Wonthaggi Recreational Reserve

Wonthaggi Recreational Reserve
Stormwater Harvesting, Detention,
Retention & Re-use
Hugh Williamson – Optimal Stormwater
Laurie Gervasi – Bass Coast Shire Council
Introduction & Background
• Wonthaggi has a history of flooding
• High water use at the recreational reserve
• Last reserve to not use treated stormwater in
Bass Coast Shire
• Desalination plant increasing the cost of
potable water
Project Location
Water Usage
• 25% of Bass Coast Shire Council’s total water
use
• 60% of Council’s Park/Reserve water use
Catchment Area
• 24 hectare residential catchment area for
Wonthaggi Recreational Reserve for
stormwater harvesting
• 78 hectares total combined catchment
Objectives
• Design to cater for current & projected future
flows and flooding issues in the area
• Design for the construction of a 1ML
underground storage tank incorporating
above ground detention to cater for a 1/10
ARI storm event
• Primary, secondary and tertiary stormwater
treatment
Objectives
• Interception and connection of the existing
stormwater pipe to underground tank
• Design to facilitate the reuse of collected
stormwater for irrigation of sporting ovals –
directly connected to the existing holding tank
and use of the existing oval irrigation system
• Incorporate stormwater filtration and
purification for use on sporting fields
Existing Pit Offtake Verification
Existing Pit Offtake Verification
Design
• Design by Optimal Stormwater &
Bass Coast Shire Council
Design
Primary Treatment
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Stormwater offtake at diversion chamber
CDS Unit P1512 GPT with double depth sump
8.13m3 of pollution storage
Non blocking screen (reliable operation)
Connection into Raw Water Storage Tank
Provides 95% pollution screening to 1mm
Raw Water Storage Tank
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Invisible Structures Rainstore3
1,000,000L of raw water storage
Flexibility in shape to suit site constraints
Environmentally friendly
Raw Water Storage Tank
• Most cost effective multi megalitre long term
matrix system available
• Extremely design friendly; 100mm increments
in any direction including irregular shapes
Raw Water Storage Tank
• Very high load capability; Any road vehicle
NATA tested (safety factor of 2)
• Locally manufactured to ISO 9001:2008,
turnkey installed & warranted by Invisible
Structures
Raw Water Storage Tank
Secondary & Tertiary Treatment
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4 L/S treatment flowrate to match irrigation
Screen Filter, Media Filter & UV disinfection
Purpose built treatment shed
Utilises existing irrigation holding tank and
existing 4 L/S irrigation pump
Existing Irrigation Tank
Existing Irrigation Tank
Flood Detention
Treatment by Bioinfiltration
• 125m collection trench with biofiltration to
tank
Flood Mitigation
Flood Mitigation
• All of 10 year ARI overland flow mitigated
• Half of 10 year ARI pipe flow mitigated
Flow type
ARI storm event
Overland
100 yr 2 hour
Total volume
(m3)
18,127
Overland
10 yr 2 hour
3,710
Pipe
100 yr 2 hour
2,224
Pipe
10 yr 2 hour
1,956
Results
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Primary treatment via GPT
Underground storage tank of 1ML
Secondary & tertiary treatment
Above ground detention, retention and reuse
of a 10 year ARI storm event, with treatment
via bioinfiltration
• Irrigation water is recycled in continuous loop
• Capacity for increased water usage in future
Results
• 98.6% reliability of supply for future irrigation
• 25% of Councils total water use has been
removed
• 60% of Councils Park/Reserve water use has
been removed
• Last oval to be removed from potable water
usage in Bass Coast Shire
Conclusion
• Captures piped stormwater flow via GPT and
overland stormwater flow via hard and soft
engineering
• Secondary and tertiary treatment via media
filter and UV disinfection
• Flood mitigation downstream
• Virtual elimination of potable water use for
irrigation at Wonthaggi Recreational Reserve
• Solves stormwater’s trickiest problem of
combined flood detention, retention & reuse
This project combines:
• Stormwater treatment – hard engineering
• Stormwater treatment – soft engineering
• Stormwater harvesting for reuse, reducing
potable demand and increasing sustainability
• Flood detention
• Flood retention for reuse, and
• Improved environmental conditions in nearby
wetland, via water level control.
Its rare to have so many stormwater elements
all in one great project.

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