Minnesota Department of Transportation

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NS757: Characterization, functional longevity, and performance of natural textiles configured as sediment control retention materials

Problem

Sediment control BMPs are composed of synthetic materials that degrade slowly but never disappear (microplastics). Synthetic fabrics used for sediment control are typically single use products that ultimately end up in landfills or forgotten in project ROWs and never removed. Failure to remove affects gravity flow movement of stormwater on slopes, mowing, and wildlife connectivity. There have been examples of silt fence harming riders of snowmobiles and ATVs (does not matter that they were trespassing). The sediment control materials are defined in standard specification, shown in standard detail sheets and on plan layouts. To increase efficiency, the majority of silt fence materials are installed by machines that slice open soils and place 12 inches into the temporarily open furrow. Natural textile materials that completely degrade to water, air and minerals would not be a problem if left behind to naturally decompose after construction operations are completed.

After many years of requests for natural products, several industries are now supplying coir (coconut fiber) fabrics that could be configured as perimeter control. There is movement towards weaving hemp fibers into textiles, along with flax as burlap sediment control products. However, there are many unknowns. It is not known if existing machines are capable of installing natural fabrics. It is not known if natural textiles are effective in retaining, removing or filtering sediment. It is not known how long natural textiles last in repeating cycles of wet and dry. It is also not known what will keep natural textiles in a vertical position once installed.

EPA lists plastic waste as an emerging concern (Congressional Research Service, 2021, R45998). MnDOT recognizes this concern and is addressing reduction in plastic utilization when alternative technologies are sufficiently available at similar cost. Even if all synthetics were removed at the end of the project (a NPDES Permit requirement), synthetic fabrics shed plastic fragments over the span of use. This includes routine damage events and inadvertent burials during grading operations.

Objectives

  • Research physical properties of natural textiles suitable for sediment control applications using requirements of synthetic fabrics as the starting point.
  • Research performance properties for flow rates and sediment retention, filtration, or flocculation.
  • Provide recommendations on how flow rate changes by textile weave spacing influence sediment performance.
  • Perform functional longevity tests, especially at the soil/air boundary.
  • Verify machine install methods exist or suggest machine modifications.
  • Research soil retention capacity and maximum height of sediment load to failure (example hypothesis of 1/3 height vs ½ of synthetics).
  • Research methods for attachment to wood stakes.
  • Research methods for attaching to itself as the roll ends or starts, and to other perimeter control products like (but not limited to) bale barriers, and synthetic silt fence.
  • Develop guidance for proper installation and replacement schedule factors.
  • Develop design criteria, and limits of performance where it is not recommended for use.
  • Develop Special Provision appropriate for 2573 and 3886.
  • Develop detail sheet showing examples of proper installation, overlaps, connections to itself and other materials, and damage (separation, tears) repair methods.

Previous research

Existing research has focused mainly on synthetic woven and non-woven (needle punched) fibers. The only research relating to natural fences as pond baffles in temporary sediment traps is that by Thaxton and McLaughlin (2005). There was no publicly available research on natural sediment control textile fabrics as silt fence or sleeves on sediment control logs. Personal communication with Jay Sprague at TRI Environmental backs this up. While they have examined natural fibers, the result are limited and retained by their clients.

  • Bugg et. al. 2017. Performance evaluations of three silt fence practices using full-scale testing apparatus. https://pdfs.semanticscholor.org
  • Coir Sediment Control | Nedia Enterprises
  • Cooke et al., 2015. On the apparent failure of silt fences to protect freshwater ecosystems from sedimentation: A call for improvements in science, technology, training and compliance monitoring. Envrion. Manage 1:164:67-73.
  • Gatz, L., 2021. Contaminates of emerging concern under the clean water act. CRS Report R45998.
  • Thaxton, C.S., and R.A. McLaughlin 2005. Sediment capture effectiveness of various baffle types in a sediment retention pond. Trans. of ASCE 48 (5).
  • Whitman et. al., 2021. Practical silt fence design enhancements for effective dewatering and stability. J Irrigation and Drainage Eng 147(1): 04020039.
  • Whitman et. al., 2023. The Silt Fence: keeping sediment where it belongs. FHWA-HRT-23-004. Public roads – Summer 202387(2).
  • Whitman et al., 2019. Evaluation of sediment barrier practices using large-scale testing techniques: small-scale performance evaluation of geotextiles used in silt fence applications. FHWA/ALDOT 930-869 Highway Research Center.
  • Zech et al., 2009. Field evaluation of silt fence tieback systems at a highway construction site. Practice Periodical on Structural Design and Construction 14(3).
  • Zech et. al. 2008. Intermediate-scale experiments to evaluate silt fence designs to control sediment discharge from highway construction sites. J. Hydrologic Eng. 13(6).

Expected outcomes

  • New or improved tool or equipment

Expected benefits

The numbers 1 and 2 indicate whether the source of the benefit measurement is from: 

  1. A specific research task in your project that will be measuring this particular benefit, or
  2. A separate effort to analyze data provided by the state or local agency involved in this project.
  • Environmental Aspect: (2)
    • Estimate statistical reduction in plastic utilization (i.e., landfill waste) with the use od alternative natural fiber textiles for sediment control by analyzing data provided by the state or local agency involved in this project.

Technical advisory panel