The Power of Information

National Drinking Water Database


726 systems serving 1,063,278 people

This drinking water quality report shows results of tests conducted by water utilities in Idaho, provided to the Environmental Working Group (EWG) by the Department of Health and Welfare- Division of Environmental Quality. It is part of EWG's national database that includes 47,667 drinking water utilities and 20 million test results from 45 states and the District of Columbia. Water utilities nationwide detected more than 300 pollutants between 2004 and 2009. More than half of these chemicals are unregulated, legal in any amount. Despite this widespread contamination, the federal government invests few resources in protecting rivers, reservoirs, and groundwater from pollution in the first place. The information below summarizes drinking water quality for this state.

Water Utilities
Population Served
Detected Chemicals
Exceed health guidelines*
Exceed Legal Limits*
Unregulated chemicals detected
* Water utilities are noted as exceeding the legal limit if any test is above the maximum contaminant level (MCL). Most MCLs are based on annual averages so exceeding the MCL for one test does not necessarily indicate that the system is out of compliance.

40 Contaminants Exceeding Health Based Limits

Contaminants detected in Idaho drinking water above health guidelines, according to an Environmental Working Group analysis of data obtained from state water authorities

Number of Systems
At Any Level Above Health Limits At Any Level Above Health Limits
Arsenic (total)756,833756,833298298
Alpha particle activity (excl radon and uranium)590,518590,5188484
Total haloacetic acids (HAAs)644,199571,327149142
Combined Radium (-226 & -228)531,680531,6808080
Total trihalomethanes (TTHMs)836,618390,35123386

Water Utilities in Idaho Reporting Chemicals Exceeding Health Guidelines

Water utilities in Idaho reporting chemicals exceeding health guidelines, according to an Environmental Working Group analysis of data obtained from state water authorities, include:

Chemicals tested
Chemicals found
Chemicals exceeding
health guidelines
United Water Idaho Inc185,787933221
Meridian Water Dept46,500842313
City of Pocatello53,932751812
Capitol Water Corp7,400751310
Mountain Home Air Force Base7,50066128
City of Idaho Falls51,50776147
City of Twin Falls36,00071147
Riverside Trailer Court3567107
Wilderness Ranch Owners Association Inc52575147
Belmont Heights19060117
City of Weiser5,3436597
City of Fruitland4,11673127
City of Nampa63,80083187
Caldwell Housing Authority1,10076127
Blackhawk Estates10061116
Falls Water Company Inc10,90054136
Comore Loma62078106
Meander Point Subd1403476
Elm Park Water System1203476
Jug Mountain Ranch Subdivision4070116

Sources of Idaho Drinking Water Contaminants

The contaminants identified in Idaho drinking water come from a wide variety of sources, including agriculture, industry, water treatment plants, and polluted storm runoff from urban areas.

61Total Contaminants Detected (2004 - 2009)
13Agricultural Pollutants
(pesticides, fertilizer, factory farms)

Arsenic (total), Cyanide, Nitrate & nitrite, Nitrate, Nitrite, Selenium (total), Phosphorus, Endothall, Simazine, Atrazine, 2,4-D, Ethylene dibromide (EDB), Ethylbenzene

18Sprawl and Urban Pollutants
(road runoff, lawn pesticides, human waste)

Nitrate, Copper, Nitrate & nitrite, Lead (total), Arsenic (total), Tetrachloroethylene, Nitrite, Xylenes (total), Cadmium (total), Antimony (total), Mercury (total inorganic), Dichloromethane (methylene chloride), Cyanide, Di(2-Ethylhexyl) adipate, Phosphorus, 2,4-D, bis(2-ethylhexyl) phthalate, 2,3,7,8-TCDD (Dioxin)

44Industrial Pollutants

Aluminum, Bromide, Arsenic (total), Barium (total), Cadmium (total), Chromium (total), Cyanide, Lead (total), Manganese, Mercury (total inorganic), Nitrate & nitrite, Nitrate, Nitrite, Selenium (total), Antimony (total), Beryllium (total), Thallium (total), Phosphorus, Asbestos, Di(2-Ethylhexyl) adipate, Di(2-ethylhexyl) phthalate, Hexachlorocyclopentadiene, 2,3,7,8-TCDD (Dioxin), bis(2-ethylhexyl) phthalate, Ethylene dibromide (EDB), Xylenes (total), Dichloromethane (methylene chloride), trans-1,2-Dichloroethylene, 1,2-Dichloroethane, Carbon tetrachloride, Trichloroethylene, 1,1,2-Trichloroethane, Tetrachloroethylene, Toluene, Ethylbenzene, Alpha particle activity (excl radon and uranium), Alpha particle activity (incl. radon & uranium), Combined Uranium (mg/L), Combined Radium (-226 & -228), Radium-226, Radium-228, Alpha particle activity, Combined Uranium (pCi/L), Gross beta particle activity (pCi/L)

13Water Treatment and Distribution Byproducts
(pipes and fixtures, treatment chemicals and byproducts)

Total trihalomethanes (TTHMs), Total haloacetic acids (HAAs), Chloroform, Bromodichloromethane, Dibromochloromethane, Dichloroacetic acid, Trichloroacetic acid, Bromoform, Dibromoacetic acid, Monochloroacetic acid, Di(2-ethylhexyl) phthalate, Cadmium (total), Asbestos

24Naturally Occurring
(naturally present but increased for lands denuded by sprawl, agriculture, or industrial development)

Nitrate, Copper, Nitrate & nitrite, Barium (total), Lead (total), Arsenic (total), Manganese, Radium-228, Radium-226, Alpha particle activity, Alpha particle activity (excl radon and uranium), Combined Radium (-226 & -228), Gross beta particle activity (pCi/L), Combined Uranium (pCi/L), Chromium (total), Alpha particle activity (incl. radon & uranium), Combined Uranium (mg/L), Aluminum, Selenium (total), Nitrite, Bromide, Mercury (total inorganic), Cyanide, Phosphorus

6Unregulated Contaminants
EPA has not established a maximum legal limit in tapwater for these contaminants

Bromide, Lead (total), Phosphorus, bis(2-ethylhexyl) phthalate, Uranium-234 (pCi/L), Uranium-238 (pCi/L)

Testing Summary for Idaho

The federal government has set standards for some of the pollutants found in tap water supplies.

Contaminants reported as tested by water suppliers in Idaho144
 Contaminants tested due to federal law: 89
 Contaminants tested in addition to those required by federal law: 55

Violation Summary for Idaho

Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in Idaho since 2004

Violation TypeNumber of Violations
Failure to monitor regularly1,679
Failure to monitor, Routine Major (Coliform bacteria)500
Maximum contaminant level, Monthly (Coliform bacteria)421
Monitoring and Reporting Disinfection Byproduct Rule421
Over maximum contaminant level, Average407
Failure to monitor, Routine Minor (Coliform bacteria)134
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination)106
Over maximum contaminant level, Single Sample96
Treatment Technique (Surface Water Treatment Rule)74
Follow-up and Routine Tap Sampling51
Filter Turbidity Reporting23
Failure to monitor, Repeat Major (Coliform bacteria)22
Initial Tap Sampling for Lead and Copper21
Failure to monitor, Repeat Minor (Coliform bacteria)12
Maximum contaminant level, Acute (Coliform bacteria)10
Failure to notify public of violation3
Failure to monitor or report, Routine/Repeat (Indicators of microbial or virus contamination)2
Optimal Corrosion Control Treatment Study Recommendation1
Non-Acute maximum residual disinfectant level1
Failure to Filter (Surface Water Treatment Rule)1