Pre-Chlorination Procedure for Rehabilitation of Existing Water Lines

Method One

All work involving the renewal of water lines using pipe insertion techniques shall be carried out as hygienically as practicable in accordance with applicable specifications, procedures, codes, regulations and laws of governing regulatory authorities, as applicable and the American Water Works Association with all reasonable steps being taken to avoid contamination of water supplies.

Inform the water provider immediately of any renal dialysis patients or other critical supplies which may be affected.

Where possible the inside section of the replacement pipe shall be inspected for debris before any work commences and any visible matter removed.

The new length of main should be positioned and jointed on the surface, each end capped and charged with chlorinated water. A free chlorine residual of 25 mg/L should be maintained for a minimum contact time of 24 hours.

Where coils are used, they should be laid on their side rather than in a vertical, making sure that air can escape, and charged slowly to ensure tablets (which must be the instant dissolve type) are evenly distributed. The ends of the pipe should be closed and sealed at all times and the disinfection/swabbing procedure repeated if a coil is cut and not used until the next day. Normally, the maximum period between emptying chlorinated water from a coil and subsequent laying/commissioning shall not exceed two hours.

Access holes should be kept dry as possible, the excavation being taken 12” below the pipe invert to prevent ingress of contamination.

The existing main shall be cut and capped at the access holes and the services disconnected. All fittings including the internal surfaces of the existing main, should be sprayed or rinsed with dilute solution of freshly prepared chloros of 1-5%. This should be freshly prepared on sites as dilute chloros solutions will deteriorate after a week.

Approximately one hour before being laid, the length of main to be installed shall be drained of super-chlorinated water and capped.

Note: The environment to which the chlorinated water is to be discharged shall e inspected. If there is any possibility that the chlorinated discharge will cause damage to the environment, then a neutralizing chemical shall be applied to the water to be wasted to neutralize thoroughly the residual chlorine. Where necessary, federal, state, provincial and local regulatory agencies should be contacted to determine special provisions for the disposal of heavily chlorinated water.

During the reconnection operation all pipework and fittings shall be rinsed or sprayed with chloros solution (1-5% strength).

Once the main has been laid it shall be chlorinated to 50 – 100 mg/L and stood for three hours or 300 mg/L and stood for 15 minutes before being flushed, swabbed and commissioned.

Notes: The discharge of large quantities of water from a main must be planned to avoid flooding or causing dangerous road conditions.

After thorough flushing, two consecutive acceptable bacteriological samples, taken at least 24 hours apart, shall be taken downstream by fully qualified rehabilitation staff who are involved in the valving operations. Where no pollution hazard has been present, the main can be returned to service prior to completion of bacteriological testing in order to minimize the time customers are without water. Where there is any doubt, the affected section of main shall not be re-commissioned until satisfactory bacteriological sample results have been obtained. If positive bacteriological samples are recorded, the water system and the appropriate Department of Environmental Protection District Office or appropriate approved County Health Department shall be notified immediately.

Only fully trained and certified personnel shall be allowed to undertake disinfection and piece-up operations involving mainlaying, fittings, installation and all reconnections.

All samples, when taken, must have a maximum holding time of 30 hours.

Wherever practical, work should progress in such a way that location of the commissioned water slug is known and not distributed widespread throughout the system until the bacteriological sample is confirmed and satisfactory.

Revised Edition 19 December 2000

Pre-Chlorination Procedure for Rehabilitation of Existing Water Lines

Method Two

This procedure outlines the steps to be followed when pre-chlorination of the new water line in used to enable the process of pipebursting to replace an existing water supply line. It is essential that all precautions are taken in order that a water quality is maintained and standards are not compromised.

Definitions

Pipebursting – The replacement of an existing water line by bursting out the main using a moling devise and simultaneously introducing the new pipe.

Sliplining – The replacement of an existing water line by inserting a smaller diameter pipe inside the old main. The water quality considerations of this procedure are also appropriate to sliplining where the sliplining process of laying and commissioning is undertaken during one operation in the same pattern as pipebursting.

Starting the Scheme

Ensure all persons are fully qualified, medically cleared to work on restricted operations and are fully competent in company procedures of hygiene.

Check with the water supplier’s system operations team for potential problems that may occur to the flow patterns during the works.

Sample incoming water upstream of the pipebursting project, at the customer’s tap to determine that existing water quality is satisfactory. As a guide it is recommended to take samples at least 10 working days before the project is started. This will allow three days for the bacteriological sample to pass and seven-day card warning notice to be sent to the affected customers. A 24-hour warning card will also be delivered to notify the customers of the actual times water supplies will be interrupted.

Disinfection

An appropriate solution for disinfection of tools, equipment, fittings and materials to be used in pipebursting is made up of minimum 1-5% of available chlorine. Fresh solutions should be made regularly as dilute chloros solutions deteriorate after seven days. Old solutions should be disposed of after dechlorination. No chlorinated water shall be discharged to a water course or surface drain.

Disinfection should be carried out using hand held spray equipment and care taken to ensure the whole surface is treated.

All tools and equipment to be used in contact with water shall be disinfected using the appropriate strength chlorine solution detailed above, with hand held spray equipment. Special care needs to be taken with hired-in equipment to ensure that no contamination risk is present and off-site washing may be necessary before disinfection prior to use.

All fittings and materials used in pipebursting shall be stored hygienically and reasonable measures taken to exclude vermin, debris, or dirty water. Ensure all fittings and materials are disinfected before installation with hand held spray equipment using the appropriate strength chlorine solution detailed above.

Preparation of the Coil

An area to prepare the new pipe for pre-chlorination shall preferably be of hard standing (asphalt, concrete or stone), which is free from any visible contamination.

When using coiled pipe, this should be laid on its side rather than in a vertical position, making sure that air can escape.

One end of the coil shall be capped then at the other end, firstly insert a clean swab, then install the correct amount of tablets for the size of pipe to be pre-chlorinated, (tablets should be the instant dissolve type), then the cap fitted to this end (ensure the caps and pipe ends are disinfected using the appropriate strength chlorine).

Slowly charge the new pipe allowing the tablets to be distributed evenly.

A free chlorine residual of 25 mg/L should be maintained for a minimum contact time of 24 hours.

After thorough flushing the new pipe shall be sampled at each end at intervals of 1200 feet, only by fully qualified rehabilitation staff, who will then fill in a log book/passport form detailing the date, coil number and time sample was taken. A copy of this form will also be taped to the coil to ensure the correct pipe is referred to.

Note: The environment to which the chlorinated water is to be discharged shall be inspected. If there is any possibility that the chlorinated discharge will cause damage to the environment, then a neutralizing chemical shall be applid to the water to be wasted, to neutralize thoroughly the residual chlorine. Where necessary, federal, state, provincial and local regulatory agencies should be contacted to determine special provisions for the disposal of heavily chlorinated water.

Once two consecutive sets of acceptable bacteriological samples, taken at least 24 hours apart, have been obtained, the coil must be stored hygienically with the ends sealed and secured to prevent tampering. The date and time of the cleared samples must be entered onto the relevant log book/passport sheet for that coil. The coil must be used in 14 days of clearance or it will need to be flushed and re-sampled.

Pre Chlorinated Coil

When required for use, cleared coils will be drained and sealed at both ends using two pressure test ends. Care must be taken to avoid contamination, and all fittings must be disinfected by spraying using the chloros solution. The coil will be transported to site and used the same day.

Only coils with valid log book/passport attached and which remain hygienically secure will be used for pipebursting. Others will be returned for re-sampling.

Access holes should be kept as dry as possible, the excavation being taken 12” below the pipe invert to prevent ingress of contamination. The existing main shall be cut and capped at the access holes and the services disconnected. All fittings including the internal surfaces of the existing main, shall be sprayed using the dilute solution of freshly prepared chloros of 1-5% of available chlorine.

A clean chloros soaked sway shall be inserted behind the pulling eye attached to the coil.

Pipeburst the dead section of main.

Cut away the pulling eye and swab and install a blank flange with a sample tap.

Re-chlorinate the new section of main using instant dissolve tablets, ensuring that enough tablets have been inserted to reach a minimum free chlorine residual of 50 mg/L.

After two hours of super-chlorination, check there has been no chlorine loss, after thorough flushing (checking chlorine levels frequently) until water samples are equal to the sample of the incoming water.

Note: If there is a possibility that the chlorinated discharge will cause damage to the environment, then a neutralizing chemical shall be applied to the water to be wasted to neutralize thoroughly the residual chlorine. The discharge of large quantities of water from a main must be planning to avoid flooding or causing dangerous road conditions.

Samples should be taken downstream by fully qualified rehabilitation staff who are involved in the valving operations. Where no pollution hazard has been present the main can be returned to service.

Only fully trained and certified personnel shall be allowed to undertake disinfection and piece-up operations involving mainlaying, fittings installation and all reconnections.

All samples, when taken, must have a maximum holding time of 30 hours.

Revised Edition 19 December 2000

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