Asset Management Plan Sewer
Sewer This Supporting Section should be read in conjunction with Council’s Asset Management Plan, the Asset Management Policy (which sets out Council's philosophy of asset management) and Council’s Asset Management Strategy (which provides Council with a clear direction and goal for managing the community's $1.185 billion (as at June 2010) worth of assets).
1
Current Asset Base
The condition of Council’s assets has been audited as part of the asset inspection regime, rated against the asset condition reference sheet and captured in Council’s electronic mapping system. The condition of all Council’s assets is rated from excellent to very poor. As at 2010, the condition of entire sewer pipe network has not been rated. In 2010 CCTV investigations were conducted on approximately 5km of the network. The condition rating for the network which has not been CCTV rated has been extrapolated from the age and material of each section of the sewer infrastructure. As more of the network is CCTV rated the appropriate actual condition ratings will be applied and the subsequent change in value to the network will be calculated and recorded. Council’s electronic mapping system for sewer, PipePAK differentiates between the sections which have been audited and those which have not. The colours on the following maps indicate the condition of the asset, as detailed in the below table. 1 2 3 4 5
Excellent Good Average Poor Very Poor
Dark Green Green Yellow Orange Red
The first map indicates the condition of sewer pipes from excellent to very poor in the Wagga Wagga Local Government Area (LGA). This condition rating is based on extrapolated condition rating and the CCTV condition rating. The following table highlights the proportion of sewer pipes in each condition ranging from excellent to very poor.
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Sewer Excellent Good Average Poor Very Poor
47% 39% 11% 2% 1%
288km 239km 69km 15km 1km
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Sewer The second map indicates where pump stations and sewerage treatment plants are located in the Wagga Wagga LGA.
NB there is also a Treatment Works in the outlying area to the south east of Forest Hill, which is not included in this map.
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Sewer Size of the Network Council owns and maintains approximately 612km of sewer pipe, 37 pump stations and 5 treatment plants conducting secondary and tertiary sewerage treatment. In the Wagga Wagga LGA 23,610 properties in the Wagga Wagga urban area, Ladysmith and Uranquinty are connected to the system which collects 5,380 ML of sewage each year (Sewer Business Plan).
Challenges of the Network The challenges facing the sewer network include:
the need to ensure the effluent reuse schemes fully comply with the requirements of the Australian Guidelines for Water Recycling 2006 reviewing greenhouse gas emissions and implementing processes to minimise emissions maximising effluent reuse and development alternative schemes the size of the sewage treatment plant in Forrest Hill may not meet the demand when new areas are developed the need to provide safe, reliable and cost effective services to unserviced rural villages high number of sewer main chokes and collapse, service complaints and frequent customer interruptions compared to other NSW sewer utilities of similar size the management of increasing energy costs the management of the non-sequential development on the fringe of the Wagga Wagga urban area and the management of the high biological and chemical load from liquid trade waste
There are also a number of challenges facing the business of sewer management, including:
potential impacts of on-going drought and climate change on revenue and assets
ageing infrastructure proposed and potential changes to the businesses as a result of the review of water utilities in NSW non-compliances with OEH (Office of Environment and Heritage) Licenses for effluent discharges failures of onsite wastewater treatment systems in the rural villages and the retention and attraction of skilled employees
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Sewer 2
Condition Assessment
Condition Ratings Reference Sheets The condition of the sewer pipe infrastructure network is audited against a rating scale which ranges from excellent to very poor. This scale is used as the basis of all assessments of the sewer pipe infrastructure network by Council’s Surveillance Team. The rating scale forms the Condition Rating Reference Sheet below.
NB Condition Rating Reference Sheets will be developed for pump stations and treatment works in future revisions of this Asset Management Plan.
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Sewer Risk and Condition Rating Indicators Council also uses Risk and Condition Rating Indicators to determine a prioritised works schedule for the maintenance, renewal and replacement of large asset categories. These indicators are used in addition to the Condition Ratings Reference Sheet to enable further analysis of the worst sections of the asset class. The Indicators are used to develop an overall Works Schedule Priority Rating for each individual asset or section of an asset. The first stage considers the risk that the condition of the asset poses to the community. The following table details the Risk Rating Indicators for the sewer network. Sewer Risk Rating Indicators Weighting 1.2 1.1 1.0 Weighting 1.3 1.2 1.1 1.0
Number of chokes reported > 6 chokes per annum 4-6 chokes per annum 1-3 chokes per annum Number of connections >30 21-30 11-20 1-10
The second stage of the process considers the Condition Rating Indicators. The age of the pipe is considered for the sewer network. The older the sewer pipe (or the closer the pipe is to the end of its design life), the high the risk of failure due to internal and external pressure, cracking, root penetration and/or chemical corrosion. Each section of sewer pipe is rated against the Condition Rating Indicators detailed in the below table.
Score 1 2 3 4 5
Sewer Condition Rating Indicator Within percentage of its design life 30% of design life ending 25% of design life ending 20% of design life ending 10% of design life ending 5% of design life ending
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Sewer The results of the Risk and Condition Rating Indicators analysis are combined to give an individual asset or section of the asset a Works Schedule Priority Rating. For example a section of sewer could be rated as follows: Sewer Section XYZ Number of chokes (CH) 1.1 Number of Connections (C) 1 Age (A) 3 Works Schedule Priority Rating (C+A)CH Formula Works Schedule Priority Rating (1 + 3 )1.1 = 4.1 The Work Schedule Priority Ratings for sections of sewer infrastructure are then ranked from highest to lowest to produce prioritised schedule of works for maintenance, replacement and renewal of the network.
Intervention Levels To guide Council’s response to customer requests a set of reactive triggers has been developed for each asset category. These triggers are called intervention levels and include target response times. The following table details the intervention levels and response times for maintenance of the sewer network. Sewer Intervention Levels Mains Blockages and Corrective action taken within 60 minutes collapsed pipes during work hours or 120 minutes after hours Overflows Corrective action taken within 60minutes during work hours or 120 minutes after hours Pump or other breakdown 60 minutes during work hours or 120 including power failure minutes after hours Spur line blockages and 60 minutes during work hours or 120 collapsed pipe minutes after hours Odour Corrective action taken within 4 working days.
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Sewer Condition Inspection Regime The condition and risk of the sewer pipe network will be assessed simultaneously as part of the Condition Inspection Regime. This inspection will audit the condition of each section of the sewer pipe network against the Condition Rating Reference Sheet and also assess the risk based on location and usage. The entire sewer network will be audited via CCTV over the next 3 years. Until Council has completed a network wide surveillance of the sewer network it is difficult to accurately state a realistic interval for the frequency of these inspections. Subsequent revisions of this Asset Management Plan will identify the inspection frequency and regime once determined from the completed first surveillance. It is proposed the inspection regime should address the pipe material most at risk of failure, for example clay, then by the age of the pipe. Obviously the older the pipe, the closer it is to the end of its design life. Pipes closer to the end of their design life need to be inspected more frequently. A new pipe or one less than 10-15 years old may only need to be inspected once during that time. Ad hoc inspections will be conducted in response to customer requests, on a needs basis and where the asset degrades due to un-foreseen or unusual circumstances, like a storm event. These inspections are done onsite by trained Surveillance Officers and the results are captured in Council’s electronic mapping system (ArcGIS).
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Sewer 3
Life Cycle Management
Life cycle management details how Council plans to manage and operate the asset category at the agreed level of service while minimising life cycle costs throughout the useful life of the asset. For most local government assets there are four key phases to the life cycle, namely: acquisition, operation and maintenance, renewal, and disposal.
Costs occur in each phase of the asset life cycle. It is important to attribute these life cycle costs to each phase to allow for effective decision making about how the asset will be managed. The life cycle costs of assets include:
initial capital investment operation and maintenance refurbishment and renewal administration, overheads and taxes depreciation capital use rate charges or rate of return and disposal of the asset at the end of its useful life
The initial capital or investment cost of a new asset is a significant cost and often dominates the decision as to whether to acquire the asset or expand the infrastructure network. However, it is important to include all the costs associated with each phase of the asset life cycle, including ongoing operation and maintenance, future renewal and disposal.
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Sewer Estimated Useful Life The lifespan of sewer pipe depends on the material used. The following table details the useful life of the various sewer pipes. Pipe Material Galvanised iron Asbestos cement Cast Iron, or uPVC, or HDPE Cement lined ductile iron, or concrete, or reinforced concrete Earthenware or vitreous clay
Design Life 20 years 45 years 70 years 90 years 100ars
* uPVC – Unplasticised Polyvinyl Chloride * HDPE – High Density Polyethylene
Target Maintenance Events The Sewer network, operates on a cost recovery basis. The maintenance of the network is not financed by Council’s General Purpose Reserve, but from the income of the network, the Sewer Reserve. For this reason, maintenance events of the network are not included in this Asset Management Plan. However, this information will be considered in future revisions of the Plan as Council moves towards strategic asset management.
Renewal A detailed work plan for the renewal of the sewer infrastructure is developed annually to support this Asset Management Plan. This renewal program is prioritised based on condition and risk.
Disposal Currently, Council includes the cost to dispose of an asset in the unit rate of that asset type. As Council moves towards strategic asset management this cost will be captured separately. The Asset Management Plan will be updated to reflect this change as it occurs across the asset types.
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Sewer 4
Level of Service
The Asset Management Plan for 2011 has been developed based on data collation, research outcomes and the results of Council’s internal stakeholder engagement process. The next stage of the process is to ask the community to identify which asset condition is satisfactory to them. This will begin with an extensive community consultation process. The consultation will be in the form of a community survey which will be conducted online, at community gatherings, through focus groups and stakeholder meetings. The survey will use new technology, be based on images and a simple selection process. The outcomes of the consultation will form the foundation for true community engagement to occur in relation to the management of infrastructure across the Wagga Wagga LGA, in particular the development of agreed levels of service, supported by Council and the community. As Council gathers data from the community about the level of service for each asset category the outcomes will be integrated into the Asset Management Plan. Until the outcomes of the community engagement are known Council will provide costings to achieve an average condition for each asset category and use this as the satisfactory level of service.
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Sewer 5
Financial Considerations
The following graph details the proportion of the sewer pipe network in each condition.
Current Liability of the Sewer Network Council’s current liability in relation to the infrastructure network is the sum of all asset units which have a condition rating of poor and very poor. The current liability of the sewer network is estimated to be $51,812,452 (in 2010 dollars). The Forest Hill Treatment Plant has an estimated current liability of approximately $451,634 (in 2010 dollars).
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Sewer The following tables detail the current estimated liability of the gravity mains and rising mains of the sewer network, based on extrapolated condition data. Gravity Main Diameter 100 150 225 300 375 450 500 600 750
Current Liability $63,524 $31,094,535 $7,677,427 $2,096,122 $708,859 $2,359,800 -
Rising Main Diameter 100 150 225 300 375 450 500 600 750
Current Liability $640,454 $425,541 $1,203,463 $2,499,670 $472,415 $2,119,008 -
Projected Annual Maintenance Costs The sewer network is not financed by Council’s General Purpose Reserve, but from the income of the network, the Sewer Reserve. For this reason, projected maintenance costs of the network are not included in this Asset Management Plan. However, this information will be developed and included in future revisions of this Plan.
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Sewer 6
Assumptions
There are some generic assumptions made in the management of assets in Wagga Wagga City Council, these are found in the Asset Management Plan. In addition, the following assumptions have been made in relation to the sewer network:
The extrapolated costings for the sewer network in this Asset Management Plan are based on the following: o NSW Reference Rates for a STW 200 EP o Victoria Local Government Adjustment Rates and o Sewer 2010 contract The extrapolated costings also consider the age, type and diameter of the sewer pipe. The estimated useful life of the sewer pipes included in this Plan are based on the NSW Reference Rates for STW 200 EP.
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