Rock City, IL
Exceeded the action level in the past
Latest 90th-percentile lead: reported as 0 (not detected) (monitoring period 2026-2026). The federal action level is 15 ppb today and drops to 10 ppb in Nov 2027; EPA's health goal is 0. The latest result is under the action level, but this system has gone over 15 ppb before. Lead comes from pipes, not the source water, so a home with a lead service line can still be exposed. Test your own tap.
Who runs the water here
Rock City serves about 293 people through 128 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 Stephenson County, Illinois. EPA system ID: IL1770500; phone on file: 815-865-1029. They can tell you what your service line is made of and whether they pay to replace it.
Rock City's lead record
Against the period ending 2025 (0 ppb) the latest result is about the same. The highest 90th-percentile result EPA holds for Rock City is 16.95 ppb across 6 monitoring periods, 1 of them over the 15 ppb action level.
| Period ending | 90th-percentile lead |
|---|---|
| 2026 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2025 | 0 (not detected) |
| 2024 | 0 (not detected) |
| 2021 | 0 (not detected) |
| 2016 | 16.95 ppb over 15 |
How Rock City compares
Of the 1,744 Illinois systems with a lead result, the median latest reading is 0 ppb; 22 are over 15 ppb right now and 152 have gone over at some point. Rock City's reported as 0 (not detected) sits at the 13th percentile in Illinois and the 18th nationally (higher means more lead). Systems reporting 0 tie at the bottom, so the rank mostly reflects size among them.
Other water systems in Stephenson County
12 other systems share Stephenson County; 4 of them have a higher latest lead result than Rock City. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Freeport | 23,930 | 3.6 ppb |
| Lena | 2,680 | 0 (not detected) |
| Pearl City | 790 | 0.45 ppb |
| Orangeville | 780 | 0 (not detected) |
| Cedarville | 663 | 19 ppb |
| Il American-Northern Hill | 600 | 0 (not detected) |
| Davis | 589 | 0 (not detected) |
| Dakota | 500 | 0 (not detected) |
| German Valley | 463 | 1.1 ppb |
| Winslow | 350 | 0 (not detected) |
Next steps for Rock City, IL
Test your own tap with a certified lab first-draw sample; Rock City, IL 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 Rock City 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. Why an old exceedance still matters: over the limit before, under it now.