The Hidden Threat of Stephenville-Urban land-Newalla complex, 1 to 8 percent slopes for Homeowners in Edmond
Geological Profile: Edmond, OK
What is Stephenville-Urban land-Newalla complex, 1 to 8 percent slopes?
Stephenville-Urban land-Newalla complex, 1 to 8 percent slopes is a moderate clay soil formation common in Edmond. It is characterized by a high silica content that causes it to absorb water and swell volume by up to 0.6%. Engineers value it for agriculture but fear it for construction due to its "shrink-swell" volatility.
Why Edmond Foundations Fail
If you live in North Edmond Meadows, South Edmond Village, East Edmond Heights, or West Edmond Park, your home is interacting with this critical geology. Unlike stable sandy loams, Stephenville clay moves.
The defining metric is the Plasticity Index (PI) of 7.0. This PI indicates relatively stable ground, though localized drainage issues can still undermine grade beams.
The "Active Zone" Depth
In Edmond, the "Active Zone"—where moisture levels fluctuate—extends 12-15 feet deep. Standard builder piers often stop at 8 feet. This mismatch is why we see repetitive failures in 73034.
- Elias Thorne, Lead Forensic Engineer
3 Signs of Stephenville Soil Failure
- Diagonal Shear Cracks: Extending from door/window corners (45-degree angles).
- Friable Soil Gap: Soil pulling 1-2 inches away from the foundation perimeter in summer.
- Sticking Doors: Specifically on the exterior walls relative to the center of the home.
Engineering Protocol: Correct vs. Incorrect
| Method | Suitability for Stephenville-Urban land-Newalla complex, 1 to 8 percent slopes | Verdict |
|---|---|---|
| Pressed Concrete Piling | Often shallow (8-10ft); relies on friction in active clay. | Avoid ❌ |
| Steel Piers (E3000) | Driven to absolute refusal (rock/shale) below active zone. | Recommended ✅ |
| Bell-Bottom Piers | Drilled concrete; excellent stability but higher cost/mess. | Viable Option |
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