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Mercedes, Texas
Inside Mercedes' city limits, shrink-swell clay limits houses without basements on 40% of mapped land. A shallow water table limits basements on under 1%.
That clay share is above Hidalgo County's 12%. FEMA's flood data list 430 flood losses since 2016 in ZIP code 78570 overlapping the city. Of its 6,031 homes, 31% were built before 1980; the median dates from 1991.
Data as of October 13, 2026 · sources · in Hidalgo County
expansive clay: shrink-swell limits slab homes
high water table: limits basements
flood losses since 2016 in 1 overlapping ZIP
of homes built before 1980
Foundation repair in Mercedes
Foundation repair in Mercedes: shrink-swell clay limits slab homes on 40% of Mercedes' mapped land.
About 3,700 of Mercedes' 6,031 homes are detached houses.
| Who designs the repair | The ASCE Texas Section's repair guidelines say a Texas-licensed engineer should evaluate the foundation and design the repair (2022 guidelines) |
| Prices | Cost guide ranges compared |
Soil under Mercedes city limits
| Expansive clay (limits slab homes) | 40.4% |
| High water table (limits basements) | 0.2% |
| Septic fields very limited | 43.6% |
| Clay swell (LEP, by area) | 8.5% |
| High-swell land (LEP 6%+) | 40.4% |
| Urban land, not rated | 6.7% |
| Mapped soil | 7,594 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Hidalgo | 32% | 0% |
| Harlingen | 20% | n/a |
| Raymondville | 17% | n/a |
| Mercedes | 5% | n/a |
| Racombes | 3% | n/a |
| Willacy | 3% | n/a |
What the numbers mean here
Clay swell averages a linear extensibility of 8.5% by land area here, and 40% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 40% of the mapped land.
Clay shrinks as it dries: 100% of Hidalgo County is in drought on the latest map, and 40% of Mercedes' mapped land has shrink-swell clay.
Drought in Hidalgo County
100% of Hidalgo County is in drought (D1 or worse) on the October 13, 2026 map. County detail.
Flood losses by ZIP code
FEMA flood records since 2016 in the ZIP codes that overlap Mercedes. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 78570 | over 99% | 430 | $14.5 million |
Homes in Mercedes
| Housing units | 6,031 |
| Median year built | 1991 |
| Built before 1980 | 31% |
| Built 2000 or later | 36% |
| Owner-occupied | 63% |
| Median value, owner-occupied | $111,800 |
| Single-family detached | 62% |
Nearby cities
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Weslaco | 5 mi | 16% | under 1% |
| Progreso | 5 mi | 73% | 2% |
| La Feria | 5 mi | 24% | under 1% |
| Progreso Lakes | 7 mi | 50% | 6% |
| Donna | 8 mi | 26% | 1% |
| Santa Rosa | 9 mi | 50% | 2% |
| La Villa | 10 mi | 24% | 2% |
| Edcouch | 10 mi | 20% | under 1% |
Sources: USDA SSURGO (August 5, 2026) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · Census ACS 2020-2024. Methods · Data status