Is Twain Harte Valley Mwc Tap Water Safe? Quality Report

Water source: Surface water
Ownership: Private
Counties served: Tuolumne

Compliance record

Formal violations the EPA has on file for this supplier. A health-based violation means a contaminant limit or a required treatment was breached; the rest are monitoring or reporting failures — still violations, but not a measured health risk.

health-based violations

violations on file

still open

Violation	Type	Status	Period
TT	Health-based	Unaddressed	2024-10-17
RPT	Monitoring	Unaddressed	2025-07-02
MON	Monitoring	Resolved	2025-04-01 → 2025-05-31
MON	Monitoring	Resolved	2025-04-01 → 2025-05-31
RPT	Monitoring	Unaddressed	2024-10-17
Other	Monitoring	Archived	1984-09-01 → 1984-09-30
Other	Monitoring	Archived	1984-08-01 → 1984-08-31
Other	Monitoring	Archived	1984-07-01 → 1984-07-31
Other	Monitoring	Archived	1984-06-01 → 1984-06-30
Other	Monitoring	Archived	1984-05-01 → 1984-05-31

Other contaminants detected

Each bar shows the measured level as a share of the EPA limit: green is well under, amber is close to it, red is over. For lead and copper the limit applies to exactly the 90th-percentile figure shown, so red there means a real exceedance. For everything else the limit applies to a running annual average while the figure is the 95th percentile of this system's samples — over 100% is worth reading, but is not by itself a violation. Where a single sample came in higher than that percentile, it is noted under the bar. Formal violations are listed separately.

Contaminant	Level vs EPA limit	Detection rate	Source	Period
Chloroform	60.23 µg/L No EPA limit set worst single sample: 72.9 µg/L	23/23	SYR4	2014–2019
Dichloroacetic Acid	18.09 µg/L No EPA limit set worst single sample: 18.3 µg/L	23/23	SYR4	2014–2019
TTHM	61.04 µg/L 76% of the EPA limit 80 µg/L worst single sample: 74.3 µg/L	23/23	SYR4	2014–2019
Total Haloacetic Acids (HAA5)	47.51 µg/L 79% of the EPA limit 60 µg/L worst single sample: 48.2 µg/L	23/23	SYR4	2014–2019
Trichloroacetic Acid	29.25 µg/L No EPA limit set worst single sample: 30.5 µg/L	23/23	SYR4	2014–2019
Bromodichloromethane	1.872 µg/L No EPA limit set worst single sample: 2.08 µg/L	14/23	SYR4	2014–2019
Lead	0.0 mg/L 0% of the EPA limit 0.0150 mg/L	10/10	LCR	2023
Monochloroacetic Acid	3.413 µg/L No EPA limit set worst single sample: 3.59 µg/L	7/23	SYR4	2014–2019
Monobromoacetic Acid	10.7 µg/L No EPA limit set	1/23	SYR4	2014–2019

17 contaminants tested, none detected

Antimony, TotalArsenicBariumBeryllium, TotalBromoformCopperCadmiumChromiumDibromoacetic AcidDibromochloromethaneFluorideLeadMercuryNitrateNitriteSeleniumThallium, Total

Utility contact

Contact: GAST, SEAN
Phone: 209-770-6265
Email: gastsean@yahoo.com

Frequently asked questions about Twain Harte Valley Mwc

Is Twain Harte Valley Mwc tap water safe to drink?

EPA monitoring detected 9 contaminants in Twain Harte Valley Mwc's water. A detection isn't the same as a violation — most levels are within federal limits. See each level and source above, and the utility's annual Consumer Confidence Report for its official compliance status.

What contaminants were detected in Twain Harte Valley Mwc's water?

EPA monitoring detected Chloroform, Dichloroacetic Acid, TTHM, Total Haloacetic Acids (HAA5), Trichloroacetic Acid, and others. The full list with the level and data source for each is above.

How many people does Twain Harte Valley Mwc serve?

Twain Harte Valley Mwc reports serving 202 people in California, per its EPA record.

Has Twain Harte Valley Mwc had any water quality violations?

The EPA has 31 violations on file for Twain Harte Valley Mwc, of which 1 is health-based (a contaminant limit or required treatment was breached) and 3 remain open. The rest are monitoring or reporting failures.

Where does this data come from?

Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.