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Counties → California

Sonoma County, California

SDWIS compliance plate

Sheet CA097 · Sonoma County 440 sys · 6,052 viol · #147/3254

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

  • VIOL-SEVERE 83.6% flagged
  • HEALTH-MID 31.3% health
  • RANK-TOP #147/3254
  • PHOTO-FINISH ±0.1 pp
  • PFAS-MID 29.4% detect
  • SRC-GW GW lead 93%
  • SYS-LARGE 440 systems
  • BOOK-FULL 7/7 fields

Nearest flagged-rate peer: Placer County (+ 0.1 pp flagged-rate)

According to EPA SDWIS county population served used on /counties, Sonoma County ranks #147 of 3,254 counties by people served, and #18 of 58 counties in California. See methodology · corpus placement.

Sonoma County standing, lower-flagged corpus third

Flagged-system rate 83.6% is at or below the corpus lower third (≤ 92.7% 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 29.4% is UCMR5 detect rate in the tested-pool middle third (≤ 33.3%) . Population served ranks #147 of 3,254 · #18 of 58 in California.

Flagged-rate neighbourhood around Sonoma County

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

0% 20% 40% 60% 80% 100% Alpine · lowest Solano · near Placer · near Sutter · highest 70% 81.8% 82% 83.6% 83.7% 84.5% 97.1%

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

Water Systems

System Name Population Violations PFAS
Santa Rosa, City Of 175,396 4 Clean
Petaluma, City Of 60,781 4 Clean
Rohnert Park, City Of 43,821 561 Detected
Windsor, Town Of 25,561 6 Clean
Valley of the Moon Water District 23,107 9 Detected
Sonoma, City Of 11,725 17 Detected
Sonoma State University 10,986 22 Clean
Healdsburg, City Of 10,985 11 Detected
Cloverdale, City Of 10,398 24 Clean
California-American Larkfield (Puc) 7,913 6 Clean
Sebastopol, City Of 7,522 19 Clean
Cotati, City Of 7,303 3 Clean
Sweetwater Springs Cwd - Guerneville 6,000 7 Clean
Russian River County Water District 4,150 13 Clean
Forestville Water District 3,788 2 -
Csp-Salt Point State Park 3,513 1 -
Csp-Fort Ross State Park 3,501 17 -
Sweetwater Springs Cwd - Monte Rio 3,000 0 -
Penngrove Water Company (Puc) 1,742 19 -
Sonoma County CSA 41-Fitch Mountain 1,265 5 -
Camp Meeker Water System 1,171 0 -
Sea Ranch Water Company,the (Puc) 1,160 11 Detected
Bodega Bay Public Utility District 1,069 7 -
California-American Geyserville (Puc) 1,046 1 Clean
Kenwood Village Water Company (Puc) 1,029 8 -
Sutter Santa Rosa Regional Hospital 1,000 0 -
Canon Manor Water System 805 6 -
Odd Fellows Recreation Club 757 8 -
Urj Camp Newman 705 7 -
Moon Valley Water System 691 4 -
Jehovah S Witnesses Hall 650 8 -
Diamond a Mutual Water Company 640 18 -
Csp-Armstrong Redwoods State Reserve 611 0 -
Korbel Brothers Winery 546 8 -
Occidental Community Services District 533 25 -
Cazadero Water Company, Inc. (Puc) 525 57 -
Csp-Wrights Beach State Park 502 4 -
Wright Elementary School 500 7 -
Oak Grove School 500 10 -
Cline Cellars 500 10 -
Armstrong Valley-Cal Water Service (Puc) 473 1 -
U.S. Coast Guard Training Center 469 7 -
Rincon Valley Mobile Estates 460 14 -
Willowside School 460 6 -
Willowside Mutual Water Company 448 16 -
Casini Ranch Campground 442 9 -
Bennett Ridge Mutual Water Company 439 9 -
Sereno del Mar Water Company (Puc) 435 19 -
Sonoma County CSA 41-Salmon Creek 427 15 -
Santa Rosa Mobile Estates 420 9 -

Compare beyond California

Lower-flagged peers for Sonoma County

Cross-state counties nearest Sonoma County on flagged-system share (83.6%) and cumulative violation count (6,052). 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.