL0314710 | 12,840 | Surface water purchased | 1 | Below all study benchmarks |
| O FALLON | IL1631100 | 46,603 | Surface water purchased | 1 | Below all study benchmarks |
| OAK BROOK | IL0430700 | 9,400 | Surface water purchased | 1 | Below all study benchmarks |
| OAK FOREST | IL0312190 | 27,478 | Surface water purchased | 1 | Below all study benchmarks |
| OAK LAWN | IL0312220 | 58,362 | Surface water purchased | 1 | Below all study benchmarks |
| OAK PARK, IL | IL0312250 | 54,583 | Surface water purchased | 1 | Below all study benchmarks |
| OGLESBY | IL0990700 | 4,500 | Ground water | 1 | Below all study benchmarks |
| OLNEY | IL1590200 | 8,877 | Surface water | 1 | Below all study benchmarks |
| OLYMPIA FIELDS | IL0312280 | 4,922 | Surface water purchased | 1 | Below all study benchmarks |
| OREGON | IL1410400 | 3,449 | Ground water | 4 | Below all study benchmarks |
| ORLAND PARK | IL0312310 | 58,020 | Surface water purchased | 1 | Below all study benchmarks |
| OSWEGO | IL0930150 | 38,169 | Ground water | 8 | Below all study benchmarks |
| OTTAWA | IL0990800 | 18,097 | Ground water | 2 | Below all study benchmarks |
| PALATINE | IL0312340 | 70,875 | Surface water purchased | 1 | Below all study benchmarks |
| PALOS HEIGHTS | IL0312370 | 15,500 | Surface water purchased | 1 | Below all study benchmarks |
| PALOS HILLS | IL0312400 | 18,530 | Surface water purchased | 1 | Below all study benchmarks |
| PALOS PARK | IL0311000 | 4,873 | Surface water purchased | 1 | Below all study benchmarks |
| PANA | IL0210500 | 5,800 | Surface water | 1 | Below all study benchmarks |
| PARIS | IL0450300 | 9,100 | Ground water | 1 | Below all study benchmarks |
| PARK CITY | IL0971400 | 5,425 | Surface water purchased | 1 | Below all study benchmarks |
| PARK FOREST | IL0314740 | 21,687 | Ground water | 1 | Below all study benchmarks |
| PARK RIDGE | IL0312460 | 39,800 | Surface water purchased | 1 | Below all study benchmarks |
| PAXTON | IL0530250 | 4,200 | Ground water | 1 | Below all study benchmarks |
| PEORIA HEIGHTS | IL1434750 | 5,908 | Ground water | 1 | Below all study benchmarks |
| PERU | IL0990850 | 10,300 | Ground water | 1 | Below all study benchmarks |
| PETERSBURG | IL1290200 | 4,725 | Ground water | 1 | Below all study benchmarks |
| PIKE COUNTY PWD 1 | IL1495000 | 5,375 | Ground water | 2 | Below all study benchmarks |
| PINGREE GROVE | IL0890160 | 10,365 | Ground water | 1 | Below all study benchmarks |
| PITTSFIELD | IL1490750 | 4,697 | Ground water | 1 | Below all study benchmarks |
| PLAINFIELD | IL1970800 | 50,000 | Surface water purchased | 1 | Below all study benchmarks |
| PLANO | IL0930200 | 12,600 | Ground water | 3 | Below all study benchmarks |
| PLEASANT VALLEY PWD | IL1435470 | 3,783 | Ground water | 3 | Below all study benchmarks |
| PONTOON BEACH PWD | IL1195300 | 3,325 | Surface water purchased | 1 | Below all study benchmarks |
| POPLAR GROVE WEST-COUNTRYSIDE | IL0070350 | 790 | Ground water | 1 | Below all study benchmarks |
| POSEN | IL0312520 | 5,331 | Surface water purchased | 1 | Below all study benchmarks |
| PRINCETON | IL0110850 | 7,832 | Ground water | 1 | Below all study benchmarks |
| Prairie Path Water Co. - Clarendon | IL0435300 | 625 | Ground water | 1 | Below all study benchmarks |
| Prairie Path Water Co. - Lake Holiday | IL0995200 | 4,750 | Ground water | 1 | Below all study benchmarks |
| Prairie Path Water Co. - Whispering Hills | IL1115700 | 8,300 | Ground water | 5 | At or above a study benchmark |
| QUINCY | IL0010650 | 42,000 | Surface water | 1 | Below all study benchmarks |
| RACCOON WATER COMPANY | IL1215100 | 7,080 | Surface water purchased | 3 | Below all study benchmarks |
| RANTOUL | IL0190650 | 13,000 | Ground water | 1 | Below all study benchmarks |
| RED BUD | IL1570450 | 3,804 | Ground water | 1 | Below all study benchmarks |
| RICHTON PARK | IL0312550 | 12,504 | Ground water | 3 | Below all study benchmarks |
| RIVER FOREST | IL0312610 | 11,717 | Surface water purchased | 1 | Below all study benchmarks |
| RIVER GROVE | IL0312640 | 10,282 | Surface water purchased | 1 | Below all study benchmarks |
| RIVERSIDE | IL0312670 | 9,298 | Surface water purchased | 1 | Below all study benchmarks |
| RIVERTON | IL1670950 | 4,279 | Ground water | 1 | Below all study benchmarks |
| RIVERWOODS | IL0971450 | 3,618 | Surface water purchased | 1 | Below all study benchmarks |
| ROBBINS | IL0312700 | 5,415 | Surface water purchased | 1 | Below all study benchmarks |
| ROBINSON-PALESTINE WATER COMMISSION | IL0335030 | 11,331 | Ground water | 1 | Below all study benchmarks |
| ROCHELLE | IL1410500 | 9,446 | Ground water | 5 | Below all study benchmarks |
| ROCHESTER | IL1671000 | 3,856 | Surface water purchased | 1 | Below all study benchmarks |
| ROCK ISLAND | IL1610650 | 39,018 | Surface water | 1 | Below all study benchmarks |
| ROCK ISLAND ARSENAL, US ARMY | IL1615387 | 7,800 | Surface water | 1 | Below all study benchmarks |
| ROCKFORD, IL | IL2010300 | 147,051 | Ground water | 23 | Below all study benchmarks |
| ROCKTON | IL2010350 | 7,685 | Ground water | 4 | Below all study benchmarks |
| ROLLING MEADOWS | IL0312730 | 23,329 | Surface water purchased | 1 | Below all study benchmarks |
| ROMEOVILLE | IL1970900 | 50,458 | Ground water | 8 | Below all study benchmarks |
| ROSELLE | IL0434820 | 22,897 | Surface water purchased | 1 | Below all study benchmarks |
| ROUND LAKE BEACH | IL0971550 | 27,200 | Surface water purchased | 1 | Below all study benchmarks |
| ROUND LAKE PARK | IL0971600 | 4,900 | Surface water purchased | 2 | Below all study benchmarks |
| SALEM | IL1210450 | 7,905 | Surface water | 1 | Below all study benchmarks |
| SALINE VALLEY CONSERVANCY DISTRICT | IL1655300 | 3,921 | Ground water | 2 | Below all study benchmarks |
| SANDWICH | IL0374850 | 7,156 | Ground water | 2 | Below all study benchmarks |
| SANGAMON VALLEY PWD | IL0195150 | 5,300 | Ground water | 1 | Below all study benchmarks |
| SCHAUMBURG | IL0314890 | 75,750 | Surface water purchased | 1 | Below all study benchmarks |
| SCHILLER PARK | IL0312850 | 11,709 | Surface water purchased | 1 | Below all study benchmarks |
| SHADY OAKS MHP | IL0635225 | 912 | Ground water | 1 | Below all study benchmarks |
| SHELBYVILLE | IL1730300 | 5,600 | Ground water | 1 | Below all study benchmarks |
| SHOREWOOD, IL | IL1975080 | 18,645 | Ground water | 5 | Below all study benchmarks |
| SILVIS | IL1610700 | 7,473 | Surface water purchased | 1 | Below all study benchmarks |
| SOUTH ELGIN | IL0890800 | 23,648 | Ground water | 8 | At or above a study benchmark |
| SOUTH HIGHWAY PWD | IL0775400 | 4,972 | Surface water purchased | 1 | Below all study benchmarks |
| SOUTH HOLLAND | IL0312970 | 22,000 | Surface water purchased | 2 | Below all study benchmarks |
| SOUTH JACKSONVILLE | IL1370400 | 3,501 | Ground water | 2 | Below all study benchmarks |
| SOUTHERN IL UNIVERSITY-EDWARDSVILLE | IL1195550 | 2,817 | Ground water purchased | 1 | Below all study benchmarks |
| SPRING VALLEY | IL0111000 | 5,582 | Ground water | 1 | Below all study benchmarks |
| SPRINGFIELD, IL | IL1671200 | 117,444 | Surface water | 1 | Below all study benchmarks |
| ST CHARLES | IL0894830 | 33,103 | Ground water | 5 | Below all study benchmarks |
| STAUNTON | IL1171050 | 5,756 | Surface water | 1 | Below all study benchmarks |
| STEGER | IL0314860 | 9,700 | Ground water | 2 | Below all study benchmarks |
| STICKNEY | IL0313000 | 6,902 | Surface water purchased | 1 | Below all study benchmarks |
| STONE PARK | IL0313030 | 4,576 | Surface water purchased | 1 | Below all study benchmarks |
| STREAMWOOD | IL0313060 | 39,577 | Surface water purchased | 1 | Below all study benchmarks |
| SUGAR GROVE | IL0890850 | 11,243 | Ground water | 5 | Below all study benchmarks |
| SULLIVAN | IL1390300 | 4,729 | Ground water | 1 | Below all study benchmarks |
| SUMMIT | IL0310060 | 11,161 | Surface water purchased | 1 | Below all study benchmarks |
| SYCAMORE | IL0370550 | 18,500 | Ground water | 5 | Below all study benchmarks |
| TAYLORVILLE | IL0210600 | 12,806 | Surface water | 1 | Below all study benchmarks |
| TINLEY PARK | IL0314910 | 56,703 | Surface water purchased | 1 | Below all study benchmarks |
| TRITOWNSHIP WATER DISTRICT | IL1190080 | 3,470 | Surface water purchased | 1 | Below all study benchmarks |
| TROY, IL | IL1191000 | 16,962 | Ground water | 1 | Below all study benchmarks |
| TUSCOLA | IL0415030 | 4,875 | Ground water purchased | 1 | Below all study benchmarks |
| U OF I-CHAMPAIGN | IL0195500 | 13,000 | Ground water purchased | 1 | Below all study benchmarks |
| UTL INC-GALENA TERRITORY | IL0855050 | 2,294 | Ground water | 6 | Below all study benchmarks |
| VALMEYER | IL1330250 | 1,263 | Ground water purchased | 1 | Below all study benchmarks |
| VANDALIA | IL0510350 | 7,616 | Surface water | 1 | Below all study benchmarks |
| VANDALIA CORRECTIONAL CENTER | IL0515500 | 700 | Surface water purchased | 1 | Below all study benchmarks |
| VERNON HILLS - LAKE CO PW | IL0971750 | 33,207 | Surface water purchased | 1 | Below all study benchmarks |
| VILLA PARK | IL0430800 | 22,263 | Surface water purchased | 1 | Below all study benchmarks |
| VIRDEN | IL1171100 | 3,274 | Surface water purchased | 1 | Below all study benchmarks |
| VOLO | IL0971770 | 6,629 | Surface water purchased | 1 | Below all study benchmarks |
| WARRENVILLE | IL0430833 | 12,350 | Ground water | 4 | Below all study benchmarks |
| WASCO SD | IL0890110 | 4,000 | Ground water | 1 | Below all study benchmarks |
| WASHINGTON COUNTY WATER COMPANY | IL1895600 | 11,374 | Surface water purchased | 4 | Below all study benchmarks |
| WASHINGTON, IL | IL1790750 | 14,793 | Ground water | 2 | Below all study benchmarks |
| WATERLOO | IL1330300 | 10,190 | Ground water | 1 | Below all study benchmarks |
| WAUCONDA | IL0971850 | 15,349 | Surface water purchased | 1 | Below all study benchmarks |
| WAUKEGAN | IL0971900 | 87,149 | Surface water | 1 | Below all study benchmarks |
| WEE-MA-TUK WATER DISTRICT | IL0570040 | 863 | Purchased ground water under influence of surface water source | 1 | Below all study benchmarks |
| WEST CHICAGO | IL0430900 | 25,166 | Ground water | 1 | Below all study benchmarks |
| WEST DUNDEE | IL0890950 | 7,845 | Ground water | 2 | Below all study benchmarks |
| WEST FRANKFORT | IL0550700 | 8,650 | Surface water purchased | 1 | Below all study benchmarks |
| WESTERN SPRINGS | IL0313180 | 13,274 | Ground water | 1 | Below all study benchmarks |
| WESTVILLE | IL1830950 | 3,917 | Surface water purchased | 1 | Below all study benchmarks |
| WHEATON | IL0431050 | 53,970 | Surface water purchased | 1 | Below all study benchmarks |
| WHEELING | IL0314970 | 39,725 | Surface water purchased | 1 | Below all study benchmarks |
| WILDWOOD SUBDIVISION - LAKE CO PW | IL0977350 | 14,832 | Surface water purchased | 1 | Below all study benchmarks |
| WILLIAMSVILLE | IL1671300 | 6,198 | Surface water purchased | 1 | Below all study benchmarks |
| WILLOW LAKE ESTATES MHP | IL0894400 | 920 | Surface water purchased | 1 | Below all study benchmarks |
| WILLOWBROOK | IL0431100 | 9,000 | Surface water purchased | 1 | Below all study benchmarks |
| WILMETTE | IL0313300 | 27,087 | Surface water | 1 | Below all study benchmarks |
| WINFIELD | IL0431150 | 9,835 | Surface water purchased | 1 | Below all study benchmarks |
| WINNETKA | IL0313330 | 12,475 | Surface water | 1 | Below all study benchmarks |
| WINTHROP HARBOR | IL0971950 | 6,565 | Surface water purchased | 1 | Below all study benchmarks |
| WONDER LAKE | IL1115750 | 3,870 | Ground water | 3 | Below all study benchmarks |
| WOOD DALE | IL0431200 | 14,012 | Surface water purchased | 1 | Below all study benchmarks |
| WOODHAVEN, IL | IL1035100 | 4,100 | Ground water | 1 | Below all study benchmarks |
| WOODLAWN | IL0810450 | 3,587 | Surface water purchased | 1 | Below all study benchmarks |
| WOODRIDGE | IL0431250 | 33,566 | Surface water purchased | 1 | Below all study benchmarks |
| WOODSTOCK, IL | IL1110950 | 25,630 | Ground water | 2 | Below all study benchmarks |
| WORTH | IL0313360 | 10,970 | Surface water purchased | 1 | Below all study benchmarks |
| XENIA | IL0250300 | 542 | Surface water purchased | 1 | Below all study benchmarks |
| YORKVILLE | IL0930250 | 23,000 | Ground water | 3 | Below all study benchmarks |
| ZION | IL0972000 | 24,442 | Surface water purchased | 1 | Below all study benchmarks |
How the count works
What is included
Each active community water system with enough required samples for a yearly average is counted once, even if it is linked with several ZIP codes. This does not mean every home was tested. Private wells are excluded, and UCMR 5 did not comprehensively monitor every small system. This page does not apply Illinois's state-specific standards or determine compliance. Use the official state or territory drinking-water program for current regulatory information.