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Counties → California

San Luis Obispo County, California

SDWIS compliance plate

Sheet CA079 · San Luis Obispo County 167 sys · 1,652 viol · #199/3254

VIOL-SEVERE · HEALTH-MID · RANK-TOP · ABOVE-PEER · PFAS-MID · SRC-GW · SYS-LARGE · BOOK-FULL

  • VIOL-SEVERE 74.9% flagged
  • HEALTH-MID 38.3% health
  • RANK-TOP #199/3254
  • ABOVE-PEER +2.1 pp
  • PFAS-MID 47.1% detect
  • SRC-GW GW lead 81%
  • SYS-LARGE 167 systems
  • BOOK-FULL 7/7 fields

Nearest flagged-rate peer: Lassen County ( -2.1 pp flagged-rate)

According to EPA SDWIS county population served used on /counties, San Luis Obispo County ranks #199 of 3,254 counties by people served, and #23 of 58 counties in California. See methodology · corpus placement.

San Luis Obispo County standing, lower-flagged corpus third

Flagged-system rate 74.9% is at or below the corpus lower third (≤ 92.7% flagged) across 2,973 counties with ≥3 SDWIS systems . Health-based share 38.3% is health-based share above the upper third (> 24.5%) . UCMR5 detect rate 47.1% is UCMR5 detect rate above the tested-pool upper third (> 33.3%) . Population served ranks #199 of 3,254 · #23 of 58 in California.

Flagged-rate neighbourhood around San Luis Obispo County

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

0% 20% 40% 60% 80% 100% Alpine · lowest San Luis Obisp · this county Sutter · highest 70% 70.4% 72.7% 74.9% 77.6% 79.1% 97.1%

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

Water Systems

System Name Population Violations PFAS
Santa Margarita Recreation Area 50,001 0 -
San Luis Obispo Water Department 47,788 2 Clean
City of Paso Robles Water Division 31,176 9 Detected
Atascadero Mutual Water Co 30,618 3 Detected
City of Arroyo Grande Utilities Division 17,963 7 Detected
California Mens Colony 15,000 11 Clean
Nipomo Comm Services Dist 13,771 8 Clean
Morro Bay Pw Dept - Water Division 13,757 13 Clean
City of Grover Beach Public Works Dept 12,701 8 Clean
Brecon Estate 9,012 0 -
Pismo Beach Water Department 8,036 13 Clean
Templeton Csd 8,011 4 Detected
Oceano Comm Services Dist. 7,601 23 Clean
Los Osos Community Services District 7,086 3 Detected
Golden State Water Company - los Osos 5,924 0 Detected
Cambria Comm Services Dist 5,532 22 Clean
Golden State Water Company - Nipomo 4,506 0 Detected
Atascadero State Hospital 4,100 6 Detected
Woodlands Development 3,862 3 -
Grosso Kresser Winery 3,606 0 -
Heritage Ranch Csd 2,956 38 Clean
San Miguel Community Services District 2,600 2 -
Cayucos Beach Mutual Water Company 2,567 1 -
Morro Rock Mutual Water Co 2,181 1 -
Nacimiento Water Company 2,181 103 -
Golden State Water Company-Cypress Ridge 2,026 48 -
Avila Beach Community Services District 1,630 0 -
Tiger Water Supply 1,600 5 -
San Miguelito MWC 1,600 5 -
Lopez Project 1,569 5 -
County of Monterey-Lake Nacimiento 1,521 10 -
Golden State Water Company - Edna 1,493 2 -
Caltrans - Shandon Rest Stop 1,300 10 -
Slo Cwwd No. 23 - Santa Margarita 1,291 2 -
Pg&e 1,200 26 -
Slocsa #10a - Cayucos 1,200 0 -
Slo CSA No. 16 - Shandon 1,085 0 -
Daou Vineyards, LLC 1,025 2 -
Montana de Oro State Park 990 7 -
Laureate Water Company 700 14 -
Coastal Christian School 650 0 -
Mesa Dunes Mobile Home Estates 600 15 -
S & T Mutual Water Company 591 3 -
Woodland Park Mutual Water Co 538 21 -
Hearst Memorial State Beach 500 2 -
Walnut Hills Mutual Water Co 486 4 -
San Simeon Csd 462 8 -
Garden Farms C.w.d. 440 13 -
Los Robles Mobile Home Estates 420 4 -
Vines R.V. Resort 400 0 -

Compare beyond California

Lower-flagged peers for San Luis Obispo County

Cross-state counties nearest San Luis Obispo County on flagged-system share (74.9%) and cumulative violation count (1,652). 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.