Em4885 irrigation management practices to protect ground water

4 CHAPTER
SECTION 2 - MANAGE SURFACE RUNOFF TO
MINIMIZE CONTAMINATION POTENTIAL
IP 5.02.01 - Install Sedimentation Pits
Objective
Collect all of the tailwater from a furrow irrigation system and allow time for sediment
to settle out of solution.
Description
Sediment pits are intended to temporarily store surface runoff. The runoff continues to
flow through the pit to its final destination but the pit is designed so the runoff is in the pit
for a sufficient amount of time and flows at such a low velocity that sediment settles before
reaching the outlet. To optimize the size of a sediment pit, this practice should be used
only after all other practices to reduce erosion and tailwater volumes have been
implemented. Although this practice does not affect overall irrigation system efficiency
or distribution uniformity, it provides final treatment of runoff before discharged to the
receiving surface water.
Sedimentation pits may be used in conjunction with a runoff return system.
IMPORTANT!!! Pits should not be installed in highly permeable soil if possible as
impounded water may leach excessively into the underlying soil.
SCS National Practice 350 addresses design and installation of sediment pits, as does
American Society of Agricultural Engineers Standard S442.
IP 5.02.02 - Install Vegetative Buffering Strips
Objective
Remove sediments and other contaminants from surface runoff before it reaches other
surface waters.
Description
These are strips of land covered with grass or other vegetation that will slow runoff so
that any sediments or other contaminants fall out of suspension. This practice is primarily
applicable to surface irrigation systems and their tailwater, however it can apply to the
management of runoff from any type system. It can reduce the quantity of sediment and
any attached contaminants that leaves the field with the tailwater. This practice should be
used in conjunction with techniques for reducing soil erosion losses.
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