Thornton Water Association, WA
Lead detected, under the action levels
Latest 90th-percentile lead: 2.5 ppb (monitoring period 2023-2025). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. Lead was measured in sampled homes but the 90th percentile is under both action levels. EPA's health goal for lead is zero, so test your own tap if your home was built before 1986 or anyone in it is pregnant or a young child.
About Thornton Water Association
Thornton Water Association serves about 55 people through 16 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws groundwater, in Whatcom County, Washington. EPA system ID: WA5388050. Ask the utility on your bill for your address in their service line inventory.
Every lead result on file
That is up 1.5 ppb from 1 ppb in the period ending 2022. The highest 90th-percentile result EPA holds for Thornton Water Association is 2.5 ppb across 4 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 2.5 ppb |
| 2022 | 1 ppb |
| 2019 | 2.5 ppb |
| 2016 | 1 ppb |
How Thornton Water Association compares
Of the 2,218 Washington systems with a lead result, the median latest reading is 1 ppb; 18 are over 15 ppb right now and 62 have gone over at some point. Thornton Water Association's 2.5 ppb sits at the 75th percentile in Washington and the 77th nationally (higher means more lead).
Neighbouring systems
100 other systems share Whatcom County; 27 of them have a higher latest lead result than Thornton Water Association. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Bellingham-Water Division City Of | 141,127 | 3.4 ppb |
| Lynden Water Department | 20,062 | 2.3 ppb |
| Ferndale | 19,305 | 5.6 ppb |
| Lwwsd - South Shore Water System | 10,028 | 4.2 ppb |
| Birch Bay Water & Sewer District | 9,046 | 1.8 ppb |
| Blaine City Of | 6,800 | 1.6 ppb |
| Everson City Of | 3,893 | 2.1 ppb |
| Columbia Valley Water District | 2,648 | 1.5 ppb |
| Nooksack Water Dept | 2,427 | 0 (not detected) |
| Glacier Water District | 2,383 | 1.1 ppb |
Your move
Test your own tap with a certified lab first-draw sample; Ferndale, WA may offer free or low-cost kits through the utility. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Thornton Water Association whether it covers that cost before hiring anyone - many utilities now do.
These figures describe homes the utility sampled, not your tap. Only your service line record or a test of your own water answers the question for your house. What a 90th-percentile result does and does not tell you: how to read a lead result. Size matters more than most people expect: small vs large water systems.