W Central RWA - Denison Subsys

What EPA’s and Iowa’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: 2,428 people
Connections: 971
Water source: Groundwater bought from another system
Based in: Denison, IA
County: Crawford
Owner: Private

The ZIP code it serves

51432

The short answer

Nothing in EPA’s and Iowa’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

Total trihalomethanes (TTHM) and haloacetic acids (HAA5): Iowa’s own results, samples taken from Aug. 11, 2020 to Aug. 11, 2026, with EPA’s 2012 to 2019 file for earlier years.

Below EPA’s limits2

Total trihalomethanes (TTHM)

Forms or is added in treatment

Below EPA’s limits

59.5ppb

Highest yearly average, 2020 to 2026

2026 average: 52 ppb

Averaged by year, the highest was 59.5 ppb, in 2025, below EPA’s legal limit of 80 ppb. Its highest single sample was 59.5 ppb. In 2026, the latest year on file, its two samples averaged 52 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 45.5 ppb, in 2012.

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

17.9ppb

Highest yearly average, 2020 to 2026

2026 average: 11 ppb

Averaged by year, the highest was 17.9 ppb, in 2024, below EPA’s legal limit of 60 ppb. Its highest single sample was 19.6 ppb. In 2026, the latest year on file, its two samples averaged 11 ppb. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 8.0 ppb, in 2014.

What handles it

No certification claim covers this compound yet.

One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.

Lead

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) and haloacetic acids (HAA5) results here are Iowa’s own from 2020 on, with EPA’s national file for 2012 to 2019. W Central RWA - Denison Subsys’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; Iowa’s results run from Aug. 11, 2020 to Aug. 11, 2026.

Testing your own tap

W Central RWA - Denison Subsys’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 Iowa certifies.

No lab Iowa certifies is within 75 miles of the area W Central RWA - Denison Subsys serves on the state’s list. Some take samples by mail; the state’s page lists them all.

State Hygienic Laboratory at the University of Iowa: Through the Grants-to-Counties program, private well owners in participating counties can have their water tested for total coliform bacteria and nitrate. Start with the county sanitarian at your county health department. No cost in a participating county. The Grants-to-Counties Program, State Hygienic Lab at the University of Iowa.

All 36 certified labs for Iowa