Attachment B - Engineering Response · 132001.210127.4

Advice Item




Response
As noted, the documented minor layout changes have reduced the fraction impervious by 0.3%. The effect of
this is to reduce both the developed runoff and the generated pollutants.

As the current development has no stormwater treatment, the reduction of generated pollutants discharged
from the site is effectively zero. Under the circumstances, a MUSIC model can only be used to analyse the
proposed development and determine a strategy to reduce pollutant runoff generated by that development.
Comparison with an untreated model is not a relevant exercise and will produce no useful information.

The quoted impervious fractions refer to the site in its entirety. The submitted MUSIC model analyses and
treats only the areas of proposed new development totalling 10,530m2, not the entire site.

It is noted that the impervious areas and catchments have been modified since the submission of the original
SQMP and a revised model is attached with this response.