State Well Water Guide
Wyoming Private Well Water Guide
About 45% of Wyomingites rely on private wells — one of the highest rates in the Mountain West, reflecting Wyoming's vast rural landscape and sparse population. Wyoming's groundwater quality is shaped by its geology and resource extraction: naturally occurring arsenic, uranium, and fluoride from volcanic and sedimentary formations; oil and gas contamination from the state's extensive petroleum industry; and coal bed methane extraction that has affected groundwater in parts of the Powder River Basin. The Wyoming DEQ regulates well construction and maintains a private well program.
Testing Guidance
Wyoming DEQ recommends annual testing for coliform bacteria and nitrates. All Wyoming well owners should test for arsenic and uranium given the state's geological setting. Powder River Basin well owners should test for methane, barium, and TDS from coal bed methane activity. Green River Basin well owners should test for fluoride. Oil and gas area well owners should test for total petroleum hydrocarbons.
What to Test For in Wyoming
Total coliform bacteria and E. coli — annual minimum
Arsenic — widespread from volcanic and sedimentary geology statewide
Uranium — extensive uranium-bearing geology throughout the state
Fluoride — naturally elevated in some Wyoming aquifer systems, especially Green River Basin
Methane and TDS — Powder River Basin coal bed methane area wells
Barium — oil and gas producing areas
Total petroleum hydrocarbons — near oil and gas operations statewide
Iron and manganese — alluvial and sedimentary aquifer wells
Nitrates — agricultural areas and feedlots
Common Contamination Risks in Wyoming
Arsenic from volcanic and sedimentary geology — elevated throughout much of Wyoming's geology; one of the most widespread natural water quality concerns in the state
Uranium from uranium-rich geology — Wyoming has extensive uranium deposits; natural groundwater uranium is elevated in many parts of the state
Coal bed methane impacts — the Powder River Basin's coal bed methane production has introduced high-TDS produced water into some groundwater zones
Oil and gas contamination — Wyoming's oil and gas industry creates potential for brine spills and wellbore integrity issues
Fluoride from geological sources — some Wyoming aquifer systems have naturally elevated fluoride above the EPA MCL
Contaminant Guides Relevant to WY 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 Wyoming
Use the Wyoming state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
WY Certified Lab Directory ↗Wyoming 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
WY Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
WY Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides