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County profile · EPA SDWIS + UCMR5

Colusa County, California

29 SDWIS-listed public water systems serve 35,121 people in Colusa County. Violation rates use that full inventory; PFAS rates use only the UCMR5-tested subset.

29
SDWIS water systems Middle third of counties
273
Total violations Lower third of counties
86.2%
SDWIS systems w/ a violation Lower third of counties
0.0%
UCMR5 PFAS rate (2 tested) Lower third of counties with tests

SDWIS compliance plate

Sheet CA011 · Colusa County 29 sys · 273 viol · #1220/3254

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

  • VIOL-SEVERE 86.2% flagged
  • HEALTH-HIGH 47.3% health
  • RANK-UPPER #1220/3254
  • PHOTO-FINISH ±0.0 pp
  • PFAS-CLEAN 0.0% detect
  • SRC-GW GW lead 97%
  • SYS-SMALL 29 systems
  • BOOK-FULL 7/7 fields

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

According to EPA SDWIS county population served used on /counties, Colusa County ranks #1,220 of 3,254 counties by people served, and #50 of 58 counties in California. See methodology · corpus placement.

Colusa County standing, lower-flagged corpus third

Flagged-system rate 86.2% is at or below the corpus lower third (≤ 92.7% flagged) across 2,973 counties with ≥3 SDWIS systems . Health-based share 47.3% 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 #1,220 of 3,254 · #50 of 58 in California.

Flagged-rate neighbourhood around Colusa County

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

0% 20% 40% 60% 80% 100% Alpine · lowest Shasta · near Santa Barbara · near Sutter · highest 70% 85.7% 86.1% 86.2% 86.2% 86.7% 97.1%

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

Water Systems

System Name Population Violations PFAS
Caltrans-Maxwell Reststops 15,000 3 -
City of Colusa 6,447 8 Clean
City of Williams 5,538 6 Clean
Arbuckle Public Utility District 2,778 12 -
Maxwell Public Utility District 1,175 9 -
Colusa Industrial Properties 533 5 -
Menf-Fouts Springs Cg 531 0 -
Colusa Co. Wwd #1 - Grimes 512 104 -
Morning Star Pkg. Co.-Wms. 390 9 -
Colusa Co. Wwd #2 - Princeton 382 21 -
Colusa Co. Service Area #2-Stonyford 250 15 -
Colusa Co. Service Area #1-Century Ranch 246 10 -
Del Oro WC - Arbuckle District 185 2 -
Colusa Landing 168 4 -
Sun Valley Rice Company 151 8 -
Arbuckle Golf Club 126 0 -
Menf-Letts Lake Cg 118 5 -
Wilbur Hot Springs 97 6 -
Adam's Vegetable Oils 95 10 -
Adm Rice Inc. 87 7 -
Highway 20 Trailer Park 63 10 -
Grimes Boat Landing 50 0 -
Richmond Hunting Club-Maxwell 40 4 -
Willow Creek M.W.C.-Lambertville 31 2 -
Terhel Farms Trailer Park 01 26 6 -
Kingdom Hall of Jehovah's Witness-Wms 26 2 -
Terhel Farms Trailer Park 02 26 2 -
Ward's Boat Landing 25 3 -
T&p Farms 25 0 -

Compare beyond California

Lower-flagged peers for Colusa County

Cross-state counties nearest Colusa County on flagged-system share (86.2%) and cumulative violation count (273). 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. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.