Willowside Terrace Water Association
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
- 100 people
- Connections
- 32
- Water source
- Groundwater
- Based in
- Alpine, CA
- County
- San Diego
- Owner
- Private
- Hardness
- Very hard
The ZIP code it serves
The short answer
1 result is above EPA’s legal limit, and 1 more is above the health goal. The worst: Uranium, above the legal limit. 11 health-based violations since 2016.
What handles itWhat was found
Uranium, arsenic, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5), chromium (total) and fluoride: California’s own results, samples taken from Feb. 4, 2020 to June 16, 2026, with EPA’s 2012 to 2019 file for earlier years.
Above the legal limit1
Uranium
Comes from the source
163ppb
Highest yearly average, 2020 to 2026
2026 average: 127 ppb
Averaged by year, the highest was 163 ppb, in 2024, about 5.4 times EPA’s legal limit of 30 ppb. Its highest single sample was 173 ppb. In 2026, the latest year on file, its two samples averaged 127 ppb, above the limit. EPA recorded violations for uranium at this utility in 2023 and 2024. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.4 ppb, in 2015.
What handles it
- NSF/ANSI 58 look for “Uranium”
Above the health goal1
Arsenic
Comes from the source
6.1ppb
Highest yearly average, 2023 to 2026
Averaged by year, the highest was 6.1 ppb, in 2026: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That was also the latest year on file.
What handles it
- NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
- NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
Below EPA’s limits3
Nitrate
Comes from the source
1.9ppm
Highest sample; found in 11 of 15
2026: not found
The highest sample, in 2020, was 1.9 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 13.7 ppm, in 2018, and EPA recorded violations in 2014, 2015, 2016, 2017 and 2018.
What handles it
- NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
- NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
Total trihalomethanes (TTHM)
Forms or is added in treatment
8.9ppb
Highest yearly average, 2020 to 2025
2025 average: 8.0 ppb
Averaged by year, the highest was 8.9 ppb, in 2023, below EPA’s legal limit of 80 ppb. Its highest single sample was 16 ppb. In 2025, the latest year on file, its two samples averaged 8.0 ppb.
What handles it
- NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
- NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”
Haloacetic acids (HAA5)
Forms or is added in treatment
1.4ppb
Highest yearly average, 2020 to 2025
2025: not found
Averaged by year, the highest was 1.4 ppb, in 2021, below EPA’s legal limit of 60 ppb. In 2025, the latest year on file, it wasn’t found in its one sample.
What handles it
No certification claim covers this compound yet.
3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
- Chromium (total)
- Fluoride
- Lead
What handles it
A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”
- NSF/ANSI 53
Claim: Arsenic (Pentavalent)<=50 ppb Reduction
For: Arsenic
Other certifiers’ wording: Arsenic (III) (50 ppb influent level)
- NSF/ANSI 58
Claims: Uranium, Arsenic (Pentavalent)<=50 ppb Reduction
For: Uranium, Arsenic
Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)
At the tap, or for the whole house?
These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. How whole-house systems compare.
Filters with those claims on a certifier’s listing
Disclosure: TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money
Countertop reverse osmosis
- IAPMO listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 4, 2026
Certified for: Arsenic
Aquasana SmartFlow Reverse Osmosis (AQ-SFRO2)
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic
Brondell Capella RC250 Reverse Osmosis System
Under-sink reverse osmosis
- WQA listing:NSF/ANSI 42NSF/ANSI 53NSF/ANSI 58NSF/ANSI 401checked Oct. 9, 2026
Certified for: Arsenic
Hardness
Very hard, typically 219 mg/L (12.8 grains per gallon), across 2 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
| Contaminant or rule | Type | Period | Measured | Status |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | The required inventory of lead service lines was not completed or submitted on time.EPA: LSL Inventory | Oct. 17, 2024 | — | Unaddressed |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | March 1, 2024 to May 31, 2024 | 107 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Jan. 1, 2024 to March 31, 2024 | 99.7 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | Oct. 1, 2023 to Dec. 31, 2023 | 115 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | July 1, 2023 to Sept. 30, 2023 | 90.9 PCI/L | Archived |
| Combined Uranium | The running average was above the legal limit.EPA: Maximum Contaminant Level Violation, Average | April 1, 2023 to June 30, 2023 | 90.5 PCI/L | Archived |
| Nitrate-Nitrite | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2018 to March 31, 2018 | 13.7 MG/L | Resolved |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | April 1, 2017 to June 30, 2017 | 12.6 MG/L | Resolved |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2017 to March 31, 2017 | 13.3 MG/L | Resolved |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | April 1, 2016 to June 30, 2016 | 12 MG/L | Resolved |
| Nitrate | A sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single Sample | Jan. 1, 2016 to March 31, 2016 | 14.3 MG/L | Resolved |
| Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 3 monitoring or reporting violations not shown. | ||||
What this report can’t tell you
Everything else. Uranium, arsenic, nitrate, total trihalomethanes (TTHM), haloacetic acids (HAA5), chromium (total) and fluoride results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Willowside Terrace Water Association’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 Feb. 4, 2020 to June 16, 2026.
Testing your own tap
The 3 labs California certifies closest to the area Willowside Terrace Water Association serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.
Environmental Laboratory Network, Inc.
San Diego, CA · about 24 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, radioactivity
Metropolitan Solutions
National City, CA · about 25 miles
Certified for bacteria
Analytical Environmental Lab, LLC
San Diego, CA · about 25 miles
Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, disinfection byproducts
Sources
- 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
- Certified labs: California State Water Resources Control Board, ELAP accredited laboratories and their fields of accreditation, read Oct. 17, 2026; distances from the Census 2020 ZIP code tabulation area gazetteer
- Hardness: California State Water Resources Control Board, Division of Drinking Water, results from May 4, 2021 to Dec. 9, 2024, read Oct. 10, 2026
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
PWSID CA3701995. Rebuilt from EPA data on Oct. 18, 2026.
What to do next
- Read up on the 2 results above a lineWhat each one does to health, where it comes from, and the certification claim that addresses it.Start with Uranium
- Get the utility’s own reportWillowside Terrace Water Association 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
- Compare certified filtersWhat the filters certified for these results cost over five years, cartridges included.Compare five-year costs