Stormwater Management Plan -OPW (A) · OPW25/0042

Individual sub-catchments are applied to corresponding RIPs/RICs.

Existing vegetated areas where no significant works are proposed are
excluded from modelling on the basis that they will continue to infiltrate
incident rainfall as per the existing pre-development case.

Largely soft landscaped catchments 4/1, 4A/1 and 4B/1 are to be directed to
RIPs constructed along the external catchment drainage line discussed in
Section 6. This arrangement is consistent with the existing stormwater line.

The above RIPs are not modelled via spreadsheet in recognition of the fact
that they will accept commingled runoff from both internal and external
catchments. They are however addressed in the overall development site
Quantitative MUSIC model.

Spreadsheet model results for all proposed RIPs and the RIC appear below in
Table 5.1.1


Table 7.1.1 Summary of Excel Spreadsheet Modelling




By inspection criteria of infiltrating all flows up to the 10% AEP over the
developed site has been demonstrated.

Excel model files are attached at Appendix H with catchment drawings
appearing at Appendix A.


Emergency Overland Flow Weir calculations model the unlikely case of
complete RIC failure with full 100 Year ARI flows conveyed toward existing
vegetated swale areas and appear on engineering drawings at Appendix A.
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A6769/25/SWMP/Rev OpW(A) – Feb 2025
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SH/PL
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