Referenced Document MCU13/0171

With the exception of downpipes which discharge to the adjacent creek, there is very little
drainage infrastructure servicing the hardstand pavements and open surfaces around the
factory.

There is no upstream catchment for the factory site as it is effectively bordered by the
adjacent creek and road reserve drainage along Lake MacDonald Drive.



6.2 Post Developed Drainage

The developed site will remain largely unchanged. There will be no increase to roof area
and minimal, if any, increase to impervious driveway / car park area. The existing
amenities block & staff offices near the site entry at ‘Gate 2’ is to be demolished and
replaced with carpark and landscaping.

The carpark near the site entry will drain via overland flow to the central landscaping rain-
garden in the middle of the car park. The garden discharges into a Fox brand GPT, which
is connected to the existing drainage pipe flowing east. Minor rehabilitation works to the
existing vegetation buffer along the site frontage provides the opportunity to prevent the
erosion of garden beds and transportation of sediment off-site.

The adjacent delivery truck driveway along the side of the factory will be reinstated as
necessary where it is currently damaged and sloped eastward to drain onto the existing
grassed hardstand between the factory and the creek. A grassed or vegetated swale, as
described in section 5.2, will be established in the grassed area to convey and naturally
filter most sediments and hydrocarbons from the delivery driveway surface wash-off. The
length of the swale will also lengthen the time of concentration for the factory site
catchment, helping to reduce the peak stormwater discharge flow rate into the creek and
off site.

Rainwater harvesting tanks provide a nominal volume of detention storage both in the
remainder volume required to top up the tank and in the overflow volume between the
invert of the overflow pipe and tank lid. Again, this increases the time of concentration for
the catchment and reduces the peak discharge flow rate of stormwater leaving site.

We believe these nominal control measures for both stormwater quality and will reduce
peak stormwater discharge flow rates below that of the current site, thereby satisfying the
non-worsening of flows condition in section 3.01 of the Queensland Urban Drainage
Manual (QUDM).




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