Free Idaho water report: PFAS & lead levels for every water system, worst-affected cities, and EPA violations. Check your ZIP.
Idaho's water supply is defined by one of the most productive aquifer systems in the western United States: the Eastern Snake River Plain Aquifer. This massive groundwater system, stretching approximately 200 miles across southern Idaho, supplies drinking water to the majority of the state's agricultural communities and several cities. The state's approximately 1.9 million residents depend on a mix of groundwater and surface water, with groundwater serving the dominant role – particularly across the Snake River Plain where agriculture and population are concentrated.
The Idaho Department of Environmental Quality (IDEQ) oversees drinking water for approximately 2,100 public water systems. Northern Idaho relies more on surface water from mountain streams and lakes, while southern Idaho draws heavily from the Snake River Plain Aquifer. Boise, the state's capital and largest city, uses a combination of Boise River surface water and groundwater wells.
Agriculture is central to Idaho's economy and its water quality picture. The state is a major producer of potatoes, dairy, and grain, and agricultural runoff – carrying nitrates, phosphates, and pesticides – is the most widespread water quality challenge. According to the USGS, nitrate concentrations in the Snake River Plain Aquifer have been rising for decades due to agricultural activity, with some monitoring wells exceeding the EPA's MCL of 10 mg/L.
Idaho's PFAS picture is less documented than in more industrialized states, but the EPA's UCMR5 monitoring is filling in data gaps. PFAS detections have been confirmed at public water systems in the state, though generally at lower concentrations than in states with heavy military or industrial PFAS sources.
Idaho does not have state-specific PFAS MCLs. The state follows federal EPA standards, with the 2024 MCLs of 4 ppt for PFOA and PFOS now applying to public water systems. IDEQ has not announced plans to adopt stricter state-level standards.
The state's heavy groundwater dependence means that any PFAS reaching the aquifer has a direct pathway to drinking water. The Snake River Plain Aquifer, in particular, moves water relatively quickly through basalt formations, which can transport contaminants over significant distances.
Mountain Home Air Force Base, located about 50 miles southeast of Boise, is the primary military PFAS source in Idaho. The Air Force has confirmed PFAS in groundwater from AFFF use in firefighting training at the base. Mountain Home AFB operates as a major fighter training installation, and decades of AFFF use on the flight line have contributed to contamination.
The contamination at Mountain Home is particularly concerning because the base overlies the western portion of the Snake River Plain Aquifer. PFAS that enters the aquifer here has the potential to migrate with groundwater flow, though the distance and timeline depend on local geology and flow rates.
The Department of Defense has been conducting investigation and monitoring at Mountain Home AFB and has worked with IDEQ on sampling surrounding areas. Remediation planning is underway, but the timeline for cleanup at military PFAS sites typically spans years to decades.
The Idaho National Laboratory (INL), a Department of Energy facility on the Snake River Plain, also sits above the aquifer and has its own environmental contamination history – primarily radioactive and chemical waste rather than PFAS. However, the INL's presence adds to the overall burden on the Snake River Plain Aquifer as a drinking water source.
Our military bases page tracks the current status of PFAS investigations at Idaho installations.
IDEQ has taken a measured approach to PFAS, relying primarily on UCMR5 data and targeted investigations at known contamination sites. The agency has conducted sampling around Mountain Home AFB and has coordinated with the Department of Defense on investigation planning.
Under UCMR5, Idaho's larger public water systems tested for 29 PFAS compounds. Results have provided the most systematic PFAS data the state has seen, confirming detections at some systems and non-detects at others. The geographic distribution of detections tracks closely with the location of known PFAS sources.
According to IDEQ data, a significant portion of Idaho's rural population – particularly in agricultural areas – relies on private domestic wells. These wells are not subject to PFAS testing requirements and are also at risk for elevated nitrates from agricultural activity. For private well owners, the burden of testing falls entirely on the homeowner.
Idaho's legislature has not passed PFAS-specific legislation addressing testing mandates, cleanup standards, or manufacturer liability. The state's approach remains primarily reactive, responding to contamination as it is discovered rather than proactively expanding monitoring.
For background on PFAS compounds and how they move through groundwater systems, see our PFAS guide.
Idaho's water quality challenges center on agricultural contamination statewide and military PFAS in specific areas. The actions you should take depend on where you are and what your water source is.
1. Check your ZIP code at the homepage to see available monitoring data for your water system. We compile UCMR5, IDEQ, and utility data in one place. 2. If you are near Mountain Home AFB and rely on a private well, PFAS testing is recommended. Certified lab tests cost $200-400. 3. If you are on a private well anywhere on the Snake River Plain, nitrate testing is also important given the documented aquifer contamination from agricultural sources. Both PFAS and nitrate filters are available – our water filter guide covers options for each. 4. Request a detailed water report for your address to see historical data and how your area compares to state and federal standards.
Idaho's groundwater is a shared resource under increasing pressure from agriculture, population growth, and contamination. Check your specific location to see what the data shows for your water supply.