City of Stirling Drainage Asset Managment Plan

Critical risks are those assessed with ‘extreme’ (requiring immediate corrective action) and ‘high’ (requiring corrective action) risk ratings as identified in the Infrastructure Risk Management Plan. The residual risk and treatment cost after the selected treatment plan is implemented is shown in the following Table 6.2.1. These risks are reported to management and Council. Table 6.2.1: Critical risks and treatment plans

Risk r ating (high, extreme) Risk t reatment p lan

Service or a sset at r isk

What can h appen

Residual risk *

Drainage pits, pipes and underground tanks

Asset collapse High

Monitoring condition of assets CCTV monitoring on identified pipes Periodic reduction programs on low-point assets Annual road reserve inspections

Low

Drainage pits and structures

Pit blockage and collapse

High

Low

Gross pollutant traps

Cover collapse High

Monitoring condition of the GPT

Low

Open sumps

Personal injury High

Building fences at critical locations and monitoring the conditions

Low

Note * The residual risk is the risk remaining after the selected risk treatment plan is operational

6.3 Risk assessment matrix The risk assessment process compares the likelihood of a risk event occurring against the consequences of the event occurring. In the risk rating table below, a risk event with a likelihood of ‘possible’ and a consequence of ‘major’ has a risk rating of ‘high’. Table 6.3: Risk assessment matrix – level of risk

Consequence

Level

Insignificant

Minor

Moderate

Major

Catastrophic

Almost Certain

Extreme/ Exceptional

Extreme/ Exceptional Extreme/ Exceptional

Medium

High

High

Likely

Medium

Medium

High

High

Likelihood

Possible Unlikely

Low Low

Medium

Medium Medium

High

High High

Low Low

Medium Medium

Rare

Very low

Low

Medium

6.4 Service and risk trade-offs The decisions made in adopting this DRAMP are based on the objective of achieving the optimum benefits from the available resources. 6.4.1 What we cannot do

6.4.3 Risk trade-off The operations and maintenance activities and capital projects that cannot be undertaken may maintain or create risk consequences. These consequences include: • Increased expenses of renewal/ upgrade projects due to delays caused by the practice of deferring maintenance activities • Failure of drainage assets • Stormwater entering houses at low points. These actions and expenditures are considered in the projected expenditures, and where developed are included in the risk management plan.

6.4.2 Service trade-off Operations and maintenance activities and capital projects that cannot be undertaken will maintain or create service consequences for users. These consequences include: • Flooding issues • Infrastructure damage due to water build-up

Currently the funding allocated to meet the five-year capital upgrades plan is sufficient. However, changes in council priorities on occasion have required works to be deferred. The City’s CCTV inspection program has identified pipes requiring renewal or replacement. Due to limited funding for renewals, not all pipes can be renewed within current service levels. At this time it is not known if Stephenson Avenue Stage One drainage construction works will proceed in 2019/20. If this project proceeds, it is likely that other drainage projects will be deferred and included in subsequent capital works programs.

• Community dissatisfaction • Reduced level of service.

Drainage Asset Management Plan 2019 – 2029 | 33