On-Site Wastewater Treatment and Disposal Systems - Forced ...

FIGURE 7-3
ALTERNATING TRENCH SYSTEM WITH DIVERSION VALVE
2. In areas with severe winters, avoid areas that are kept clear
of snow. Automobiles, snowmobiles, and other vehicles should
not be allowed on the area. Compacted or cleared snow will
allow frost to penetrate the system, and compacted soil and
loss of vegetation from traffic over the system will reduce
evapotranspiration in the summer.
3. Preserve as many trees as possible. Trenches may be run be-
tween trees. Avoid damaging the trees during construction.
Confi;urationfz Trenches should be used wherever possible. Not only do
trenc es per arm better than beds, but they also conform to the site
more easily. Trenches do not need to be straight, but should be curved
to fit the contour of the lot or to avoid trees. A multi-trench system
is preferable to a single trench because of the flexibility it offers in
wastewater application.
On lots with insufficient area for trenches or on sites with granular
soils, beds may be used. If only a sloping site exists, the bed should
be constructed with long axes following the contour. However, beds
should not be constructed on sites with slopes greater than 10% because
the excavation becomes too deep on the upslope side. In such instances,
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