Attachment D - Stormwater and Water Quality report

                                                                                   Callaghan & Toth


1.0 SUMMARY
The key points of this investigation are as follows:

    1. Runoff from new access roads, car parks and landscaped areas around the existing
       Lower Mill site buildings is to be cleaned of nutrients and gross pollutants via the
       existing refurbished biobasins and existing and new grass swales. Treated runoff is then
       released to existing outlets into the adjacent Cooroy Creek.
    2. Pollutant loads from the development are to be attenuated.
    3. The flood study detailed that filling for the new carpark areas will not affect flood levels in
       the Cooroy Flood Study.
    4. The previous MUSIC model for the Lower Mill development, did incorporate a similar
       sized carpark on Lot 5, compared to the proposed new carpark on Lot 7.


2.0 INTRODUCTION
This Stormwater Quality Management Plan (SQMP) has been prepared as part of a Material
Change of Use application to Noosa Council. This SQMP is in accordance with:
   1. Water Sensitive Design Code in the Noosa Plan, and
   2. The latest Water Sensitive Urban Design Technical Design Guidelines for South East
       Queensland, published by Health Waterways.

The proposed carparking and new access road works are located on Lot 5 SP213104 and Lot 7
SP173771 and the site is shown in Site Location Plan, Fig 1.1. The site is located at 4-8 Lower
Mill Road, Cooroy and the Cooroy Creek Bushland Reserve (Environmental Reserve 16 Lower
Mill Road, Cooroy).

This SQMP considers the new hardstand areas, including new access road, carparks, and
footpaths, for the existing community uses at the Lower Mill site. The proposed new carparks
will also service the existing Library and the proposed new Hinterland Playground.

There is a total of 52 new carparks proposed in two locations at the Lower Mill site:
    22 carparks adjacent the existing buildings on Lot 5 require formalisation with some
       extension to existing asphalt or concrete; and
    30 new carparks on Lot 7.

In order to receive planning approval from Noosa Council, this site must demonstrate that it
complies with Council’s Water Sensitive Design Code and that the storm water runoff will not
change the surrounding hydrology. There is an existing biobasin located on Lot 7 SP173771
which can accept the flows from the new hardstand areas for treatment. Two existing grass
swales will also treat runoff and two new grass swales will treat and convey flows to the existing
biobasin. These devices will enable the water quality objectives to be achieved.

The Model for Urban Stormwater Improvement Conceptualization (MUSIC) has been used to
assess the suitability of various treatment devices and to model existing and predicted pollution
export loads and concentrations.




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2001 Lower Mill Carpark Extension SWMP                                          February 2020