RFI - Attachment F - Engineering Report

Introduction
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 assessment involved collecting sediment and debris samples from the Enviropod
units during the first 12 months operation.

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.

The catchment was divided into 3 different areas based around land use and topography.
These were named as below;
   1. Commercial: a commercial area with an arterial road at the top of the catchment,
   2. Urban: a steep graded urban sub-catchment.
   3. Base: an urban sub-catchment at the base of a hill, close to the receiving
       environment, (Blackbutt Creek)

Background
Many factors influence the mobilisation and transportation of stormwater contaminates
from surfaces. Size, mass and density of the contaminants will greatly affect their ability
to be transported to the receiving water body. Contaminates are transported by four main
mechanisms:

   5.   Dissolved.
   6.   In suspension (suspended solids).
   7.   Saltation or bed load (bouncing along the bottom).
   8.   Floating.

Research by the CRC (CRC 1997) has identified a strong relationship between suspended
solids and more illicit contaminants such as nutrients, heavy metals and PAHs in
stormwater runoff. However sampling techniques which obtain data on suspended solids
loads tend not to measure bed or gross pollutants loads.

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 inturn
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. Work by Allison at the CRC (CRC 1998) examined gross
pollutant loads and identified a relationship between gross pollutants, organic matter and


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