Oakdale Waterworks

What EPA’s and Wisconsin’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: 317 people
Connections: 140
Water source: Groundwater
Based in: Oakdale, WI
County: Monroe
Owner: Local government
Hardness: Moderately hard

The ZIP code it serves

54660

The short answer

Nothing in EPA’s and Wisconsin’s records for this utility is above a health goal. That covers nitrate, arsenic and other regulated chemicals, plus lead and copper, not everything. 1 health-based violation since 2016.

What was found

Haloacetic acids (HAA5), total trihalomethanes (TTHM), fluoride, nitrate, arsenic and chromium (total): Wisconsin’s own results, samples taken from Sept. 19, 2020 to Aug. 12, 2026, with EPA’s 2012 to 2019 file for earlier years.

Below EPA’s limits4

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

22ppb

Highest yearly average, 2022 to 2025

Averaged by year, the highest was 22 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 9.9 ppb, in 2016.

What handles it

No certification claim covers this compound yet.

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

9.3ppb

Highest yearly average, 2022 to 2025

2025, one sample: 9.0 ppb

Averaged by year, the highest was 9.3 ppb, in 2022, below EPA’s legal limit of 80 ppb. In 2025, the latest year on file, its one sample was 9.0 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 5.2 ppb, in 2013.

What handles it

NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.1ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.04 ppm

Averaged by year, the highest was 0.1 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.04 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.12 ppm, in 2014.

What handles it

NSF/ANSI 58 look for “Fluoride Reduction”
NSF/ANSI 53 look for “Fluoride”

Nitrate

Comes from the source

Below EPA’s limits

0.21ppm

Highest sample; found in 7 of 7

2026, one sample: 0.21 ppm

The highest sample, in 2025, was 0.21 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 0.21 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 0.078 ppm, in 2019.

What handles it

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

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

Moderately hard, 118 mg/L (6.9 grains per gallon), at its one sampling point, 2017 to 2026.

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 6.9 grains per gallon, salt included Softener or salt-free conditioner?Wisconsin water hardness, utility by utility

Violations since 2016

Contaminant or rule	Type	Period	Measured	Status
Stage 1 Disinfectants and Disinfection Byproducts Rule	Treatment was not run by a certified operator as required.EPA: Treatment Technique No Certif. Operator	Aug. 2, 2025	—	Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 1 monitoring or reporting violation not shown.

What this report can’t tell you

Everything else. Haloacetic acids (HAA5), total trihalomethanes (TTHM), fluoride, nitrate, arsenic and chromium (total) results here are Wisconsin’s own from 2020 on, with EPA’s national file for 2012 to 2019. Oakdale Waterworks’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; Wisconsin’s results run from Sept. 19, 2020 to Aug. 12, 2026.

Testing your own tap

Oakdale Waterworks’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 Wisconsin certifies.

The 3 labs Wisconsin certifies closest to the area Oakdale Waterworks serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

Monroe County Health Department
Sparta, WI · about 15 miles
Certified for bacteria
(608) 269-8666
Jackson County Public Health Water Lab
Black River Falls, WI · about 25 miles
Certified for bacteria, nitrate
(715) 284-4301
A1 Advanced Pumping Service, Inc.
West Salem, WI · about 30 miles
Certified for bacteria, nitrate
(608) 784-1888

Wisconsin State Laboratory of Hygiene: Well water test kits ordered by phone and shipped free; you pay to mail the sample back, and the lab bills you after testing. Tests run from bacteria alone to a homeowner package covering bacteria, nitrate, fluoride, metals, hardness, volatile organic compounds and atrazine. Bacteria is $35, nitrate $35, lead $38, and the homeowner package $450, as of July 1, 2026. Public Environmental and Water Testing Prices, Wisconsin State Laboratory of Hygiene.

All 156 certified labs for Wisconsin