Stormwater harvesting in urban environments Overview of engineering practice 1 Results through Experience

Definitions Urban stormwater - “net increase in run off and decrease in groundwater recharge resulting from the introduction of impervious surfaces such as roofs and roads within urban development” “Urban stormwater” is only available within the urban growth boundary Base/dry weather flows in drains & waterways are not considered urban stormwater - no access to base flows will be permitted 2 Results through Experience

Current allocation rules for stormwater harvesting (DSE Sustainable Water Strategy – 2006) If stormwater is flowing to the sea via a drain, 100% of the stormwater may be harvested If stormwater is flowing to a stream from an existing development up to 50% of existing stormwater can be harvested for use and 50% is reserved for the environment If there is a scheme to harvest more than 50% of the resource a study is required to assess implications for the environment All stormwater generated from new development is available for harvesting with the aim of the development having no nett impact 3 Results through Experience

Who Administers Stormwater Assets? 4 The harvesting of water from Melbourne Water’s drains and waterways requires a licence under Section 51 of the Water Act Results through Experience

Australian Rainfall Australian rainfall is low, seasonal and highly variable compared with other continents such as Europe and North America 5 Results through Experience

Rainfall patterns 6 Results through Experience

Annual rainfall Melbourne 7 Results through Experience

Rainfall – monthly distribution 8 Results through Experience

Typical irrigation demands (Melbourne) 9 Results through Experience

Some thoughts.. Rainfall is cyclical meaning there are peaks and troughs The demand for water could also be cyclical e.g. irrigation Distribution of “peaks and troughs” in a year can be more important than the total annual rainfall Statistical Average Rainfall data can be misleading Selection of the rainfall years for further modelling is a risk – based exercise 10 Results through Experience

Stormwater Harvesting Scheme Major Components 11 Results through Experience

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Diversion of flows 13 Results through Experience

Diversion Structures divert the pre-determined range of flows for harvesting while allowing flows outside of this range (larger/by-pass flows and smaller base/environmental flows) to continue via the designated conveyance system These functions could be delivered by various controlling mechanisms generally falling into the two major categories… 14 Results through Experience

15 Flow Diversions i) Transverse weir ii)Side weir iii)Drop structure Flow Control i) Throttle pipe ii) Adjustable Penstock iii) Hydrobrake or similar proprietary device iv) Orifice plate/Sutro weir Results through Experience

Treatment for reuse - Stormwater 16 Results through Experience

National Guidelines 17 Results through Experience

State guidelines 18 Results through Experience

Overview of Treatment Requirements - Stormwater Small to medium schemes No supply to third parties Unrestricted spray irrigation Requirements are to achieve:  Disinfection to achieve >2.5 log reduction in viruses, parasites and bacteria  EC < 10 CFU/100 mL  Turbidity 10 – 25 NTU (subject to satisfying disinfection requirements ) 19 Results through Experience

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Storages Above ground Underground 21 Results through Experience

Example one – for those who love bright colour… 22 Results through Experience

and for those who are more traditional with colour… 23 Results through Experience

and for those who use concrete and concrete only 24 Results through Experience

and the above ground tanks… 25 Results through Experience

Distribution system 26 Results through Experience

Distribution Pipe Work Colour coded pipes (lilac) Removable handles for hose taps Signage e.g. “Recycled Water – Do Not Drink” Allow flush valves for periodic flushing of the system 27 Results through Experience

Definition of Volumes 28 Results through Experience

Operation & Management of Stormwater Harvesting Schemes 29 Results through Experience

O&M itemized Catchment management Incident response (oil spillage, pumps failure etc) OH&S (e.g. confined space entry requirements) Regular inspections Maintenance of equipment (cleaning) Monitoring 30 Results through Experience

ACKNOWLEDGEMENTS In preparation of this presentation the author would like to acknowledge the support and contribution from the following professionals: Steve Hosking, Melbourne Water Corporation Water & Carbon Group Daryl Stevens, Atura Pty Ltd Murray Powell, Optimal Stormwater Pty Ltd Results through Experience 31

QUESTIONS TIME… 32 Results through Experience

THANK YOU Results through Experience