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Massachusetts water profile

Nitrate in Massachusetts community water systems

Massachusetts' nitrate story is Cape Cod: a sandy sole-source aquifer where septic systems supply about four-fifths of the nitrogen, plus a quieter scatter through the suburban stratified-drift valleys. See where the pattern concentrates and what each reporting system measured in the three years from August 9, 2023 to August 9, 2026.

Browse all 465 Massachusetts systems →

Search by the utility or system name shown on a water bill. Example: Town of Falmouth. Private wells are not in this inventory.

88%
of the state’s 526 active community water systems have a current result here
465
systems with a current nitrate result
9,028,348
people served by those reporting systems
2.2%
of reporting systems at or above 5 mg/L
How to read these numbers Each system is placed into a band by its most recent reported result within a rolling three-year window. The bands describe how strongly human activity, read from nitrate, has marked a water source; they are not a safety verdict. Figures describe system reporting, not nitrate measured at an individual tap.

How Massachusetts's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
308 systems · 7,615,977 served
Human impact likely
1.00–2.99 mg/L as N
123 systems · 997,970 served
Human impact clear
3.00–4.99 mg/L as N
24 systems · 362,540 served
Health-study range
5.00–9.99 mg/L as N
10 systems · 51,861 served
Above the federal limit
10.00 mg/L and above
0 systems · 0 served

Each system appears in one band only, placed by its most recent reported result in the current three-year window. Counts sit beside people served so a small number of larger systems cannot hide behind a row of tiny ones. Of the 10 systems reporting 5 mg/L or more, 1 stayed at or above 5 across the whole three-year range; the other 9 reached it only on a high sample and otherwise ran lower.

Most recent reading Jul 2026; the typical system was last tested around Apr 2026. 464 systems sampled their own water; 1 system carries a supplier’s result.

The named systems

Every reading here belongs to a utility with a name

Highest recent readings
SystemMost recent resultBandBased onPeople served
Deerfield Fire District7.01 mg/LApr 2026Health-study range12 samples1,300
Waterview Park Llc6.70 mg/LApr 2026a high point — runs lowerHealth-study range13 samples102
Marshfield Water Department6.70 mg/LJun 2026a high point — runs lowerHealth-study range53 samples34,000
Hamilton Water Dept6.58 mg/LMay 2026a high point — runs lowerHealth-study range15 samples7,377
Old Farm Road Water Trust6.28 mg/LJun 2026Health-study range12 samples40
Orange Water Dept6.25 mg/LJun 2026a high point — runs lowerHealth-study range21 samples6,526
Beechwood Point Condos5.80 mg/LApr 2026a high point — runs lowerHealth-study range11 samples112
Wellfleet Apartments5.50 mg/LApr 2026Health-study range13 samples48
Largest systems
SystemMost recent resultBandBased onPeople served
Mwra0.10 mg/LJun 2026Natural background681 samples2,660,000
Boston Water And Sewer Commission (Mwra)0.43 mg/LNov 2023Natural background2 samples675,647
Worcester Dpwp, Water Supply Division0.09 mg/LMay 2026Natural background3 samples206,518
Springfield Water And Sewer Commission0.13 mg/LOct 2025Natural background4 samples167,954
Cambridge Water Department0.62 mg/LJun 2026Natural background176 samples118,214

Each result shows its date and what it rests on, so a lone sample is never taken for a settled measurement. A single high sample is not a complete account of what a household drinks.

Where higher nitrate concentrates

The Cape and the suburban southeast

Human impact is clear on drinking water served in nine of Massachusetts’s 14 counties. Each is shaded by how many of its systems reported 3.00 mg/L as N or above. Shading counts systems, not severity — a county with many small utilities can outrank one holding a single larger system that reads higher. The table beside the map splits the two bands so that difference stays visible.

MA counties shaded by number of community water systems reporting nitrate at or above 3.00 mg/L as NCounties are shaded by how many community water systems reported nitrate at or above 3.00 mg/L as N in the three years from August 9, 2023 to August 9, 2026. The same counts appear in the table below this map.Franklin County — 0 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or abovePlymouth County — 4 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveBristol County — 2 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveNorfolk County — 5 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveHampden County — 2 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveEssex County — 3 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveWorcester County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveBarnstable County — 3 systems at 3.00–4.99 mg/L as N; 2 systems at 5.00 mg/L as N or aboveMiddlesex County — 4 systems at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or above
none1–23–56–1112–2526+Number of drinking water systems reporting ≥3.00 mg/L NO₃–N per county as of August 9, 2026

Barnstable leads this layer with 2 reporting systems, followed by Franklin, Norfolk, Plymouth. The Cape and the suburban southeast.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Norfolk527
Plymouth426
Barnstable325
Essex314
Middlesex404

Counts use each system's most recent reported result in the current three-year window. A system appears in only one of the two bands.

Find a specific Massachusetts system

What the statewide pattern says

A sole-source aquifer on septic

Massachusetts' documented nitrate center is the Cape Cod sole-source aquifer — roughly 80–85 percent of its nitrogen from septic systems — with a secondary signal in the suburban stratified-drift valleys of the southeast.

Cape Cod is one of the country's clearest septic-nitrate cases. The sandy Cape Cod aquifer is the region's sole drinking-water source, streams barely exist to carry nitrogen away, and about 80 percent of watershed nitrogen enters through septic systems (USGS SIR 2025-5066). Under the aquifer's aerobic conditions nitrate moves conservatively — it does not break down on the way to ponds and estuaries (USGS SIR 2024-5100).

The well record shows it reaching drinking water. Of 5,118 Barnstable County private-well analyses reviewed in the national water summary, 130 equaled or exceeded the 10 mg/L federal limit and 294 more ran 5–10 mg/L, attributed mostly to septic systems and lawn fertilizer (USGS National Water Summary, Massachusetts). On the Cape, nitrate above about 0.5–1 mg/L is itself used as the marker of wastewater impact (Gallagher and others, 2010).

Off-Cape, the map's Norfolk, Plymouth, Essex and Middlesex systems sit in stratified-drift valleys under dense suburbs — permeable sand and gravel with septic and lawn nitrogen on top. USGS describes these coastal aquifers as extremely susceptible to exactly that (USGS Circular 1338).

The supported source reading is septic-system nitrogen first, lawn fertilizer second — not a certified source at any individual system (Nolan and Hitt, 2006).

The general science — how nitrate moves, why some ground is vulnerable, and why the legacy lingers — is laid out with its sources on Where nitrate comes from.

Questions this page answers

What the Massachusetts pattern does—and does not—say

Where does nitrate concentrate in Massachusetts community water systems?

Barnstable leads this layer with 2 reporting systems, followed by Franklin, Norfolk, Plymouth. The Cape and the suburban southeast.

Why is Cape Cod a national nitrate reference case?

Three facts combine: a sole-source sandy aquifer with no alternative supply, almost no streams to carry nitrogen away, and wastewater returned to the ground — about 80 percent of watershed nitrogen arrives via septic systems. Aerobic sand lets nitrate travel unattenuated to ponds, wells and estuaries.

How much nitrate reached Cape Cod's private wells?

In the national water summary's review of 5,118 Barnstable County private-well analyses, 130 wells equaled or exceeded the 10 mg/L federal limit and another 294 ran 5–10 mg/L — attributed mostly to septic systems and lawn fertilizer. On the Cape, anything above roughly 1 mg/L marks human impact.

Does a high public-system result mean a nearby private well is high?

No. It is a local sentinel, not a well-specific result. It shows that nitrogen and a transport pathway have reached groundwater in the area; a certified-lab test is still the only way to know a specific private well.

Sources and provenance

What this page rests on

  1. NitrateSmart inventory: 465 Massachusetts community water systems with a current nitrate result in the three years from August 9, 2023 to August 9, 2026. Figures count people served by reporting systems, not measured tap exposure.
  2. Nolan BT, Hitt KJ (2006). Vulnerability of Shallow Groundwater and Drinking-Water Wells to Nitrate in the United States. Environmental Science & Technology 40(24):7834–7840.
  3. Dubrovsky NM, and others (2010). Nutrients in the Nation's Streams and Groundwater, 1992–2004. USGS Circular 1350.
  4. USGS (2025). Simulated effects of proposed wastewater-management actions in Falmouth, Cape Cod. SIR 2025-5066 — Cape Cod sole-source aquifer; ~80% of watershed nitrogen enters via septic systems.
  5. USGS (2024). Wastewater-derived nitrogen in Cape Cod groundwater. SIR 2024-5100 — conservative nitrate transport under aerobic conditions; septic leaching fields inefficient at nitrogen removal.
  6. USGS National Water Summary 1986 — Massachusetts. Ground-Water Quality summary — of 5,118 Barnstable County private-well analyses, 130 ≥10 mg/L and 294 at 5–10 mg/L.
  7. Gallagher LG, and others (2010). Using residential history and groundwater modeling to examine drinking-water exposure on Cape Cod. Environmental Health Perspectives — nitrate >1 mg/L used as the wastewater-impact marker.