Oaks Water Users Association, SD
Lead detected, under the action levels
Latest 90th-percentile lead: 2 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.
Who runs the water here
Oaks Water Users Association serves about 180 people through 73 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws groundwater, in Pennington County, South Dakota. EPA system ID: SD4602135. Ask the utility on your bill for your address in their service line inventory.
Lead results over time
Against the period ending 2022 (1 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Oaks Water Users Association is 2 ppb across 4 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 2 ppb |
| 2022 | 1 ppb |
| 2019 | 1 ppb |
| 2016 | 1 ppb |
How Oaks Water Users Association compares
Of the 458 South Dakota systems with a lead result, the median latest reading is 2 ppb; 0 are over 15 ppb right now and 6 have gone over at some point. Oaks Water Users Association's 2 ppb sits at the 60th percentile in South Dakota and the 70th nationally (higher means more lead).
Nearby utilities
64 other systems share Pennington County; 17 of them have a higher latest lead result than Oaks Water Users Association. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Rapid City | 72,009 | 6 ppb |
| Box Elder | 14,000 | 2 ppb |
| Rapid Valley Sanitary District | 11,408 | 3 ppb |
| Ellsworth Afb | 9,100 | 1 ppb |
| Colonial Pine Hills Sanitary Distric | 1,200 | 1 ppb |
| Chapel Lane Water Company | 1,200 | 2 ppb |
| Hill City | 872 | 1 ppb |
| Wall | 699 | 1 ppb |
| New Underwood | 679 | 1 ppb |
| Hisega Meadows Water Inc | 493 | 1 ppb |
Next steps for New Underwood, SD
Test your own tap with a certified lab first-draw sample; New Underwood, SD 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 Oaks Water Users 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. Why sampled homes are the worst-case ones is in the guide to reading the number. The action level is dropping - the 10 ppb rule from 2027.