RFI - Attachment F - Engineering Report

Executive summary

Introduction and background
Ingal Environmental Services (I.E.S) was contracted by Ku-Ring-Gai Municipal Council
(KMC) to undertake an investigation into the performance of the Enviropod units in
removing nutrients.

The aim was to investigate the contaminant characteristics associated with topography
and land use in a typical Ku-Ring Gai catchment. It was also intended to investigate how
nutrients are transported into the reticulation system and in turn into the receiving
environment.

Contaminates are transported in stormwater by four main mechanisms:

   1.   Dissolved.
   2.   In suspension (suspended solids).
   3.   Saltation or bed load (bouncing along the bottom).
   4.   Floating.

It is hypothesised that a considerable amount of the material in stormwater, is being
transported into the reticulation system as bed load or gross pollutants. This in turn
contributes a significant proportion of overall contaminants in stormwater. To date there
has been limited research carried out on quantifying the loads and effects of bed load or
gross pollutants

For the purpose of this study the following definitions for suspended solids, bed load and
gross pollutants have been adopted.

   •    Suspended Solids (TSS) <1mm
   •    Gross Pollutants (GP) >5mm
   •    Bed Load (BL) 1mm<x<5mm

Enviropod filters were retrofitted into 80 gully pits at the head of the Blackbutt Creek
Catchment. By installing the Enviropods in the gully pits, an extremely large screening
area and storage volume is obtained within the catchment. For the Blackbutt Creek
catchment the 80 Enviropods provided approximately 8.5 m3 of storage and 90m2
screening area.




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