waterbycounty
Compiled federal source snapshot

Massachusetts Water Quality

Drinking water data for all 14 counties.

Avg SDWIS Compliance Index

72.2

Most Common Five-Year SDWIS Compliance Band

A

Counties with Data

14

of 14 total

County water atlas

Massachusetts water signals by county

A state-level 2.5D view across drinking-water compliance, watershed impairment, monitoring density, and streamflow snapshot context. Pin any county, switch layers, then use the lens controls to compare index ranges, recorded violation rates, or impaired watersheds without leaving the page.

Counties

14

Avg SDWIS index

72.2

Watersheds

0

ATTAINS counties

Monitoring

14

11 fresh USGS snapshots

State atlas layers combine EPA SDWIS health-based violations, EPA ATTAINS 303(d) impairment assessments, EPA Water Quality Portal monitoring sites, and representative USGS NWIS streamflow gauges. Streamflow values appear only for fresh pipeline snapshots, not as a continuously updated stream. County pages include the observation time and year.

Prepared by ByCounty Editorial TeamPublished by WaterByCounty

Multi-source coverage in Massachusetts

Beyond Drinking Water

EPA SDWIS

14/ 14

counties with drinking-water compliance data

69 health violations statewide (5yr)

EPA ATTAINS

—

No §303(d) assessments yet for Massachusetts

EPA WQP

2,827

monitoring sites across 14 counties

366,541 total readings (5yr window)

USGS NWIS

11

counties with a fresh pipeline snapshot

1 above9 below

State atlas notes

What stands out in Massachusetts

County water quality is not one number. The strongest read comes from comparing drinking-water compliance against watershed impairment, monitoring density, and streamflow context. Use these signals as a starting point, then open any county profile for source-level detail.

Compliance spread

Dukes County has the highest value in the published state SDWIS Compliance Index table at 86.2/100, while Franklin County has the lowest at 60.5/100. That is a 25.7 point gap inside one state.

Zero health violations

3

3+ health violations

7

Monitoring hubs

Barnstable County1,168 sitesPlymouth County374 sitesEssex County282 sites

Lowest flow reads

Essex County22%Franklin County30%Norfolk County31%

Highest fresh streamflow pipeline snapshots: Hampshire County (253%, observation 2026), Berkshire County (102%, observation 2026), Plymouth County (81%, observation 2026). These are source-data observations, not household tap-water conclusions.

All Massachusetts Counties

CountySDWIS Compliance Index
Dukes County86.2
Nantucket County86.2
Suffolk County86.2
Barnstable County71.7
Hampshire County70.3
Essex County69.8
Berkshire County69.3
Hampden County69.3
Middlesex County69.3
Bristol County68.8
Norfolk County68.2
Plymouth County67.4
Worcester County66.9
Franklin County60.5

Frequently Asked Questions

Which Massachusetts county has the highest SDWIS Compliance Index?
Dukes County has the highest SDWIS Compliance Index in the published Massachusetts cohort at 86.2/100. This WaterByCounty relative comparison is not an EPA score and does not establish current conditions for a utility or address.
What does the Five-Year SDWIS Compliance Band mean?
The band is derived only from each county aggregation's recorded health-violation rate per 100,000 people served for the stated five-year source window. It is separate from the relative SDWIS Compliance Index and is not a current determination for a specific utility or address.
Which USGS streamflow records are shown across Massachusetts?
WaterByCounty has 11 fresh USGS pipeline snapshots in the published Massachusetts cohort. Each county page shows its observation timestamp and year. A pipeline snapshot is not a continuously updated reading or a tap-water safety measure.
Where can Massachusetts residents find current official information?
Review the applicable utility's Consumer Confidence Report, active notices, and the state drinking-water agency. WaterByCounty's county-level historical aggregations do not establish the current status of a specific utility, address, private well, or household plumbing system.
What does Water Quality Portal monitoring volume show in Massachusetts?
The published county records contain 366,541 results from 2,827 monitoring locations in the site's five-year aggregation. Monitoring volume does not by itself indicate better or worse water quality.

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. The WaterByCounty SDWIS Compliance Index reflects the recorded rate and is not an EPA score.

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.

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