The clay subgrades in Johnson County can swell 2 inches between wet and dry seasons. That movement destroys pavement. In Overland Park, we see this failure pattern on collector streets built before the 2005 Unified Development Standards tightened subgrade preparation rules. A proper flexible pavement design accounts for that seasonal volume change. It distributes wheel loads through asphalt layers into a prepared foundation. Most commercial parking lots here need 4 to 6 inches of asphalt on 8 inches of aggregate base to survive 20-year cycles. Skipping the geotechnical investigation is not an option when the underlying shale and limestone bedrock varies in depth from 3 to 20 feet across a single site. We run Proctor and CBR tests on site-specific borrow before computing layer coefficients.
A subgrade resilient modulus below 5,000 psi in wet months demands either lime stabilization or a thicker aggregate base. We measure that directly.
Methodology and scope
Local considerations
A nuclear density gauge tests every 150-foot lift. The operator walks behind the roller. The numbers flash on the LCD screen. 92 percent. Not enough. The roller makes another pass. In Overland Park, we have rejected base course that was compacted 2 percent below specification. Why? Because a parking lot at 119th and Quivira failed within 18 months from exactly that error. Rutting appeared after the first spring thaw. The owner paid triple the initial cost in demolition and replacement. The fix involved removing 8 inches of asphalt, recompacting the base to 95 percent modified Proctor, and installing edge drains to intercept perched groundwater. That failure was entirely preventable with proper field density testing during construction. Our technicians run sand cone correlations on every nuclear gauge measurement to eliminate calibration drift.
Applicable standards
AASHTO Guide for Design of Pavement Structures (1993), ASTM D1557 – Modified Proctor, ASTM D1883 – CBR, KDOT Standard Specifications (2015)
Associated technical services
Subgrade evaluation
Resilient modulus testing, CBR measurement, and soil classification to ASTM D2487 for the upper 3 feet below subgrade elevation.
Layer thickness design
AASHTO 93 structural calculations using site-specific traffic projections and seasonal moisture adjustment factors for Johnson County.
Construction QA/QC
Nuclear density testing with sand cone correlation, asphalt core extraction, and subdrain inspection per KDOT Section 602.
Typical parameters
Frequently asked questions
How much does flexible pavement design cost in Overland Park?
Typical design packages range from US$1.590 to US$5.220 depending on site size and traffic classification. A small commercial lot with one borings and AASHTO design runs near the lower end. Larger arterial projects requiring multiple soil profiles, drainage analysis, and KDOT coordination approach the upper range.
What is the difference between flexible and rigid pavement?
Flexible pavement uses asphalt concrete layers over granular base. Loads distribute through aggregate interlock. Rigid pavement uses Portland cement concrete slabs that bridge small subgrade defects through beam action. Flexible costs less upfront. Rigid lasts longer under heavy static loads. In Overland Park clays, flexible pavement requires better subgrade preparation because it cannot span settlement depressions the way a reinforced concrete slab can.
How long does the design process take?
Field investigation takes 2 to 3 days including borings and dynamic cone penetration. Laboratory testing requires 5 to 7 working days for Proctor and CBR results. The engineering report with structural layer recommendations is delivered 10 to 12 business days after field work completion. More info.