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Public water system record

Lake Don Pedro CSD

Serves Lake Don Pedro, Tuolumne County and Mariposa County, CA · 3,240 people served

Federal records show 1 health-based violation and 4 monitoring/reporting issues for Lake Don Pedro CSD in the last ten years, including an unresolved LEAD AND COPPER RULE REVISIONS violation.

  • CA5510008
  • LA GRANGE
  • CA
  • 3,240 served

System profile

Source water Surface water
ZIP 95329
EPA system ID CA5510008

Verify this system on EPA ECHO →

Health-based violations, last 10 years
1
Resolved
0
Unresolved
1
Any acute record
No
Monitoring issues, last 10 years
4

Key facts

  • Lake Don Pedro CSD draws water from 4 wells and 1 surface water intake (3 of them for emergency, seasonal or other part-time use).
  • Most recent formal enforcement: compliance order (no penalty) by California, February 2025.
  • Record on file since 1989, with 12 health-based violations before October 19, 2016.
  • Lead pipe inventory: 0 lead and 0 unknown out of 1,546 service lines.

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Health-based violations

Since October 2016

Violation data reflects EPA records through March 2026. For the most current status, visit the EPA ECHO database.

Contaminant Rule family Start date Status Acute
LEAD AND COPPER RULE REVISIONS
Treatment technique failure
 350 Oct 17, 2024 Active No

Monitoring and reporting issues

Since October 2016

Missed tests or reports, not contaminants found above a limit.

Issue Start date Status
Revised Total Coliform Rule
Monitoring violation
 Apr 1, 2025 Resolved
LEAD AND COPPER RULE REVISIONS
RPT
 Oct 17, 2024 Active
Nitrate
Monitoring and reporting
 Jan 1, 2024 Resolved
Lead and Copper Rule
Monitoring and reporting
 Oct 1, 2017 Resolved

Full record since 1989

EPA's records for Lake Don Pedro CSD go back to 1989. Before October 19, 2016 they list 12 health-based violations (12 resolved) and 10 monitoring or reporting violations.

Violations that began in Health-based Monitoring and reporting
1980s 0 4
2000s 12 6
October 19, 2016 to 2019 0 1
2020s 1 3

Most recent health-based violation before October 19, 2016: Total Trihalomethanes (TTHMs), began April 2009, Resolved.

Show all 12 health-based violations before October 19, 2016
Contaminant Start date Status
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0862 mg/L, federal limit 0.08 mg/L (1.1 times the limit)
 Apr 1, 2009 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0836 mg/L, federal limit 0.08 mg/L (at or just above the limit)
 Oct 1, 2008 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.0955 mg/L, federal limit 0.08 mg/L (1.2 times the limit)
 Jul 1, 2007 Resolved
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0618 mg/L, federal limit 0.06 mg/L (at or just above the limit)
 Jul 1, 2007 Resolved
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.089 mg/L, federal limit 0.06 mg/L (1.5 times the limit)
 Apr 1, 2007 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1285 mg/L, federal limit 0.08 mg/L (1.6 times the limit)
 Apr 1, 2007 Resolved
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0961 mg/L, federal limit 0.06 mg/L (1.6 times the limit)
 Jan 1, 2007 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1418 mg/L, federal limit 0.08 mg/L (1.8 times the limit)
 Jan 1, 2007 Resolved
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.1024 mg/L, federal limit 0.06 mg/L (1.7 times the limit)
 Oct 1, 2006 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1513 mg/L, federal limit 0.08 mg/L (1.9 times the limit)
 Oct 1, 2006 Resolved
Haloacetic Acids (HAA5)
Contaminant limit exceeded
Measured 0.0804 mg/L, federal limit 0.06 mg/L (1.3 times the limit)
 Jan 1, 2006 Resolved
Total Trihalomethanes (TTHMs)
Contaminant limit exceeded
Measured 0.1377 mg/L, federal limit 0.08 mg/L (1.7 times the limit)
 Jan 1, 2006 Resolved

Enforcement actions

California regulators took 3 formal enforcement actions against Lake Don Pedro CSD between 2007 and 2025. The most recent was a compliance order (no penalty) in February 2025.

Date By Action Violations covered
Feb 6, 2025 California Compliance order (no penalty) 1 violation: Nitrate
Dec 18, 2008 California Compliance order (no penalty) 2 violations (2 health-based): Total Trihalomethanes (TTHMs)
Jan 12, 2007 California Compliance order (no penalty) 8 violations (8 health-based): Total Trihalomethanes (TTHMs), Haloacetic Acids (HAA5)

What the violations mean

LEAD AND COPPER RULE REVISIONS

1 incident

The system did not complete a treatment step or action that the LEAD AND COPPER RULE REVISIONS requires (a treatment technique violation).

The utility had to notify customers about this violation.

Where the water comes from

Lake Don Pedro CSD draws water from 4 wells and 1 surface water intake (3 of them for emergency, seasonal or other part-time use).

Annual water quality report

Lake Don Pedro CSD must give its customers an annual water quality report (Consumer Confidence Report) by July 1, with the levels its tests found in the previous year.

Where the state allows it, systems serving fewer than 10,000 people may publish the report in a local newspaper or news site instead of mailing it, and must provide a copy on request.

Find a posted report with EPA's Consumer Confidence Report search

Testing your own water

To test the water at your tap, or a private well this record does not cover, use a laboratory certified for drinking water by California.

Certified drinking water labs by state EPA guidance for private wells