Sub-locations
| Name | Sites | Samples |
|---|---|---|
| Allamakee County | 10 | 20 |
| Appanoose County | 2 | 2 |
| Audubon County | 1 | 1 |
| Boone County | 11 | 18 |
| Buena Vista County | 2 | 8 |
| Cedar County | 2 | 11 |
| Cherokee County | 8 | 71 |
| Clay County | 1 | 2 |
| Clayton County | 6 | 12 |
| Crawford County | 3 | 7 |
| Dallas County | 3 | 3 |
| Delaware County | 1 | 3 |
| Des Moines County | 3 | 6 |
| Dubuque County | 3 | 12 |
| Franklin County | 1 | 4 |
| Fremont County | 1 | 0 |
| Hardin County | 4 | 8 |
| Harrison County | 2 | 4 |
| Henry County | 3 | 5 |
| Jackson County | 4 | 13 |
| Jasper County | 1 | 3 |
| Jefferson County | 1 | 1 |
| Johnson County | 2 | 5 |
| Jones County | 3 | 12 |
| Kossuth County | 1 | 1 |