Referenced Document - OPW20-0037

Mr Andrew Jensen                                                                                 20013-001-Rev0
                                                                                                 4 February 2020




                Text Figure 11: Footing depth required to prevent undermining or surcharge loading



Footing bases must be cleaned following mechanical excavation to expose undisturbed materials over the
full base area. A suitably qualified and experienced engineer should inspect footing excavations to confirm
adequate foundation materials are encountered.

4.5   Drainage
Adequate site drainage must be installed to ensure that runoff is directed away from the building walls and
footings (e.g. swales, mounds, grated drains).

Subsurface drainage must be installed behind any retaining walls in order to prevent the development of
hydrostatic pressure (e.g. slotted ‘aggi’ pipe wrapped in filter ‘sock’ placed in gravel backfill).

All stormwater collected around the residence (including overflow from rainwater tanks) must be directed by
pipes or lined channels to discharge at a point(s) at least 10 m down slope of any structures or fill batters,
preferably into the natural drainage line/gullies present on site. It would be prudent to construct a rock
dissipator or rock contour drain at the drainage outlet point(s) to minimise erosion.
The embankment located on the western side at the top of the driveway is noted to cut off surface water
flows from the slope above so a culvert or some form of adequate diversion drainage system should be
developed to enable surface water flows to be directed around or under the embankment.

Subsurface disposal of stormwater must not be undertaken.




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