Community Water System · PWS CA3310017
South Mesa WC
Operator location Calimesa, California - 29% of 14 violations are health-based (upper-third health share (> 23%)); groundwater source; 10,108 served per SDWIS.
- 10,108
- People served (this PWS)
- 14
- EPA violations (this PWS)
- 4
- Health-based (this PWS)
- 4 PFAS
- UCMR5 (this PWS)
South Mesa WC standing, low SDWIS violation third
29% of 14 recorded violations are health-based - upper-third health share (> 23%). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 29% is upper-third health share (> 23%). UCMR5: middle-third PFAS panel (≤ 4 compounds). Population rank #4,636 of 29,740 among systems serving 500+.
The verdict
South Mesa WC is in the lower third by violation count (14; lower-third violation load (≤ 21 violations)). A low count does not mean the system is unmonitored - monitoring and reporting violations still appear in SDWIS. Population served is large (10,108; larger served population (> 3,309)), so household exposure scale sits behind the violation mix. Health-based share is 29% - most of this ledger is MCL or treatment-technique exceedance. UCMR5 detected 4 PFAS compounds (middle-third PFAS panel (≤ 4 compounds)).
- #4,636 of 29,740
- Population · /systems
- #475 of 1,701
- Population · CA
- 14
- Total EPA violations on record
- 29%
- Health-based (MCL / treatment failure)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
4 PFAS "forever chemicals" detected in testing under EPA's UCMR5 monitoring program.
System Details
- System Type
- Community
- Owner Type
- Private
- Connections
- 3,108
- County
- Riverside
- School/Daycare
- No
- MCL Violations
- 4
- Monitoring Violations
- 9
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Fluoride | MCL | 4 | 2014 |
| Lead and Copper Rule | MR | 3 | 2013 |
| Total Haloacetic Acids (HAA5) | MR | 2 | 2009 |
| Fluoride | MR | 2 | 2010 |
| TTHM | MR | 2 | 2009 |
Violation Count vs. the National Corpus
South Mesa WC has 14 recorded EPA violations, 24% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 75% carry more. 29% of this system's own violations are health-based (4 of 14), and it ranks #4,636 of 29,740 by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
14 Among the lowest violation counts fewer violations than 75% of 29,740 water systems
the national water-system corpus, bucketed by value
Each bar is a band; taller bars hold more water systems. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS · 2026-05-15
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 6 of 464 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| PFMPA | 9/20/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFPeA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMBA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFEESA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| NFDHA | 9/20/2023 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFPeS | 9/20/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpS | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 8:2 FTS | 9/20/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFNA | 9/20/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHxS | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOA | 9/20/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| 4:2 FTS | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFUnA | 9/20/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 9/20/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 9Cl-PF3ONS | 9/20/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| ADONA | 9/20/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 9/20/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFBA | 9/20/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 6:2 FTS | 9/20/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFOS | 9/20/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFEESA | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFUnA | 9/13/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 9Cl-PF3ONS | 9/13/2023 | <2.00 ppt | 2.00 ppt | Not Detected |
| ADONA | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBA | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| 4:2 FTS | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 8:2 FTS | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMPA | 9/13/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFPeS | 9/13/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFMBA | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| NFDHA | 9/13/2023 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFPeA | 9/13/2023 | 8.90 ppt | 3.00 ppt | Detected |
| PFHpS | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| 6:2 FTS | 9/13/2023 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFDoA | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 9/13/2023 | 6.80 ppt | 3.00 ppt | Detected |
| PFBS | 9/13/2023 | 4.70 ppt | 3.00 ppt | Detected |
| PFHpA | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxS | 9/13/2023 | 3.50 ppt | 3.00 ppt | Detected |
| PFNA | 9/13/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 9/13/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOA | 9/13/2023 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFDA | 9/13/2023 | <3.00 ppt | 3.00 ppt | Not Detected |
Health-based violations on South Mesa WC
4 health-based rows in the tables above map to MCL or treatment-technique exceedances, verify each contaminant code on the federal SDWIS report for CA3310017.
Sources: EPA SDWIS · California State Water Resources Control Board, Division of Drinking Water
Nationwide peers
14 violations · 10,108 served: nearest cross-state SDWIS matches.
Cross-state systems with similarly light violation ledgers
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
Cross-state systems with similar served population
Nearest cross-state systems by EPA SDWIS population_served (same 500+ sitemap gate).
What to do with South Mesa WC
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in California compares on the same EPA violation measures. California systems
- Check whether PFAS was detected at this system under UCMR5 testing. PFAS guide
- Find and compare another public water system by name or PWSID. Search systems
EPA SDWIS and UCMR5 figures are informational only, not a substitute for a certified lab test of your own tap water.