Swmp Rfi

Executive Summary
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.

The location of the proposed development site has a total land holdings area covering 3.33ha. The site is
consistent with a rural residential land use type with some wooded vegetation cover over the site. The site is
accessed by Pavilion Street to the east and Majestic Place to the south and is bounded by private allotments to the
north, east and south. Cooroora Creek is located in the adjacent property to the west.

It can be seen from the results presented 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. 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.

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




23-0167SMP01-V2 | Stormwater Management Plan | 33 Pavilion Street, Pomona