www.graf.info
14 / 32
5.
Installation and assembly
5.2.1 Slope, embankment, etc.
On installation of the tank in the immediate vicinity (< 5
m) of a slope, earthen mound or slope, a statically
calculated supporting wall must be erected to absorb the
soil pressure. The wall must exceed the dimensions of
the tank by at least 500 mm in all directions, and must be
located at least 1000 mm away from the tank.
5.2.2 Groundwater and cohesive (water-
impermeable) soils (e.g. clay soil)
With only occasional ground water and cohesive, water-
impermeable soils (e.g. loam), adequate drainage of the
ground water or leakage water must be ensured so that
the tanks never stand deeper in the ground water than
indicated in the table. If necessary, the drainage line
must end in a vertical DN
300 pipe in which an
immersion pressure pump is installed to pump off the
excessive water. The pump must be checked at regular
intervals.
If it is to be expected that the tanks could sink lower,
adequate drainage must be ensured in all cases.
We recommend the general laying of a drainage line,
since in the event of prolonged rainfall the ground
water level can rise unexpectedly.
5.2.3 Installation adjacent to surfaces used by
vehicles
If the underground tanks are installed adjacent to
surfaces which are used by heavy vehicles weighing
over 12 t, the minimum distance away from these
surfaces is at least the depth of the trench.
5.3
Insertion and filling
The tanks must be inserted, impact-free, into the
prepared trench using suitable equipment. The tank is
filled with 1/3 water before filling the tank surround.
Afterwards the surrounding (roundgrain gravel, max.
grain size 8/16) is then filled in layers of max. 40 cm
steps and is compacted.
The individual layers must be well-compacted (manuel
tamper). Damage to the tank must be avoided during
compaction. Mechanical compaction machines must not
be used under any circumstances. The surrounding
must be at least 500 mm wide.
Tank size
10.000 L
Immersion depth
1142,50 mm
>800 <2000
