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Maine water profile

Nitrate in Maine community water systems

Maine's nitrate has an address: Aroostook County, the state's potato belt, where most of the higher-reporting systems sit on sandy glacial outwash under intensive cultivation. 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 376 Maine systems →

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

98%
of the state’s 385 active community water systems have a current result here
376
systems with a current nitrate result
687,460
people served by those reporting systems
1.9%
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 Maine's systems fall across the five bands

Most systems report below 3 mg/L

Natural background
0.00–0.99 mg/L as N
297 systems · 601,939 served
Human impact likely
1.00–2.99 mg/L as N
62 systems · 78,368 served
Human impact clear
3.00–4.99 mg/L as N
10 systems · 5,341 served
Health-study range
5.00–9.99 mg/L as N
7 systems · 1,812 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 7 systems reporting 5 mg/L or more, every one of them stayed at or above 5 across its whole three-year range.

Most recent reading Dec 2025; the typical system was last tested around Apr 2025.

The named systems

Every reading here belongs to a utility with a name

Highest recent readings
SystemMost recent resultBandBased onPeople served
Limestone Water & Sewer District7.88 mg/LApr 2025Health-study rangeCCR summary, unverified875
322 Roosevelt Trail7.04 mg/LMay 2025Health-study rangeCCR summary, unverified46
Pleasant Ridge6.98 mg/LJan 2025Health-study rangeCCR summary, unverified45
Windermere Apartments6.81 mg/LSep 2025Health-study rangeCCR summary, unverified50
Windswept Estates Mh Park6.07 mg/LJul 2025Health-study rangeCCR summary, unverified75
Washburn Water & Sewer District5.20 mg/LHealth-study rangeCCR summary, unverified688
Lynns Way5.00 mg/LDec 2025Health-study rangeCCR summary, unverified33
Havasu Pines Mhp4.97 mg/LNov 2025Human impact clearCCR summary, unverified75
Largest systems
SystemMost recent resultBandBased onPeople served
Portland Water District-Greater0.05 mg/LNatural background*1 sample135,068
Maine Water Company Biddeford Saco Div0.25 mg/LNatural background*1 sample42,508
Kennebunk, Kennebunkport & Wells Wd0.25 mg/LNatural background*1 sample35,663
Bangor Water District0.01 mg/LNatural background*1 sample27,298
Lewiston Water & Sewer Division0.05 mg/LNatural background*1 sample23,720

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

Higher results gather in potato country

Human impact is clear on drinking water served in five of Maine’s 16 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.

ME 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.Aroostook County — 5 systems at 3.00–4.99 mg/L as N; 4 systems at 5.00 mg/L as N or aboveYork County — 1 system at 3.00–4.99 mg/L as N; 0 systems at 5.00 mg/L as N or aboveSomerset County — 1 system at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or aboveCumberland County — 0 systems at 3.00–4.99 mg/L as N; 1 system at 5.00 mg/L as N or abovePenobscot County — 3 systems at 3.00–4.99 mg/L as N; 1 system 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

Aroostook leads this layer with 4 reporting systems, followed by Cumberland, Penobscot, Somerset. Higher results gather in potato country.

Counties with the most systems at or above 3 mg/L as N
County3–4.99≥5Total ≥3
Aroostook549
Penobscot314
Somerset112
Cumberland011
York101

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 Maine system

What the statewide pattern says

The potato belt on sandy outwash

Maine's nitrate signal concentrates in Aroostook County — the state's dominant agricultural county, growing potatoes on permeable glacial soils — with a thin scatter elsewhere.

Aroostook County grows about 90 percent of Maine's roughly 47,000 acres of potatoes, the state's most valuable agricultural commodity (University of Maine Cooperative Extension). Potato production is nitrogen-intensive and the county sits on sandy glacial outwash and till — the combination the national vulnerability work ties to elevated nitrate (Nolan and Hitt, 2006).

The state has known to look there: when the Maine Geological Survey ran its pesticides-in-groundwater study, the private-well sampling was concentrated mostly in Aroostook County (Maine Geological Survey, final report) — an acknowledgment that the county's shallow farm-country wells are Maine's exposed groundwater population.

Elsewhere Maine runs low: the state is the most forested in the nation, most of its groundwater moves through glacial deposits and fractured bedrock with modest nitrogen loading, and Penobscot, Somerset and York counties show only scattered mid-band systems.

The supported source reading is potato-belt agricultural nitrogen on permeable glacial ground in Aroostook County — 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 Maine pattern does—and does not—say

Where does nitrate concentrate in Maine community water systems?

Aroostook leads this layer with 4 reporting systems, followed by Cumberland, Penobscot, Somerset. Higher results gather in potato country.

Why does Maine's nitrate concentrate in one county?

Aroostook is Maine's farm belt: about 90 percent of the state's potato acreage, its most valuable crop, grown with intensive nitrogen on sandy glacial outwash that drains fast. The rest of Maine is the most forested state in the nation, with correspondingly little nitrogen loading.

Did Maine study its farm-country wells?

Yes — the Maine Geological Survey's pesticides-in-groundwater study concentrated its private-well sampling mostly in Aroostook County, reflecting where the state expects agricultural groundwater impacts. Maine also recommends periodic nitrate testing for private wells, which carry no regulatory monitoring.

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: 376 Maine 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. University of Maine Cooperative Extension. Aroostook County potato production and soil management — ~47,000 potato acres statewide, ~90% in Aroostook County; potatoes Maine’s most valuable agricultural commodity.
  5. Maine Geological Survey. Final report: pesticides in ground water study — private-well sampling concentrated mostly in Aroostook County.