SUMMARY

Use of Sustainable Materials for Erosion and Sediment Control Practices

Erosion and sediment control (ESC) practices are used to minimize soil loss from active construction sites and to capture suspended sediment before offsite discharge of stormwater runoff. Traditional practices, such as rolled erosion control products (nettings, silt fences, and others), have relied heavily on the use of plastic materials. Increasing public awareness about microplastic pollution and concerns about wildlife entanglement within plastic-based products have raised the interest in many state departments of transportation (DOTs) to seek alternative solutions for traditional ESC plastic-based products and practices. The objective of this synthesis is to document current use of plastics in ESC practices across state DOTs and state DOT policies and plans to reduce or eliminate the use of plastic-based ESC practices.

The synthesis objectives were achieved by utilizing a three-step methodology. First, an extensive literature review was conducted that involved collecting and reviewing journal articles, reports, guidelines, stormwater manuals, and supporting documents pertaining to the use of plastics in ESC products and practices. Second, information attained through the literature review was used to create a web-based survey distributed to all 50 state DOTs, as well as the District of Columbia DOT. A total of 42 states completed the survey, yielding an 82% response rate. Third, semi-structured virtual interviews were conducted with six state DOTs. These interviews gathered additional information pertaining to the development and implementation of policies to reduce or eliminate dependency on plastic in their ESC programs and were used to develop case example write-ups that document and highlight the unique aspects of their approaches. State DOTs that opted to participate in case example interviews include Colorado, Georgia, Minnesota, North Carolina, Vermont, and Washington.

The following bullets outline select key findings identified from the literature review, survey, and case example interviews. A complete review of findings is provided in Chapter 5.

• Among ESC measures, rolled erosion control products (RECPs) have the greatest potential to cause wildlife entanglement.
• Erosion control practices are likely to introduce higher concentrations of microplastics into the environment due to their application locations and contact with stormwater runoff.
• Alternatives to plastic-based materials, such as slash mulch berms and net-free and natural-fiber erosion control blankets (ECBs), are highly effective.
• Nine of the 41 responding state DOTs provide guidelines, initiatives, policies, or specifications to facilitate the reduction of plastic-containing ESC materials.
• Evaluating materials and products is one of the most challenging aspects associated with the use of sustainable materials in ESC measures.
• Wildlife concerns/entanglement was the highest motivational factor for reducing plastic-based materials.

• All state DOTs interviewed perceived ECBs as having the most negative impact on the environment or wildlife due to entanglement and entrapments. All DOTs that have shifted away from plastics started by reducing plastics used for ECBs.
• State DOTs interviewed indicated that silt fence is also one of the most problematic practices; however, a viable alternative does not exist.
• Interviewed state DOTs did not report a decrease in functional performance of non-plastic alternatives and, in some cases, reported better performance when compared to plastic-based measures.
• Interviewed state DOTs reported that plastic-free ESC products are installed in the same way as are traditional plastic-based products, and that additional installation oversight, inspection, and maintenance are not required.

In addition to identifying the current state of the practice, this synthesis also identifies areas for additional research to aid state DOTs in their shift away from plastic-based materials used in temporary ESC. Areas of recommended exploration include the following: (1) development of alternative, plastic-free, geotextiles for silt fences; (2) creation of a reference guide for natural-based materials used for RECPs; (3) analysis of microplastics emanating from ESCs and biodegradability of ESCs; and (4) analysis of the effects of hydromulch dyes on soil microbiota and aquatic life.