Yosemite NPS - El Portal
What EPA’s and California’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.
- Serves
- 635 people
- Connections
- 226
- Water source
- Groundwater
- Based in
- Yosemite Np, CA
- County
- Mariposa
- Owner
- Federal government
- Hardness
- Varies by source
The short answer
Nothing in EPA’s and California’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. No health-based violations on file since 2016.
What was found
Copper: EPA’s file records a utility’s copper only when it exceeds the action level. The last here was 1.8 ppm, for the period ending Dec. 31, 2002. None since is on file, so it is not counted as a current finding.
Total trihalomethanes (TTHM), nitrate, haloacetic acids (HAA5), fluoride, arsenic and chromium (total): California’s own results, samples taken from Aug. 20, 2020 to Oct. 16, 2025, with EPA’s 2012 to 2019 file for earlier years.
Below EPA’s limits4
Total trihalomethanes (TTHM)
Forms or is added in treatment
14ppb
Highest yearly average, 2020 to 2025
Averaged by year, the highest was 14 ppb, in 2025, below EPA’s legal limit of 80 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 12 ppb, in 2016.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Nitrate
Comes from the source
0.46ppm
Highest sample; found in 3 of 30
2025 average: 0.078 ppm
The highest sample, in 2020, was 0.46 ppm, below EPA’s legal limit of 10 ppm. In 2025, the latest year on file, its five samples averaged 0.078 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.47 ppm, in 2012.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Haloacetic acids (HAA5)
Forms or is added in treatment
2.5ppb
Highest yearly average, 2020 to 2025
Averaged by year, the highest was 2.5 ppb, in 2025, below EPA’s legal limit of 60 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.0 ppb, in 2019.
What handles it
No certification claim covers this compound yet.
Fluoride
Forms or is added in treatment
0.044ppm
Highest yearly average, 2021 to 2024
2024: not found
Averaged by year, the highest was 0.044 ppm, in 2021, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.22 ppm. In 2024, the latest year on file, it wasn’t found in any of its five samples.
What handles it
- NSF/ANSI 58 look for “Fluoride Reduction”
- NSF/ANSI 53 look for “Fluoride”
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Arsenic
- Chromium (total)
- Lead
Hardness
Soft to moderately hard depending on the source, 34 to 79 mg/L (2 to 4.6 grains per gallon), across 5 sampling points, 2021 to 2024.
Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.
Violations since 2016
No health-based violations on file with EPA since 2016.
What this report can’t tell you
Everything else. Total trihalomethanes (TTHM), nitrate, haloacetic acids (HAA5), fluoride, arsenic and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Yosemite NPS - El Portal’s own annual report, which it must send you every year, has the contaminants this page does not show.
Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.
Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; California’s results run from Aug. 20, 2020 to Oct. 16, 2025.
Testing your own tap
No lab California certifies is within 75 miles of the area Yosemite NPS - El Portal serves on the state’s list. Some take samples by mail; the state’s page lists them all.
All 145 certified labs for CaliforniaSources
- EPA UCMR 5 occurrence data, file of Oct. 15, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q3
- California State Water Resources Control Board, Division of Drinking Water, results from Jan. 1, 2020 to July 17, 2026, read Oct. 8, 2026
- EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, file of Feb. 5, 2024
- Hardness: California State Water Resources Control Board, Division of Drinking Water, results from July 20, 2021 to June 12, 2024, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA2210515. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Nothing here is above a health goalIn EPA’s and California’s records for this utility. They don’t cover everything, which is why the next step matters.Every contaminant TapBuff tracks
- Get the utility’s own reportYosemite NPS - El Portal must send you a water quality report every year. It covers contaminants this page does not show.How to read it
- Test your own tap for leadYour service line, solder and fixtures decide the lead at your faucet, not the utility’s average.Lead in your water: what to do
- Decide if you want a filter at allA filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.NSF/ANSI standards, decoded