Community Water System · PWS CA4100582
County Service Area 11
Operator location Redwood City, California - smaller served population (≤ 999) at 450 people served; 47 SDWIS violations on record from groundwater sources.
- 450
- People served (this PWS)
- 47
- EPA violations (this PWS)
- 2
- Health-based (this PWS)
- Untested
- UCMR5 (this PWS)
County Service Area 11 standing, mid SDWIS violation third
450 people served (SDWIS) - smaller served population (≤ 999). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 4% is middle-third health share (≤ 23%).
The verdict
County Service Area 11 lands in the middle third by violation volume (47), large enough for peer comparisons without matching the fleet's heaviest ledgers. Population served is smaller (450; smaller served population (≤ 999)), so each violation row represents a compact service footprint. Health-based share is 4% (middle-third health share (≤ 23%)). No UCMR5 PFAS test appears for this system in this extract.
- 47
- Total EPA violations on record
- 4%
- Health-based (MCL / treatment failure)
- 450
- People served by this PWS (SDWIS)
- N/A
- PFAS compounds detected (UCMR5)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
System Details
- System Type
- Community
- Owner Type
- Local
- Connections
- 103
- County
- San Mateo
- School/Daycare
- No
- MCL Violations
- 0
- Monitoring Violations
- 45
- Treatment Tech Violations
- 2
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Coliform (TCR) | MR | 3 | 1996 |
| Toluene | MR | 2 | 2004 |
| Benzene | MR | 2 | 2004 |
| Tetrachloroethylene | MR | 2 | 2004 |
| 1,1-Dichloroethylene | MR | 2 | 2004 |
| 1,1,1-Trichloroethane | MR | 2 | 2004 |
| 1,2-Dichloroethane | MR | 2 | 2004 |
| 1,2-Dichloropropane | MR | 2 | 2004 |
| p-Dichlorobenzene | MR | 2 | 2004 |
| Vinyl chloride | MR | 2 | 2004 |
| Trichloroethylene | MR | 2 | 2004 |
| cis-1,2-Dichloroethylene | MR | 2 | 2004 |
| Styrene | MR | 2 | 2004 |
| Xylenes, Total | MR | 2 | 2004 |
| Revised Total Coliform Rule | TT | 2 | 2019 |
| 1,1,2-Trichloroethane | MR | 2 | 2004 |
| 1,2,4-Trichlorobenzene | MR | 2 | 2004 |
| DICHLOROMETHANE | MR | 2 | 2004 |
| trans-1,2-Dichloroethylene | MR | 2 | 2004 |
| Carbon tetrachloride | MR | 2 | 2004 |
| o-Dichlorobenzene | MR | 2 | 2004 |
| Ethylbenzene | MR | 2 | 2004 |
| CHLOROBENZENE | MR | 2 | 2004 |
Violation Count vs. the National Corpus
County Service Area 11 has 47 recorded EPA violations, 55% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 45% carry more. 4% of this system's own violations are health-based (2 of 47), and it ranks unranked by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
47 Around the middle fewer violations than 45% 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
Population served record for County Service Area 11
EPA SDWIS lists 450 people served and 103 connections for this PWS, confirm the service-area footprint on the federal report before comparing to municipal census totals.
Sources: EPA SDWIS · California State Water Resources Control Board, Division of Drinking Water
Nationwide peers
47 violations · 450 served: nearest cross-state SDWIS matches.
Cross-state systems near this violation count
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
What to do with County Service Area 11
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.