SDA-1116-034770 - Proposed nbn Facility at 23 Jirrima Cres Cooroibah - Response to Information Request

Please provide the following information in relation to the culvert crossing design:

   -   please provide information on why a bridge is not suitable at this site (i.e. the reason a
       culvert has been proposed instead of a bridge)

       The proposed works consist of replacing an existing culvert. A bridge would not be a practical option
       for a low height structure in this instance.

   -   provide information or drawings which detail that the culverts cells extend 100 per cent of
       the main channel width or that they comply with the self-assessable code.

       The culvert cells are designed to extend 100 per cent of the main channel width, and the crossing
       incorporates at least one (box) culvert with a minimum width of 1200mm in accordance with
       WWWBW01 Part 3 for amber waterways.

   -   confirm that the culvert crossing and associated erosion protection are installed at no
       steeper gradient than the waterway bed gradient
   -
       The culvert crossing is to be installed at the gradient of the existing waterway bed.

       Prior to undertaking the works, the appointed contractor will prepare a Construction Environmental
       Control Plan (CEMP) for approval, identifying risks and management of these risks during
       construction, including associated erosion and sediment control/protection required.

   -   provide detailed designs showing that there are no drops in elevation at the joins of the
       culvert invert, apron and scour protection, and how this will be maintained for the life of the
       crossing

       As shown within the detailed design drawings attached as Appendix B, there will be no drops in
       elevation at the joints of the culvert invert, apron or scour protection.

   -   Confirm which is applicable:
          o The culvert will be buried a minimum of 300millimetres to allow bed material deposit
              and reform the natural bed on top of the culvert base, or;
          o The base of the culvert is the stream bed, or;
          o The base of the culvert cell is roughened throughout the culvert floor to simulate
              natural bed conditions.

       The culvert will be buried a minimum of 300mm to allow for bed material deposit and reform the
       natural bed on top of the culvert base.

   -   Please indicate if any baffles or other roughening elements are to be used

       According to WWBW01 Part 3, roughening is only required for red waterways, or amber waterways
       where the culvert is installed at less than 300mm below the natural bed level. In this instance, the
       proposed culvert will be installed at approximately 550mm below bed level, therefore no baffles or
       other roughening elements are proposed to be used.

7. PO25 All waterway barriers are designed, constructed and maintained to provide adequate fish
passage for the site and fish passage is provided for the life of the barrier.




                                                                                                          5