RFI Eng response notice items 4-19 MCU150111

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Therefore analysis methodology and results presented in the November 2015 report are appropriate.

    (b) The SWMP shall investigate the impact of the development on the existing drainage conditions on other
        properties, including road reserve and parks areas, and make recommendations for any necessary
        stormwater works and/or mitigation measures to ensure no adverse impact caused to other properties
        (reference is made to downstream Discharge Locations A and B on the submitted plans).

Our Response

The report shows that mitigated flows at discharge location A and B are below predevelopment levels (Refer Table 3-9 in
report B14158.W 03A) therefore there is no adverse impacts on other properties.

Please note that we are not changing the swale between the Central basin and Point B. Therefore only the same flow will
enter the Council reserve at Point B and swale banks will overtop in the current manner in higher events. At Point A we
will provide an energy dissipater and level spreader to ensure no concentration of the flows to the adjoining site.

Additional pipework is to be installed at the Trading Post Road cul de sac to ensure that flood conditions are not impacted
once the cul-de-sac is formed and adjacent gully filled.

As indicated in the attached DWG B14158.W-SK111 and SK110 Issue A, a stormwater drainage pipe will be constructed
from the cul-de-sac head to the Northern swale. This pipeline will convey at least the 1 in 20year ARI flow. This greater
than the Council standards. Flows in excess of the pipe system will be conveyed through the site. Final details subject to
detailed design.

    (c) All underground piped stormwater drainage must be designed to accommodate 5 years storm event with
        all overland flows be located with the roads and open space area and catering for 100 years storm event
        as minimum.

Our Response

Council’s request is acknowledged. This will be incorporated into future detail design drawings.

    (d) General plan/s showing the proposed stormwater system including pipe sizes and the overland
        secondary flow paths. Where possible, overland flow paths should be streamlined and sharp bends be
        avoided to alleviate the potential of breach and damage. The plan/s should also indicate any proposed
        external stormwater drainage works (eg stormwater drainage collection in Trading Post Road).

Our Response

The pipe system has been designed to comply with the site layout which is consistent with previous site approvals. As
discussed with Council on 13 January, the pipe systems will be designed for minimal overland flow at the sharp bends of
the pipelines. Additional pits will be incorporated upstream of bends so that there will be minimal overland flow. Refer to
Drawing B14158.W Sheets SK110 and SK111 for details.

Concept details of pipeline sizes downstream of basins have been indicated on the attached drawings.



    (e) All the necessary drainage easements on the site in Council’s favour where required.

Our Response

As discussed with Council on 13 January, minimal measures are required. Proposed stormwater easements are now
shown on drawings. Refer to Drawing B14158.W Sheets SK110 Issue A and SK111.