Attachment D - Stormwater and Water Quality report

                                                                               Callaghan & Toth

Biobasin 1 will be:
           a. Located in Lot 7 SP173177 in the same footprint of the existing biobasin
                adjacent to Cooroy Creek.
           b. Designed with a filter area of 144m2.
           c. Filter layer depth of 0.5m, transition layer of 0.1m and drainage layer of 0.2m and
                an extended detention depth of 0.3m.
           d. The size and depth of the systems have been designed in accordance with
                Water by Design Guidelines and IPWEAQ standard drawings in Appendix C.

Biobasin 2 will be:
           a. Located in Mary River Road road reserve in the same footprint of the existing
                biobasin adjacent to Cooroy Creek.
           b. Designed with a filter area of 26m2 (3m wide x 8.65m long)
           c. Filter layer depth of 0.4m, transition layer of 0.1m and drainage layer of 0.2m and
                an extended detention depth of 0.3m.
           d. The size and depth of the systems have been designed in accordance with
                Water by Design Guidelines and IPWEAQ standard drawings in Appendix C.

Grass Swales will form part of the treatment train, with one existing grass swale accepting flows
form carpark areas adjacent the buildings and the new carpark flowing to two new swales and
flowing to the biobasin BB1.

Swale 1
       Existing swale located in Lot 5 formalised,
       Length of 50m, top width of 4.2m, base width of 0.2m with 1 in 4 batters,
        approximate grade of 1.0%.
       The size and depth of the systems have been designed in accordance with Water by
        Design Guidelines.

Swales 2 and 3
       Located in Lot 7 two new swales adjacent the new carpark,
       Length of 40m and 45m respectively, and top width of 2.6m, base width of 0.2m with
          1 in 3 batters, approximate grade of 1.0%.
       The size and depth of the systems have been designed in accordance with Water by
          Design Guidelines.

Swale 4
       Existing swale located in drainage easement between Lot 4 and Lot 5.
       Length of 40m, top width of 4.2m, base width of 0.2m with 1 in 4 batters,
        approximate grade of 1.0%.
       The size and depth of the systems have been designed in accordance with Water by
        Design Guidelines.

4.3.3 Rainfall Data

The meteorological data used for the MUSIC Model was the data for Cooroy from 01/01/73 –
31/12/83.

The mean Annual Rainfall for Cooroy                 1973 – 1983 = 1600mm

The MUSIC Modelling Guidelines for South East Queensland – Version 1 December 2010
details that Cooroy data for 1973 to 1983 should be used.



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2001 Lower Mill Carpark Extension SWMP                                      February 2020