Attachment C - Stormwater report

         To achieve the relevant load based reduction targets, a bioretention system of 400m² filter area
          would be required. Construction of this system would come at considerable cost to the client, and
          would not greatly reduce the pollutant loads entering the waterway due to the quality of runoff
          entering the bioretention system.

The following recommendations are made in relation to the site and operation of the tomato farm within
the proposed 140m x 144m greenhouse:

        A media filtration system, as detailed in Section 4.4.3.2, should be provided to treat runoff from the
         greenhouse roof area.
             o While the media filtration system does not achieve the load based reduction target of 45%
                 removal of TN, it meets the load based reduction targets for TSS and TP, and is able to
                 remove a considerable portion of TN from runoff. It is considered the additional cost
                 associated with constructing a bioretention system cannot be justified by the potential
                 increase in TN load removal.
             o The media filtration system will also facilitate infiltration of runoff into the soil profile. No
                 modelling has been undertaken to determine the volume of runoff that would be
                 infiltrated, and this would vary due to the groundwater levels at the site. However, it will
                 assist in returning the predevelopment hydrologic regime and reduce the volume of
                 additional runoff from the greenhouse roof that enters the creek system.
             o Any overflows from the media filtration system should be conveyed to the creek in an open
                 drain to further increase the infiltration potential. Detailed design of the media filtration
                 system should be undertaken as part of any future works, and the spillway designed to
                 convey the relevant design storm event.
        All exposed surfaces should be stabilised with either a vegetative cover (i.e. turf or topsoil and
         hydromulch), or mulching. Ideally, access tracks around the site will also be stabilised using gravel
         sheeting (refer Main Roads Specification Type 2.3).
        Any future works for the site will require an ESCP to be developed for the project.




Stormwater Management Plan – Lot 1 on SP108094, 305 Lake Macdonald Drive                                 Page 32

D’VINERIPE
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