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

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

In short: Okemah is a deep, somewhat poorly drained soil of eastern Oklahoma's prairies, with silt loam over a silty clay subsoil. Water perches 2 to 3 feet below the surface each winter and spring, and the clay subsoil shows slickensides, a sign of shrink-swell. Homes on Okemah deal with both seasonal wetness and clay movement.

What is Okemah soil?

Okemah is an official USDA soil series classified as "Fine, mixed, active, thermic Aquic Paleudolls" ¹. "Aquic" in a soil name indicates periodic saturation and the oxygen-poor conditions that come with it ³. The soil formed in material weathered from loamy and clayey alluvium or colluvium derived from Pennsylvanian shale ¹.

It lies on broad, smooth high terraces and lower upland slopes in the Cherokee Prairies, with slopes of 0 to 5 percent ¹. The series occurs in eastern Oklahoma and southeastern Kansas and is rated as extensive ¹. Its type location is in Okmulgee County, about 5.5 miles west of Beggs, and it was established in Okfuskee County in 1948 ¹. Mean annual precipitation is about 41 inches (range 37-46) ¹. Native vegetation is tall grass prairie ¹.

In Oklahoma, Okemah areas fall in the Tulsa Metro and East-Central (Arkoma) regions, on Pennsylvanian shales and Quaternary alluvium and terraces.

What is its typical soil profile?

Source for the table: ¹. Other properties from the official description ¹:

• Water table: perched seasonal high water table at 2 to 3 feet, December to April in normal years ¹.
• Drainage: somewhat poorly drained; permeability slow; saturated hydraulic conductivity moderately low ¹.
• Solum thickness: more than 60 inches. Depth to bedrock is not stated ¹.
• Subsoil texture range: clay loam to clay ¹.

What does it mean for foundations?

Clay movement

Slickensides are polished, grooved surfaces formed by repeated shrinking and swelling of clay ⁴. Okemah's upper subsoil has a few slickensides, and its subsoil is silty clay to clay ¹. Clayey soils swell as they gain water and shrink as they dry, and uneven moisture change around a shallow foundation causes uneven movement ⁵.

The USDA rates shrink-swell as linear extensibility: 3 to 6 percent is moderate, 6 to 9 percent high and 9 percent or more very high ⁶. The rated value for a mapped unit is in Web Soil Survey ². Patterns to read about:

• Perimeter drying settlement (edge drop)
• Perimeter wetting heave (edge lift)

Seasonal perched water

A perched water table forms where one or more saturated layers sit above unsaturated layers, a condition called episaturation ³. On Okemah, this happens 2 to 3 feet below the surface from December to April ¹.

Related topics:

• Groundwater and perched water
• Crawl space moisture and wood decay

Moisture control

The ASCE Geo-Institute guide lists roof runoff, grading, irrigation, trees, plumbing leaks and shallow seepage as the moisture sources to manage around shallow foundations ⁵. For shallow seepage it describes an upslope trench drain with a water barrier membrane ⁵.

How can the soil at a property be confirmed?

Web Soil Survey shows mapped soil units and soil data for an area and can generate custom reports ². The water table described for Okemah is seasonal, present from December to April in normal years ¹, so the time of year matters when water levels are checked on site.

Related

• Parsons soil
• Muskogee soil
• Soil series in the Tulsa metro
• Seasonal movement calendar
• Soil series index