Broomfield County, Colorado
Shrink-swell clay limits houses without basements on 46% of Broomfield County's mapped land, a higher share than 89% of US counties and the 3rd highest of 63 Colorado counties. A shallow water table limits basements on 1%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 5 flood losses here since 2016. 21% of homes were built before 1980, against 50% nationally; the median home dates from 2002.
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 Broomfield County
| Expansive clay (limits slab homes) | 45.5% |
| High water table (limits basements) | 0.7% |
| Septic fields very limited | 67.6% |
| Clay swell (LEP, by area) | 6.2% |
| High-swell land (LEP 6%+) | 69.3% |
| Urban land, not rated | 1.1% |
| Mapped soil | 28,766 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Platner | 23% | n/a |
| Nunn | 17% | n/a |
| Ulm | 8% | n/a |
| Blakeland | 6% | n/a |
| Renohill | 5% | n/a |
| Samsil | 4% | n/a |
How we count · survey areas CO001 (2025-08-29), CO641 (2025-08-29), CO643 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 6.2% by land area here, and 69% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 46% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 46% of Broomfield County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 10.24 in, 4.95 in below the 1991-2020 average year of 15.19 in.
USDA rates 68% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 46 of the last 52 weeks; the most was 100% of its area, in 46 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 100% |
| D3 extreme or worse | 100% |
| D4 exceptional | 100% |
Flood losses since 2016
5 flood losses since 2016, $154,511 paid. The worst year was 2023, with 2.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 1 |
| 2018 | 0 |
| 2019 | 1 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 2 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 15.19 in |
| 12 months to August 2026 | 10.24 in (-4.95) |
| 2025 | 13.67 in (-1.52) |
| Wettest year since 1895 | 1923: 22.86 in |
| Driest year since 1895 | 1939: 7.81 in |
| Days with 1 inch or more, normal at NORTHGLENN (4 mi away) | 2 |
Homes
| Housing units | 33,202 |
| Median year built | 2002 |
| Built before 1980 | 21% |
| Built 2000 or later | 55% |
| Owner-occupied | 63% |
| Median value, owner-occupied | $664,500 |
| Single-family detached | 58% |
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 |
|---|---|---|---|
| Denver County, CO | 16 mi | 15% | 3% |
| Boulder County, CO | 21 mi | 9% | 6% |
| Gilpin County, CO | 26 mi | 0% | 3% |
| Jefferson County, CO | 28 mi | 17% | 2% |
| Clear Creek County, CO | 38 mi | 0% | 3% |
| Adams County, CO | 39 mi | 11% | 2% |
| Arapahoe County, CO | 44 mi | 22% | 1% |
| Douglas County, CO | 44 mi | 3% | 2% |
Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status