Colorado CDOT Geotextile Fabrics

Solmax DOT Standard Specification Product Chart (click image to expand)

Colorado CDOT - Geotextile Uses

Colorado highways traverse steep mountain corridors, wind-blown plains, expansive Front Range clays, and decomposed granite. Add freeze–thaw cycles, snowmelt, summer cloudbursts, post-wildfire debris flows, and heavy truck traffic, and you get ground that can pump, rut, erode, and move fines. Geotextiles are the quiet engineering layer that helps these systems hold together.

The first job is separation and stabilization. On new lanes, shoulder widenings, and staged construction over marginal subgrade, a woven geotextile is placed between native soils and imported base. It keeps fines from migrating up into the aggregate under traffic, spreads load, and preserves base thickness. On very soft or wet areas—think saturated valley bottoms or zones disturbed by utility work—the fabric creates a working platform so trucks and pavers don’t punch through during construction.

Because water drives many failures, filtration and drainage are constant priorities. Nonwoven geotextiles line underdrain trenches, wrap perforated pipes, and separate drainage aggregate from surrounding soils behind retaining walls and abutments. Matching pore size and permittivity to local soils—granite sands in the high country, silts and clays along the Front Range—lets water move while fines stay put, reducing clogged outlets, wet spots, and shoulder drop-offs. In cold regions, pairing a nonwoven geotextile with open-graded aggregate can also act as a capillary break, limiting upward moisture that fuels frost heave.

Where flow concentrates—culverts, storm outfalls, river bends, and channel linings—geotextiles serve as riprap underlayment. A robust nonwoven filter goes on the prepared slope before armor rock. It prevents subgrade from piping through voids during high velocities, snowmelt surges, or debris-laden post-fire storms, helping the rock “lock in” and protecting embankments at bridge approaches and mountain creek crossings.

CDOT corridors include long stretches of MSE walls and grade separations. Here, geotextiles act as joint and face filters, placed behind panel or block joints to keep backfill fines from migrating to the face while maintaining drainage continuity. The same concept applies at wingwalls, backwalls, and around structural penetrations, where a filter layer preserves outlets and weeps.

Colorado also makes effective use of pavement interlayers. Asphalt-impregnated nonwoven geotextile beneath overlays improves waterproofing and slows reflective cracking—valuable where large daily temperature swings and deicing brines accelerate pavement aging. On chip seals, paving fabrics can extend service life by limiting water intrusion into the base.

For temporary erosion and sediment control, geotextiles show up in silt fence, inlet protection, curb socks, and check structures. They complement blankets and wattles by filtering flow while trapping fines, which is crucial for stormwater compliance on steep grades and disturbed ground. At project entrances, stabilized construction exits typically include a nonwoven geotextile under coarse rock to distribute wheel loads and limit track-out.

Finally, geotextiles provide liner protection in detention basins, lined ditches, salt-shed pads, and containment areas. Heavy nonwoven fabrics cushion geomembranes from angular aggregate and construction traffic, reducing puncture risk and extending system life.

Field practice ties it together: prepare subgrades smooth, avoid wrinkles, overlap seams generously, secure with pins or initial lifts, and cover promptly to limit UV exposure at high altitude. Selection is function-driven—woven for stabilization and tensile strength; nonwoven for filtration, drainage, and protection—tuned to the project’s soils, hydraulics, and traffic demands.

Bottom line: on CDOT projects, geotextile isn’t “landscape fabric.” It’s a purpose-chosen engineering layer that stabilizes variable subgrades, controls water and fines through harsh seasons, protects structures and channels, and stretches pavement life across Colorado’s demanding conditions.

Colorado CDOT