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County water report

St. Croix County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for St. Croix County, Wisconsin.

Water grade

C

Water score

53.8

State rank

#16

of 71

Health violations

5

EPA SDWIS, 5-year lookback

Watershed impaired

5.1%

370 water bodies assessed

Monitoring sites

69

6,979 recent measurements

Live streamflow

87%

APPLE RIVER ABOVE 05341499 AT PARK IN SOMERSET, WI

Water at a glance

Key Water Indicators for St. Croix County

EPA SDWIS

Safety Grade

C

Score: 53.8 / 100

EPA SDWIS

Active Violations

5

5-year health-based lookback

EPA ATTAINS

Watershed Health

5% impaired

370 bodies assessed

USGS NWIS

Streamflow Snapshot

87% of mean

APPLE RIVER ABOVE 05341499 AT PARK IN SOMERSET, WI

EPA WQP

Monitoring Sites

69

6,979 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

C

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

53.8/100

Health violations

5

Health-based violations

Violations per 100K served

11.5

Population-normalized SDWIS rate

Editorial analysis

Understanding St. Croix County’s Water

Drinking Water Quality Overview

EPA SDWIS

St. Croix County's drinking water earned a C grade, scoring 53.8 out of 100. Over the past five years, EPA SDWIS records 5 health-based violations — a pattern that public water utilities are required to disclose and correct.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). A small share — 5.1% — of assessed waterways are impaired (19 of 370 water bodies) across St. Croix County's watersheds. The leading impairment causes are phosphorus, total and polychlorinated biphenyls (pcbs). Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T14:00:00.000-05:00) puts APPLE RIVER ABOVE 05341499 at 368.0 cfs — running somewhat below its historical average at 87% of mean. Streamflow is a leading indicator of drought stress, sediment load, and dilution capacity: low flows concentrate pollutants and warm water temperatures, stressing aquatic life and, in surface-water-dependent systems, the source water quality for treatment plants.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. St. Croix County has extensive coverage with 69 active monitoring sites with 6,979 recent measurements on record. Predominant monitoring categories include physical and organics, pesticide. More monitoring sites generally indicate greater scientific attention to local water conditions — and provide the baseline data that regulators use to set future impairment listings.

Editorial advisory

What the data suggests for St. Croix County

Water Verdict

St. Croix County receives a below-average water quality assessment with a grade of C and a score of 53.8 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

St. Croix County has recorded 5 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 11.5 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Tap water in St. Croix County meets baseline standards but the compliance record shows room for improvement, with a Grade C rating. St. Croix County's drinking-water compliance score is 53.8 out of 100. The violation rate for St. Croix County is 11.5 per 100,000 people served. Residents who are immunocompromised, pregnant, or have young children may benefit from using an NSF 53-certified filter. Contacting your local utility for the current Consumer Confidence Report will confirm which specific violations were recorded and whether they have been resolved. Phosphorus, Total is the leading impairment cause in St. Croix County's watershed. With 69 active water-quality monitoring sites in St. Croix County, data coverage is strong. A pipeline streamflow snapshot from the APPLE RIVER ABOVE 05341499 gauge is also available on this page.

Regional Context

St. Croix County has better water quality than the average county in Wisconsin. Its water score is 14.3 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Advisory text summarizes county-level public records and is not a replacement for your utility's current Consumer Confidence Report or direct local notices.

Contaminants & Resources

Key issues flagged in St. Croix County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Phosphorus (excess nutrients)

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 2

    Polychlorinated Biphenyls (Pcbs)

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 3

    E. coli (bacteria)

    Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for St. Croix County

EPA How's My Waterway

Interactive watershed health data for St. Croix County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for St. Croix County

Consumer Confidence Reports (WI)

Annual water quality reports from utilities in Wisconsin

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

5.1%

19 of 370 assessed

Mostly healthy

Top Impairment Causes

  • 1

    PHOSPHORUS, TOTAL

  • 2

    POLYCHLORINATED BIPHENYLS (PCBS)

  • 3

    ESCHERICHIA COLI (E. COLI)

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state; counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

69

Active in the past 5 years

Measurements Recorded

7.0K

6,979 total readings

Most Measured

  • Physical
  • Organics, Pesticide
  • Nutrient

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

368cfs

May 14, 7:00 PM UTC

vs Long-Term Average

87%

Below typical

Primary Streamgage

APPLE RIVER ABOVE 05341499 AT PARK IN SOMERSET, WI

USGS site
05341498
Drainage area
545 sq mi
Long-term mean
422 cfs

One representative streamgage (the one with the largest drainage area in the county). Many counties have multiple gauges; this view summarizes the primary one. The long-term mean is the full-record annual average; the percent-of-typical value compares the latest reading against that average.

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Estimate Your Water Costs

Water Cost Estimate

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for St. Croix County:C — Moderate

Some violations or watershed impairment detected.

Estimates use the national average residential water rate ($0.0068/gal, EPA/AWWA 2023) and EPA WaterSense per-person consumption baseline (75 gal/person/day). Actual bills vary by utility, usage tier, and local infrastructure fees. For informational purposes only.

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Frequently Asked Questions

What is the water quality in St. Croix County, Wisconsin?
St. Croix County, Wisconsin has a drinking-water quality grade of C with a score of 53.8/100, based on EPA SDWIS compliance data. The county has 5 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and streamflow snapshots are reported separately on this page.
Are there any water violations in St. Croix County?
St. Croix County has 5 health-based drinking water violations recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.
How healthy are the watersheds in St. Croix County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 5.1% of St. Croix County's 370 assessed water bodies are classified as impaired (19 impaired). The top reported causes are PHOSPHORUS, TOTAL, POLYCHLORINATED BIPHENYLS (PCBS), ESCHERICHIA COLI (E. COLI). Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in St. Croix County?
EPA's Water Quality Portal records 6,979 measurements from 69 monitoring sites in St. Croix County over the past five years. The most frequently measured characteristic groups are Physical, Organics, Pesticide, Nutrient. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
What's happening with rivers in St. Croix County right now?
St. Croix County's primary USGS streamgage on the APPLE RIVER ABOVE 05341499 has a pipeline snapshot of 368 cubic feet per second — 87% of the long-term mean of 421.6 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.
How does St. Croix County water compare to the Wisconsin average?
St. Croix County's SDWIS water quality score of 53.8/100 is higher than the Wisconsin state average of 39.5. The average water quality grade across Wisconsin is F, based on data from 71 counties with available SDWIS data.
Is tap water safe to drink in St. Croix County?
Based on EPA SDWIS data, St. Croix County has a water quality grade of C (53.8/100). This indicates moderate compliance. Some violations have been recorded but overall standards are maintained. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Does St. Croix County have clean drinking water?
St. Croix County has 5 health-based drinking water violations according to EPA records. With a water quality score of 53.8/100 and grade C, the county's drinking water has had some compliance issues but continues to be monitored. Note: drinking-water compliance speaks to the public water system, not necessarily to the watershed itself — check the Watershed Health zone for ATTAINS §303(d) data.
How does St. Croix County rank for water quality in Wisconsin?
St. Croix County ranks #16 out of 71 counties in Wisconsin by SDWIS water quality score (1 = best). With a score of 53.8/100, it falls in the top third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Eau Claire County

Wisconsin

C

53.6

Water score

Manitowoc County

Wisconsin

C

51.8

Water score

Chippewa County

Wisconsin

C

56.0

Water score

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments, state-reported and EPA-finalized.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP), federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Live streamflow from the USGS National Water Information System (NWIS), continuous discharge measurements from the largest-drainage gauge in each county, compared against the full-record long-term annual mean.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

By Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

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