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Federal water data

County water report

LaSalle County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for LaSalle County, Illinois.

Water grade

F

Water score

15.3

State rank

#98

of 102

Health violations

182

EPA SDWIS, 5-year lookback

Watershed impaired

42.7%

681 water bodies assessed

Monitoring sites

31

11,610 recent measurements

Live streamflow

73%

ILLINOIS RIVER AT MARSEILLES, IL

Water at a glance

Key Water Indicators for LaSalle County

EPA SDWIS

Safety Grade

F

Score: 15.3 / 100

EPA SDWIS

Active Violations

182

5-year health-based lookback

EPA ATTAINS

Watershed Health

43% impaired

681 bodies assessed

USGS NWIS

Streamflow Snapshot

73% of mean

ILLINOIS RIVER AT MARSEILLES, IL

EPA WQP

Monitoring Sites

31

11,610 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

F

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

15.3/100

Health violations

182

Health-based violations

Violations per 100K served

193.2

Population-normalized SDWIS rate

Editorial analysis

Understanding LaSalle County’s Water

Drinking Water Quality Overview

EPA SDWIS

LaSalle County's water systems carry a failing grade, scoring 15.3 out of 100. Over the past five years, EPA SDWIS records 182 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 substantial 42.7% of assessed waterways are impaired (291 of 681 water bodies) across LaSalle County's watersheds. The leading impairment causes are phosphorus, total and mercury. 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 2026-05-14T12:45:00.000-06:00) puts ILLINOIS RIVER at 7.9k cfs — running somewhat below its historical average at 73% 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. LaSalle County has moderate coverage with 31 active monitoring sites with 11,610 recent measurements on record. Predominant monitoring categories include physical and inorganics, minor, metals. 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 LaSalle County

Water Verdict

LaSalle County receives a poor water quality assessment with a grade of F and a score of 15.3 out of 100. The water supply has documented quality issues. Residents are strongly encouraged to use filtered or bottled water for drinking and to stay informed about utility improvement plans.

Violation Context

LaSalle County has recorded 182 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 193.2 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

LaSalle County has a Grade F compliance record with 182 health-based violations — among the highest levels in the country. LaSalle County's drinking-water compliance score is 15.3 out of 100. Residents are strongly advised to use a certified NSF 58 reverse-osmosis filter or bottled water for all drinking and cooking until violations are corrected. Contacting the Illinois Department of Environmental Quality or Health can expedite utility compliance action. Phosphorus, Total is the leading impairment cause in LaSalle County's watershed. With 31 active water-quality monitoring sites in LaSalle County, data coverage is strong. A pipeline streamflow snapshot from the ILLINOIS RIVER gauge is also available on this page.

Regional Context

LaSalle County has poorer water quality than the average county in Illinois. Its water score is 32.5 points lower than the state average, suggesting more challenges with contamination control or infrastructure than 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 LaSalle County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Phosphorus (excess nutrients)

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

  • 2

    Mercury

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

  • 3

    Total Suspended Solids (Tss)

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for LaSalle County

EPA How's My Waterway

Interactive watershed health data for LaSalle County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for LaSalle County

Consumer Confidence Reports (IL)

Annual water quality reports from utilities in Illinois

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

42.7%

291 of 681 assessed

Moderate concern

Top Impairment Causes

  • 1

    PHOSPHORUS, TOTAL

  • 2

    MERCURY

  • 3

    TOTAL SUSPENDED SOLIDS (TSS)

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

31

Active in the past 5 years

Measurements Recorded

12K

11,610 total readings

Most Measured

  • Physical
  • Inorganics, Minor, Metals
  • Organics, Other

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

7,860cfs

May 14, 6:45 PM UTC

vs Long-Term Average

73%

Below typical

Primary Streamgage

ILLINOIS RIVER AT MARSEILLES, IL

USGS site
05543500
Drainage area
8,259 sq mi
Long-term mean
10.8K 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.

Free tool

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 LaSalle 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 LaSalle County, Illinois?
LaSalle County, Illinois has a drinking-water quality grade of F with a score of 15.3/100, based on EPA SDWIS compliance data. The county has 182 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 LaSalle County?
LaSalle County has 182 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 LaSalle County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 42.7% of LaSalle County's 681 assessed water bodies are classified as impaired (291 impaired). The top reported causes are PHOSPHORUS, TOTAL, MERCURY, TOTAL SUSPENDED SOLIDS (TSS). 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 LaSalle County?
EPA's Water Quality Portal records 11,610 measurements from 31 monitoring sites in LaSalle County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Minor, Metals, Organics, Other. 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 LaSalle County right now?
LaSalle County's primary USGS streamgage on the ILLINOIS RIVER has a pipeline snapshot of 7,860 cubic feet per second — 73% of the long-term mean of 10,826.45 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.
How does LaSalle County water compare to the Illinois average?
LaSalle County's SDWIS water quality score of 15.3/100 is lower than the Illinois state average of 47.8. The average water quality grade across Illinois is D, based on data from 102 counties with available SDWIS data.
Is tap water safe to drink in LaSalle County?
Based on EPA SDWIS data, LaSalle County has a water quality grade of F (15.3/100). This indicates below-average compliance with significant violations. Residents may want to consider home water filtration or independent testing. 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).
Why does LaSalle County have so many water violations?
LaSalle County has 182 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.
How does LaSalle County rank for water quality in Illinois?
LaSalle County ranks #98 out of 102 counties in Illinois by SDWIS water quality score (1 = best). With a score of 15.3/100, it falls in the bottom 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

Wayne County

Illinois

F

15.4

Water score

Johnson County

Illinois

F

15.8

Water score

Macoupin County

Illinois

F

16.5

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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