Tap and WellTreasure Valley water, from the public record

Arsenic in Treasure Valley drinking water

70 of 86 systems that tested for it in the last 36 months detected it; 64 are above the limit, elevated, or an aesthetic issue. Arsenic is an inorganic contaminant. Certified filters are in the list.

Naturally elevated in Treasure Valley groundwater, especially deeper wells in the western valley and Canyon County. Species (III vs V) varies by well; certified reduction claims are usually for arsenic V only.

SystemCounty36 mo maxLatestStatusLast sample
Locust SubdivisionCanyon73.1ppbNDAbove limit2026-06-09
Hammett Haven ApartmentsElmore57.1ppb57.1ppbAbove limit2023-10-31
Idaho City Water DepartmentBoise53.7ppb37.0ppbAbove limit2024-11-22
El Rancho HeightsCanyon27.9ppb7.2ppbAbove limit2026-06-09
Edgemont SubdivisionGem22.1ppb8.0ppbAbove limit2026-06-28
Valley View WaterCanyon21.3ppbNDAbove limit2025-12-31
Apache Heights Subdivision (2)Canyon19.2ppbNDAbove limit2026-06-28
Sunnyridge I SubdivisionCanyon19.0ppbNDElevated2026-06-16
Leisure Heights Homeowners AssociationCanyon17.2ppb3.9ppbElevated2026-04-15
Stanley Pond Inc.Ada15.2ppb5.4ppbElevated2026-07-30
Veolia Water IdahoAda14.5ppb14.0ppbElevated2026-08-25
Ranch SubdivisionBoise14.0ppb12.0ppbElevated2026-06-29
Indian VillageCanyon13.7ppb10.4ppbAbove limit2026-06-09
Decoy Inn and RV ParkCanyon13.0ppb6.4ppbElevated2026-07-23
Purple Sage CommunityCanyon12.0ppbNDAbove limit2025-11-05
Drake SubdivisionCanyon10.5ppb9.0ppbElevated2025-12-26
Duquette Pines Homeowners AssociationBoise9.3ppb9.0ppbElevated2025-08-08
Forrey HeightsAda9.2ppbNDElevated2025-10-15
Lakeview Water Company 1Canyon8.9ppb8.9ppbElevated2025-06-05
City of KunaAda7.7ppb6.5ppbElevated2026-06-22
IDOC Idaho State Correctional CenterAda7.7ppb7.3ppbElevated2026-07-23
City of CaldwellCanyon7.5ppb7.5ppbElevated2025-08-20
Karcher Ranchette Water Corp.Canyon7.5ppb7.5ppbElevated2025-11-24
Wymosa Water Association Inc.Ada7.3ppb7.3ppbElevated2025-11-19
Lakeview Hills Water Users AssociationCanyon7.0ppb7.0ppbElevated2025-12-02
Krizview ParkAda6.9ppb6.9ppbElevated2025-04-08
Twin Bridges SubdivisionCanyon6.9ppb6.9ppbElevated2025-12-02
Vanal Heights Sweet WaterCanyon6.7ppb6.7ppbElevated2025-12-29
Dry Creek Water Company LLCAda6.6ppb5.4ppbElevated2025-09-24
Grouse Point Water Company LLCAda6.6ppb6.6ppbElevated2023-12-29
Rolling Hills Estates Water CompanyCanyon6.5ppb6.5ppbElevated2025-05-09
Stecher Water Users AssociationCanyon6.5ppb6.5ppbElevated2025-06-09
City of Eagle (Western Zone)Ada6.3ppb6.3ppbElevated2025-04-29
Caldwell Housing AuthorityCanyon6.3ppb6.3ppbElevated2025-06-16
City of MelbaCanyon6.3ppb6.3ppbElevated2025-08-14
Woodview Acres Property OwnersCanyon6.3ppb4.0ppbElevated2025-12-11
Riley Trailer ParkAda6.1ppb6.1ppbElevated2025-08-13
Somerset West Water Corp.Canyon6.0ppb6.0ppbElevated2025-11-24
Clark Theurer Water AssociationCanyon5.9ppb5.9ppbElevated2025-05-19
Pleasant View ManorCanyon5.9ppb5.9ppbElevated2025-12-10
Willowbrook Estates Property OwnersAda5.9ppb5.9ppbElevated2025-11-25
Covert Water Users AssociationCanyon5.6ppb5.6ppbElevated2025-10-20
Stecher Mutual Water CompanyCanyon5.5ppb5.5ppbElevated2025-11-13
Hi View WaterAda5.4ppb5.4ppbElevated2025-05-07
City of ParmaCanyon5.3ppb5.3ppbElevated2025-09-09
Evergreen Mobile ParkCanyon5.3ppb5.3ppbElevated2025-12-03
Horseshu Vue Ranch SubdivisionBoise5.3ppb5.3ppbElevated2025-12-16
Sunlight TerraceCanyon5.2ppb5.2ppbElevated2025-12-19
Wildrose EstatesCanyon5.2ppb5.2ppbElevated2025-10-14
City of NampaCanyon5.1ppb2.5ppbElevated2024-11-13
Simplot Livestock Company GrandviewElmore5.0ppb5.0ppbElevated2025-11-04
Meridian Water DepartmentAda4.9ppbNDDetected2026-03-24
Danskin Properties Association Inc.Elmore4.9ppb4.9ppbElevated2025-10-29
Camas Estates Water UsersElmore4.7ppb4.7ppbElevated2025-05-06
Verde Hills Water Users Association Inc.Canyon4.3ppb4.3ppbElevated2025-04-22
Garden City Water and Sewer SystemAda3.8ppb3.8ppbElevated2025-08-06
Shalimar SubdivisionCanyon3.8ppb3.4ppbElevated2025-07-21
Trinity Estates Water Users AssociationElmore3.8ppb3.1ppbElevated2026-06-17
Rich SubdivisionCanyon3.8ppb3.8ppbElevated2025-08-13
Star Sewer and Water District Water SystemAda3.6ppb3.6ppbElevated2025-08-07
Malad and Hilton Water Company Inc.Ada3.6ppb3.6ppbElevated2025-06-26
Capitol Water Corp.Ada3.5ppb3.5ppbElevated2025-08-14
Blue Sage SubdivisionElmore3.3ppb3.3ppbElevated2025-10-28
City of Mountain HomeElmore3.1ppb3.1ppbElevated2025-09-30
Sawtooth Estates Water UsersElmore2.6ppb2.6ppbDetected2025-05-06
Camelot Water Association Inc.Canyon2.6ppb2.6ppbDetected2025-11-24
Arrowrock RanchAda2.5ppbNDElevated2025-12-04
City of Glenns FerryElmore2.3ppb2.3ppbDetected2024-04-25
Mores Creek Rim Ranch Water DistrictBoise2.2ppb2.2ppbDetected2024-11-22
West Meadows EstatesAda2.1ppb2.1ppbDetected2025-08-12

Limits

Federal limit (MCL)
0.01 mg/L (10.0ppb)
Health goal (MCLG)
0.0ppb
Health guideline
0.0ppb (California OEHHA Public Health Goal)
Some people who drink water containing arsenic in excess of the MCL over many years could experience skin damage or problems with their circulatory system, and may have an increased risk of getting cancer.EPA, quoted.

Removal methods in the reference list: reverse osmosis, adsorptive media, anion exchange, distillation. A method name is not a product certification.

By city: Arsenic in Idaho City drinking water, Arsenic in Nampa drinking water, Arsenic in Boise City drinking water, Arsenic in Garden City drinking water, Arsenic in Meridian drinking water, Arsenic in Kuna drinking water, Arsenic in Caldwell drinking water, Arsenic in Eagle drinking water, Arsenic in Parma drinking water, Arsenic in Star drinking water, Arsenic in Mountain Home drinking water, Arsenic in Glenns Ferry drinking water.

772 groundwater zones in the region have confident (grade A or B) estimates for Arsenic. See well estimates by ZIP.

Numbers are the system's samples at its taps and wells, not yours. Lead and copper are 90th percentiles from sampled homes. Well pages are nearby-sample estimates. Health text restates EPA and DEQ. Methodology.