Twin Knolls Fourth/Fifth Addition, IA
Lead detected, under the action levels
Latest 90th-percentile lead: 1 ppb (monitoring period 2022-2024). 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.
Twin Knolls Fourth/Fifth Addition at a glance
Twin Knolls Fourth/Fifth Addition serves about 90 people through 36 service connections, which makes it a very small system under EPA's size classes. It is privately owned and draws groundwater, in Linn County, Iowa. EPA system ID: IA5784326; phone on file: 319-310-3227. They can tell you what your service line is made of and whether they pay to replace it.
Lead results over time
That is down 9 ppb from 10 ppb in the period ending 2021. The highest 90th-percentile result EPA holds for Twin Knolls Fourth/Fifth Addition is 10 ppb across 3 monitoring periods, none of them over 15 ppb.
| Period ending | 90th-percentile lead |
|---|---|
| 2024 | 1 ppb |
| 2021 | 10 ppb |
| 2018 | 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. Twin Knolls Fourth/Fifth Addition's 1 ppb sits at the 40th percentile in Iowa and the 51st nationally (higher means more lead).
Nearby utilities
39 other systems share Linn County; 24 of them have a higher latest lead result than Twin Knolls Fourth/Fifth Addition. If you are unsure which one supplies your house, the name on your water bill decides it.
| System | People | Latest lead |
|---|---|---|
| Cedar Rapids Water Department | 142,364 | 1.62 ppb |
| Marion Municipal Water Dept | 41,623 | 8.3 ppb |
| Hiawatha Water Dept | 7,183 | 0 (not detected) |
| Mount Vernon Water Supply | 4,527 | 1 ppb |
| Fairfax Water Supply | 2,828 | 2 ppb |
| Center Point Water Supply | 2,579 | 0 (not detected) |
| Ely Water Supply | 2,328 | 4 ppb |
| Lisbon Water Supply | 2,233 | 1.7 ppb |
| Palo Water Supply | 1,407 | 1.6 ppb |
| Central City Water Supply | 1,264 | 3 ppb |
What to do in your house
Test your own tap with a certified lab first-draw sample; Cedar Rapids, 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 Twin Knolls Fourth/Fifth Addition 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. What a 90th-percentile result does and does not tell you: how to read a lead result. Systems that went over once often dip back under; here is what that means.