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Riverdale Park Tract CSD

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
610 people
Connections
180
Water source
Groundwater
Based in
Modesto, CA
County
Stanislaus
Owner
Private
Hardness
Very hard
The ZIP code it serves

95358

The short answer

1 result is above EPA’s legal limit, and 3 more are above the health goal. The worst: Uranium, above the legal limit. 4 health-based violations since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2015 to 2024.

Uranium, nitrate, arsenic, total trihalomethanes (TTHM), haloacetic acids (HAA5), fluoride and chromium (total): California’s own results, samples taken from Feb. 3, 2020 to June 2, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the legal limit1

Uranium

Comes from the source

Above the legal limit

31.3ppb

Highest yearly average, 2020 to 2026

2026 average: 29.8 ppb

Averaged by year, the highest was 31.3 ppb, in 2021, above EPA’s legal limit of 30 ppb. Its highest single sample was 35.8 ppb. In 2026, the latest year on file, its two samples averaged 29.8 ppb. EPA recorded a violation for uranium at this utility in 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 35.8 ppb, in 2014, and EPA recorded violations in 2015 and 2016.

What handles it

Above the health goal3

Nitrate

Comes from the source

Above the health goal

13ppm

Highest sample; found in 28 of 28

2026 average: 11 ppm

From 2023 to 2026, five samples were above EPA’s legal limit of 10 ppm, the highest 13 ppm in 2026. The next sample at the same point, within 30 days, kept the average above the limit for one; two came back under and two have no follow-up sample on file within 30 days. 10 ppm is also EPA’s health goal. That was also the latest year on file, and its three samples averaged 11 ppm, above the limit. EPA recorded no violation for nitrate at this utility since 2020. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 10.1 ppm, in 2013.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Arsenic

Comes from the source

Above the health goal

7.2ppb

Highest yearly average, 2020 to 2023

Averaged by year, the highest was 7.2 ppb, in 2023: below EPA’s legal limit of 10 ppb, but above its health goal of zero. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 5.8 ppb, in 2017.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Lead

Comes from pipes, often your own

Above the health goal

5.0ppb

90th percentile, 2022 to 2024

In the latest period, 9 in 10 homes sampled were at or below 5.0 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits3

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

24ppb

Highest yearly average, 2020 to 2023

2023: not found

Averaged by year, the highest was 24 ppb, in 2022, below EPA’s legal limit of 80 ppb. In 2023, the latest year on file, it wasn’t found in its one sample.

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

Below EPA’s limits

6.8ppb

Highest yearly average, 2020 to 2023

2023: not found

Averaged by year, the highest was 6.8 ppb, in 2022, below EPA’s legal limit of 60 ppb. In 2023, the latest year on file, it wasn’t found in its one sample.

What handles it

No certification claim covers this compound yet.

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.14ppm

Highest yearly average, 2020 to 2023

2023, one sample: 0.13 ppm

Averaged by year, the highest was 0.14 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2023, the latest year on file, its one sample was 0.13 ppm.

What handles it

One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)

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

    Claims: Nitrate/Nitrite (30 ppm challenge), Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Nitrate, Arsenic, Lead

    Other certifiers’ wording: Arsenic (III) (50 ppb influent level)

  • NSF/ANSI 58

    Claims: Uranium, Nitrate/Nitrite Reduction, Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Uranium, Nitrate, Arsenic, Lead

    Other certifiers’ wording: Nitrate; Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. 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

Compare five-year costs

The best reverse osmosis systems, ranked

The best water filters for lead, ranked

Hardness

Very hard, 196 mg/L (11.4 grains per gallon), at its one sampling point, 2020 to 2023.

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.

Softeners compared at 11.4 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageOct. 1, 2020 to Dec. 31, 202021 PCI/LArchived
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2016 to Sept. 30, 201621 PCI/LArchived
Combined UraniumA sample was above the legal limit, for a contaminant judged one sample at a time.EPA: Maximum Contaminant Level Violation, Single SampleApril 1, 2016 to June 30, 201621 PCI/LArchived
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2016 to March 31, 201622 PCI/LArchived
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 2 monitoring or reporting violations not shown.

What this report can’t tell you

  • Everything else. Uranium, nitrate, arsenic, total trihalomethanes (TTHM), haloacetic acids (HAA5), fluoride and chromium (total) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. Riverdale Park Tract CSD’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. 3, 2020 to June 2, 2026.

Testing your own tap

Riverdale Park Tract CSD’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab California certifies.

The 3 labs California certifies closest to the area Riverdale Park Tract CSD serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Institute of Environmental Health, Inc. dba IEH-JL Analytical

    Modesto, CA · about 7 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (209) 538-8111

  • Aemtek, Inc.

    Modesto, CA · about 9 miles

    Certified for bacteria

    (510) 979-1979

  • Certified Laboratories - Turlock

    Turlock, CA · about 15 miles

    Certified for bacteria

    (209) 664-1100

All 145 certified labs for California

Sources

PWSID CA5000019. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Stanislaus County

All California utilities

What to do next