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

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

In short: Quinlan is a shallow, well-drained loam on hills, ridges and escarpments of western Oklahoma's red plains. Soft, noncemented Permian sandstone begins only 10 to 20 inches below the surface. For foundations, the main issues are shallow soft rock, steep slopes and fast runoff rather than clay swelling.

What is Quinlan soil?

Quinlan is an official USDA soil series classified as "Loamy, mixed, superactive, thermic, shallow Typic Haplustepts" ¹. It formed in loamy residuum (rock weathered in place) from noncemented, calcareous Permian sandstone or siltstone ¹.

The soil occurs on interfluves and side slopes of hills, ridges and escarpments on dissected plains, with slopes of 1 to 50 percent ¹. It is found in the Central Rolling Red Plains (MLRAs 78B and 78C) of western Oklahoma, a few counties in southern Kansas and northwestern Texas, and is of large extent ¹. The series was established in 1932 in Woodward County, where its type location lies about 1.5 miles west of Quinlan ¹. Mean annual precipitation is about 25 inches (range 20-30) ¹. Most areas are used for grazing; native vegetation is mainly little bluestem and grama grasses ¹.

In Oklahoma, Quinlan is part of the Northwest (Gypsum Hills) landscape, on the Western Permian red beds.

What is the typical soil profile?

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

• Depth to bedrock: densic bedrock at 10 to 20 inches; densic contact at about 13 inches in the typical profile ¹.
• Drainage: well drained; moderate permeability in the soil and moderately slow in the bedrock ¹.
• Runoff: medium on 1-5 percent slopes, high on 5-20 percent and very high above 20 percent ¹.
• Clay in control section: 10 to 30 percent ¹.

What does it mean for foundations?

Shallow, dense but soft rock

Densic materials are compact, noncemented layers that restrict roots, with compaction from geologic or human causes rather than soil formation ³. Quinlan's sandstone fits this description: noncemented and dense enough to restrict roots, and it breaks down to very fine sandy loam, loam or silt loam ¹. It begins within 20 inches of the surface ¹.

Steel push piers in Oklahoma typically reach about 8 to 16 feet, with a median near 12 feet in Tulsa, based on installation records ⁴. On a shallow-rock soil like Quinlan, a pier may stop shallower. Whether that layer is adequate bearing is a matter for installation pressure records and, where needed, an engineer. See steel push piers, shale weathering and bearing strata and working with engineers.

Slopes and runoff

With slopes up to 50 percent and high to very high runoff on steeper ground ¹, Quinlan sites can be steep and shed water fast. Related pages:

• Erosion, undermining and washout voids
• Slope creep and lateral movement
• Surface drainage and grading

Shrink-swell

The USDA rates shrink-swell as linear extensibility, with under 3 percent low and 3 to 6 percent moderate ⁵. Quinlan's subsoil is loam with mostly 10 to 20 percent clay ¹. The rated value for each mapped unit is in Web Soil Survey ².

Related

• Lucien soil
• Woodward soil
• St. Paul soil
• Depth to rock from borings
• Soil series index