R ISK A SSESSMENT

Risk assessment is very important for determining the feasibility of a stormwater use scheme. This is especially the case with the update of ARMCANZ et al. (2000) being

based on risk management principles (CRC for Water Quality and Treatment, 2003). Hazard Analysis and Critical Control Point (HACCP) is a risk analysis tool that was originally developed for the food industry and is based on the engineering system Failure, Mode and Effect Analysis (FMEA). These tools identify problems or hazards in different stages of operation and have been adapted to the water management industry. HACCP uses a preventative approach so that potential hazards are identified and can be effectively monitored and risks minimised. These principles clarify the method to identify hazards in the process system, prioritise hazards, manage critical hazards and monitor the implementation of the risk management system including documentation. These principles are just as valid for a stormwater use scheme as in the food industry. The hazards may be similar in terms of risk of contamination and health concerns. The processes that need to be examined are the collection, storage, treatment and distribution systems.

NHMRC and NRMMC (2002) adapted the HACCP principles to determine risk management requirements for the supply of drinking water. The links between the draft Australian Drinking Water Guidelines (NHMRC and NRMMC, 2002) and HACCP is provided below in Table 4.14.

Table 4.14Comparison of HACCP and the Proposed Drinking Water Guidelines Framework

HACCP Framework for management of drinking water quality

1. Hazard identification and preventive measures Water supply system analysis, hazard identification and risk assessment(element 2)

Preventive measures and multiple barriers (element 3) 2. Critical control points Critical control points (element 3)

3. Critical limits Operational monitoring (element 4) 4. Monitoring system for each critical control point Operational monitoring (element 4) 5. Corrective actions Corrective action (elements 4 and 5)

6. Verification / validation Equipment capability and maintenance (element 4) Drinking water quality monitoring, consumer satisfaction (element 5)

Validation of processes, design of equipment (element 9) Audit of drinking water quality management (element 11) 7. Documentation and record keeping Management of documentation and records (element 10)

Source: NHMRC and NRMMC (2002)

An example of another risk management tool that has been used for stormwater management is described in Victorian Stormwater Committee (1999). This risk management system requires input through a stakeholder workshop to identify and rank

the risks of the stormwater management system. The processes to most effectively manage these risks are then determined and included in the stormwater management plan.

Risks specific to stormwater use schemes are similar to those related to other recycled water schemes. One of the main risks relates to health concerns based on possible contamination of supplied water or human consumption, particularly if the stormwater is not treated to drinking water guidelines. Risk management principles may identify access to stormwater treated to non-potable standards as being a priority. The risk of contamination may be minimised through limiting access to the area where the stormwater would be applied. This could be either through closing of irrigation areas to the public or irrigating during night times when there is less risk of the water coming into human contact.

Supplied stormwater that is not being used for the intended use may also be identified as a risk. There is a chance that people may consume water from any number of sources within or external to the house. For example, water supplied to the shower may not be required to meet drinking water guidelines although some people may unintentionally or deliberately drink some of the shower water through washing their teeth in the shower. The risk of the treatment system failing may also be examined. Overflows or bypasses of the treatment system can result in untreated water being supplied to the end uses. There is also the risk of contamination of the potable water supply with stormwater provided for non-potable uses. Backflow prevention and ensuring there are no cross connections between the potable water and stormwater use distribution system reduces these risks.

Safety risks include general water body safety issues with access to children and the risk of drowning. Safety fences or signage can be constructed to ensure children do not have access to the open water body. This results in a compromise between aesthetic values of the water body and safety concerns. Better slopes may also be utilised to minimise the possibility of people slipping or falling into the storage system.

Open storage areas may become areas of fauna habitats. While this can add to the aesthetic value, measures to reduce the impact of animal droppings contaminating the storage area and decreasing water quality may need to be examined. Quality concerns also need to be managed with the possibility of toxic algae impacting on the stored water. This is of particular concern when the water body is relatively still. Still water can also result in mosquito breeding and health concerns. Quality and health issues may be improved through ensuring regular draw down and replenishment of the water supply.

Flood protection issues may lead to another form of risk. Where a system is meant to be used for both stormwater utilisation and flood protection, the risk of the system failure and flood occurrence needs to be considered. Back-up or alternative systems may need to be considered.

Legal risks also need to be identified. Moore (2003) examines the potential legal risks for use of reclaimed water, based on the regulatory framework in Victoria. There are a number of areas of potential legal liability which are classified as “common law liability in tort, liability under contract and liability under specific legislation” (Moore, 2003, p.

70). The key issue that is identified is that in order to reduce potential legal liability, guideline requirements should be complied with. Where the water is not treated to potable standards, the water should be treated to standards suiting the proposed end use. Additionally, practices should be put in place to minimise the risk of the water being used in situations where it is not intended.