Kingston City Council: Turning a Water Strategy into a Practical Capital Works Program
Posted under: More and more local councils are starting to develop integrated stormwater management strategies that set targets for stormwater quality, harvesting and reuse. The aim is to transform their municipality into a ‘Water Sensitive City’ with a more holistic approach to using stormwater effectively.
Whilst the documentation of key objectives and targets is an important first step, many councils struggle with converting their good work into a logical and practical implementation program.
This project examines successfully develops a prioritised capital works program that compares projects using a unique ranking system. It uses real data to map which catchments are treated to best practice, so that gaps and opportunities can be identified. Potential improvement opportunities were then modeled and rated to maximize outcomes.
Description
1 Introduction & Background
The City of Kingston prepared a detailed ‘Integrated Water Cycle Strategy’ 12 months ago. The strategy was a ground breaking document that was recognized nationally as setting the bench mark for water management. It included the establishment of guiding principles and targets for wastewater, stormwater, potable mains water and groundwater. This award application follows on from the above strategy and aims to fill a key asset management knowledge gap relating specifically to stormwater capture and reuse. Design Flow was commissioned to prepare a detailed report (January 2012 to February 2013) to realize the City of Kingston’s vision to create a system to guide cost-effective investment in Council’s future capital works projects and influence private sector planning decisions.
2 Objectives
This project has adopted a ‘catchment based approach’ to help identify the most cost effective way to implement a works program that would achieve ‘Water Sensitive Living’
across the entire municipality. The key steps in the process included:
• Modelling the performance of existing assets (where are we now?)
• Developing catchment maps (where are the gaps?)
• Modelling larger regional scale opportunities (what is possible?)
• Reviewing generic smaller site scale opportunities (how effective are they?)
• Calculating the cost effectiveness of options (ensure value for money?)
• Developing a prioritised implementation program (what, where, when?)
• Reviewing the ‘Integrated Water Cycle Strategy’ targets (are they achievable?)
3 Outcomes
The main outcomes from this project include:
· A greater understanding of existing conditions, where the City of Kingston’s current is, and what is required to achieve our Council’s vision of becoming a Water Sensitive City by 2040.
· A greatly improved appreciation of the level of public and private sector investment required to achieve the City of Kingston’s stormwater treatment and reuse targets.
· A prioritised capital works program that clearly identifies which projects provide the best ‘value for money’.
· Colour coded GIS maps that will help guide engineers, town planners and decision makers on the location of stormwater improvement projects and the level of investment required within each catchment.
4 Best Practice Engineering Principles
This project is very innovative and quite complex. The following sections highlight the aspects of the project that showcase current best practice and aim to establish new standards:
(i) A Catchment based Approach
Melbourne Water has expressed a strong desire to encourage other Council’s to follow Kingston’s approach towards developing holistic catchment models rather than considering proposed projects in isolation.
This project has resulted in a series of colour coded maps that will be available within Council’s GIS computer system. It will allow decision makers to review the location of a proposal (e.g private development or road construction project) to understand the existing performance of the catchment and the relationship to proposed improvement opportunities.
(ii) Best Practice Improvement Opportunities
The feasibility of 34 large scale projects (called regional opportunities) and a series of 11 generic smaller allotment or streetscape sized projects (called distributed opportunities) were investigated.
MUSIC models were developed to investigate and compare the benefits
The criteria used to identify and prioritise regional opportunities include:
• Stormwater availability e.g A stormwater pipe > 900mm diameter close to a reserve.
• Space availability e.g A council reserve with space for a bio-retention system.
• Water demand e.g the need to water a golf course or high profile reserve.
• Value for money e.g Comparison of $/kg treated and $/ML harvested.
The majority of the proposed regional opportunities identified in this project involved harvesting water from main drains, treating via GPTs and medium sized bio-retention systems located with Council reserves, and pumping to above or below ground tanks for storage and reuse (predominately for reserve irrigation purposes).
The investigation of distributed opportunities included combinations of private rainwater tanks (on typical sized residential, commercial and industrial sites), rain gardens located along nature strips and other small scale treatments.
5 Innovative Features
There are a number of innovative features with one of the most interesting being the development of a unique ‘Project Comparison Factor’ (PCF).
This factor can be used to compare the relative benefits of each improvement opportunity based on the unit cost of removing pollutants and the unit cost of harvesting stormwater for reuse. The factor incorporates the ‘real’ cost per annum based on estimated construction and maintenance costs averaged over a 30 year ‘whole of life’ for each project.
The ‘Project Comparison Factor’ is calculated by adding together the following two benefitcost factors:
· A factor that measures the cost-effectiveness of treating stormwater based on $/kg per year for removing Total Nitrogen from the catchment.
· A factor that measures the cost-effectiveness of harvesting stormwater based on $/KL per year of water that can be stored for reuse.
The factor can then be used to ‘rank’ projects and compare the value of investing in one large project versus many smaller projects. The factor can be considered similar to a Benefit – Cost factor where scores higher than 1.0 are an indication of viable projects. Typically the distributed opportunities (e.g rainwater tanks and rain gardens) achieved factors around 1.0 whereas the top 10 larger regional projects (e.g large rain gardens in parks) achieved factors ranging from 5 to 39.
6 Community
This project is expected to have significant ‘flow on’ benefits to the community, namely:
· The implementation of cost effective stormwater harvesting projects located within Council reserves. This will result in improved irrigation and alternative water storage availability for watering street trees.
· It will strengthen Council’s position to seek private sector development contributions to help fund cost-effective regional opportunities (where they exist) in preference to the comparatively less cost effective approach that requires developers to treat their own stormwater on-site.
· Ultimately, this project will provide a mechanism to deliver projects which will result in a cleaner bay and waterways.
· It will also provide valuable leadership to the broader engineering sector, both council engineers and specialist consultants, by providing a clear methodology for prioritising projects and seeking funding for construction works.
7 Overcoming Barriers
This study was carefully project managed by Council’s engineer’s to minimise risks and maximise the practicality of the end results. Strategies included:
· Detailed co-ordination between numerous Council departments. This was critical to ensure support and maximise opportunities including alignment with recreational master plans, irrigation demands, location of drainage flood mitigation projects, maintenance programs and environmental planning objectives.
· Detailed site inspections were undertaken by Council and consulting engineers to investigate feasibility constraints and ensure the validity of construction estimates.
· Council pitched the concept to Melbourne Water to receive a grant to fund the consultancy component of this project.
· Modelling assumptions were reviewed to confirm the appropriateness of the end data
8 Cost/Benefits
This project has resulted in a detailed understanding of the level of public and private sector investment required to achieve Council short term and long term pollution reduction and alternative water source targets. The data clearly identifies the most cost effective and the least cost effective types of stormwater projects. As a ‘bottom line’ comparison:
· Council’s existing assets already contributed 40% towards achieving best practice for the entire municipality. The original target was to achieve 100% by 2040.
· Constructing distributed scale projects such as rain gardens would require an investment of around $8.0M for every 1% contribution towards achieving best practice.
. Constructing regional scale projects would require an investment of around $2.2M for every 1% contribution towards achieving best practice with the added benefit of also providing harvesting & reuse.
· The data indicates that there is ‘diminishing return on investment’ for seeking higher than 70% of best practice for the entire municipality. i.e Increasing from 40% to 70% is affordable, however increasing from 70% to 100% becomes cost prohibitive.
As a direct result of this project, more realistic long term targets have been recommended.
Contribution to Engineering Excellence
We firmly believe that this project will be of interest to the broader engineering industry. Kingston’s Team Leader of Engineering Design (Alan West) has already made a submission to present this project to the IPWEA national conference in Darwin later this year (currently short-listed and awaiting confirmation). This project has identified the following key outcomes which represent a significant contribution towards the advancement of current practice relating to integrated stormwater management:
· The catchment maps developed as part of this project provide an effective visual tool for displaying the location and effectiveness of existing and proposed projects within each catchment. This information can now be used to understand the performance and priorities within each catchment. For example, should future public and private expenditure within a specific catchment focus on contributing towards a regional solution, or based on a lack of opportunities, should there be a greater emphasis towards ‘on-site’ solutions.
· This project has confirmed that it is both feasible and cost effective to find locations where stormwater can be harvested from large pipes and treated within Council reserves or open space. This should change current thinking that focuses on either large wetlands (involving expensive or limited land) or small onsite solutions. The idea of ‘unlocking’ land for medium sized solutions is both cost-effective and practical.
· The ‘project comparison factor’ developed for this project has proven to be very useful tool to evaluate the benefits of individual projects to help guide the development of a prioritised works program.
This project has also resulted in the following key learnings that are very important to the City of Kingston and demonstrate that other authorities could achieve similar benefits if they adopted a similar strategy:
· Existing WSUD assets contribute a significant 40% towards achieving best practice pollution reduction objectives for the entire municipality.
· The identified 34 proposed regional opportunities are more cost-effective than the current approach that encourages smaller scale onsite WSUD solutions.
· The original targets adopted in Kingston’s Integrated Water Cycle Strategy aimed to achieving 100% best practice for the entire municipality by 2040. These were found to be too optimistic. Recommended alternative targets are based on achieving 70% by 2050.
· The data for this report will help to support a Kingston Planning Scheme amendment to imbed a sustainable approach to Integrated Water Cycle management