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Federal water data

County water report

Calvert County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Calvert County, Maryland.

Water grade

D

Water score

50.0

State rank

#12

of 24

Health violations

6

EPA SDWIS, 5-year lookback

Watershed impaired

48.9%

47 water bodies assessed

Monitoring sites

73

45,513 recent measurements

Live streamflow

No gauge

Primary USGS station not mapped

Water at a glance

Key Water Indicators for Calvert County

EPA SDWIS

Safety Grade

D

Score: 50.0 / 100

EPA SDWIS

Active Violations

6

5-year health-based lookback

EPA ATTAINS

Watershed Health

49% impaired

47 bodies assessed

USGS NWIS

Streamflow Snapshot

No gauge

Primary USGS gauge not mapped

EPA WQP

Monitoring Sites

73

45,513 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

D

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

50.0/100

Health violations

6

Health-based violations

Violations per 100K served

16.6

Population-normalized SDWIS rate

Editorial analysis

Understanding Calvert County’s Water

Drinking Water Quality Overview

EPA SDWIS

Calvert County's drinking water received a D grade, scoring 50.0 out of 100. Over the past five years, EPA SDWIS records 6 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 48.9% of assessed waterways are impaired (23 of 47 water bodies) across Calvert County's watersheds. The leading impairment causes are total suspended solids (tss) and fecal coliform. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Calvert County has extensive coverage with 73 active monitoring sites with 45,513 recent measurements on record. Predominant monitoring categories include physical and nutrient. 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 Calvert County

Water Verdict

Calvert County receives a below-average water quality assessment with a grade of D and a score of 50.0 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Calvert County has recorded 6 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 16.6 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Calvert County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Calvert County's drinking-water compliance score is 50.0 out of 100. The violation rate for Calvert County is 16.6 per 100,000 people served. Residents are encouraged to use an NSF 53 or NSF 58-certified filter for drinking and cooking water until the underlying violations are resolved. Running tap water for 30 seconds before use and avoiding older lead-pipe connections can also reduce exposure risk. The current Consumer Confidence Report from your utility will specify the contaminants of concern. Total Suspended Solids (Tss) is the leading impairment cause in Calvert County's watershed. With 73 active water-quality monitoring sites in Calvert County, data coverage is strong.

Regional Context

Calvert County has water quality close to the average county in Maryland. Its water score is within 0.5 points of the state average, meaning its overall water system performance is broadly representative of Maryland as a whole.

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 Calvert County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Total Suspended Solids (Tss)

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

  • 2

    Fecal coliform bacteria

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

  • 3

    Phosphorus (excess nutrients)

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Calvert County

EPA How's My Waterway

Interactive watershed health data for Calvert County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Calvert County

Consumer Confidence Reports (MD)

Annual water quality reports from utilities in Maryland

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

48.9%

23 of 47 assessed

Moderate concern

Top Impairment Causes

  • 1

    TOTAL SUSPENDED SOLIDS (TSS)

  • 2

    FECAL COLIFORM

  • 3

    PHOSPHORUS, TOTAL

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

73

Active in the past 5 years

Measurements Recorded

46K

45,513 total readings

Most Measured

  • Physical
  • Nutrient
  • Microbiological

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).

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 Calvert 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 Calvert County, Maryland?
Calvert County, Maryland has a drinking-water quality grade of D with a score of 50.0/100, based on EPA SDWIS compliance data. The county has 6 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 Calvert County?
Calvert County has 6 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 Calvert County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 48.9% of Calvert County's 47 assessed water bodies are classified as impaired (23 impaired). The top reported causes are TOTAL SUSPENDED SOLIDS (TSS), FECAL COLIFORM, PHOSPHORUS, TOTAL. 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 Calvert County?
EPA's Water Quality Portal records 45,513 measurements from 73 monitoring sites in Calvert County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Microbiological. 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.
How does Calvert County water compare to the Maryland average?
Calvert County's SDWIS water quality score of 50.0/100 is lower than the Maryland state average of 50.5. The average water quality grade across Maryland is D, based on data from 24 counties with available SDWIS data.
Is tap water safe to drink in Calvert County?
Based on EPA SDWIS data, Calvert County has a water quality grade of D (50.0/100). 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 Calvert County have so many water violations?
Calvert County has 6 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 Calvert County rank for water quality in Maryland?
Calvert County ranks #12 out of 24 counties in Maryland by SDWIS water quality score (1 = best). With a score of 50.0/100, it falls in the middle 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

Allegany County

Maryland

D

48.6

Water score

Dorchester County

Maryland

D

47.7

Water score

Worcester County

Maryland

D

46.7

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.

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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