San Juan County, Colorado
USDA's soil survey flags shrink-swell clay on 0% of San Juan County's mapped land and a shallow water table under basements on 1%, both below the national shares of 15% and 29%. 23% of the county is in drought on the October 13, 2026 Drought Monitor map, down from 65.1% a week earlier.
FEMA's flood data list no flood losses here since 2016. 51% of homes were built before 1980, against 50% nationally; the median home dates from 1979.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under San Juan County
| Expansive clay (limits slab homes) | 0.0% |
| High water table (limits basements) | 1.1% |
| Septic fields very limited | 77.5% |
| Clay swell (LEP, by area) | 1.4% |
| High-swell land (LEP 6%+) | under 0.1% |
| Mapped soil | 226,100 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Needleton | 14% | n/a |
| Whitecross | 9% | n/a |
| Snowdon | 9% | n/a |
| Henson | 4% | n/a |
| Quazar | 2% | n/a |
| Moran | 2% | n/a |
How we count · survey areas CO672 (2025-08-29), CO674 (2025-08-29)
What the numbers mean here
Rain over the 12 months to August 2026: 36.35 in, 2.74 in below the 1991-2020 average year of 39.09 in.
USDA rates 78% of the land very limited for septic absorption fields.
With shrink-swell clay on 0% and a shallow water table on 1% of the land, the soil survey points to neither problem across most of San Juan County; conditions still vary lot by lot.
Drought
23% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 36 weeks, most recently on the September 22, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 23% |
| D2 severe or worse | 2.8% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in San Juan County since 2016.
Rain
| Average year, 1991-2020 | 39.09 in |
| 12 months to August 2026 | 36.35 in (-2.74) |
| 2025 | 34.05 in (-5.04) |
| Wettest year since 1895 | 1941: 65.17 in |
| Driest year since 1895 | 1900: 25.15 in |
| Days with 1 inch or more, normal at SILVERTON (2 mi away) | 1.7 |
Homes
| Housing units | 738 |
| Median year built | 1979 |
| Built before 1980 | 51% |
| Built 2000 or later | 19% |
| Owner-occupied | 53% |
| Median value, owner-occupied | $432,500 |
| Single-family detached | 59% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Hinsdale County, CO | 18 mi | under 1% | 2% |
| Ouray County, CO | 27 mi | 19% | 6% |
| La Plata County, CO | 36 mi | 10% | 3% |
| Mineral County, CO | 41 mi | 1% | 5% |
| San Miguel County, CO | 44 mi | 3% | 1% |
| Dolores County, CO | 46 mi | 12% | 2% |
| Archuleta County, CO | 52 mi | 53% | 3% |
| Montrose County, CO | 54 mi | 22% | 5% |
Sources: USDA SSURGO (August 29, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status