Ponderosa Basin Mutual Wtr Co, CA
Lead reported as not detected
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2025-2025). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. The latest 90th-percentile result was reported as 0 (not detected at the lab's limit). That says the sampled homes were low, not that your home has no lead service line. Check your utility's service line inventory for your address.
Who runs the water here
Ponderosa Basin Mutual Wtr Co serves about 798 people through 317 service connections, which makes it a small system under EPA's size classes. It is privately owned and draws groundwater, in Mariposa County, California. EPA system ID: CA2210002; phone on file: 209-742-6572. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is down 2.5 ppb from 2.5 ppb in the period ending 2021. The highest 90th-percentile result EPA holds for Ponderosa Basin Mutual Wtr Co is 2.9 ppb across 3 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 0 (not detected) |
| 2021 | 2.5 ppb |
| 2018 | 2.9 ppb |
How Ponderosa Basin Mutual Wtr Co compares
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. Ponderosa Basin Mutual Wtr Co's reported as 0 (not detected) sits at the 40th percentile in California and the 25th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Nearby utilities
10 other systems share Mariposa County; 5 of them have a higher latest lead result than Ponderosa Basin Mutual Wtr Co. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Mariposa Public Utility Dist | 2,000 | 0 (not detected) |
| Yosemite Nps-Yosemite Valley | 1,000 | 0 (not detected) |
| Yosemite Nps-El Portal | 635 | 0 (not detected) |
| Yosemite West Water System | 420 | 2.2 ppb |
| Mariposa Pines Mutual | 294 | 0 (not detected) |
| Mpwd-Coulterville Csa 1 | 193 | 1.4 ppb |
| Yosemite Nps-Wawona | 150 | 0 (not detected) |
| Yosemite Terrace Estates | 130 | 6.6 ppb |
| Mcclure Boat Club, Inc. | 36 | 10 ppb |
| Cedar Lodge | 28 | 3.7 ppb |
Your move
Look up your address in Ponderosa Basin Mutual Wtr Co's service line inventory. If it says lead, galvanized or unknown, test your tap. If your own line is lead, replacing the private side runs about $1,200-$12,300 (EPA average about $4,700). Ask Ponderosa Basin Mutual Wtr Co 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. Small systems behave differently: why small systems go over more often.