Community Water System · PWSID CA3701793

Twin Lakes Resort

Serves 400 peopleGroundwaterOwner: PrivatePotrero, California
Nothing open that measures the water, but 5 open testing or paperwork violations.

A missed test is not evidence of bad water. It also is not evidence of good water: for that period nobody checked.

On record since 1993: 43 violations. 32 over the limit · 9 missed or late tests · 2 notices or reports. Most recent began 2025-04-01.

For this year's test results, ask the utility for its annual Consumer Confidence Report. Every community system must publish one.

32Over the limit
0Treatment lapse
9Missed or late test4 open
2Notice or report1 open

More violations on record than 97% of active water systems in California. Small systems with no staff chemist often rack up missed-test violations; big utilities rarely do.

The record, year by year

1993 · Missed or late test: 1199520002005 · Notice or report: 120052007 · Missed or late test: 12009 · Missed or late test: 1201020152016 · Over the limit: 32016 · Over the limit: 32016 · Over the limit: 32016 · Notice or report: 12017 · Over the limit: 42017 · Over the limit: 42017 · Over the limit: 42017 · Over the limit: 42017 · Missed or late test: 12018 · Over the limit: 32018 · Over the limit: 32018 · Over the limit: 32019 · Over the limit: 32019 · Over the limit: 32019 · Over the limit: 32019 · Missed or late test: 12020 · Over the limit: 32020 · Over the limit: 32020 · Over the limit: 320202021 · Over the limit: 32021 · Over the limit: 32021 · Over the limit: 32021 · Missed or late test: 12022 · Over the limit: 42022 · Over the limit: 42022 · Over the limit: 42022 · Over the limit: 42023 · Over the limit: 32023 · Over the limit: 32023 · Over the limit: 32023 · Missed or late test: 22023 · Missed or late test: 22024 · Over the limit: 42024 · Over the limit: 42024 · Over the limit: 42024 · Over the limit: 42024 · Missed or late test: 12025 · Over the limit: 22025 · Over the limit: 22025
One square = one violation, by the year it began. Empty columns are years with nothing on EPA's record.
74% over the limit · 3221% missed or late test · 95% notice or report · 2

Across California, 52% of violations are missed or late tests and 29% are water over a limit.

How far over the limit

at the limit2×5×10×100×+Arsenic2025-04-01 · Arsenic: measured 11.70 UG/L vs limit 10.00 UG/L (1.2×)2025-01-01 · Arsenic: measured 12.00 UG/L vs limit 10.00 UG/L (1.2×)2024-10-01 · Arsenic: measured 11.70 UG/L vs limit 10.00 UG/L (1.2×)2024-07-01 · Arsenic: measured 11.70 UG/L vs limit 10.00 UG/L (1.2×)2024-04-01 · Arsenic: measured 12.00 UG/L vs limit 10.00 UG/L (1.2×)2024-01-01 · Arsenic: measured 12.00 UG/L vs limit 10.00 UG/L (1.2×)2021-01-01 · Arsenic: measured 11.80 UG/L vs limit 10.00 UG/L (1.2×)2020-07-01 · Arsenic: measured 11.60 UG/L vs limit 10.00 UG/L (1.2×)2020-04-01 · Arsenic: measured 11.40 UG/L vs limit 10.00 UG/L (1.1×)2020-01-01 · Arsenic: measured 11.30 UG/L vs limit 10.00 UG/L (1.1×)2019-04-01 · Arsenic: measured 11.00 UG/L vs limit 10.00 UG/L (1.1×)2019-01-01 · Arsenic: measured 11.20 UG/L vs limit 10.00 UG/L (1.1×)2018-10-01 · Arsenic: measured 11.30 UG/L vs limit 10.00 UG/L (1.1×)2018-04-01 · Arsenic: measured 12.00 MG/L vs limit 0.0100 MG/L (1200.0×)2018-01-01 · Arsenic: measured 12.00 MG/L vs limit 0.0100 MG/L (1200.0×)2017-10-01 · Arsenic: measured 12.00 MG/L vs limit 10.00 MG/L (1.2×)2017-07-01 · Arsenic: measured 11.75 MG/L vs limit 0.0100 MG/L (1175.0×)2017-04-01 · Arsenic: measured 0.0120 MG/L vs limit 0.0100 MG/L (1.2×)2017-01-01 · Arsenic: measured 0.0115 MG/L vs limit 0.0100 MG/L (1.1×)2016-10-01 · Arsenic: measured 0.0115 MG/L vs limit 0.0100 MG/L (1.1×)2016-07-01 · Arsenic: measured 0.0114 MG/L vs limit 0.0100 MG/L (1.1×)2016-04-01 · Arsenic: measured 0.0116 MG/L vs limit 0.0100 MG/L (1.2×)
Each dot is one over-the-limit violation: the measured value divided by the limit it broke, on a log scale. Most legal limits for chemicals are running averages set for a lifetime of drinking, so “just over” and “ten times over” are very different news. Hover a dot for the numbers.

Lead & copper at the tap

Utilities sample taps in homes most likely to have lead pipes, and report the 90th-percentile result: 9 in 10 homes sampled came in at or below this number. Above the red line (the action level) the utility must act. The action level is not a safe level; EPA's health goal for lead is zero. EPA's file does not date these results, so they are shown highest first.

Lead, 90th percentile 2 results on file · action level 15 ppb

0 ppb
0 ppb

Open now (5)

  1. 2021-10-01Lead and Copper RuleFollow-up Or Routine LCR Tap M/ROpen
  2. 2016-12-23Public NoticePN Violation for NPDWR ViolationOpen
  3. 2009-04-14Lead and Copper RuleInitial Tap Sampling for Pb and CuOpen
  4. 2007-06-25Lead and Copper RuleInitial Tap Sampling for Pb and CuOpen
  5. 1993-07-01Lead and Copper RuleInitial Tap Sampling for Pb and CuOpen

Every violation on record

  1. 2025-04-01ArsenicMCL, Averagemeasured 11.70 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  2. 2025-01-01ArsenicMCL, Averagemeasured 12.00 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  3. 2024-10-01ArsenicMCL, Averagemeasured 11.70 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  4. 2024-07-01ArsenicMonitoring, Check/Repeat/ConfirmationPeriod ended · no return to compliance on file
  5. 2024-07-01ArsenicMCL, Averagemeasured 11.70 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  6. 2024-04-01ArsenicMCL, Averagemeasured 12.00 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  7. 2024-01-01ArsenicMCL, Averagemeasured 12.00 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  8. 2023-10-01ArsenicMCL, Single Samplemeasured 12.00 UG/LPeriod ended · no return to compliance on file
  9. 2023-07-01ArsenicMCL, Single Samplemeasured 12.00 UG/LPeriod ended · no return to compliance on file
  10. 2023-04-01ArsenicMonitoring, Check/Repeat/ConfirmationPeriod ended · no return to compliance on file
  11. 2023-01-01NitrateMonitoring, RegularPeriod ended · no return to compliance on file
  12. 2023-01-01ArsenicMCL, Single Samplemeasured 12.00 UG/LPeriod ended · no return to compliance on file
  13. 2022-10-01ArsenicMCL, Single Samplemeasured 12.00 UG/LPeriod ended · no return to compliance on file
  14. 2022-07-01ArsenicMCL, Single Samplemeasured 12.50 UG/LPeriod ended · no return to compliance on file
  15. 2022-04-01ArsenicMCL, Single Samplemeasured 12.00 UG/LPeriod ended · no return to compliance on file
  16. 2022-01-01ArsenicMCL, Single Samplemeasured 11.20 UG/LPeriod ended · no return to compliance on file
  17. 2021-10-01Lead and Copper RuleFollow-up Or Routine LCR Tap M/ROpen
  18. 2021-07-01ArsenicMCL, Single Samplemeasured 12.20 UG/LPeriod ended · no return to compliance on file
  19. 2021-04-01ArsenicMCL, Single Samplemeasured 11.60 UG/LPeriod ended · no return to compliance on file
  20. 2021-01-01ArsenicMCL, Averagemeasured 11.80 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  21. 2020-07-01ArsenicMCL, Averagemeasured 11.60 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  22. 2020-04-01ArsenicMCL, Averagemeasured 11.40 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  23. 2020-01-01ArsenicMCL, Averagemeasured 11.30 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  24. 2019-10-01ArsenicMonitoring, Check/Repeat/ConfirmationPeriod ended · no return to compliance on file
  25. 2019-07-01ArsenicMCL, Averagemeasured 11.02 UG/LPeriod ended · no return to compliance on file
Show the other 18 entries
  1. 2019-04-01ArsenicMCL, Averagemeasured 11.00 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  2. 2019-01-01ArsenicMCL, Averagemeasured 11.20 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  3. 2018-10-01ArsenicMCL, Averagemeasured 11.30 UG/L · limit 10.00 UG/LPeriod ended · no return to compliance on file
  4. 2018-04-01ArsenicMCL, Averagemeasured 12.00 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  5. 2018-01-01ArsenicMCL, Averagemeasured 12.00 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  6. 2017-10-01ArsenicMCL, Averagemeasured 12.00 MG/L · limit 10.00 MG/LPeriod ended · no return to compliance on file
  7. 2017-07-01ArsenicMCL, Averagemeasured 11.75 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  8. 2017-04-01ArsenicMonitoring, Check/Repeat/ConfirmationPeriod ended · no return to compliance on file
  9. 2017-04-01ArsenicMCL, Averagemeasured 0.0120 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  10. 2017-01-01ArsenicMCL, Averagemeasured 0.0115 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  11. 2016-12-23Public NoticePN Violation for NPDWR ViolationOpen
  12. 2016-10-01ArsenicMCL, Averagemeasured 0.0115 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  13. 2016-07-01ArsenicMCL, Averagemeasured 0.0114 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  14. 2016-04-01ArsenicMCL, Averagemeasured 0.0116 MG/L · limit 0.0100 MG/LPeriod ended · no return to compliance on file
  15. 2009-04-14Lead and Copper RuleInitial Tap Sampling for Pb and CuOpen
  16. 2007-06-25Lead and Copper RuleInitial Tap Sampling for Pb and CuOpen
  17. 2005-07-01Consumer Confidence RuleCCR Complete Failure to ReportBack in compliance
  18. 1993-07-01Lead and Copper RuleInitial Tap Sampling for Pb and CuOpen

System details

Population served400
Service connections153
Water sourceGroundwater
System typeCommunity Water System
OwnerPrivate
StatusActive
CityPotrero
EPA ZIP on file91963

Areas served

  • San Diego County

Reading this record

Twin Lakes Resort is a community water system that draws from groundwater and serves about 400 people in Potrero, California. Everything above comes from the EPA's Safe Drinking Water Information System (SDWIS), where states report every violation by every public water system.

Four kinds of violation. Only one is a measurement of the water: over the limit means a test came back above a legal maximum (an MCL). A treatment lapse means a required protective step was not done, such as disinfection, filtration, fixing a defect an inspector found, or filing a lead-pipe inventory. A missed or late test means a required test was skipped or never reported. That is the most common kind, and the most misread: it does not mean the water was bad, and it does not mean the water was fine. Notices and reports covers public notices and the annual Consumer Confidence Report.

Status. “Back in compliance” means the state recorded a return to compliance. “Period ended” means the violation's compliance period is over but no return to compliance was ever filed, which is common in older records. EPA's federal copy lags state records by months, so call the utility for anything current.