Sub-locations
| Name | Sites | Samples |
|---|---|---|
| Lee County | 6 | 13 |
| Linn County | 1 | 2 |
| Louisa County | 12 | 69 |
| Lyon County | 1 | 10 |
| Mahaska County | 1 | 4 |
| Marion County | 6 | 27 |
| Mills County | 27 | 135 |
| Monona County | 3 | 5 |
| Muscatine County | 4 | 15 |
| O'Brien County | 2 | 17 |
| Osceola County | 1 | 4 |
| Plymouth County | 10 | 71 |
| Polk County | 6 | 29 |
| Pottawattamie County | 1 | 1 |
| Scott County | 1 | 1 |
| Sioux County | 3 | 10 |
| Story County | 1 | 28 |
| Tama County | 1 | 1 |
| Warren County | 2 | 5 |
| Washington County | 2 | 2 |
| Webster County | 1 | 1 |
| Woodbury County | 6 | 42 |