BBNE00529_0002_0001-REP-001-1-73 Eumundi-Noosa Rd SMP

    d.   A 50m3 detention tank is proposed within the townhouse site to ensure pipe flows in the 10% AEP event are less than design flows
         determined as part of the original operational works design of the stormwater system. This will ensure that HGL levels in the
         network do not increase and as such compliance with QUDM drainage criteria.

    e.   The design of the townhouse site will be completed in line with recent ARR updates and SSP2-4.5 for climate change. Given the
         existing development (which is constructed) was designed in 2016 and the townhouse site will connect into existing stormwater
         infrastructure, it is not considered appropriate to assess the existing infrastructure using higher rainfall intensities. Further
         assessment of the existing basin and gap flow down Starboard Street is discussed in Sections 4.1.4 and 4.3.


Internal Drainage Design

Issue

Stormwater drainage design details for the internal site have not been provided to a standard suitable for OPW approval.

Information Required

10. Provide stormwater drainage calculations and stormwater long-sections for the 0.5EY, 10%AEP and 1%AEP (including HGL long-sections)
for the internal site drainage.

11. Provide details for the major event (1%AEP 2100) showing where overland flow paths will be located, that adequate freeboard is achieved
for the subject dwellings and that no overland flow path from the development will enter



Response: Engineering Plans have been updated to reflect the updated sizing’s required (refer Appendix B) and response has been provided
by TOD Consulting.



Stormwater Quality

Information Required

12. Provide an updated SWMP and MUSIC model which includes the hydrologic and pollutant loading from the external catchments which
drain to the existing bioretention basin. The total load removed by the system should then be compared to the load reduction required to
be removed from the development and subdivision alone.



Response: The additional assessment requested above results in a more conservative outcome then if the development is assessed in
isolation. However, to respond to this item, the external catchment (1.41ha) was added a lumped residential node with 50% impervious.
Table 2.1 below, compares the loads removed with the external catchment and when assessing the development in isolation. These results
highlight that when including the external catchment there are more pollutant loads removed then when comparing the development in
isolation. It is considered these results highlight compliance with this request.

TABLE 2.1: MUSIC MODEL RESULTS


 Parameter                          Load Reduction with         Load Reduction Required          Difference            Compliance
                                    External Catchment         for Development Alone to            (kg/yr)              Achieved
                                      Included (kg/yr)            Achieve WQO (kg/yr)

 Total Suspended Solids (TSS)                8,550                        6,450                     2,100                   ✓

 Total Phosphorus (TP)                       14.65                        10.87                      3.78                   ✓

 Total Nitrogen (TN)                         62.2                          51.4                      10.8                   ✓

 Gross Pollutants (GP)                       1,261                         916                       345                    ✓




73 EUMUNDI - NOOSA ROAD, NOOSAVILLE I BBNE00529_0002_0001-REP-001-1                                                                      5