Mason City Water Department, IA
Lead detected, under the action levels
Latest 90th-percentile lead: 2.9 ppb (monitoring period 2021-2023). 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
Mason City Water Department serves about 27,338 people through 13,320 service connections, which makes it a large system under EPA's size classes. It is owned by a local government (city, town, county or district) and draws groundwater, in Cerro Gordo County, Iowa. EPA system ID: IA1750048; phone on file: 641-421-3683. Call that number and ask whether your address has a lead, galvanized or unknown service line.
Lead results over time
That is down 4.5 ppb from 7.4 ppb in the period ending 2020. The highest 90th-percentile result EPA holds for Mason City Water Department is 7.4 ppb across 3 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2023 | 2.9 ppb |
| 2020 | 7.4 ppb |
| 2017 | 4.3 ppb |
Against other Iowa systems
Of the 1,066 Iowa systems with a lead result, the median latest reading is 1.4 ppb; 4 are over 15 ppb right now and 36 have gone over at some point. Mason City Water Department's 2.9 ppb sits at the 73rd percentile in Iowa and the 80th nationally (higher means more lead).
Other water systems in Cerro Gordo County
8 other systems share Cerro Gordo County; 2 of them have a higher latest lead result than Mason City Water Department. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Clear Lake Water Department | 7,687 | 3.63 ppb |
| Rockwell Water Supply | 1,071 | 2.28 ppb |
| Ventura Water Works | 717 | 0 (not detected) |
| Thornton Water Supply | 400 | 2 ppb |
| Plymouth Water Supply | 378 | 2 ppb |
| Meservey Water Supply | 222 | 2 ppb |
| Swaledale Water Supply | 144 | 5.34 ppb |
| Long Beach Mobile Park | 50 | 0 (not detected) |
Next steps for Mason City, IA
Test your own tap with a certified lab first-draw sample; Mason City, IA 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 Mason City Water Department 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.