Reference Document - RAL23/0013.02 - Part 2 (As Published)

6. CONCLUSION
Colliers Engineering and Design have been engaged by PSP Developments Pty Ltd to prepare a Stormwater
Management Plan (SMP) in support of a development application to Noosa Shire Council (NSC) over land
located at 33 Pavilion Street, Pomona (Lot 4 RP809059). This development application seeks a development
permit for a Reconfiguration a Lot (ROL) to create 8 residential lots. The site has an existing building at Lot 1
and no works are required to create lot 1.

It can be seen from the results, presented in Table 3-7 that the treatment measures proposed for the
development site achieve the performance criteria set by the NSC Planning Scheme (2020) and SPP (July
2017). Annual Load Reductions of Total Suspended Solids (TSS), Total Phosphorus (TP), Total Nitrogen (TN)
and Gross Pollutants (GP) between the Mitigated and Unmitigated Scenarios have been achieved through
the upgrade of the existing bioretention basin from 80m2 to 130m2.

It has been demonstrated that non-worsening of peak flows has been achieved to the discharge point for
events up to the 1% AEP event (refer Table 2-8). The results show that there is non-worsening for events up
the 1% AEP. The intent of sizing the detention basin is to mitigate flows up to the 10% AEP storm event to
ensure non-worsening of discharges into the downstream flow path. In larger events, flows from the site
will start to sheet flow across the rear of the site to Cooroora Creek. As the discharge point for the site
becomes inundated from Cooroora Creek flooding in the major storm event, it is considered non-worsening
has been achieved. The catchment size of Cooroora Creek reporting past the site is approximately 1,400 ha
and it is considered that no quantifiable change to downstream flooding conditions would result.

This plan demonstrates that effective treatment of stormwater at the proposed development can be
achieved through the integration of Water Sensitive Urban Design (WSUD) principles. Through the
incorporation of bioretention basins, the plan successfully demonstrates:

    Compliance with the requirements of the NSC Planning Scheme and SPPs Load Based Objectives;

    The end of line bioretention basin is upgraded to 130m2 to cater for the proposed development.

    Ecological sustainability in terms of the development’s impact upon receiving waters and the viability of
    the proposed site development.

    Non-worsening of peak flows is achieved through the upgrade of the existing basin.

    The development is located above the regional 1% (2100 AEP flood extent with 500mm freeboard
    recommended to future dwellings on the new allotments.

We therefore request Council approval of the engineering components for the proposed development with
reasonable and relevant conditions. Detailed design may result in changes to the proposed strategy;
however, the design objectives will be maintained.




23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona                               Page 37