What is Dalhart soil and how does it affect Oklahoma foundations?

Reviewed by Preston, Oklahoma foundation repair consultant · Updated 2026-10-14

In short: Dalhart is a deep, well-drained soil of the Oklahoma Panhandle that formed in loamy sediment laid down by wind. Its subsoil is sandy clay loam over limy loam, and the area averages only about 18 inches of rain a year. For foundations, the main soil questions are how the wind-laid material responds to wetting and how water is managed around the house.

Where does Dalhart soil occur?

The USDA Natural Resources Conservation Service (NRCS) Official Series Description (OSD) places Dalhart in the Southern High Plains, Northern Part (Major Land Resource Area 77A) of Kansas, Oklahoma and Texas, and describes the series as extensive ¹. The type location is in Cimarron County, about 8 miles west and 1 mile south of the Boise City courthouse, at roughly 4,295 feet elevation ¹.

Dalhart forms on interdunes and sand sheets on tablelands, on slopes of 0 to 8 percent ¹. Its parent material is loamy eolian (wind-deposited) sediment of Holocene age ¹. This is the Panhandle (High Plains) landscape, where wind-laid deposits cover the Ogallala Formation.

What are its key properties?

"Btk" marks a subsoil layer that has gained both clay and calcium carbonate (lime). "Aridic" signals a dry moisture regime. Dalhart is used mainly for wheat and grain sorghum, with some grazing on native mixed grasses ¹.

What do the properties mean for foundations?

Wind-laid soil and wetting

Collapsible soils are unsaturated soils that lose volume when wetted, loaded, or both, and wind-deposited soils such as loess and dune sands are among the deposits where they occur, especially in dry climates ⁴. Collapse depends on a loose, open grain structure held together by weak bonds such as clay or calcium carbonate, which water can weaken ⁴. Common wetting sources include irrigation, leaking pipes, septic fields and redirected rainwater ⁴. The OSD does not rate Dalhart's collapse potential, so this is a site question; see hydrocollapse (collapsible soil) and collapsible and loess soils.

Shrink-swell

Clayey soils swell when wet and shrink when dry ⁵. Dalhart's control section has 18 to 30 percent clay ¹. NRCS classes linear extensibility (LEP) under 3 percent as low, 3 to 6 percent moderate, 6 to 9 percent high and 9 percent or more very high ³; the LEP for each Dalhart map unit is published in Web Soil Survey ².

Water management

The ASCE homeowner guide stresses keeping soil moisture uniform around a foundation, grading soil away from the house and having leaks found and repaired ⁵. On wind-laid soils, the same steps limit the wetting that can trigger collapse ⁴. See surface drainage and grading and plumbing leaks under slab.

How do you check a specific lot?

• Look up the map unit and LEP in Web Soil Survey ².
• Route downspouts and irrigation water away from the foundation ⁵.

Related

• Collapsible and Loess Soils
• Ogallala Formation and Loess
• Panhandle (High Plains)
• Freeze-Thaw and Frost Depth
• Soil Series Index