Attachment C - Engineering Technical Note · 132008.1128.02

WATER & WASTEWATER NETWORK INVESTIGATION | BLUE CARE




During residential fire flow, the critical node shown on Drawing No. 18-001942-SK203 within Appendix D fails to comply with
DSS requirements. With the number of failing nodes remain the same, with the critical node experiencing a pressure drop of
approximately 4m.

Assessment of commercial file flows indicates that the existing network fails in two locations. These critical nodes are identified
on Drawing No. 18-001942-SK203 within Appendix D. Through inclusion of the proposed development and associated DN150
loop water main, these failures are resolved with the critical node moving to a different location in the network.


3.7        Internal and External Water Network Assessment Summary
Investigation of internal and external water network conditions indicate that the existing water network is capable of servicing the
proposed development without negatively impacting existing network customers. The strategies proposed as part of this report,
illustrated within Appendix D are conceptual only and require detailed engineering design during the operational works phase.



4 Wastewater Network Planning
The Service Advice Notice (SAN) issued by Unitywater (refer Appendix D) advised that existing sewer infrastructure has
sufficient capacity to cater for demands generated by the proposed development. As a result sewerage network modelling of the
site and external infrastructure has not been undertaken as part of this assessment.


4.1     Existing Network
The existing wastewater infrastructure within the vicinity of the site is outlined in the Unitywater existing network maps within
Appendix C. There is currently no existing wastewater infrastructure within the boundaries of the site. An existing DN225
gravity main and DN150 pressure main intersect the two site accesses.

The DN225 gravity main continues for approximately 100 meters before discharging into the existing sewerage pump station
(SPS-SSB019) to the west of the site on lot 800 SP252905. Flows are then conveyed to Sewerage Treatment Plant (STP-
NHD001) through external trunk infrastructure.


4.2     Flow Projections
Sewer flow projections calculated for the development have been determined in accordance with SEQ Code DSS requirements
and are detailed in Table 4-1.


Table 4-1: Projected Wastewater Demands

        Land Use               EP                C2            ADWF (L/s)            PDWF (L/s)              PWWF (L/s)
 Attached Dwellings            242              2.64               0.56                   1.48                   2.80
  Aged Care Facility           257              2.62               0.60                   1.56                   2.98
 Community Facility            103              2.89               0.24                   0.69                   1.19
         Total                 602                                 1.39                   3.73                   6.96


A Peak Wet Weather Flow (PWWF) rate of 6.96 L/s is estimated for the proposed site.


4.2.1      Gravity Sewer Design
The proposed Development Area 1 will be serviced internally via a DN150 gravity network connection to the existing DN225
gravity main within Grasstree court. The proposed Development Area 2 will be serviced internally via a DN150 gravity network
which will also discharge into the existing DN225 gravity main within Grasstree court.

The proposed servicing strategy is outlined in Drawing No. 18-001942-SK202 within Appendix B. It is recommended that
during detailed design, the proposed internal services be reviewed and certified by a hydraulic engineer in accordance with the
relevant codes and guidelines.




18-001942-WER01                                                                                                               Page 6