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Counties → Iowa

Johnson County, Iowa

SDWIS compliance plate

Sheet IA103 · Johnson County 125 sys · 10,912 viol · #384/3254

VIOL-SEVERE · HEALTH-MID · RANK-TOP · PHOTO-FINISH · PFAS-CLEAN · SRC-GW · SYS-LARGE · BOOK-FULL

  • VIOL-SEVERE 96.0% flagged
  • HEALTH-MID 31.3% health
  • RANK-TOP #384/3254
  • PHOTO-FINISH ±0.0 pp
  • PFAS-CLEAN 0.0% detect
  • SRC-GW GW lead 98%
  • SYS-LARGE 125 systems
  • BOOK-FULL 7/7 fields

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

According to EPA SDWIS county population served used on /counties, Johnson County ranks #384 of 3,254 counties by people served, and #4 of 99 counties in Iowa. See methodology · corpus placement.

Johnson County standing, mid-flagged corpus third

Flagged-system rate 96.0% is in the corpus middle third (≤ 100.0% flagged) across 2,973 counties with ≥3 SDWIS systems . Health-based share 31.3% is health-based share above the upper third (> 24.5%) . UCMR5 detect rate 0.0% is UCMR5 detect rate at or below the tested-pool lower third (≤ 0.0%) . Population served ranks #384 of 3,254 · #4 of 99 in Iowa.

Flagged-rate neighbourhood around Johnson County

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

0% 20% 40% 60% 80% 100% Mahaska · lowest Johnson · this county Kossuth · near Ringgold · highest 75% 95.5% 96% 96% 96.3% 96.4% 100%

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

Water Systems

System Name Population Violations PFAS
Iowa City Water Department 68,753 130 Clean
University Water System 26,684 89 Clean
Coralville Muni Water System 22,318 198 Clean
North Liberty Water Supply 20,491 46 Clean
Tiffin Water Supply 4,512 40 -
Solon Water Dept 3,018 30 -
Lone Tree Muni Water System 1,357 46 -
Lake Ridge, Incorporated 1,300 106 -
F W Kent Park 1,169 27 -
Modern Manor, Inc 915 72 -
Hills Water Supply 863 5 -
Coralville Lake-West Overlook 861 82 -
Western Hills (Mobile) Estates 760 177 -
Oxford Water Supply 722 127 -
Iowa City Regency Mobile Home Community 700 229 -
Coralville Lake-Sugar Bottom 689 27 -
Cedar Ridge Vineyards 470 87 -
Oakdale Hospital Water System 450 8 -
Shueyville United Methodist Church 410 106 -
Gateway Development 400 99 -
River Heights Property Owners Assoc. 390 74 -
Fox Ridge Farm 374 8 -
Sunrise Village Mobile Home Pk 340 75 -
Coralville Lake Terrace 340 362 -
Parkview Mobile Home Court 300 32 -
Lake Crest Manor HOA #3 300 65 -
Iowa City MHP LLC 280 87 Clean
Coralville Lake-Ad Bldg 275 88 -
Kalona Creamery, LLC 262 33 -
380Bp Swisher 258 58 -
Sutliff Holdings LLC 250 4 -
High Point City Church 233 8 -
Johnson County Ag Association 218 137 -
Cottage Reserve Corporation 198 70 -
Sharon Bethel Church/School 195 30 -
North Twin View Heights 180 89 -
Iadu Clear MHP LLC 173 50 -
Coralville Lake Manor 170 82 -
Spring Valley Homeowners Assn. 163 73 -
Royal Oaks Subdivision 163 41 -
Plum Creek Boutique Dance Mor 160 0 -
Prairie View Estates Assoc Johnson Cnty 155 544 -
Twin View Heights 155 113 -
Coralville Lake-Sandy Beach 147 38 -
Forestgate Subdivision 140 10 -
Lake Vista Subdivision 134 34 -
Pleasant Valley Golf Course 130 33 -
Lakeview Knolls Homeowners Assn. 122 153 -
Westcott Heights HOA Part Three 120 14 -
Lake Woods HOA 114 126 -

Compare beyond Iowa

Mid-flagged peers for Johnson County

Cross-state counties nearest Johnson County on flagged-system share (96.0%) and cumulative violation count (10,912). 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

Read our methodology · Check your water system - how this data is sourced, computed, and verified.

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.