The preparation of a Legionella Risk Assessment to an acceptable is a vital part of compliance with the Approved Code of Practice and Guidance for the Control of Legionella Bacteria in Water Systems (L8) 2001. This legislation derives from the Management of Health and Safety at Work Regulations 1994 (MHSWR) and the Control of Substances Hazardous to Health Regulations 1999 (COSHH) and applies to all water systems on industrial or commercial premises. Not to comply with these regulations is an offence and prosecution may result.

L8 requires all employers and self employed people to assess the risks from Legionella bacteria to workers and others who may be affected by their work or business. Those who employ five or more employees should record the findings of that Risk Assessment. Where Risk Assessments are recorded, employees are required to consult their employees or their representatives to notify them that Risk Assessments have been carried out and allow their employees an opportunity to comment on the Assessments.

Risk management requires a process which identifies every water system, (capable of producing an aerosol in operation or maintenance and operating at water temperatures of <60°C) and adequately assesses the risk from legionellosis and identifies the necessary control measures to eliminate, reduce or control the risk.

L8 recognises that, in conducting a Risk Assessment, the Duty Holder for the premises needs to have access to competent help to compile Risk Assessments to enable the risks of exposure to legionella bacteria in water systems to be assessed and to identify the necessary control measures required to reduce the risk. Without adequate training it is unlikely that personnel employed directly by the plant will be qualified to carry out an acceptable Risk Assessment as part of their normal duties.

The process for carrying out a suitable and sufficient Risk Assessment should be based on the following stages:

1. Prepare a screening list of ALL water systems within a building/facility. This will demonstrate at any future audit that all water systems have been considered and allows for a simple reason to be given why any particular water system has not been formally assessed. When carrying out a Risk Assessment it is important to consider the complete water system, e.g. test loops, potential dead legs, water temperature - even if is <20°C.
2. Prepare accurate drawings for the water systems that require a Risk Assessment. It is impossible to carry out a Legionella Risk Assessment without accurate and up to date drawings. Drawings for cooling systems should contain all cooling towers, all system control valves, all standby plant, the location of system bleed valve, any associated storage tanks, all pipework (including dead legs identified), the location of chemical dosing/injection points, the location of the system drain valve, the origin of the water supply and detail any parts of the circuit that may be temporarily out of use, i.e. for batch operation, maintenance or isolation. Drawings for hot & cold water services should show all system plant (water softeners, filters, strainers, pumps, non return valves, outlets), all standby equipment, all associated pipework, all associated storage & header tanks, the origin of the water supply and any parts that are temporarily out of use.
3. Describe the correct and safe operation of the system. This should include the potential for legionella bacteria to enter the system, the conditions suitable for proliferation and the means by which exposure potential could be disseminated. Possible sources of contamination to the water system should be included in the system description.
4. Record the temperature at which the water system operates at under normal conditions should be listed.
5. Identify personnel likely to be exposed to aerosols should be listed, including contractors and the general public.
6. Record the precautions taken to prevent the proliferation of legionella bacteria, these include ongoing control measures and maintenance procedures. A table should be generated detailing all control measures and maintenance procedures to be carried out, at what frequency and by whom.
7. Generate an improvement plan with timescales to complete actions.
8. Define the system legionella management structure. There should be named personnel and deputies nominated for all roles. A list of responsibilities for day to day operations and out of specification results should be included.
9. Develop an audit plan and incorporate it into the Risk Assessment.

The audit plan is vital element of the Risk Assessment as this will demonstrate that the Risk Assessment is technically good enough to achieve compliance and the control measures listed are being carried out at the correct frequency.

Where the Risk Assessment concludes there is an insignificant risk from Legionella bacteria, no further action is required, However, care should be taken when using this option as in reality the number of water systems this statement is limited to is very small.

Review of a Legionella Risk Assessment is well defined in L8. The review should take place:

• absolute minimum of every 2 years
• if there is a change to the water system or its use, for example adding or removing outlets, increasing or decreasing production etc
• there is a change in use of a building, for example if the Risk Assessment was based on a water usage within a building containing 30 people and the population of the building was reduced by 10 people the pattern of water usage in that building would change dramatically
• the results of the checks indicating control measures are now in effective
• a case of Legionnaires disease/legionellosis is associated with the system

In conclusion a well derived and managed Risk Assessment is an essential component in reducing the risk from exposure to Legionella bacteria.

Article by:
Mel Hall
Water Technology Consultant
Mel.hall@gb.abb.com
Tel 01925 741279