Lower Pioneer Mountain Water System, MT
Lead detected, under the action levels
Latest 90th-percentile lead: 1 ppb (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. 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.
Lower Pioneer Mountain Water System at a glance
Lower Pioneer Mountain Water System serves about 350 people through 211 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws groundwater, in Madison County, Montana. EPA system ID: MT0004462; phone on file: 406-577-4936. They can tell you what your service line is made of and whether they pay to replace it.
Lead results over time
Against the period ending 2025 (2 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Lower Pioneer Mountain Water System is 12 ppb across 10 monitoring periods, none of them over 15 ppb (1 over 10 ppb).
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 1 ppb |
| 2025 | 2 ppb |
| 2024 | 0 (not detected) |
| 2022 | 1 ppb |
| 2021 | 4 ppb |
| 2021 | 3 ppb |
| 2020 | 1 ppb |
| 2019 | 1 ppb |
| 2017 | 1 ppb |
| 2016 | 12 ppb over 10 |
Against other Montana systems
Of the 753 Montana systems with a lead result, the median latest reading is 1 ppb; 5 are over 15 ppb right now and 28 have gone over at some point. Lower Pioneer Mountain Water System's 1 ppb sits at the 57th percentile in Montana and the 53rd nationally (higher means more lead).
Nearby utilities
10 other systems share Madison County; 4 of them have a higher latest lead result than Lower Pioneer Mountain Water System. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Big Sky County Water And Sewer Dist 363 | 4,132 | 4.84 ppb |
| Virginia City Water Dept | 1,500 | 0 (not detected) |
| Ennis Town Of | 1,400 | 0 (not detected) |
| Sheridan Town Of | 632 | 2 ppb |
| Andesite Ridge Water System | 450 | 3 ppb |
| Twin Bridges Town Of | 424 | 2 ppb |
| Mt Moonlight Basin | 355 | 0.28 ppb |
| Valley Garden Golf Village Hoa | 195 | 1 ppb |
| Encampment Trail | 100 | 0 (not detected) |
| Lone View Ridge Water System | 37 | 1 ppb |
Next steps for Big Sky, MT
Test your own tap with a certified lab first-draw sample; Big Sky, MT 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 Lower Pioneer Mountain 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.