RFI -21-10-13 - 20169 - RFI Response

                                                                      MORGAN CONSULTING
                                                                     E NGINEERS P TY LTD
                                                                                      20169
                                                                                      Page 2




Item 3:   Investigate and confirm the existing discharge patterns from the development
          site in the North-Eastern corner of the proposed development and demonstrate
          that the design will not result in any changes in flow patterns or discharge onto
          additional land which is not inundated by stormwater runoff from the site in the
          existing case.

Response: The existing drainage catchment and flows have been demonstrated on the
          updated Concept Stormwater Catchment Plan (20169-SK20-E) for the north
          eastern corner of the site. As shown in the updated Stormwater Management
          Details – Sheet 2 (20169-SK13-D) all flows up to Q100 are contained within the
          basin. The high flow weir has been designed as the top of the proposed pit
          structure within the basin. The proposed weir overflow over the retaining wall
          across the boundary will be in emergency cases only. Therefore, all flows up to
          Q100 is not expected to inundate downstream properties.

          The wall of the basin has also been set back 300mm from the downstream
          boundary to ensure that any overflow has an opportunity to return to existing
          conditions prior to crossing the boundary.

          Furthermore, a site investigation reveals that the existing earth bund does not
          exist and it is more so a local depression surrounding the existing stormwater
          pit. Therefore, it is expected that any stormwater runoff (likely in major storm
          events) exceeding the capacity of the existing pit will likely surcharge and sheet
          flow across boundaries of Lot 79 and 80, meaning that the proposed basin will
          improve drainage conditions across the boundary as a result of withholding flows
          up to Q100 storm events.

Item 4:   Investigate and confirm the existing discharge patterns from the development
          site in the South-Eastern corner of the proposed development and demonstrate
          that the design will not result in any changes in flow patterns or discharge onto
          additional land which is not inundated by stormwater runoff from the site in the
          existing case. Confirm the weir design is able to be realised within normal
          construction tolerances.

Response: The existing drainage catchment and flows have been demonstrated on the
          updated Concept Stormwater Catchment Plan (20169-SK20-E) for the south
          eastern corner of the site. As shown in the updated Stormwater Management
          Details – Sheet 1 (20169-SK12-D) all flows up to Q100 are contained within the
          basin. The high flow weir has been designed as the top of the proposed pit
          structure within the basin. Therefore, the proposed weir overflow over the
          retaining wall across the boundary will be in emergency cases only. It is
          anticipated that the weir design is able to be constructed within normal
          construction tolerances. Flows will not inundate properties that are not
          currently inundated.