Idaho IDT Geotextile Fabrics

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

Idaho IDT  - Geotextile Uses

Idaho highways span basaltic plains, loessal hills, alluvial valleys, and steep mountain corridors. Add freeze–thaw cycles, rain-on-snow events, spring runoff, wildfire-driven debris flows, and heavy truck traffic, and you get subgrades that can pump, rut, scour, and lose fines. Geotextiles are the quiet engineering layer that helps these systems keep working.

The first role is separation and stabilization. On new lanes, shoulder widenings, and rehab projects, a woven geotextile is placed between weak native soils and imported base. It prevents fine soils from migrating up into the aggregate under traffic, spreads load, and preserves base thickness—especially valuable over saturated valley bottoms, silty loess, and disturbed utility trenches. Where subgrades are very soft or wet, the fabric establishes a working platform so haul trucks and pavers don’t punch through; on exceptionally weak ground it’s often paired with a geogrid for added stiffness.

Because water drives many failures, filtration and drainage are constant priorities. Nonwoven geotextiles line underdrain trenches, wrap perforated pipe, and separate drainage stone from surrounding soils behind retaining walls and abutments. Matching apparent opening size and permittivity to local soils—clean sands along river terraces versus tighter silts and clays on the Palouse—lets water move freely while fines stay put. In cold regions, pairing a nonwoven with open-graded aggregate also forms a capillary break, limiting upward moisture that fuels frost heave and base softening.

Where flows concentrate—culverts, storm outfalls, river bends, and channel linings—geotextiles serve as riprap underlayment. A robust nonwoven filter is placed on the prepared slope before armor rock. It prevents underlying soils from piping through voids during high velocities, snowmelt surges, and debris-laden post-fire storms, helping the rock “lock in” and protecting embankments at bridge approaches and mountain creek crossings. Along the Snake and Salmon systems, where stage changes can be rapid, the filter underlayment helps maintain scour protection through fluctuating hydraulics.

ITD corridors also include extensive mechanically stabilized earth (MSE) walls and grade separations. Here, geotextiles act as joint and face filters, tucked behind panel or block joints so backfill fines don’t migrate to the face while drainage continuity is preserved. The same concept applies at wingwalls, backwalls, and structural penetrations, where a filter layer keeps weeps functioning and fascia clean.

Idaho makes strategic 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 limit water intrusion into the base, extending service life on rural routes and heavy-haul corridors alike.

For temporary erosion and sediment control, geotextiles appear in silt fence, inlet protection, curb socks, and check structures. They complement blankets and wattles by filtering flow while trapping fines—critical for stormwater compliance on steep cuts, utility work, and wildfire recovery sites. At project entrances, stabilized construction exits typically include a nonwoven geotextile beneath coarse rock; the fabric spreads wheel loads and prevents stone from punching into wet soils, reducing track-out.

Finally, geotextiles provide liner protection in stormwater basins, lined ditches, salt-shed pads, and deicing-brine containment. Heavy nonwoven fabrics cushion geomembranes from angular aggregate and construction traffic, lowering puncture risk and boosting system life.

Good field practice ties it together: prepare subgrades smooth, avoid wrinkles, overlap or sew seams as needed, anchor with pins or initial lifts, and cover promptly to limit UV exposure at altitude. Selection is function-driven—woven for stabilization and tensile capacity; nonwoven for filtration, drainage, and protection—tuned to Idaho’s soils, hydraulics, and traffic demands.

Idaho IDT