State Well Water Guide
Massachusetts Private Well Water Guide
Approximately 18% of Massachusetts residents — around 1.2 million people — rely on private wells. Massachusetts' crystalline granite bedrock generates naturally occurring arsenic and radon, while the Cape Cod region faces nitrate contamination from high-density septic systems and a legacy of PFAS from Joint Base Cape Cod (formerly Otis Air National Guard Base). Massachusetts has among the strictest PFAS standards in the nation (20 ppt sum of six compounds) and was among the first states to document widespread PFAS in drinking water. The MA DEP certifies labs for private well testing and offers guidance through its Private Well Owner Resources program.
Testing Guidance
MassDEP recommends annual testing for coliform bacteria. Test for arsenic in all bedrock wells — Cape Ann, Boston Basin, and Bristol County have elevated concentrations. Test for PFAS if within 3 miles of Joint Base Cape Cod, Camp Edwards, or any airport or industrial site. Cape Cod and Plymouth County well owners should test annually for nitrates due to high septic density. Test for radon in water if your home shows elevated airborne radon.
What to Test For in Massachusetts
Total coliform bacteria and E. coli — annual minimum
Arsenic — crystalline bedrock wells; Cape Ann, Boston Basin, Bristol County particularly
PFAS — Cape Cod (JBCC/Otis area), any site near military installations or airports
Nitrates — Cape Cod, Plymouth County, areas with high septic system density
Radon in water — granite bedrock statewide; particularly eastern Massachusetts
Lead — homes built before 1986 with older plumbing or lead solder
Manganese — glacial deposits in central and western MA; staining, health concerns
Volatile organic compounds — wells near dry cleaners, former industrial sites, or gas stations
Common Contamination Risks in Massachusetts
PFAS from Joint Base Cape Cod — one of the most extensively documented PFAS contamination cases in the U.S.; decades of AFFF use from Otis AFB have impacted private wells across a large area of Barnstable County
Naturally occurring arsenic from granite bedrock — documented in many towns, particularly Cape Ann (Rockport, Gloucester, Essex areas) and parts of Bristol and Plymouth counties
Nitrate contamination on Cape Cod — the Cape's sandy soils and shallow water table, combined with dense septic systems, create a high nitrate loading risk; some monitoring wells on Cape Cod exceed 10 mg/L
Radon in water from granite — eastern Massachusetts bedrock is uranium-bearing granite; radon released from tap water contributes to indoor air radon levels
VOC contamination near former industrial sites — MassDEP has documented VOC plumes from dry cleaners, gas stations, and manufacturing sites affecting private wells, particularly in eastern MA
Septic system contamination for dug wells — older dug wells with inadequate setbacks are vulnerable to coliform and nitrate contamination
Contaminant Guides Relevant to MA Wells
PFAS
Synthetic Chemicals
EPA limit: 4 ppt
Lead
Heavy Metals
EPA limit: 15 ppb (action level)
Nitrates
Agricultural Chemicals
EPA limit: 10 mg/L
DBPs
Disinfection Byproducts
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Heavy Metals
EPA limit: 10 ppb
Hard Water
Minerals
EPA limit: No federal limit
Chlorine
Disinfection Chemicals
EPA limit: 4 mg/L (MRDL)
Microplastics
Emerging Contaminants
EPA limit: No federal limit
Bacteria
Microbial Contamination
EPA limit: Zero E. coli / < 1 coliform per 100 mL
Fluoride
Minerals
EPA limit: 4 mg/L (MCL) / 2 mg/L (Secondary MCL)
Chromium-6
Heavy Metals
EPA limit: 100 ppb (total chromium)
Copper
Heavy Metals
EPA limit: 1.3 mg/L (action level)
Radon
Radioactive Contaminants
EPA limit: No finalized MCL
Iron & Manganese
Minerals
EPA limit: 0.3 mg/L iron / 0.05 mg/L manganese (aesthetic SMCLs)
Atrazine
Agricultural Chemicals
EPA limit: 3 ppb (0.003 mg/L)
Uranium
Radioactive Contaminants
EPA limit: 30 µg/L (30 ppb)
Perchlorate
Industrial Chemicals
EPA limit: 0.056 mg/L (56 ppb)
VOCs
Industrial Chemicals
EPA limit: Varies by compound: benzene 5 ppb; TCE 5 ppb; PCE 5 ppb; vinyl chloride 2 ppb
Radium
Radioactive Contaminants
EPA limit: 5 pCi/L (combined Ra-226 + Ra-228)
Crypto & Giardia
Microbial Contamination
EPA limit: Zero (treatment technique standard)
Hydrogen Sulfide
Naturally Occurring Compounds
EPA limit: No MCL; Secondary MCL (aesthetic) of 0.05 mg/L
Selenium
Minerals
EPA limit: 50 ppb (0.05 mg/L)
Cadmium
Heavy Metals
EPA limit: 5 ppb (0.005 mg/L)
Mercury
Heavy Metals
EPA limit: 2 ppb (0.002 mg/L)
Barium
Heavy Metals
EPA limit: 2 mg/L
Find a Certified Lab in Massachusetts
Use the Massachusetts state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
MA Certified Lab Directory ↗Massachusetts Well Water FAQs
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
State program
MA Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
MA Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides