Keystone, 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.
About Keystone
Keystone serves about 349 people through 249 service connections, which makes it a very small system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws groundwater, in Pennington County, South Dakota. EPA system ID: SD4601082; phone on file: 6056664827. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is down 2 ppb from 4 ppb in the period ending 2022. The highest 90th-percentile result EPA holds for Keystone is 7 ppb across 5 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2025 | 2 ppb |
| 2022 | 4 ppb |
| 2019 | 3 ppb |
| 2018 | 1 ppb |
| 2017 | 7 ppb |
Where this result ranks
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. Keystone's 2 ppb sits at the 63rd percentile in South Dakota and the 71st nationally (higher means more lead).
Neighbouring systems
64 other systems share Pennington County; 17 of them have a higher latest lead result than Keystone. 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 |
What to do in your house
Test your own tap with a certified lab first-draw sample; Keystone, 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 Keystone 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. Size matters more than most people expect: small vs large water systems.