The need for erosion control material specifications

February 1st, 2012 / By: / Erosion Control Materials, Specifications, Updates

The authors feel that a reasonable case can be made that generic specifications have significantly aided both geotextile materials (e.g., via AASHTO specs) and geomembrane materials (e.g., via GRI specs). Such specifications address most common situations and also provide a platform from which unusual or atypical site-specific conditions can be implemented.

This is unfortunately not the case for many other geosynthetic materials such as geonets, geocomposites, geogrids and erosion control materials. That said, working drafts are available for all except erosion control materials. It is with these materials that owners, specifiers and designers are completely “at-sea” insofar as making quantitative comparisons based on like properties.

The original classifications of erosion control materials was proposed by Mark Theisen, as follows:

  • temporary erosion and revegetation materials.
  • permanent erosion and revegetation materials (biotechnical related).
  • permanent erosion and revegetation materials (hard-armor related).

It appears as though a more recent classification under the category of rolled erosion control products (or RECPs) is the following:

  • degradable rolled erosion control products.
  • nondegradable rolled erosion control products.
  • high-performance nondegradable rolled erosion control products.

In this regard, the annual Specifier’s Guide by Geosynthetics magazine publishes a section on RECPs requiring only tensile strength for the degradable RECPs and thickness, tensile strength and UV stability for nondegradable RECPs. Here it is seen that there are major differences listed in tensile strengths (e.g., from 2.3 kN/m (160 lb/ft) to 58.4 kN/m (4000 lb/ft). These upper bound values have led to the “high performance” categorization of nondegradable RECPs.

In this regard, Joel Sprague has recently suggested classes A, B, and C for nondegradable RECPs.

The point of this column is to solicit interested individuals (and, of course, companies) willing to work toward generic specifications so as to aide and grow the rolled erosion control product market.

The authors will be glad to facilitate and work within such a group, so please advise accordingly.

New inspector course offered

The Geosynthetic Certification Institute (GCI) now has a new Inspector Certification Program (ICP) for mechanically stabilized earth (MSE) walls, berms and slopes using geosynthetic reinforcement. This new GCI-ICP program is described here.

The next course and examination* is March 14, 2012. This new one-day course and subsequent certification is focused on the inspection, monitoring, and maintenance of MSE walls, berms, and slopes reinforced with geogrids and geotextiles.

Courses such as this are necessary due to the number of current problems, including excessive deformation and actual collapse. The course focuses on all aspects and details related to these reinforced structures:

  • introduction and overview
  • responsibilities before construction
  • responsibilities during construction
  • responsibilities after construction
  • long-term monitoring
  • remediation of MSE structures

If you are interested in becoming certified as a GCI-ICP inspector for MSE walls, berms, and slopes, click here.

*Applications must be approved prior to taking the examination.

Bob Koerner, Ph.D., P.E., NAE, is the director of Geosynthetic Institute (GSI) and is a member of Geosynthetics magazine’s Editorial Advisory Committee. GSI: +1 610 522 8440, robert.koerner@coe.drexel.edu.
Robert M. Koerner, Ph.D., P.E., NAE, is the director designate of GSI, gkoerner@dca.net.

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