Mammoth Cwd, CA
Lead detected, under the action levels
Latest 90th-percentile lead: 1.5 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
Mammoth Cwd serves about 8,234 people through 3,818 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 Mono County, California. EPA system ID: CA2610001; phone on file: 760-934-2596. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is up 1.5 ppb from 0 ppb in the period ending 2023. The highest 90th-percentile result EPA holds for Mammoth Cwd is 1.5 ppb across 7 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 1.5 ppb |
| 2023 | 0 (not detected) |
| 2020 | 0 (not detected) |
| 2017 | 0 (not detected) |
| 2017 | 0 (not detected) |
| 2016 | 0 (not detected) |
| 2016 | 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. Mammoth Cwd's 1.5 ppb sits at the 75th percentile in California and the 64th nationally (higher means more lead).
Nearby utilities
17 other systems share Mono County; 9 of them have a higher latest lead result than Mammoth Cwd. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Mountain Meadows Mwc | 525 | 4.4 ppb |
| Usmc - Housing Coleville | 424 | 1.3 ppb |
| Bridgeport Pud | 374 | 1.9 ppb |
| Lower Rock Creek Mutual Water Co. | 310 | 0 (not detected) |
| June Lake Pud - Down Canyon | 310 | 2 ppb |
| Usmc/Mtn Warfare Trng Ctr - Bridgeport | 300 | 1 ppb |
| June Lake Pud Village | 263 | 2.7 ppb |
| Crowley Lake Trailer Park | 230 | 9.4 ppb |
| Lee Vining Public Utility District | 222 | 8 ppb |
| Lundy Mutual Water Company | 200 | 3.7 ppb |
Next steps for Mammoth Lakes, CA
Test your own tap with a certified lab first-draw sample; Mammoth Lakes, 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 Mammoth Cwd 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. Why sampled homes are the worst-case ones is in the guide to reading the number. Size matters more than most people expect: small vs large water systems.