CHAPTER 2

Literature Review

2.1 Introduction

This chapter documents information collected from the literature review conducted on ESCs used during construction, including background, regulations, common practices, and environmental considerations. The literature review encompassed a range of literature types to provide a comprehensive overview of the existing knowledge on the topic of reducing the use of plastics in ESC practices. The literature included a range of materials, including peer-reviewed journal articles, research reports, government documents, conference papers and proceedings, gray literature, and websites. Documents were identified primarily through the Transport Research International Documentation database, Google Scholar, online journal databases and libraries, and agency websites. The objective of this chapter is to provide the background for the survey results presented in Chapter 3 and the case examples described in Chapter 4. In addition, this chapter provides an overview of existing efforts for the reduction of plastics and promotion of sustainable materials within ESC practices used on DOT project sites.

2.2 ESC Background

States DOTs are among the largest horizontal construction facilitators in U.S. roadway construction projects, which often require extensive clearing, excavation, and grading activities before stabilization, thereby resulting in continuous disturbed areas. When the land cover is stripped, bare soil is exposed and becomes susceptible to erosion from overland stormwater flows and wind drifts. When eroded sediment is entrained in stormwater flows, it is suspended and transported. The nature of linear construction results in an immense number of stormwater discharge points (outfalls); therefore, if sediment-laden stormwater is not managed on-site, sedimentation can occur in receiving conveyances or water bodies. Downstream consequences associated with sediment-laden discharge include the following: (1) increased siltation and turbidity, which hinders aquatic habitats, feeding, and reproduction; (2) reduced conveyance and storage capacities leading to flow alteration or flooding; (3) poor public perception; and (4) economic pressure from decreased recreation and increased treatment costs (Bugg et al., 2017). To mitigate these potential consequences, ESC practices are installed on-site to prevent soil dislodgement (erosion) or promote sedimentation in a designated area.

Erosion control is performed through one or more of the following mechanisms: (1) absorb or divert rainfall energy, (2) slow overland flow velocity, (3) reduce dust, (4) bind soils, or (5) increase absorption or infiltration of stormwater. Sediment control is performed by intercepting flow, creating slow-flowing impoundments, and providing volume and time for gravitational settling. Several common ESC practices are used together throughout construction phasing to prevent offsite discharge of sediment-laden stormwater. ESC practices include rolled erosion control

products (RECPs), hydromulching, track-out control, inlet protection, check dams, sediment barriers, and sediment basins. The suite of ESCs used on-site is governed by the state DOT standard specifications and details and the approved products list/qualified product lists (APLs/QPLs) or their equivalent. ESC is accomplished through a wide range of measures, materials, and manufactured products. Many structural ESC products have introduced synthetic materials, such as plastic netting, which has raised concerns regarding the environmental sustainability of practices.

2.3 ESC Regulations and Policies Pertaining to Stormwater Management

Through NPDES of the Clean Water Act, the U.S. Environmental Protection Agency (EPA) and its delegated state environmental agencies require that state DOTs attain coverage under appropriate stormwater general permits to manage stormwater runoff quantity and quality. State DOTs are subject to either state or federal municipal stormwater discharge permits, which address non-point source pollution to the maximum extent practicable. The municipal permits commonly outline six minimum control measures (MCMs): (1) public education and outreach, (2) public involvement and participation, (3) illicit discharge detection and elimination, (4) construction stormwater control, (5) post-construction stormwater control measures, and (6) pollution and prevention for permittee operations. The six MCMs must be accompanied by monitoring, evaluation, and reporting plans. Construction sites disturbing one or more connected acres or land within a development or sale plan that will ultimately disturb one or more acres must also obtain coverage under the CGP (U.S. EPA, 2024).

The CGP must address the minimum federal effluent limitation guidelines, which includes (1) the design, installation, inspection, and maintenance of ESC practices; (2) pollution prevention measures to minimize discharge of pollutants (e.g., oil and grease, concrete washout, debris); (3) stabilization of disturbed areas that will be inactive for at least 14 days; (4) controls at points of discharge; and (5) prohibited concrete washout, paint, fuel, oil, or solvent discharge. The SWPPP, or its equivalent, must include the ESCs and stormwater management measures that will be employed on-site. The SWPPP must be submitted with the Notice of Intent and approved by the NPDES authority before construction to receive permit coverage and should remain a living document through final stabilization. The SWPPP must be maintained until the Notice of Termination (NOT) is received. After NOT submission, the permitting authority conducts a review to either close out the permit or issue corrective action. If corrective action is issued, the SWPPP must be appropriately updated. Throughout its life, the SWPPP must be kept on-site and updated with the appropriate measures for grading and site activity, inspection reports, and maintenance efforts (U.S. EPA, 2024). Failure to comply with permit terms can result in civil or criminal enforcement.

The CGP, first established in 1992, has evolved over time and was updated in 2022. In all states, except for Massachusetts, New Hampshire, New Mexico, and the District of Columbia, the EPA has authorized the state to oversee their own permits. In many cases, state departments of environmental quality, or their equivalent, oversee the NPDES programs; however, the EPA can audit state NPDES programs. When individual states are not authorized to oversee permits (e.g., select Indian Country lands and federal facilities), construction activities fall under the EPA’s permitting authority (U.S. EPA, 2024).

State permit requirements must follow federal guidelines at a minimum but may be more stringent, such as basing control sizing on a rainfall threshold (e.g., design storm event) or prohibiting the use of plastics or dyes in environmentally sensitive areas (e.g., protected species). In the case of Municipal Separate Storm Sewer Systems, there may be additional local stormwater permit requirements. Consequently, state DOTs are subject to the permit requirements for their construction area.

The Build America, Buy America Act (U.S. Department of Commerce, 2021) requires all iron, steel, and construction materials and manufactured products used for federally funded infrastructure projects be produced in the United States, including state DOT projects. This creates uncertainty about the use of imported ESC materials, such as coconut coir; however, the Act has allowed for exceptions through a waiver system and has not impacted temporary ESC measures. The U.S. Department of Commerce administers the Act, which was passed by Congress as part of the Infrastructure Investment and Jobs Act.

2.4 ESC Practices

ESC practices are used in tandem for soil and water conservation during construction. Erosion controls are used to prevent the original detachment of soil by providing cover or soil stabilization, whereas sediment control practices provide an opportunity for sedimentation, or to a lesser extent, filtration prior to offsite discharge. State DOTs maintain specifications and details for ESC practices, which are non-proprietary. In addition to standard specifications and details, state DOTs maintain an APL, or its equivalent, which lists proprietary products that meet the criteria set forth by the department. APLs are developed and maintained differently depending on the state DOT, but may include third-party testing, specifications sheet review, or case studies and observations from test sites. ESCs must be used together to adequately armor the site and protect downstream waters; however, their performance is dependent on appropriate design, installation, and maintenance. Performance-based research of ESCs for state DOTs has been conducted largely in the field (Schwartz and Hathaway, 2018; Schussler et al., 2021) and through large-scale testing (Zech and Clement, 2013; Schussler et al., 2022; McFalls and Foster, 2024). Large-scale testing is characterized as “controlled testing” that mimics field conditions such as sizing, flow, and sediment introduction rates.

Erosion control practices commonly include water diversion and natural-based stabilization efforts such as seeding, mulching, sodding, preserving vegetation or buffer strips, and contouring to prevent erosion; however, synthetic-based erosion control practices are often used in critical areas (e.g., concentrated flow, slopes, or easily erodible soils). RECPs, such as erosion control blankets (ECBs) and turf reinforcement mats (TRMs), are manufactured devices anchored into the ground with metal staples, plastic stakes, or wood stakes to provide immediate stabilization and increase the allowable shear stress on the ground surface. RECPs are available in a wide range of materials and fill densities. TRMs are used for permanent stabilization, primarily within slopes, whereas ECBs, primarily used on steep slopes, provide temporary stabilization and coverage until vegetation establishes (Burns, 2011).

Traditionally, ECBs were manufactured with degradable plastic nettings (e.g., polypropylene, nylon, polyethylene, or polyester). These devices are often advertised with biodegradable, ultraviolet or photodegradable, or oxo-biodegradable plastic netting. According to ASTM D883-24, Standard Terminology Relating to Plastics, biodegradable plastics are synthetic materials that degrade through the action of naturally occurring microorganisms such as bacteria, fungi, and algae. Emblem (2012) adds that biodegradable materials must ultimately decompose into carbon dioxide, biomass, and water. According to ASTM Standard D6954-24, Standard Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation, photodegradable plastics begin degradation under exposure to natural or UV light, whereas oxo-biodegradable plastics degrade through oxidation and naturally occurring microorganisms.

A uniform definition has not been adopted across state DOTs. According to the Idaho DOT definition of “biodegradable,” the material will decompose under ambient soil conditions into carbon dioxide, water, and other naturally occurring materials within a period relevant to the product’s expected service life (Furrer, 2020). Alternatively, Washington State DOT defines

“biodegradable” as plant-based materials unaltered by synthetic materials only (McCully, 2020). “UV-degradable” designates that the products deteriorate after exposure to UV radiation that breaks down chemical bonds and results in brittleness, fading, and loss of strength. “Oxo-biodegradability” is decomposition that occurs due to a combination of oxidation and biodegradation.

The ECB market has evolved to include products consisting primarily of jute, sisal, or coir fibers that have loose-weave and mobile joints (U.S. Department of Agriculture and Natural Resources Conservation Service, 2013; Bhattarai et al., 2023; U.S. Fish and Wildlife Service, 2024). TRMs are also manufactured with plastic materials; however, they provide stability and coverage in perpetuity. TRMs do not degrade over time; therefore, the plastic mesh remains in its form in the environment. Examples of an ECB and a TRM are shown in Figure 2.1.

Hydromulching is another common erosion control practice for critical areas that may also contain synthetic components. Typically, hydromulch is a slurry of water, seed, fertilizer, cellulosic mulch, tracking dye, and an adhesive (e.g., soil binder or tackifier) that is hydraulically applied (see Figure 2.2).

Check dams may also be used as erosion control measures to intercept and slow flow, thereby reducing erosion. Check dams create impoundments that are favorable for facilitating sedimentation, thereby serving as a sediment control. Check dams are often created from materials used for various other sediment control practices (e.g., silt fence, wattles, or rock).

Sediment control is accomplished with structural practices, including check dams, inlet protection, track-out pads, sediment barriers, and stormwater detention areas. While non-synthetic sediment control practices exist, such as earthen or mulch berms, the sediment controls most often used are composed of synthetic materials (e.g., geotextiles). Even practices such as track-out pads and sediment basins will often contain a synthetic component (e.g., plastic dewatering outlets). Sediment control practices, including check dams, inlet protection, and sediment barriers, use geotextiles in the vertical plane to create a barrier to intercept sediment-laden stormwater. As a result, these practices decrease flow velocity and create impoundments of subcritical flow. These impoundments reduce erosive forces and shear stress along the channel surface and promote sedimentation to minimize offsite transport of sediment. Regarding manufactured dikes, the geotextile is wrapped around a filling, usually foam, and anchored to the ground. Like manufactured dikes, silt fences create a barrier on the vertical plane; however, the geotextile

materials are supported by posts (e.g., metal t-post or wooden stakes) (see Figure 2.3). Silt fences are often used in sediment control applications, including sediment barriers, check dams, and inlet protection. Some silt fence standards also specify using a backing support, such as a wire or plastic mesh depending on the application (e.g., inlet protection, dam, or sediment barrier).

Wattles, also known as logs or socks, are alternative products for these applications. Wattles are tubular barriers that have a sock or netting encasement filled with various types of materials (e.g., straw, wood excelsior, compost, wood chip, carpet fibers) (Schussler et al., 2021; Whitman et al., 2021). Depending on the encasement and fill combination, wattles can be composed of completely natural or synthetic materials. Two examples of wattles are shown in Figure 2.4.

Rock-based practices may also be used as inlet protection, check dams, or track-out control. While rock-based practices are not inherently synthetic-based, they often include a geotextile underlay to promote intimate ground contact and prevent rock from sinking into the ground during wet conditions. Several manufactured products are on the market as alternative track-out pads. Many of these alternative track-out pads are manufactured from heavy plastics and allow tires to flex, dropping out adhered sediment as tires roll across the pad. Detention basins are used to attenuate flow and promote sedimentation before offsite discharge. Dewatering devices,

such as perforated riser pipes or skimmers, are used to govern discharge rates. These devices are temporary and often made of heavy plastics. Additionally, auxiliary spillways are often lined with a geotextile under the stabilized outlet. The current state of the practice of the ESC industry is reliant on the use of synthetic materials and manufactured products; however, research is developing on natural alternatives.

2.5 Environmental Concerns and Consequences of Synthetic Materials

The introduction of synthetics, such as plastic netting and reinforcement, can have profound environmental impacts, including damage or injury to wildlife due to entanglement or ingestion, degradation in microplastics and bio-accumulation, or damage to maintenance equipment. Structural practices such as silt fence block the passage of small animals. Upon removal, vegetation and soil may be disrupted. The Illinois Department of Natural Resources (DNR) estimates that 12 million pounds of plastics are used in ECBs annually in North America (Illinois DNR, 2020). The U.S. Fish and Wildlife Service (USFWS) considers erosion control products that contain plastic mesh or netting as a threat to terrestrial wildlife and the environment (USFWS, 2024). Although permit and contract requirements often require that ESC practices be removed from the site when final stabilization is achieved, practices often remain on the site in perpetuity due to neglect. After vegetation is well established, it may conceal ESC practices. Neglect may result when ESC contractors move on from the site before permit closeout or from other workforce complications. If left behind, these practices can have prolonged environmental impacts.

In some cases, ESC practices such as RECPs are intentionally designed to remain in the field. RECPs are designed to establish vegetation through netting and media. A study by Ward et al. (2020) examined 98 erosion control products on the Texas DOT APL and determined that 86% of the products contained mesh, and that 56% contained at least two layers of mesh. In the same study, 65.7% of the examined products were specified as degradable. Although these practices are often specified to break down over a specified period, they often have environmental consequences before they can fully degrade.

RECPs are a widespread erosion control practice often criticized for their potential to entangle wildlife, including lizards, snakes, and birds. Ebert et al. (2019) conducted a literature review and

found at least 175 reptile entanglement reports in mesh products; 68 of the cases involved snakes entangled in ECBs. The study concluded that fixed-intersection polypropylene mesh was more likely to entangle snakes compared to woven mesh of natural fibers. The USFWS has published that netted RECPs impose potential risk factors on small, terrestrial animals. Potential harms include lacerations leading to infection, choking, or entanglement to the point of heat stress or starvation. While many animal species, including birds and small mammals, have been cited in case studies, reptiles and amphibians are the most affected species (USFWS, 2024). Several recorded cases of death due to entanglement of protected species have been recorded (USFWS, 2024), thereby leading many Departments of Wildlife and Environmental Quality to prohibit the use of netted erosion control measures in areas where there are sensitive species (Minnesota DNR 2013; USDA and NRCS, 2013; Illinois DNR, 2020). Additionally, there has been documentation of birds using plastic materials to build nests, which leads to more entanglement or ingestion.

While wildlife entanglement is the most cited environmental harm induced by ESCs, knowledge is developing about the production of plastic and microplastic pollution. As plastics degrade, they form secondary plastic fragments (e.g., microplastics). Macroplastics are plastic materials that are 5 mm in diameter or larger, whereas microplastics are small plastic materials that are less than 5 mm in diameter (Kooi and Koelmans, 2019; Cunha et al., 2023). Microplastics are commonly categorized into five types: fragments, fibers, films, foam, and beads. Definitions for these shapes are variable but have been proposed to consider the ratios between the dimensions of length, width, and height (Kooi and Koelmans, 2019).

Plastics are known to persist in the environment for long periods and can accumulate in abiotic and biotic sources (Ali et al., 2021). Microplastics have also been found in alternatives to plastic-based materials, such as compost. Much of the published literature on microplastics has focused on marine or aquatic environments; however, the concern and research about microplastic accumulation in terrestrial environments is growing (Horton et al., 2017; Frost et al., 2022). The fate and transport of microplastics are dependent on their size and materials. Guo et al. (2023) present microplastic concerns in the erosion control engineering context. Microplastics are generated through the degradation of ESC practices. Degradation of the plastic materials often begins through processes such as cracking, embrittlement, and flaking due to solar radiation, mechanical abrasion (e.g., vehicles), or water-induced erosion of materials. Since erosion control practices are used in areas prone to erosion, such as slopes and banks, microplastic creation, transport, and movement into surface waters are likely. When in the surface water system, they may stay suspended or be subject to settling and resuspension in turbulent systems. Soils have also been shown to serve as microplastics sinks. Their prolonged residency in these systems has led to ingestion by invertebrates or vertebrates (Horton et al., 2017). These plastics may accumulate in the tissues of organisms and move through the food chain due to their persistence in the environment, thus affecting many taxa (Horton et al., 2017).

Additional toxicity concerns exist with the use of ESC practices. During degradation, plastics may leach chemical additives that can harm the environment, including soil and wildlife (Rich et al., 2020). Hydromulching, a common alternative to RECPs, often contains green dyes to help operators visualize ground coverage. The dye commonly used is malachite green, a triphenylmethane, organic dye with negative environmental impacts, including slow degradation, bio-accumulation, and toxicity to mayflies, minnows, toads, and various fish species at low concentrations (as low as 0.031 mg/L) (Lyle, 2020). A 2004 review study on malachite green cited alterations to the biochemical parameters of blood and organs of exposed fish and eggs. Organ damage and mutagenic, carcinogenic, and developmental abnormalities were also cited in mammals (Srivastava et al., 2004). Minnesota DOT performed an in-house environmental hazard evaluation on malachite green and determined it was in their best interest to phase out its use (Minnesota DOT, 2013). Currently, manufacturers have produced hydromulch with a blue dye for Minnesota

DOT projects. Minnesota DOT plans to eliminate the use of dyes in hydromulch in their next specifications update.

A study by Manning et al. (2022) revealed that stormwater runoff may have elevated concentrations of polymers, which are often used with hydromulch and should be evaluated. This study highlights potential consequences from polymer additives in erosion control and potential monitoring recommendations (Manning et al., 2022). Flocculants, often used to enhance sediment control practices, are long-chain polymers that attract fine-grained suspended particles to form larger flocs that gravitationally settle more rapidly. Several types of flocculants are available: synthetic, inorganic, bio or natural, and stimuli-responsive; however, synthetic flocculants are most often used. Specifically, polyacrylamide or PAM is widely used in construction stormwater.

Flocculants are dispersed in granular, block, emulsion, and sock forms; however, the lack of guidelines for appropriate dosage and application has been documented as a concern for state DOTs (Kazaz et al., 2021). Improper dosage or application can lead to aquatic toxicity. Certain flocculants, such as chitosan, can bind with hemoglobin in aquatic species, thereby leading to gill clogging and eventual suffocation (Kazaz et al., 2022). Cationic flocculants, such as aluminum sulfate or ferric chloride, have indicated toxicity to certain species, such as water fleas, at low concentrations (< 0.025 mg/L) (Fort and Stover, 1995). PAM is an anionic flocculant typically recommended in doses up to 5 mg/L. Studies that have included brief exposure times at this dosage rate were not found to be toxic (Buczek et al., 2017). Thus, PAM is often used in construction stormwater applications due to its perceived low concern; however, overdosing can alter the viscosity of the water and consequently the settling efficiency.

Minimal dosing and quality control guidance and specifications were found in our review. Current flocculant guidelines often default to manufacturer guidelines (Kazaz et al., 2021). A study by Kazaz et al. (2023) highlights that manufacturer guidelines often lead to overdosing. Lower dosage rates lead to effective settling rates and overall lower flocculant concentrations in the water. This study highlights the need for future research on flocculant guidelines (Kazez et al., 2023).

Microplastics can also interfere with terrestrial and marine carbon fixation. In addition to hindering carbon capture, plastic products release greenhouse gases. Despite the durability and versatility of plastics, the sustainability of plastics due to emissions at all stages of the life cycle has been a topic of discussion (Shen et al., 2020; Meng et al., 2024). Plastics are derived from fossil fuels and are manufacturing-intensive. When in the environment, plastic products continue to slowly release greenhouse gases (Shen et al., 2020).

Meng et al. (2024) examine plastic alternatives for greenhouse gases for many uses (e.g., building and construction, textiles) and determine that plastic manufacturing results in fewer emissions than do the alternatives in 90% of the applications included in the study. In addition to manufacturing, emissions from the transport and distribution stages have been considered, particularly in the ESC industry. Natural materials such as coconut coir are common alternatives to synthetic materials used in RECPs and wattle practices. However, these materials are often imported, and the transport and import process can be a significant source for emissions. Therefore, life cycle assessment is a critical tool to examine these effects.

2.6 Ongoing Efforts to Limit Use of Synthetic Materials in ESC Practices

Several agencies, including the USFWS, United States Department of Agriculture, state Natural Resources Conservation Services, DNR, and state DOTs, have published literature reviews, presentations, and fact sheets on wildlife- and snake-friendly erosion control (Minnesota DNR, 2013; USDA, 2013; USFWS, 2024). Suggestions include avoiding RECPs with welded joints due to their

potential harm to wildlife (e.g., entanglement). Instead, they advise opting for net-free or natural-fiber netting with larger rectangular openings and movable joints. The NRCS factsheet from Indiana has specific guidelines for endangered species that are or could potentially be present. The guidelines include using woven netting with a 2-in. (5-cm) minimum width or products unable to entangle snakes, as approved by a biologist. The USFWS has published a wildlife-friendly erosion control product list of more than 70 products with specifications meeting wildlife-friendly criteria. Natural-fiber netting may include coir, jute, or peanut hulls (Bieak and George, 2003).

Additional recommendations include using wooden stakes for anchoring and burying the edges of products to forgo plastic stakes and using 100% biodegradable materials. They recommend practices such as hydromulching, mulching, and composting for erosion control. Additionally, the USFWS and state DOTs call for ESC practices to be promptly removed. The recommendations put forth by the USFWS have been adopted by states including California, Indiana, Minnesota, New Hampshire, and Vermont (Schuey, 2023).

In addition to wildlife concerns, Guo et al. (2023) highlight the importance of considering biodegradable alternatives. In 2020, a peer exchange between Minnesota DOT and Vermont Agency of Transportation was planned. COVID-19 shutdowns forced the peer exchange to present virtually, which allowed outside state DOTs and practitioners to participate. At the peer exchange, state DOTs and researchers defined important terms, challenged current practice, and presented potential alternatives. State DOTs exposed the environmental consequences of synthetics in the field such as microplastics in Lake Champlain (Vermont) and the mass of plastics used by Minnesota DOT. Presented initiatives included phasing out plastic-based erosion control products, tackling blankets first (Minnesota DOT), and defining biodegradable requirements as plant-based practices (Vermont Agency of Transportation) (Leete and Graeve, 2020; Russell, 2020).

Minnesota DOT presented alternatives including transitioning from silt fences to slash mulch berms. Slash mulch berms have been evaluated using large-scale testing techniques and captured a total of 98.4% of introduced sediment (Perez et al., 2024). In the same study, additional natural-based practices were evaluated, including a straw wattle and wood excelsior check dam, which captured up to 80% and 75% of introduced sediment, respectively (Perez et al., 2024). The performance of these practices was comparable to that of silt fence, which captured up to 86% of introduced sediment (Perez et al., 2024). The slash mulch berm installation used during testing is shown in Figure 2.5.

At the peer exchange, several state DOTs, including Minnesota DOT, shared requirements that other practices (e.g., hydromulch and wattles encasement) be composed of only natural fibers. Domestically grown materials, such as straw, wood excelsior, and miscanthus fibers have been used as wattle fill materials (Bhattarai et al., 2016; Whitman et al., 2021). Normalized flume performance evaluations of various wattle fill materials indicated that miscanthus was the most effective of the wattles tested at maximizing subcritical flows. The study found that coconut coir and wood chips were also effective types of wattle for creating subcritical flows (Whitman et al., 2021). In a separate study, Troxel et al. (2013) evaluated compost wattles with 18-in. and 12-in. (46-cm and 30-cm) diameters. Results indicated that reduction of total suspended solids was 93% and 88%, respectively (Troxel, 2013). Natural-filled wattles with adequate installation techniques (e.g., non-destructive staking, underlay) have been shown to have performance comparable to a synthetic silt fence (Donald et al., 2013; Schussler et al., 2021; Perez et al., 2024). Perez et al. (2024) recommended investigating additional natural-fill materials including straw, wood excelsior, compost, rice, and other byproducts for performance comparisons.

Large-scale research studies have investigated alternatives to netted ECBs, including traditional mulching (e.g., straw, hydromulching, compost) (Owen et al., 2021; Donald et al., 2022). Bhattarai et al. (2023) conducted an evaluation of natural-fiber and net-free ECBs and found that products were up to 99% sediment-capturing efficient and 97% runoff-trapping efficient under rainfall simulation on a slope. Natural fibers used in ESC are often imported products (e.g., coconut and jute), which have created questions regarding their sustainability due to fair labor practices and environmental impacts associated with international manufacturing and shipping. Therefore, efforts have been made to find domestic alternatives. At the peer exchange, the Vermont Agency of Agriculture and Minnesota Agricultural Utilization Research Institute presented hemp programs for erosion control within the United States (Smith, 2020). Almost a decade before the peer exchange, Bieak and George (2003) evaluated peanut shells as a potential for ECBs and compared them to jute and coir netting. The authors conclude that the peanut waste products could potentially be used in ESC netting applications.

Despite recent efforts to develop natural alternatives, the current state of the practice of the ESC industry remains reliant on the use of synthetic materials and manufactured products. Additional research and innovation are needed to develop performance-based, natural ESC practices. In addition to alternatives, reducing the use and dependency of ESC practices and products can be another successful approach. Often, the use of sediment barriers can be excessive, with contractors placing silt fences in areas upstream of flow or enveloping construction sites completely (Liu et al., 2021). Project phasing that reduces duration and size of disturbed areas can also reduce dependency on ESC practices. Better design guidelines and training are needed to reduce dependency on ESC.