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Tile drains consist of plastic or metal perforated
piping laid in excavated ditches usually 0.75-1m below the surface.
Water from the drain collects in a dam and is pumped from the
dam back into the channel (Wimmera Mallee Water, 1995).
The perforations are of varying size and spacing. Drains are
installed by conventional trenching and excavation techniques,
and may be installed with cut-off walls, where the drain removes
the groundwater from the front of the cut-off wall. The material
used to fill the excavation is significantly more porous than
surrounding soil to draw the groundwater to the drain.
Tile drains typically have the following features:
- They have
sufficient structural strength that the soil around it
will not collapse into the hole.
- They have slots or holes in
the pipe wall or a crack between adjacent drain tile to let
the surplus soil water enter
the pipe (water never enters through the dense pipe wall).
- They
provide the outlet for the excess soil water.
- They conduct
the water from the field to a satisfactory outfall.
An
estimate of the flow through the trench needs to be made
to determine the diameter required, the appropriate diameter
for
the pipe feeding water back into the channels, and the size
of the lift-pump required (Wimmera Mallee Water, 1995).
Tile drains cannot lower the watertable any lower than the
bottom of the tile. The tile will only run water when the
watertable
has risen to a height above the tile. Therefore tile drains
constructed adjacent to channels can be an effective way
of managing the
impact of seepage on the watertable from the channel.
The cost estimate of installing a tile drain system for seepage
control is approximately $28/m based on a 600m length of
channel project (Wimmera Mallee Water, 1995).
| Related
pages |
 |
Groundwater intervention techniques
Core
trenching
Groundwater
pumping
Vegetation |
