Six lanes of freeway are only as durable as the few feet of soil under them. Pavement design in Texas assumes a subgrade of a certain stiffness and uniformity, and every inch of asphalt or concrete above it is sized on that assumption. Road subgrade preparation is how we make the assumption true: stripping, shaping, treating, compacting and proof rolling the roadbed until it is a stable, even foundation for the base and surface courses that follow.
We prepare subgrade for city streets, county roads, industrial access roads, truck courts and the private drives inside developments. The work differs by soil and by traffic, but the logic is constant. Find the weak spots before the paving crew does, correct them while correction is cheap, and leave the subgrade crowned and sealed so the first rain does not undo the work. A pavement that fails in five years usually started with a subgrade that was accepted in a hurry.
What subgrade preparation includes
The scope starts with clearing and stripping the roadway, then cutting and filling to the subgrade elevation set by the profile. We scarify and recompact the top layer or treat it with lime or cement where the design calls for it, proof roll the surface with a loaded truck to find soft areas, and correct whatever fails. The finished subgrade is shaped to the crown and cross-slope in the plans and checked with a laser or GPS grade control.
Utilities add complexity. Trenches crossing the roadbed have to be backfilled and compacted so that they are as stiff as the soil around them, or the pavement will show the trench as a ribbon of settlement. We coordinate with the utility crews to finish crossings before the final subgrade pass, and we mark them so the paving crew can see where the soft zones were.
Roads being widened across West Texas and the Hill Country
Highway work in the Permian Basin and the Panhandle shows how much roadway is being rebuilt. TxDOT's Loop 88 page describes an approximately 12.4 mile project west of US 84 in Lubbock that converts two-lane rural roadway to an access-controlled six-lane divided freeway with frontage roads, with sections 3A and 3B completed in April 2026 and section 3C construction scheduled to begin in fall 2026. Rural two-lane roads converted to freeways need new subgrade across their full width, and the sections are built in segments that must tie to one another.
In the Odessa area, TxDOT's April 28, 2025 notice proposes widening about five miles of Loop 338 in Ector County from East Yukon Road to US 385 North from a four-lane divided highway to a four-lane freeway with frontage roads, growing the right of way from about 200 feet to 400 feet, with overpasses at Grandview Avenue, 87th Street and 100th Street. Doubling the right of way means doubling the subgrade, and the overpass approaches mean engineered embankment.
Local streets, bond projects and tie-ins
City work follows its own pattern. A Community Impact report updated December 1, 2023 lists a $6 million I-35 and FM 725 intersection project in New Braunfels, planned from June 2022 to fall 2024 per TxDOT, and a $24.78 million Loop 337 Common Street improvement between Loop 337 and Gruene Road funded by the May 2023 bond. This is a published local summary, and the figures are for context only. Projects like these run through existing traffic, so subgrade work is done in stages, with detours and tie-ins to live pavement.
Tie-ins are where subgrade failures start. New pavement meeting old pavement needs a transition, a clean saw-cut edge and a compacted subgrade right up to it, because a soft strip at the seam grows into a pothole. We take extra care at those joints, and we coordinate with concrete paving and asphalt crews so the base and surface go on while the subgrade is still in good condition, starting with asphalt paving base preparation.
Proof rolling, treatment and keeping it dry
We walk the subgrade ahead of the proof roll to mark visible problems, then run a loaded truck at a walking pace and watch for deflection. Soft spots are cut out and replaced, or treated in place, and the area is proof rolled again. The geotechnical engineer or the testing agency usually witnesses the final roll and signs off.
Water is what undoes subgrade, so we manage it from the start. We keep the subgrade crowned and graded to drain, protect it from ponding, and install temporary ditches where runoff could flow across it. Where the design calls for chemical treatment, the lime and cement soil treatment crews we coordinate mix and cure the layer, and the base goes on promptly after the cure.
Working in segments around traffic and weather
Road work is linear, and the schedule depends on the order of segments. We work with the owner and traffic control contractor to keep lanes open, sequence the cuts and fills so that material flows from one segment to the next, and avoid leaving more subgrade open than the crew can finish before weather. A closed lane that sits for a month is a complaint magnet.
Weather is the swing factor. In the clay belt, a rain can close a roadbed for days, while in dry West Texas wind and heat can dry the surface to a crust that needs scarifying again before the base. We watch the forecast and the moisture, and we adjust the daily plan, because the work that is best done in a morning may be undone by an afternoon storm.
What moves the cost of subgrade work
Soil type, treatment depth and haul distances drive the price. A roadbed that needs lime treatment to a depth of a foot costs more than one that only needs recompaction, and an import of select fill to replace unsuitable soil can double the earthwork cost. Mobilization is also significant on small jobs, so we combine subgrade with adjacent work where possible.
For municipal and public works owners, we price by the square yard with clear unit prices for undercut and replacement, which makes change orders easy to evaluate. Private owners building access roads for truck terminal and cross-dock sites get the same structure.
Send the roadway section
Send the roadway section, the soil report and the traffic phasing. We will price subgrade by the square yard, with unit prices for undercut and treatment.
We work with paving crews so the base goes down while the subgrade is still in good shape.
Common Questions
How is subgrade different from base?
Subgrade is the native or prepared soil under the pavement structure. The base is the layer of crushed stone or treated material placed on top of it. Both are compacted and tested, but they are built from different materials.
What is proof rolling and why is it required?
A heavy loaded truck is driven across the subgrade while an inspector watches for rutting or movement. It finds soft areas that density tests can miss between test locations, and it is a standard acceptance step.
When do you recommend soil treatment for a road?
When the native soil is plastic clay or otherwise too weak for the traffic, and replacement would cost more. The geotechnical engineer recommends it, and we run the work.
Can subgrade be prepared in the rain?
Light rain is workable, but heavy rain stops the work. We shape the surface so it sheds water, and we wait for it to dry before testing.
How do you handle utility crossings in the roadbed?
We make sure each trench is backfilled in compacted lifts and tested before the final subgrade pass. Crossings that are not compacted properly show up as dips in the pavement.