Compiled Reference Document - MCU25/0020 (As Published)

plumbing connection points) would not be expected to exceed 40 mm if the building is supported on a
raft. Thus, an equivalent Class M is recommended for plumbing design purposes in this case.

6.4.7        Earthquake Design Considerations
In accordance with Australian Standard AS 1170.4-2007 Structural design actions, Part 4: Earthquake
actions in Australia, Section 4.2, this site would be classified as “Class Ce” (shallow soil site).


6.5          Permanent Drainage
Design of the proposed basement walls and floor would need to include allowance for hydrostatic
pressures. The standing groundwater level was recorded at 1.8 m BGL in the standpipe installed in
borehole BH1 at the completion of fieldwork, however, groundwater could rise closer to the ground
surface following periods of heavy or prolonged rainfall, high tides and flooding. Depending on matters
such as the extent of drainage installed and hydrological analysis, the designer must make an assessment
of hydrostatic pressure to be accounted for in the design of the basement.
The use of a passive pressure relief system could be considered to enable a reduction in the allowance
for hydrostatic uplift in basement construction. This could comprise a drainage network connected to a
series of standpipes or one-way valves that allow groundwater seepage to flow into a sump-pump
collection system, once groundwater rises above a predetermined level (and for which the basement has
been designed to resist the relevant hydrostatic forces). A drawback of such a system would be the need
for water quality treatment prior to off-site discharge, and the on-going maintenance required and may
not be accepted by Council. As such a fully tanked basement structure will likely be required. Design of
basement tanking, and any pressure relief system, must be undertaken by a suitably qualified and
experienced structural RPEQ.
Permanent site drainage should be installed to ensure that stormwater runoff is directed away from
building walls and footings (e.g. perimeter paths/drains and swales where space allows), discharging into
the existing stormwater infrastructure in the surrounding streets or canal to the east. A surface
dissipation device such as rock weir must be installed at the stormwater outlet(s), where not discharging
into a constructed pit.




Geo-environmental Investigation Proposed Residence
4 June 2025 | 25040-001-Rev1                                                                           18