11.5 Tackifiers, Soil Binders, Roughening, and Temporary Cover

3. Tackifiers (12.3.7) vs. 4. Soil Binders (12.3.8)

Tackifiers (12.3.7)

Tackifiers are organic or synthetic adhesives sprayed specifically to glue dry straw, hay, or hydraulic mulch fibers to each other and to the soil surface so wind and sheet flow cannot displace the mulch:

• Organic Plant Gums / Mucilages: Guar gum (ground endosperm of Cyamopsis tetragonoloba beans), psyllium / plantago mucilage (seed husks of Plantago species), and corn or potato starch applied at $40 \text{ to } 150 \text{ lb/acre}$. These form biodegradable, non-toxic water-swelling hydro-colloid gels ideal for temporary protection ($1 \text{ to } 3 \text{ months}$).
• Pitch / Rosin and Synthetic Polymer Emulsions: Pine resin emulsions or polyvinyl acetate (PVA) / acrylic copolymers used to tack blown straw or wood fiber for longer periods ($3 \text{ to } 12 \text{ months}$).

Soil Binders (12.3.8)

Soil Binders (also called soil stabilizers or crusting agents) are liquid polymers, emulsions, or mineral powders applied directly to bare mineral soil surfaces, inactive graded pads, haul roads, or soil stockpiles to flocculate fine particles, bind surface soil grains into a permeable wind- and water-resistant crust, and suppress fugitive dust:

• Anionic Polyacrylamide (PAM): A high-molecular-weight, negatively charged, water-soluble linear polymer applied directly to bare slopes, irrigation furrows, or stockpiles at very low rates ($1 \text{ to } 5 \text{ lb/acre}$). Aided by naturally occurring divalent cations ($\text{Ca}^{2+}$, $\text{Mg}^{2+}$) in the soil water, anionic PAM bridges clay and silt particles into larger stable aggregates—reducing sheet/rill erosion and surface pore sealing by $70\% \text{ to } 95\%$ while maintaining high infiltration.
  • Chemical-treatment approval: Verify the approved product, dose, residual monomer specification, and aquatic-toxicity evaluation. The EPA CGP requires prior approval for cationic treatment and compliance with state/local restrictions; it does not categorically prohibit all neutral PAM. An anionic label alone does not establish safe use.
• Calcium Sulfate — Gypsum ($\text{CaSO}_4 \cdot 2\text{H}_2\text{O}$): A soluble mineral soil binder ($500 \text{ to } 2,000 \text{ lb/acre}$) that releases divalent calcium ions ($\text{Ca}^{2+}$) into soil pore water, displacing dispersive sodium ($\text{Na}^+$) on clay surfaces, flocculating dispersed colloidal clays, and preventing surface crusting.
• Acrylic/Vinyl Copolymers and Lignin Sulfonate: Sprayed onto inactive stockpiles, arid cut slopes, and unpaved construction roads to form a durable, dust-free surface crust ($3 \text{ to } 12 \text{ months}$).

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5. Surface Roughening (12.3.9) and 6. Non-Seed Stabilization (12.3.10)

Surface Roughening (12.3.9)

Surface Roughening is the mechanical creation of horizontal grooves, ridges, indentations, or steps running parallel to the slope contour (perpendicular to the direction of downhill runoff) across bare graded slopes. Smooth, hard-bladed or rubber-tire-rolled slopes shed water like pavement; horizontal roughening creates thousands of miniature dams across the slope that slow sheet flow velocity, increase infiltration, trap windblown soil, and hold seed and fertilizer in sheltered micro-pockets.

Additional Surface Roughening Methods:

• Contour Furrowing / Scarifying / Ripping: Pulling chisel plows, ripper shanks, or disks along the contour on slopes $\le 3\text{H}:1\text{V}$ to cut horizontal grooves $2 \text{ to } 4 \text{ inches}$ deep spaced $8 \text{ to } 15 \text{ inches}$ apart.
• Stair-Stepping / Serration (Benching): Cutting horizontal steps or serrated miniature benches ($1 \text{ to } 3 \text{ feet}$ high and wide, with the horizontal tread slightly wider than the vertical riser) into steep cohesive clay, siltstone, or soft-rock cut slopes ($\ge 2\text{H}:1\text{V}$) during excavation. As the vertical riser weathers and sloughs slightly, loose soil collects on the flat horizontal step, creating a stable bench where seed and moisture accumulate.
• Sheepsfoot / Tamping-Foot Rolling: Rolling a cylindrical steel drum studded with projecting tamping feet to punch thousands of small water- and seed-trapping pockets into the soil surface.

Non-Seed Stabilization (12.3.10)

Non-Seed Stabilization provides permanent or long-term mineral or structural surface armoring where vegetation cannot survive—such as arid/desert climates ($< 10 \text{ in.}$ annual precipitation), dense shade beneath highway bridges and overpasses, electrical substations and utility yards, or steep rocky slopes:

1. Crushed Stone / Angular Gravel Mulch: A $2\text{- to }4\text{-inch}$ layer of clean, angular crushed stone placed over a permeable non-woven geotextile filter fabric (which prevents underlying soil fines from pumping upward into the aggregate voids).
2. Decomposed Granite (DG): Well-graded angular granite screenings ($0.25 \text{ in.}$ minus), often stabilized with organic plant binders or polymer emulsions and compacted over trails, medians, and arid slopes.
3. Cellular Confinement Systems (3D Honeycomb Geocells): Expandable three-dimensional high-density polyethylene (HDPE) perforated honeycomb strips stretched across steep slopes or channels, anchored with steel J-pins or polyester tendons, and infilled with crushed aggregate, topsoil/seed, or concrete to prevent downslope sliding of the infill.
4. Articulated Concrete Blocks (ACBs) / Cable-Tied Concrete Mats: Interlocking precast concrete block matrices laid over a geotextile filter layer to armor extreme-velocity spillways, bridge abutments, and shorelines.

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Summary Comparison: Non-Vegetative & Mechanical Erosion Controls (12.3.5–12.3.10)