Site icon Method Statement HQ

Legionella Management & Prevention Plan (LMPP) For LEED & ESTIDAMA Green Building Projects

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:

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 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:

Within the site offices accommodation, the main activities will include:

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:

Control Measures for Preliminary Legionella Risk Assessment On-site

The following control measures are proposed, depending on the results of the preliminary assessment above:

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

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:

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

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:

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.

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.

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:

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:

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:

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:

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

Exit mobile version