Appendix G Water and Sewer Analysis

                       WATER SUPPLY AND SEWER NETWORK ANALYSIS
Client: Noosa Shire Council                        Location: 62 Lake Macdonald Drive, Cooroy


                              Table 9 – Emergency Storage Results
                                                             Ratio of
                                   Total         Total
                                                             available
                                  storage       storage
                      SPS I.D                               storage to
                                 required      available
                                                             required
                                    (m3)          (m3)
                                                              storage
                      CRY020         46            69           1.5



3.4.5   Gravity Sewer Performance

All sewer mains between the development connection point and pump station CRY020 maintained
a maximum allowable depth of 75% x pipe diameter (i.e. 75% maximum depth ratio) during
PWWF, with the exception of pipe 2558134 which had a depth ratio of 76% during the 2036 pre-
development scenario. The depth ratio of this pipe increased slightly to 86% in the 2036 post-
development case however surcharging was not identified in any of the manholes within this area.
Therefore, the proposed development is considered to have a non-worsening effect on the existing
gravity sewer performance.

Further, for all development scenarios the development internal gravity sewer maintained an
acceptable flow depth. Therefore, the development is considered to have a non-worsening effect
on the surrounding sewer network.


4.0 CONCLUSION
The water supply analysis identified one water connection point off Dianella Ct. It is proposed to
extend the existing water main, as described earlier in this report, through the development to
serve the proposed development which includes a subdivision for the purpose of residential
housing.

The analysis demonstrated that, within the DMA, several existing nodes fell below the minimum
required pressure of 22m head during a peak hour simulation. However, in the post-development
scenarios no additional nodes fell below the minimum required pressure. It was demonstrated that
during a fire flow event in the pre-development scenarios that several existing nodes had a
residual pressure below 12m head. However, in the post-development scenarios no additional
nodes fell below 12m head and the proposed development had a negligible effect on any other
existing nodes.

In summary, the results from the water analysis demonstrated that the proposed development will
have a non-worsening effect on the surrounding network up to and including the design horizon
(2036). Further, the proposed extension to the water network provides adequate flow and pressure
to the proposed development both during peak hour and under fire flow conditions.

The sewer network analysis analysed the network between the development connection points to
the existing sewer pump station CRY020 which ultimately discharges to STP-CRY001 via a rising
main.

The initial assessment of the existing sewer network identified that the pumps in CRY020 had
adequate capacity for all pre-development scenarios and the 2021 post-development scenario. For
the 2036 post-development scenario, with the development loading, a pump upgrade was
required. Through further analysis it was determined that the pump station capacity needed to
increase to 18 L/s. It is recommended that the pump station capacity be upgraded before 2031
based on Unitywater’s current demand forecast. With the proposed pump upgrade detailed in this

Covey Associates Pty Ltd                    8                                   Project No: 233467
Consulting Engineers                                                            M23-0030Rpt Iss A