Tud - Columbia Water System, CA
Lead detected, under the action levels
Latest 90th-percentile lead: 5.4 ppb (monitoring period 2024-2026). 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.
Who runs the water here
Tud - Columbia Water System serves about 5,482 people through 2,099 service connections, which makes it a medium-sized system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws surface water, in Tuolumne County, California. EPA system ID: CA5510013; phone on file: 209-532-5536. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Every lead result on file
Against the period ending 2023 (4.7 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Tud - Columbia Water System is 5.4 ppb across 4 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 5.4 ppb |
| 2023 | 4.7 ppb |
| 2020 | 0 (not detected) |
| 2017 | 0 (not detected) |
Against other California systems
Of the 2,884 California systems with a lead result, the median latest reading is 0 ppb; 30 are over 15 ppb right now and 215 have gone over at some point. Tud - Columbia Water System's 5.4 ppb sits at the 93rd percentile in California and the 92nd nationally (higher means more lead).
Nearby utilities
48 other systems share Tuolumne County; 7 of them have a higher latest lead result than Tud - Columbia Water System. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Tud - Upper Basin Water System | 13,331 | 0 (not detected) |
| Tud - Sonora/Jamestown Water System | 11,113 | 0 (not detected) |
| Cdcr - Sierra Conservation Center | 3,571 | 0 (not detected) |
| Groveland Community Serv Dist | 3,400 | 0 (not detected) |
| Twain Harte Community Services District | 2,378 | 0 (not detected) |
| Tud - Tuolumne Water System | 1,798 | 0 (not detected) |
| Tud - Ponderosa | 1,781 | 0 (not detected) |
| Cold Springs Water Co | 1,771 | 2.8 ppb |
| Lake Don Pedro Csd | 1,700 | 0 (not detected) |
| Phoenix Lake Estates Cc Mwc | 1,168 | 0 (not detected) |
Next steps for Sonora, CA
Test your own tap with a certified lab first-draw sample; Sonora, CA 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 Tud - Columbia Water System 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. The lead result guide covers how utilities pick the homes they sample. Systems that went over once often dip back under; here is what that means.