Silt fence

GMA techline answers from Bob Koerner

RE: Silt fence
I have read M288 and understand the different levels of material specifications for highway applications. Is there another category that can be sold to the public that does not have to meet the specifications for highway applications? For example, a home gardening category that can be sold at a hardware store.

(Barry | Georgia)

Reply You ask a difficult question and let me try to “dance” around it. At the core is the criticality and duration of the site-specifc situation. For example, landfill geosynthetics are held to a higher level than highway situations and, in turn, highways greater than home improvements.

Take a wall reinforced by geogrids and adjacent to a landfill, regulators want hundreds of years (or forever for the landfill!), while the same wall adjacent to a highway is designed for a 100-year duration, and my wife’s garden wall perhaps 15 to 20 years.

Now, regarding to geosynthetic durability, manufacturers will add antioxidants to increase lifetime but the cost goes up comparably. So for home improvements, the durability properties of a typical specification can be greatly relaxed.

That said, the mechanical properties should be maintained unless one is willing to put up with an actual failure. In ASSHTO M288 you might use the lowest survivability classification and omit the UV criterion, but the mechanical and hydraulic properties should be maintained unless the likelihood of a failure can be expected.

Hope this helps but I really don’t think it will save
you much money.

Robert M. Koerner, Ph.D., P.E., NAE; Email: Robert.Koerner@coe.drexel.edu.