MCU10/2116 Notice of Submission Spencer Jacob

The substantial hillside to the East of the proposed MCU/Lot drains to this exact point - Council's
largest Stormwater Sump serviced with large diameter pipes of 600mm width. This final point of
capture by the Council Stormwater System was overwhelmed with the overland and piped flows,
with Council's Grate disappearing under 400mm of water for approximately a quarter of an hour.

The result was ALL of the considerable stormwater and drainage provisions of our Lot which drains
directly into this Sump were overwhelmed, with stormwater backing-up from this now submerged
and not draining Sump, creating torrential overflows from our now-'blocked' Gross Pollutant Trap
across this Property's entire Driveway Area, Resident and Guest Parking Areas and Resident's patios.

Further paving and other forms of hard, non-absorbent surfaces where presently one acre of soft
grass stands will very considerably worsen these natural water flows from the hillside where they
are directed by natural contours and Council's kerbing, channelling and swales to the Stormwater
Sump in the immediate vicinity of the Club's 5 Opal Street Allotment/s subject to this MCU/DA.

Upgrade works to the Council stormwater System in this location MUST be undertaken before
increasing the unmanageable water flows already experienced from existing developments.

The next domino to fall was the Council Sewage System.

Sewage

All of our Five (5) Units at 15 Opal experienced extremely disturbing bubbling, 'burping' and
vibrations from their Sewered Appliance Connections to the Sewer Riser situate under an Easement
on our Eastern Boundary - toilet suites bubbling, bathroom and kitchen drains rumbling and venting.

On this occasion there was no spill-over of raw sewage into the interiors of any of these new homes,
but it was a disturbing, deeply troubling and uncomfortably imminent disaster.

We investigated the event with our hydraulics and plumbing contractors, who advised as follows.

This apparent relation between the Stormwater & the Sewage Systems was explained by long-term
experienced Cooroy local plumbing trades contractors (incl. former Council Plumbing staff) as a
event well known in low-lying Cooroy locations - known as infiltration - the process by which over-
lying stormwater leaks into the (mostly near-empty) Sewer System Pipes from gaps, breaks and
other failures of the Sewer pipes and seals throughout the underground Sewerage Pipe Network.

Failed/porous underground Sewer Piping operates similarly to a giant agricultural absorbtion drain
(a giant 'aggy drain') when it is immersed in and under water.

Large additional stormwater flows infiltrating the much more limited capacity of the Sewer System
quickly overwhelms the Sewer's carrying capacity which can only relieve the increased pressure and
volume increase by backing-up - blowing man-hole covers, and/or backing-up through Sewer-
connected Appliances inside Residents Properties. In both of these pressure-reducing events the
back-up will flow out as raw untreated sewage in Residents Premises (areas of human habitation).