DEMONSTRATION OF THE DECISION MAKING FRAMEWORK
COORDINATION WITH RELEVANT AUTHORITIES
As with social, environmental and economic issues, detailed examination of community participation, risk assessment and coordination with relevant authorities were beyond the scope of this project. These issues were examined briefly, as described below.
Discussions with relevant water and health authorities would be required to determine which end uses would be appropriate for the stormwater use scheme. These discussions would also identify whether there are treatment systems that would not be appropriate for stormwater use schemes. Examples of issues that would make treatment systems inappropriate are chemical residuals causing environmental concerns or insufficient treatment capabilities to achieve the required end use quality.
Approval of the proposed stormwater use scheme would need to be sought. To ensure resources and money were not wasted, regular discussions should be held with the authorities throughout the planning and implementation stages. This would ensure that too much time would not be invested in stormwater use schemes that would not be approved. Only systems that were potentially feasible and could be approved would be examined in detail. Regular discussions with the relevant authorities would also ensure approval was more easily established as the designer and the authorities would both be aware of the requirements and potential solutions.
Approval of the stormwater use scheme would include approval of the treatment systems to meet required water standards, as well as a monitoring program. Treatment requirements may be optimised by identification of the actual stormwater quality for the area being examined. This would be through stormwater monitoring programs.
Risk assessment would need to be carried out as part of the additional issues of the decision making framework. Risk assessment would be very important in terms of examining stormwater use for potable end uses and risks associated with accidental drinking of non-potable water.
Detailed analysis of providing potable water from stormwater was not examined for this case study. In addition to discussions with relevant water and health authorities, a risk assessment and identification of stormwater quality and verification of associated treatment requirements to meet drinking water standards would be required, if potable end uses were to be supplied from stormwater.
Like most other engineering projects, the case study would not be able to proceed any further without community participation. Social acceptance of the project would direct whether the project would be successful. The effectiveness of the stormwater use scheme would be influenced by community participation and understanding of the project. Community participation would also need to communicate to the community the potential costs and benefits through discussions and education programs.
5.11 SUMMARY
The decision making framework was demonstrated through the use of a case study. This case study was in an existing urban area in the suburb of Sunshine, to the west of the Melbourne central business district, in Victoria, Australia. An existing urban area possesses the greatest potential impact on water sourcing and sustainability issues, and was selected because previous research was focused on greenfield sites. The general study site conditions provided an understanding of the opportunities and limitations within the study site. This included the limited space available in the existing urban area, and the potential collection and end use areas consisting of the residential area and the Tom O’Brien Reserve.
Area characteristics as well as ground conditions were determined for construction purposes. Stormwater quality was estimated from published data as no stormwater monitoring data was available for the area. The end use required quality was identified as Victorian EPA Class A quality.
Stormwater runoff and end use demand were determined and compared with each other and identified that only the residential demand could be met with potential stormwater runoff. Therefore only the residential was examined in further detail. Within residential demand, outdoor, indoor non-potable and indoor potable end use demands were examined in that order in further detail. While all residential demand could not be met,
particularly over the summer months, there was insufficient reason to not examine all potential residential end uses in further detail.
The decision making framework assisted in determining feasible options for the different technical components of collection, end use, storage, treatment and distribution. The storage options that were examined in further detail were in-ground open storage, above-ground closed storage and underground storage within the Tom O’Brien Reserve, as well as above-ground closed storage on the stormwater reserve. The UVQ modelling tool was used to estimate the storage capacities that were required to produce an average annual reliability of 80%.
Treatment options that were identified were a wetland system in conjunction with pre- treatment and disinfection, as well as small scale on-site effluent treatment systems. However, commercial in-confidence issues and impacts of chemical residuals on receiving waterways meant that the small scale on-site effluent treatment systems could not be examined further. Feasible distribution options were identified as dual pipes for non-potable end uses and single pipe for all end uses. Since all end uses including indoor potable demand were not examined due to difficulties with package treatment systems, only the dual pipe distribution was examined in further detail.
The feasible technical components were then integrated to determine nineteen feasible stormwater use scheme options. This integration was the key to developing a holistic decision making framework. The integration of the technical components also identified opportunities to optimise the stormwater use scheme options through minimising treatment and land take opportunities.
Comparison of all the stormwater use scheme options based on financial costs determined that scheme option 08 was the most effective option in terms of reliability, quantity of stormwater used and end uses met. This option supplied outdoor and indoor non-potable demand with the use of an in-ground open storage system, wetland system with pre-treatment and disinfection, pipe collection and dual pipe distribution. However, stormwater use scheme options 07, 15 and 16 were also superior in terms of costs, reliability and use of stormwater compared to the other scheme options. These options would likely have had additional environmental, social and economic issues. However,
issues additional to technical issues were only examined briefly, due to the limitations of the scope of this project. Community participation, risk assessment and coordination with relevant authorities were also examined briefly.