This document presents the Legionella Management & Prevention Plan (LMPP) for any type of public construction project.
Project specific Legionella Prevention Plan (LPP) is prepared as per the LEED/ Estidama Requirement for Livable Buildings: Indoor Environmental Quality Requirement, Legionella Prevention.
Normally the requirements are given within the project specifications, and contractor is responsible to develop and implement a legionella management plan for all relevant water based systems.
Background to Legionnaires ‘disease
The Legionnaires’ disease is caused by the bacterium Legionella pneumophila and related bacteria.
The disease is a potentially fatal form of pneumonia which can affect anyone but is principally affects those who are susceptible due to age, illness, immunosuppression and smoking etc.
The disease is normally contracted by inhaling Legionella bacteria, either in tiny droplets of water (aerosols), or in droplet nuclei (the particles left after the water has evaporated) contaminated with legionella, deep into the lungs.
It may also be contracted by inhaling legionella bacteria following ingestion of contaminated water by susceptible individuals. Symptoms of the disease include dry cough and difficulty in breathing.
Some infected patients may develop diarrhea or vomiting and some may become confused or delirious.
The disease can be treated effectively with appropriate antibiotics. Incubation period is usually between 3 – 6 days before the symptoms are developed.
The Legionella bacteria are common and can be found naturally in environmental water sources such as rivers, lakes and reservoirs, usually in low numbers.
They are found in water at temperatures between 6 – 60°C and water in the range of 20 – 45°C seem to favor growth.
The bacteria do not appear to multiply below 20°C and will not survive above 60°C, however, they may remain dormant and multiply when the temperature is suitable.
The sources of nutrients for the Legionella bacteria to multiply may include algae, amoebae and other bacteria.
In addition, the presence of sediment, sludge, scale and other material may harbor and provide favorable conditions for the bacteria to grow.
The Legionella bacteria are commonly encountered colonizing manufactured water systems such as cooling tower systems, hot and cold water systems and other plant which use or store water.
Therefore, to control the risk of exposure to the bacteria, it is important to:
- Disallow proliferation of the bacteria in water system; and
- Reduce exposure to water droplets and aerosol
Application of Legislation for Legionella Control
The Health and Safety at Work Act 1974 (HSWA) extends to the risk from legionella bacteria, which may arise from work activities.
There are three sets of Regulations and Approved Code of Practice that apply to the control of legionella bacteria in water systems:
- The Control of Substances Hazardous to Health Regulations 1999(COSHH)
- The Notification of Cooling Towers and Evaporative Condensers Regulations
- The HSE Approved Code of Practice ACOP L8 (rev) – “The control of legionella bacteria in water systems”.
- ASHRAE 12-2000 Guideline: Minimizing the Risk of Legionellosis Associated with Building Water Systems
The site is generally divided into the building site and site offices accommodation. During the construction stage, construction activities within the building site will include the following:
- Preparation and installation of concrete foundation of the building
- Preparation and installation of main columns, core walls of the building
- Preparation and installation of main structure of the upper levels of the building including slabs, columns, block walls and roofs
- Installation of MEP services i.e. reticulation of piping and electrical systems, installation of electrical and mechanical equipment
- Preparation and installation of landscaping works
- Installation of basic interior work i.e. raised access flooring, drywall etc.
- Testing and commissioning of various MEP systems
Within the site offices accommodation, the main activities will include:
- Setting up and operation of site offices accommodation
- Installation, operation and maintenance of support services for the site offices i.e. electrical, telecommunication, internet, water supply reticulation, sewerage and waste management
- Installation and maintenance of temporary facilities i.e. carpentry, bar bending workshops, waste separation area, chemical storage area, materials storage area, rest areas, canteen, toilets etc.
Considering the site facilities and activities, the potential occurrence of Legionella bacteria on-site would be confined to water-based system with low turnover.
During the initial construction stage, the areas of concern would be within the site offices compound i.e. hot/cold water system and include the temporary facilities such as the water storage tanks.
The building site does not store water and is not expected to until the testing and commission stage, which is expected at the completion of the building construction.
In order to ascertain the risk of such occurrence during the construction stage, a Legionella Risk Assessment needs to be undertaken
Preliminary Legionella Risk Assessment On-site
A preliminary Legionella risk assessment will be conducted to identify any potential sources of the bacteria on-site and the potential risk of exposure. The assessment will be reviewed when required during the construction phase.
The preliminary risk assessment will be conducted based on the guidance provided in the Approved Code of Practice and Guidance (L8). 3rd Edition 2000, UK Health and Safety Executive:
- Conduct a survey of the construction site and identify all existing water-based systems i.e. water storage tanks, pipes, drinking water stations and any hot and cold water systems, if any.
- Assess the turnover of water usage of the existing water systems. As a general rule, high turnover rate of water usage will usually minimize the chance of the bacteria multiplying. The entire cooling water loop should be cleaned and flushed monthly.
- Note and estimate the range of temperature where the water is being stored. Water stored within the temperature range of 20 to 60°C will be noted.
- Assess whether the identified water-based systems are distributing water in droplets or aerosol forms, ensure that water is not distributed in such form.
- Tabulate a matrix system to assess the risk of exposure of the identified potential source of Legionella bacteria considering the factors of temperature, water turnover and water distribution in droplets/aerosol forms.
- Based on the risk assessment, proposed control measures to eliminate or minimize the risk.
- Avoid dead end piping, low spots and other areas in water distribution system where water may stagnate during shut down.
Control Measures for Preliminary Legionella Risk Assessment On-site
The following control measures are proposed, depending on the results of the preliminary assessment above:
- Ensure water usage turnover is less than 3 days.
- Ensure water is not distributed in droplets or aerosol.
- For water usage turnover with more than 3 days, the storage tank will be cleaned and monitored for cleanliness.
- Regular/weekly monitoring of water-based system on-site
LEGIONELLA PREVENTION PLAN FOR PROJECT
LPP for the Project is based on the study of the water-based system for the project.
The following water-based system has been identified and is described in the following sections:
- Chilled Water System
- Cold /Domestic Water System
- Hot Water System
- Fire-fighting Water System
- Irrigation Water System (this has not been confirmed at the time of this plan)
Chilled Water System
The chilled water system distributes flow of chilled water to the air handling unit and fan coil units (which is the essential equipment for the air conditioning of the project).
Two units of chilled water pump, AHU and FCU are located in the ground level.
The circuit is a closed loop.
Chilled water system is also equipped with an exclusive chemical dosing system which administers biocides and corrosion inhibitors during operation.
The biocide functions to prevent the growth of micro-organisms while corrosion inhibitors intend to avoid corrosion of the black steel pipes. The chilled water is maintained at supply network temperature of around 5.5°C and return network temperature of around 14.4°C.
Cold/Domestic Water System
The cold water supply circuit distributes water to the domestic utilities such as washrooms. Based on the current design, the cold water supply will distribute water to the washrooms at basement, ground floor, first floor & second floor.
There are 2 water tanks for this purpose (at ground floor pump room).
Water supply is provided by the “existing network” and fills up the RCC tank, water from RCC tank is pumped to fill up GRP tank and water will flow by booster pump for the washrooms in the upper levels.
The RCC tank booster pump is equipped with recirculation pump with a constant flow rate of 4 litter/second. GRP Water tank is not equipped with recirculation pump, but is designed to have a half-day utilization per working day i.e. approx. 2 times fill up per day.
As such, water within all the tanks is not expected to stagnate.
Hot Water System
Hot water system distributes water to the male and female shower rooms located at level ground floor.
The system is an open loop network with possibility of human contact.
Source of supply is from the RCC water tank which receives water from the distribution company network.
The water enters the water heaters located at same level, all hot water pipes are insulated to maintain minimum temperature of 60°C.
Fire-fighting Water System
The fire-fighting circuit is to be used during fire situation where water from the main domestic tank at ground level (fire reserve) is used for sprinklers, fire hose reel /fire hose cabinet of the project.
During fire condition, this circuit becomes an open circuit and until such unlikely event, the water forms a stagnation loop within the fire-fighting pipes.
Wastewater System
The network caters for the disposal of grey and black water to the municipality drainage lines and there is no human contact.
All the drain water system (from HVAC SYSTEM) are need to be connected to rain water system in roof and all other areas are connected to nearest waste water system.
Water Test Reports
Water test shall be arranged for all facilities which deal with water.
After getting permanent water supply connection from authority conduct water test in equal interval of time duration for all facilities which deals with water at third party testing labs.
Make records of the test and if there is any variation in the test results take necessary action as mentioned in the prevention plan.
Water Sterilization and Disinfection Procedure and Tests
Pre-Requisites:
- Ensure that the installation work has been completed. System successfully pressure tested and witnessed.
- Ensure that all the heaters are switched off and any filters/softeners are bypassed.
- The availability of electricity at site for lighting.
- Confirm the availability of Labour/Manpower at site for 24 hours operation.
- Confirm the availability of chemicals, fire extinguisher and duct for smoke exhaust at site.
- Confirm availability of safety equipment on site and ensure that workers are trained in safety requirements.
- Ensure availability of continuous supply of fresh water.
- All future tap offs should have isolation valve for flushing the chlorinated water.
- Confirm sufficient capacities of booster pumps are ready for operation.
- Confirm that Provision/arrangement to be made to collect the drain water and disposal off the same.
TESTING CRITERIA
After Addition of Chlorine Chemical Parameter Supply Water After Static Flushing
Chlorine < 0.2ppm & > 50ppm
After Flushing of the Chlorine Chemical Parameter Supply Water After Static Flushing
Chlorine > 0.2ppm < 0.5ppm
Note:
The above values are for indicative purpose based on Supply of water quality.
POTABLE DOMESTIC WATER CHLORINATION PROCEDURE
Chlorination chemical will be added in the storage tank to 50-ppm residual levels Subsequently, after 1/2 hours of residence time in the tank, the chlorinated solution shall be distributed to roof tank and then to all the parts of the water pipeline network.
Any short fall in residual level of chlorine shall be made up to achieve full 50-ppm residuals by topping up required chemical into the system.
The above shall ensure that the entire system is chlorinated as per requirement
After 24 hours of stagnancy, the chlorinated water from the basement tank will be transferred to a temporary storage tank & the de-chlorination chemical will be dosed into the temporary storage tank.
After testing of chlorine level (<0.5ppm) in the temporary storage tank, the water from the temporary storage tank shall be drained in the sewer or any approved area.
Fresh water will be added in the water storage tanks and flushed through all parts of the pipe network and will be tested for the chlorine level for < 0.5ppm.
Detailed Chlorination Method
The chlorine shall be manually dosed, into the respective tanks as recommended.
Under the supervision of the chemical treatment supplier, detailed procedure adhered for Chlorination is as follows:
- Flushing with water to remove loose debris from tank.
- Chlorination of storage tank and water pipeline network.
- Flushing of Chlorinated Water
- Testing of water in storage tank and pipe work after flushing
- Certification
Flushing with water to remove loose debris
The ground/basement & roof water storage tank of all the buildings has to be cleaned manually to remove the debris in the tank.
After the cleaning, water has to be filled in the tank.
The tank and feeding line has to be flushed till the water is clear and free of suspended solids.
In this step, the system is flushed through all the taps, with plain water to remove particulate and suspended matters from the line.
This step is required as particulate matter of any form can help in proliferation of bacteria in the system.
Chlorination of storage tank and water pipeline
After flushing with plain water, chlorine is introduced into the basement tank and roof water tank and once chlorine levels (50 ppm) is established, the chlorinated water is allowed to remain for a period of 24 hours in the tank.
The authority line to the basement tank is closed.
After adding the chemicals (with in 2 hours after adding the chemicals) the chlorinated water is distributed from the tank to roof tank.
The chlorine level will be checked for > 50ppm, if the level is low chlorine will be added to increase the level to 50ppm.
Once the chlorine level is > 50ppm in the roof tank, chlorinated water will be distributed to the domestic water network. Also chlorinated water will be distributed to lower levels .
Residual chlorine is checked at random points in the pipe work by using the Chlorocol tablets.
Flushing of Chlorinated Water
After 24 hours stagnancy, the basement tank chlorinated water and roof tanks and remaining water will be drained through the drain and collected in basement sump and will be de chlorinated.
The basement tank will be flushed with fresh water by opening the incoming supply line valve.
Flushing will be continued until the chlorine level is below 1ppm.
The drained water will be collected in the sump in basement.
Once the chlorine level is below 1ppm from the basement tank drain line, the drain valve will be closed.
The basement tank will be filled with fresh water.
Once the basement tank is full, the booster pump will be operated to transfer water from basement tank to roof tank. (Before transferring the water chlorinated water in the roof tank will be drained).
Open the taps provided on the top level (Roof Floor) and start flushing through all the taps from top most level.
Continue flushing till the chlorine level is below 0.5ppm.
Once the chlorine is below 0.5ppm stop flushing from the taps, close the taps and go to the next low level.
Continue the flushing through taps on the next low level till the chlorine level is below 0.5ppm.
Similarly continue the flushing of taps on each level till the lowest level is reached with chlorine below 0.5ppm.
All the chlorinated water from the building should be collected in a tank and the same to be disposed in the sewerage line or diluted till the chlorine level reaches required limits.
This confirms the chlorination is completed.
Testing of water in storage tank and pipe work after flushing
After all the chlorinated water is drained out, flushing with fresh water is continued till the chlorine level is below 0.5 ppm.
Then water samples are tested by comparator kit (for low range chlorine level) for final chlorine level after flushing.
All the chlorinated water from the building should be collected in a tank and the same to be disposed in the sewerage line or diluted till the chlorine level reaches required limits.
Certification
Final certification shall be provided upon satisfactory completion of the above.
A sample will be collected and submitted to external laboratory for microbiological analysis.
Legionella Prevention in Operation Stage Of the Building
Under general health and safety law, the employer has to consider the risks from legionella that may affect staff, students or members of the public and take suitable precautions. FM team must:
- identify and assess sources of risk;
- prepare a scheme (or course of action) for preventing or controlling the risk;
- implement and manage the scheme – appointing a person to be managerially responsible, sometimes referred to as the ‘responsible person’;
- keep records and check that what has been done is effective.
Legionella Risk Assessment Procedure
The risk assessment is the responsibility of facility management who are in control of the premises. The assessment can be carried out directly by a person within the FM team or from outside sources, eg consultants, specialists, etc.
The FM team needs to find out if any of the installed water systems (including the equipment associated with the system such as pumps, heat exchangers, showers etc.) are likely to create a risk.
Following shall be considered for risk assessments.
- Are conditions present which will encourage bacteria to multiply? For example, is the water temperature between 20-45°C?
- Is it possible that water droplets will be produced and, if so, could they be dispersed over a wide area? For example, consider showers.
- Is it likely that anyone particularly susceptible will come into contact with the contaminated water droplets?
Refer to appendix 1_Checklists to be conducted during operations.
On Site Domestic Potable Water Treatment and Control Program
On site water treatment
On site water treatment system, consisting of copper-silver ionization unit and media filter is employed to keep the cold water supply system clean and to control the growth of bacteria, even if temperature rise above 20 oC.
- The water storage and distribution system shall be thoroughly cleaned prior to disinfection.
- Chemical disinfection shall be carried out by chlorinating the water in the storage tank; the water should be having 50ppm residual chlorine for disinfection purpose. Each of the taps and outlets shall be systematically opened to allow water to flow until there is chlorine smell and the chlorine levels are maintained at 50ppm. There after water shall be allowed to stand in the system for about 24hours. The chlorine concentration shall be monitored throughout the entire system and up to the farthest discharge point to ensure there is enough residual chlorine level, at least 30mg/liter. The system shall be thoroughly flushed following chlorination.
- It is strongly recommended to use food grade chlorination chemical, one which has pH as near to that of water as possible, fast dissolving, rapid release type, preferably of effervescent type which will inherently aid in mixing.
- Hot water system shall be thermally disinfected by raising the hot water temperature to 600C and circulating hot water in the system for about one hour. Each tap/outlet shall be opened sequentially to allow the hot water to run for at least five minutes.
- Biocide treatment: Chlorine shall be used as an oxidizing biocide to manage and control growth of plank tonic and sensible legionella in water distribution systems. The dosage shall not exceed 0.50 mg/liter on a continuous basis.
- The concentration of chlorine shall be monitored on a daily basis to ensure that minimum level of 0.30-0.50 mg/liter is achieved.
General Legionella Monitoring
The risk of exposure to legionella shall be controlled by ensuring the precautions taken are monitored on a regular basis. This shall comprise the following:
- Visual inspection of water storage tank to check the condition of the inside of the water storage tank and the stored water. The lid of the storage tank shall be in good condition and shall fit closely. The thermal insulation of the tank and pipe work shall be in good condition.
- Hot water storage shall be drained and cleaned if necessary.
- Checking the quality of stored water for clarity, taste and odor
- Test water samples at various outlets for minimum biocide concentration levels, on monthly basis.
- Collect samples from various outlets and forward to reputed laboratories for legionella analysis on annual basis.
Preventing or controlling the risk
If a risk is identified during the operations which cannot be prevented proper controls are necessary to be introduced.
Risks from Legionella in water systems can be controlled by careful planning, successful management policy, competent staff and attention to proper control strategies.
Risks have been already eliminated during the design and verified during construction. After the building is handed over to facility management team it is their responsibility to ensure that risks are managed and controlled to avoid the growth or spread of Legionella.
The FM team will need to prepare a written scheme based upon below mentioned guidelines/requirements, which sets out how is it intend to control the risk from Legionella:
- The system – an up-to-date plan or schematic diagrams are sufficient;
- Who is responsible for carrying out the assessment and managing its implementation;
- The safe and correct operation of project system;
- What control methods and other precautions will be used; and
- What checks will be carried out on the control scheme and how often.
- Ensure that the release of water spray is properly controlled;
- Avoid water temperatures and conditions that favor the growth of Legionella and other micro-organisms;
- Ensure water cannot stagnate anywhere in the system by keeping pipe lengths as short as possible or by removing redundant pipework;
- Avoid materials that encourage the growth of Legionella;
- Keep the system and the water in it clean; and
- Treat water to either kill Legionella (and other micro-organisms) or limit their ability to grow.
Responsibilities at Operation Stage
Inspection and Maintenance frequency to be carried out by FM team:
| Service | Task | Frequency |
|
Hot Water System
|
a. Arrange for samples to be taken for hot water storage, in order to note conditions of drain water.
b. Check the temperature of the water at outlet of water heater. c. Check water temperature up to one minute to see if it has reached 500 C in the selected taps. |
a. Monthly
b. Daily c. Monthly |
|
Cold Water System
|
a. Check the temperature is below 20 oC after running the water for up to two minutes in the selected water taps.
b. Visually inspected cold water storage tanks and carry out remedial works where necessary check representative task for temperature as above on a rotational basis. |
a. Monthly
b. Annually |
| Shower heads
|
Dismantle, Clean, disinfect and de-scale shower heads and hoses. | Monthly |
| Little used outlets
|
Flush through and purge to drain, or drain immediately before use, without release of aerosols. | Weekly |
Overall Responsibility Matrix for Legionella Management
| Water System | Description of potential
risks |
Design action take | Residual risk after
installation |
Responsibility of
residual risk |
| Air conditioning
system |
Risk from water
Cooled system |
Air cooled system have been considered for this project. Water cooled system is not applicable. | Install air
conditioning as per approved design drawings/ specification |
Contractor |
| Cold water
system |
Water
supply from main and cold water storage |
All water tanks shall be
insulated and designed according to Applicable standards |
Prepare and use
a legionella management plan to monitor and manage risk |
Contractor |
| Cold water
system |
Excessive
storage and risk of stagnation |
All water tank shall be designed according to
Applicable standards |
Periodic
maintenance/ checking required throughout the life of the building. |
Client’s
maintenance team |
| Cold water
system |
Risk from
open water tanks |
Tanks designed as fully enclosed with sealed access
covered and screened vents and over flows |
Ensure tank is
kept closed and maintain fly screens. Periodic checking is required |
Client’s
maintenance team |
| Hot water
System |
Risk from
hot water |
Hot water at 60 0C shall be generated by electric heater
or solar heater |
Install hot water
system as per approved design drawing. |
Contractor |
| All hot water heaters should have a drain valve located in an accessible position at the lowest point of the vessel so that accumulated sludge can be drain easily and the vessel emptied in a reasonable time. | ||||
| The pipe branches to the individual hot taps should be of sufficient size to enable the water in each of the hot taps to reach 500C within one minute of turning on the tap. |
Legionella Training schedule
Training shall be conducted regarding legionella prevention plan to all the users of the above said systems.
All users of the above said systems should be aware of the legionella prevention plan.
MEP subcontractor shall hand over the details of the legionella prevention plan to Facilities management team to conduct training after the handing over of the project.
Legionella Risk assessment Summary
Considering the permanent water circuits in the project, only the Fire-fighting Water Circuit (within the fire-fighting pipes) presents potential risk of Legionella growth and this circuit is only activated during fire situation, where water within the pipes will be rapidly replaced with circulated water from the fire reserve tank, hence the risk is deemed very low.
On the other hand water systems identified at the project lie within the temperature range that is favorable for legionella growth. Therefore, during construction, water systems will be tested and inspected upon installation of permanent water supply.
Legionella audit checklist will be filled by QAQC engineer or commissioning Agent.
However, during operation, the water systems must be monitored to ensure all equipment is in good operating condition, otherwise, this may increase the risk.
The risk assessment will be revised, should there be any changes in the design/installation during the construction period.
The Legionella risk assessment is summarized in Table below.
| Water System | Average Circuit Temperature | Loop Description | Water Storage Area | Water Turnover | Location | Aerosol/ Droplets | Human Contact | Risk |
| Chilled Water | 10°C | Closed | None | Constant internal circulation | basement | None | None | NA |
| Cold Water Supply | 30°C | Open | Ground Water Tanks | 6 liter/s | Ground floor | Yes | Yes | YES |
| Hot Water Supply | 45°C | Open | Water heaters | None | Ground floor , 1st floor & 2nd floor | Yes | Yes | YES |
| Fire-fighting | 30°C | Open | Fire Reserve Tank | 5 liter/s | Ground floor | Yes (fire) | Yes (fire) | Yes |
| Wastewater | 25°C | Open | Gutter from ADSSC | None | Below ground | None | None | NA |
LEGIONELLA MONITORING AND INSPECTION
During the operational period, to avoid any possibility of Legionella outbreak, the project facilities management team should undertake monitoring and inspection of the water systems.
The monitoring and inspection should follow the guidelines within the Legionnaire’s Disease-The Control of Legionella Bacteria in Water Systems’, Approved Code of Practice and Guidance (L8). 3rd Edition 2000, UK Health and Safety Executive.
The following should be considered during the operational period by the facilities management team:
- Annual Legionella Risk Assessment
- Monitoring and Routine Inspection:
- Pipes, valves and fittings etc. for all water systems are in good condition
- Temperature of the chilled water circuits as specified
- All circulation pumps and stand-by pumps are in good working order
- Filtration and dosing equipment is in good working order
- Dosing chemicals and filter media are stored in good order
- Scheduled replacement/supplement of the following:
- Filter media
- Dosing chemicals
Corrective Actions For Legionella
In case of presence of Legionella bacteria in any system immediate action shall be taken to clean the area and isolate until necessary chemical treatment of the system is done.
Find the root cause and take necessary corrective action to stop occurrence of the same situation that may include:
- Avoid the water temperature between 20-45 Celsius
- Avoid the water stagnation in any area, remove any dead legs
- Keep the water system clean and well maintained
- Control the release of water spray
- Use suitable water treatment chemical
RECORD KEEPING
A copy of this Legionella Prevention Plan should be provided to the Project facilities management.
ATTACHMENTS:
Appendix 1 : Legionella Audit Checklist
Appendix 2: As Build Drawings
Appendix 3: Construction Checklist
Appendix 4: Commissioning Checklist