Erosion prevention practices - tackifiers and soil stabilizers
Erosion prevention practices - tackifiers and soil stabilizers

Tackifiers and soil stabilizers are hydraulically applied chemicals derived from natural and synthetic sources used to promote adhesion among soil particles or mulch materials. In general, soil stabilizers (also known as soil binders) are used to increase soil adhesion, which improves soil stabilization by reducing water and wind driven erosion. Tackifiers are used as “glue” to bind and immobilize straw, cellulose products, pine needles, or other mulch that has been applied to a seeded area. Tackifiers protect seedbeds by holding the product to the soil surface and preventing movement. Relevant products include polyacrylamide, guar, chloride compounds, psyllium, resins, enzymes, surfactants, and various polymers, starches, and other compounds. Petroleum based tackifiers, once widely applied to straw mulch, have largely been replaced with other products that are easier to handle, break down naturally, and present fewer overall health and environmental risks.

Purpose and function

Chemical-based soil stabilization is intended to counteract the erosive influences of rainfall, snowmelt, and wind on bare soil. The use of tackifiers to prevent the movement of mulch material by wind and rain helps to keep straw and/or other mulches in place, preventing soil erosion. Stabilizers and tackifiers are temporary measures, designed to prevent short-term (e.g., two to four weeks) erosion between construction periods, and during seed germination and early growth for permanent stabilization. While they are effective for a wide range of soil, slope, temperature, and rainfall conditions, they are not intended for use in concentrated flow locations, such as ditches and channels.

Applicability

Site stabilization with soil binders and tackifier bonded mulch (e.g., straw, other fibers) applies to 1) areas of construction sites where soil disturbing activities have temporarily ceased, and measures are needed to prevent erosion and sediment runoff during rainfall or snowmelt; and 2) areas of the site that require permanent stabilization.

Site applicability

Construction sites often have areas where soil disturbing activities such as clearing, grading, or cut/fill work has stopped for a period of time. Bare areas that are not actively being worked need some type of cover or stabilization practice to prevent or minimize erosion in the event of rainfall or snowmelt. Tackifiers and soil stabilizers are applied hydraulically to reduce erosion by binding soil particles or mulch materials, often in conjunction with temporary or permanent seeding. Applicable areas include topsoil stockpiles, rough graded areas, sediment basin dikes, temporary earthen structures, and graded areas. Tackifiers and soil stabilizers can be used in conjunction with seed and mulch materials to achieve temporary and/or permanent stabilization.

Permit applicability

The MPCA Construction General Permit has several requirements regarding temporary stabilization. See Section 8.

Permittees must stabilize all exposed soil areas, including stockpiles. Stabilization must be initiated immediately to limit soil erosion when construction activity has permanently or temporarily ceased on any portion of the site and will not resume for a period exceeding 14 calendar days. Stabilization must be completed no later than 14 calendar days after the construction activity has ceased. Stabilization is not required on constructed base components of roads, parking lots and similar surfaces. Stabilization is not required on temporary stockpiles without significant silt, clay or organic components (e.g., clean aggregate stockpiles, demolition concrete stockpiles, sand stockpiles) but must provide sediment controls at the base of the stockpile.
For Public Waters that the Minnesota DNR has promulgated work in water restrictions during specified fish spawning time frames, permittees must complete stabilization of all exposed soil areas within 200 feet of the water's edge, and that drain to these waters, within 24 hours during the restriction period.
Other permit requirements exist during the construction of post-construction/permanent stormwater and temperature control BMPs discharging to special waters and impaired waters. In those cases, Permittees must immediately initiate stabilization of exposed soil areas, as described in item 8.4, and complete the stabilization within seven (7) calendar days after the construction activity in that portion of the site temporarily or permanently ceases.
Finally, it shall be noted that stabilization requires more than seed alone. Section 25 of the 2018 MPCA Construction Stormwater General Permit states: "Stabilize", "Stabilized", "Stabilization" means the exposed ground surface has been covered by appropriate materials such as mulch, staked sod, riprap, erosion control blanket, mats or other material that prevents erosion from occurring. Grass seeding, agricultural crop seeding or other seeding alone is not stabilization. Mulch materials must achieve approximately 90 percent ground coverage (typically 2 ton/acre). [Minn. R. 7090].

Effectiveness

Hydraulically applied products have undergone rapid development and improvement during the past ten years and now provide seed establishment and soil protection performance equal or superior to conventional seeding and mulching practices. Temporary and permanent stabilization with mulch-adhered tackifiers and soil stabilizers is effective in reducing soil loss from construction sites by increasing mulch longevity and preventing mulch displacement via wind and heavy rain. Tackifiers used as adhesives in hydraulically applied mulches (e.g., bonded fiber matrix, other hydromulches) have been used for decades, and provide results similar to rolled erosion control products in non-channel applications when selected, prepared, and applied in accordance with manufacturer’s directions. Chemical soil stabilizers bind the soil, helping it to further resist raindrop, sheet, and rill erosion. Soil stabilizers, when used as adhesives, are effective for dust control, short-term erosion prevention, and roadway stabilization. Some stabilizers, such as anionic polyacrylamides, may be used as coagulants in sediment ponds to promote flocculation and settling. The following table summarizes expected performance for an array of typical water quantity and quality target constituents for tackifiers and soil stabilizers.

Expected performance for tackifiers and soil stabilizers.
Link to this table

Water Quantity
Flow attenuation	Little or no design benefit
Runoff volume reduction	Little or no design benefit

Water Quality
Pollution prevention
Soil erosion	Primary design benefit
Sediment control	Little or no design benefit
Nutrient loading	Primary design benefit
Pollutant removal
Total suspended solids	Primary design benefit
Total phosphorus	Primary design benefit
Heavy metals	Secondary design benefit
Floatables	Little or no design benefit
Oil and grease	Little or no design benefit

Planning considerations

A key benefit of hydraulically applied products is the ability to treat large sites with steep (3H:1V to 1H:1V), long slopes or other areas where installation of ECBs or turf reinforcement mats is difficult. A nearby source of water (or water tank) to mix the slurry is necessary for large sites. Typical hydraulic soil cover applications include a slurry-like mix of seed, fertilizer, and mulch. Also available for inclusion are other amendments such as tackifier and a variety of fibrous materials that dry to form a flexible net or crust that provides excellent protection for bare soil before seed germination.

Application equipment ranges from small, hand-pulled polyethylene units with electric sprayers and tanks that hold up to 15 pounds of seed, fertilizer, and mulch, to large towed or truck-mounted machines with tanks of 100 to 2,000 gallons. Mixing ratios will vary significantly by application, but a standard turf application for one acre will typically include 100 to 150 pounds of seed (or more, depending on seed variety and site conditions), 300 to 400 pounds of fertilizer, 140 pounds of binder, and 1,500 to 2,000 pounds of fiber mulch mixed with 4,000 or more gallons of water.

As soil binder types and uses have expanded in recent years, refer to the following when selecting a binder product.

Soil types, slopes, and circumstances: What types of soils are present, how steep are they, and what is the slope length? Is the slope graded smooth or is it rough? Will the binder require resistance to leaching or abrasion? Is there existing vegetation to preserve? How long will the binder need to remain effective?
Application: Is there sufficient water nearby to mix the product? Are the slopes accessible to the tank/sprayer equipment? Can the equipment effectively treat the area(s) under review? How frequently must applications be made? Are the manufacturer’s applications rates being followed?
Product requirements: What are the required application conditions for the specific product under consideration, including soils, slopes, wetness/dryness, surface conditions (i.e., smooth/rough, compacted/loose, etc.)?
Costs, equipment, and labor required for accessing, transporting, preparing, applying, and maintaining the product.

This link lists the hydraulic erosion control products currently approved/qualified by MnDOT, which requires that an Applicator’s Certification from the manufacturer be provided before applying Polyacrylamide Tackifier, Organic Fiber Matrix, Bonded Fiber Matrix or Reinforced Fiber Matrix. Below is summary information on some of the most widely used soil binders.

Binders from plant materials, lasting less than six months

Guar is a non-toxic, biodegradable, natural colloidal product treated with dispersant agents for easy field mixing. It should be mixed with water at the rate of 11 to 15 pounds per 1,000 gallons. Recommended minimum application rates range from 40 pounds per acre for flat areas to 70 pounds per acre for 1H:1V slopes.
Psyllium is composed of the finely ground coating of plantago seeds, and is applied as a dry powder or in a wet slurry to the surface of the soil. Although it dries to form a firm but re-wettable membrane that binds soil particles together, it permits germination and growth of seed. Psyllium should be sufficiently mixed and diluted to provide uniform flow for application rates of 80 to 200 pounds per acre. Note that this product requires a 12 to 18 hour drying time prior to the next precipitation event.
Starch is non-ionic, cold water soluble granular cornstarch mixed with water and applied at the rate of 150 pounds per acre. Approximate drying time is 9 to 12 hours.

Binders from plant materials, lasting six to twelve months

Pitch and rosin emulsions are manufactured from natural resins and generally have a minimum solids content of 48 percent. The rosin should be at least 26 percent of the total solids content, non-corrosive, dilutable, and cure to form a water insoluble binding and cementing agent. For soil erosion prevention applications, the emulsion is diluted and should be applied at 5 parts water to 1 part emulsion for clayey soils, or 10 parts water to 1 part emulsion for sandy soils.

Polymeric emulsion blends

Acrylic copolymers and polymers consist of a liquid or solid polymer or copolymer with an acrylic base that contains a minimum of 55 percent solids. The polymeric compound should be handled and mixed in a manner that will not cause foaming (or include an anti-foaming agent). For all such compounds, product expiration dates should be checked. These products should be readily miscible in water, non-injurious to seed or animal life, non-flammable, should stabilize the soil without totally inhibiting water infiltration, and should not re-emulsify when cured. Drying time is 12 to 24 hours. Liquid copolymers should be diluted at a rate of 10 parts water to 1 part polymer and applied to soil at a rate of 1,175 gallons per acre.
Liquid polymers of methacrylates and acrylates consist of a tackifier/sealer that is an aqueous blend of 40 percent solids by volume, free from styrene, acetate, vinyl, ethoxylated surfactants, or silicates. The product is diluted with water as per manufacturer’s recommendations and applied with a hydraulic seeder at the rate of 20 gallons/acre. Drying time is 12 to 18 hours.
Copolymers of sodium acrylates and are non-toxic, dry powders that are mixed with water and applied to the soil surface for erosion control at rates that are determined by slope gradient (i.e., 3 to 5 pounds per acre for flat areas, 5 to 10 pounds per acre for slopes 5H:1V to 10H:1V, and 10 to 20 pounds per acre for slopes 2H:1V to 1H:1V.
Polyacrylamide (PAM) and copolymer of acrylamide are packaged as a dry flowable solid and diluted at a rate of 11 pounds per 1,000 gallons of water. It is typically applied at a rate of 5 pounds per acre, or per the manufacturer’s recommendations. Ensure that the product selected is anionic. (Cationic products, which can bind to fish gills, are toxic to aquatic environments.) Stormwater flows from slopes with PAM above waterbodies should pass through a sediment trap or basin. Do not use PAM as a standalone practice, as its effectiveness improves significantly when combined with mulch.
Hydrocolloid polymers are various combinations of dry flowable polymers that are mixed with water and applied to the soil surface at rates of 55 to 60 pounds per acre. Drying times range up to four hours.
When PAM could be released to groundwater, they should have less than 0.05 percent free acrylamide monomer by weight as established by the Food and Drug Administration (FDA) and the EPA. The Minnesota Department of Health provides an overview of acrylamide and drinking water.
For anionic PAM, choosing non-oil-based liquid or dry products can reduce aquatic toxicity risks. Choosing liquid anionic PAM with the lowest mineral oil content can also minimize potential aquatic toxicity.
MnDOT has certain standard specifications regarding the use of PAM.

Cementitious binder products

Gypsum readily mixes with water and mulch to form a thin protective crust on the soil surface. Gypsum is ground, calcined and processed to be mixed in a hydraulic seeder and applied at rates 4,000 to 12,000 pounds per acre. Drying time is 4 to 8 hours. The use of gypsum may release sulfate contamination to downgradient waters.

Products used primarily for unpaved roadway stabilization:

Petroleum-based products are not recommended because of their adverse effects on plants and water resources.
Chloride compounds (calcium chloride, magnesium chloride, natural brines) have proven effective in controlling dust on roadways, and are less likely than other alternatives to increase stormwater runoff. Repeat applications, however, are necessary and the product could restrict establishment of vegetation on treated areas due to chloride toxicity to plants. Excess chloride also is toxic to fish and other aquatic life (see Chloride 101). Oil field brines may release petroleum compounds to the environment, and other salts and brines can contain cyanide and heavy metal contaminants.
Organic, non-petroleum-based chemicals such as calcium lignosulfonate and sodium lignosulfonate are also effective stabilizers. These chemicals work best on unpaved roadways with fines in the 10 percent to 30 percent range. Lignosulfonates can harm vegetation, can be corrosive, cause foaming and discoloration in surface waters, and can release ammonia, phenols, chloride, sodium, sulfate, and heavy metal (especially zinc) contaminants.

Design

Use of soil binders varies by site condition and product (see table below). Most hydraulically applied products function best when used on dry soil. Use a soil test to verify the exact type of soil at the site. When using a binder slurry or tackifier/mulch blend for seeding, leaving the top two inches of the surface loose helps to ensure good germination. If the soil is compacted, seeds won’t penetrate properly and the slurry will splatter and slide, resulting in uneven application.

Polymer tackifiers are generally applied at rates of 40 to 60 pounds per acre, and organic tackifiers are typically applied at rates of 80 to 120 pounds per acre; however, manufacturers’ recommendations vary and should be followed for both product types. Applications of liquid mulch binders should be heavier at edges, in valleys, and at crests of banks and other areas where the mulch could be moved by wind or water. All other areas must have a uniform application of the tackifier.

Example properties of soil binders for erosion prevention. Source: California Stormwater Quality Association; California Stormwater BMP Handbook.
Link to this table

Evaluation criteria	Binder type
Evaluation criteria	Plant material based (short lived)	Plant material based (long lived)	Polymeric emulsion blends	Cementitious - based binders
Relative cost	Low	Moderate to high	Low to moderate	Moderate
Resistance to leaching	High	High	Low to moderate	Moderate
Resistance to abrasion	Moderate	Low	Moderate to high	Moderate to high
Longevity	Short to medium	Medium	Medium to long	Medium
Minimum curing time before rain	9 to 18 hours	19 to 24 hours	0 to 24 hours	4 to 8 hours
Compatibility with existing vegetation	Good	Poor	Poor	Poor
Mode of degradation	Biodegradable	Biodegradable	Photodegradable / chemically degradable	Photodegradable / chemically degradable
Campatibility with existing vegetation	Good	Poor	Poor	Poor
Mode of degradation	Biodegradable	Biodegradable	Photodegradable / chemically degradable	Photodegradable / chemically degradable
Labor intensive	No	No	No	No
Specialized application equipment	Water truck or hydraulic mulcher	Water truck or hydraulic mulcher	Water truck or hydraulic mulcher	Water truck or hydraulic mulcher
Liquid / powder	PowderX	Liquid	Liquid / powder	PowderX
Surface crusting	Yes, but dissolves on rewetting	Yes	Yes, but dissolves on rewetting	Yes
Clean up	Water	Water	Water	Water
Erosion control application rate	Varies¹	Varies¹	Varies¹	4,000 to 12,000 lbs / acre

¹Application rate varies with slope steepness (i.e., steeper = more); see manufacturer’s recommendation.

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Crown or slope the ground while grading to avoid ponding. Follow manufacturer's written recommendations for application rates, pre-wetting of application area (if necessary), and cleaning of equipment after use. Prior to application, roughen embankment and fill areas. Also, consider the drying time for the selected soil binder and apply with sufficient time before anticipated rainfall. Soil binders should not be applied during or immediately before rainfall. Avoid overspray onto roads, sidewalks, drainage channels, sound walls, existing vegetation, etc. Spraying of hydraulic mulch should not be performed during windy conditions, which would prevent the proper placement. Do not apply to frozen soil, areas with standing water, under freezing or rainy conditions, or when the air temperature is below 40°F during the curing period. If more than one treatment is necessary, the second treatment may be diluted or have a lower application rate. Generally, soil binders require a minimum curing time of 24 hours before they are fully effective.

Additional important considerations for soil stabilizers include the following.

Per the Construction General Permit:
- Conventional erosion and sediment controls must be used prior to using chemical addition.
- The SWPPP must describe any specific chemicals and the chemical treatment systems that may be used for enhancing sedimentation processes.
- Mulch, hydromulch, tackifier, polyacrylamide or similar erosion prevention practices must not be applied within any portion of the normal wetted perimeter of a temporary or permanent drainage ditch or swale section with a continuous slope of greater than 2 percent.
Chemical soil stabilizers and tackifiers must be applied in a manner so they do not enter surface waters. A minimum 30-foot setback from surface waters when applying soil stabilization/tackifier chemicals is recommended. Visible tracer or colorant to visually track application can be helpful.
When used alone, chemical stabilizers do not insulate the soil or retain moisture. Therefore, they do little to aid seedling establishment.
They are easily damaged by traffic and lose their effectiveness more rapidly than organic mulches.
They decompose with varying times, some within 60 to 90 days. Decomposition (especially of the hydrocarbon/organic-based stabilizer materials) has the potential to deplete oxygen in downgradient surface waters, so these products should be used with care, and mindful of MPCA guidelines for such materials when used for dust control.
Application of soil stabilizer is intended to be conducted with conventional hydraulic seeding equipment. Soil stabilizer may also be placed by dry spreading.
When dry spreading is used, the contractor must ensure that the material is applied uniformly and remains in place during subsequent wind events.
The manufacturer should provide detailed instructions on the storage, mixing and application procedures to insure proper safety and effectiveness of the product.
Safety data sheets should be provided to verify that products are free of toxics and to ensure proper handling. These safety data sheets must include whole product aquatic toxicity information with at minimum the results of: a) a 48-hour LC50 or EC50 acute study for a North American freshwater planktonic crustacean (either Ceriodaphnia or Daphnia sp.) and b) a 96-hour LC50 acute study for rainbow trout, bluegill or fathead minnow or another North American freshwater aquatic species other than a planktonic crustacean. The safety data sheets also should include the commercial and chemical names and Chemical Abstract Survey (CAS) number for all ingredients in the product.
The composition of surfactant ingredients in particular must be fully disclosed. Products containing nonylphenol and nonylphenol ethoxylates must not be used.
Seeding must be done in a manner that ensures direct contact with the soil.
When using soil stabilizer, seed must be sown separately from the time when the soil stabilizer is applied.
Application rates should be as recommended by the manufacturer.
When soil stabilizer is used on permanent slopes, an approved mulch should be applied as well to protect and facilitate germination of new seed.

Standards and specifications

MnDOT Standard Specifications 2575.3 part E.1, provides guidance for placing hydraulic erosion control products including tackifiers (natural and synthetic) and polyacrylamide. Part E.2 covers soil stabilizer matrixes and application methods, rates, and timing. Specification 2575.4., Part G, covers measurement of hydraulic erosion control products. Hydraulic erosion control products should meet Specification 3884 (“Hydraulic Erosion Control Products”).

Inspection and maintenance

Inspect the area before anticipated storm events (or series of storm events such as intermittent showers over one or more days), within 24 hours after the end of a rainfall event of one-half inch or more, and at least once every 14 calendar days. If possible, maintenance needs identified in inspections or by other means must be addressed before the next storm event, but in no case more than 7 days after the need is identified. If properly applied, little additional maintenance is required during the first weeks. After high winds or significant rainstorms, treated areas should be checked and re-treated if necessary.

Areas where erosion is evident should be repaired and treated again as soon as possible. Care is needed to minimize the damage to protected areas while making repairs, as any area damaged will require reapplication of treatment. In all cases, follow manufacturers’ recommendations regarding initial and follow-up application of hydraulically applied products. For example, some products require reapplication after specified time intervals and/or if treated areas become disturbed.

Costs

The following table summarizes estimated BMP costs based on MnDOT data summarizing average bid prices for awarded projects.

Average bid trafficker prices for Specification Year 2014
Link to this table

Bid Item	Item Description	Units	Average Price
2575.561/00010	Hydraulic Tackifier Type Natural	SY	💲0.39

Reference materials

Except where more stringent requirements are presented in this guidance, BMPs shall comply with MnDOT and other state requirements. Primary design references include the following.

The following is a list of additional resources that are not specific to Minnesota.

CASQA (California Stormwater Quality Association) California Stormwater BMP Handbook
Clark County Washington Stormwater Manual (BMP C121: Mulching)
Clean Water Services Erosion Prevention and Sediment Control Manual (4.1.4 Hydraulic Applications)
North Carolina Erosion and Sediment Control Planning and Design Manual (6.14 Mulching)
Tennessee Department of Environment and Conservation (TDEC) Erosion and Sediment Control Handbook (7.12 Hydro Applications, 7.13 Soil Binders)
Virginia Erosion and Sediment Control Handbook (3.35 Mulching)

Related pages

Stabilization practices

Erosion prevention practices - tackifiers and soil stabilizers Erosion prevention practices - tackifiers and soil stabilizers

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