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Trench
systems consist of shallow, level excavations, usually
one to five feet deep and one to three feet wide. The excavated
area is usually filled with six inches or more of a porous
medium, such as gravel. Next, a distribution network is laid
out over the media. A single line of perforated distribution
pipe is laid in each trench. Building paper, straw, or some
other semi-permeable barrier is then placed on top of the
network before the system is covered with soil. The wastewater
trickles through the distribution network, through the media,
and into the soil. Treatment of the wastewater occurs in both
the media and soil sections of the trench system.
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