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

Please detail how fish passage will be maintained with particular reference to expected or modelled
hydraulic conditions from the downstream to the upstream limit of the crossing.

Please confirm through providing plans that the culvert design will comply with the design
provisions of the self-assessable code WWBW01- Part 3 Culvert Crossings. If the plans are not in
line with the self-assessable code;
    - please detail how hydraulic conditions over the barrier will allow for fish passage over all
        flow conditions.
    - how water quality across the barrier will allow for fish passage.

Response

    •   how hydraulic conditions over the barrier will allow for fish passage over all flow conditions;

    Please refer to Appendix C for detailed design drawings of the proposed culvert replacement.

    Hydraulic conditions over the barrier will allow for fish passage over all flow conditions given the
    following:

        •   The culvert crossing is to be installed at a no steeper gradient than the waterway bed gradient
            to limit velocity increases through the culvert as fish can only swim against relatively low
            velocities;
        •   A larger cell cross-sectional area compared to the existing culvert configuration is proposed.
            This will prevent increased water depth upstream of the barrier which can result in a loss of in-
            stream plants, leading to reduced food supply or loss of breeding habitat; and
        •   The obvert of the culvert is installed at approximately 550mm below the bed level.

    •   how water quality across the barrier will allow for fish passage.

    Water quality across the barrier will allow for fish passage given the following:

        •   Impacts on water quality during construction will be minimised by undertaking works set out in
            the Best Practice Erosion and Sediment Control guidelines 2008;
        •   Prior to undertaking the works, the contractor shall 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; and
        •   The culvert will be recessed into the natural bed by 550mm and backfilled with bed material
            comparable to the natural substrate size and consistency to minimise impact on water quality.

We consider that the information above provides an adequate response to all of the information requested
in accordance with s.278 of the Sustainable Planning Act. Please contact Kelly Pickering on (07) 3173 8353,
or alternatively by e-mail [email protected] if you require further information.

Yours Sincerely,




Kelly Pickering
Town Planner (Aurecon)



                                                                                                           6