What About the Posts?
Posts are installed after the fabric is properly placed and
compacted in the soil. EvTec found
that compaction before posting significantly improved effectiveness. Posting
independently allows the contractor to space posts as they are
needed - where water concentrates posts are spaced closer together
possibly at 3' apart, and on legs with concentration 8' apart.
Steel or wood? Doesn't matter to a tommy installation. Wood posts
are allowed or specified in many parts of the country, but as
regulations and suppliers are now preparing silt fence to actually
pond water and hold sediment, steel posts are likely to continue
gaining presence.
Problem with wood stakes
If not sized appropriately, (actual 2x2) smaller sizes break
while installing them. Properly sized wood stakes will perform
acceptably, but their physical size (40 inches) prohibit achieving
proper depth to support the horizontal load. Generally, stakes
must lie as deep in the ground as the potential load above ground.
Wood Stakes may be less expensive than steel, but if the fence
won't hold up it doesn't matter.
Providing 18" of sediment and storm water is a major difference
and benefit of proper installation by slicing with the tommy.
The fabric doesn't work out and inferior posts are no longer
adequate (as in pre-fabricated silt fence).
Steel posts are often the best
option. Steel posts can be driven the proper depth into very
hard clay and even rocky soils. Steel posts can support the 18" horizontal
sediment load (when properly placed)... and can be recycled - often wood posts are not recyclable.
