ZIP 81638 falls in Moffat County, Colorado. We have not measured septic data for this county yet. The county page below has what we do know: where records are kept and whether the portal is public.
ZCTA 81638 is not entirely inside one county. Land-area share is from the 2020 Census ZCTA-to-county relationship file.
| County | Land in this ZIP | Documents held | On septic (county) | On sewer (county) |
|---|---|---|---|---|
| Moffat County, Colorado | 77% | — | — | — |
| Routt County, Colorado | 23% | — | — | — |
Land-area overlap is from the 2020 Census Bureau ZCTA5-to-county relationship file, not an estimate of ours. Parcel and document counts are rows we hold, not a survey of every property in the ZIP. Last verified 2026-09-01.
We have not measured septic-versus-sewer status for this county yet.
ZIP 81638 spans 2 counties: Moffat County, Colorado, Routt County, Colorado.