Document Title: Work Procedure Mains Flushing Document Reference: DOM-WN-PRC-00000310 Approved By: Asset Management Title: General Manager
Record of Changes and Amendments Amendment No. Document Section/ Reference Number Document / Section Title Version Number Amendment Date Archived Document / Section Text Affected Archived Document / Section Replaced By 1 Section 3 Description B Oct 2013 A Updated DOMS Training Guidelines - 2 Foreword Foreword C Aug 2014 B New legal notice inserted - 3 Section 3 Description D Oct 2014 C New text & guidance for all flushing activities W Langan Sheet i
FOREWORD Background DOMS stands for Distribution Operation & Maintenance Strategy and is being used by Scottish Water to: safeguard the quality of water to customers ensure that Scottish Water apply due diligence to their Scottish Water distribution network The DOMS procedures and work instructions affect all functional staff who works on the network, which includes internal employees and employees of external organisations (i.e. planners, operators, delivery teams, Framework Contractors, or any other contractors). Through the application of the DOMS principles in day-to-day network activities, Scottish Water and their approved contractors will operate and maintain their water distribution networks through operational best practice. This will allow Scottish Water to meet the following objectives: to maintain water quality; to maintain continuity of supply; to maintain water supply hygiene; to undertake water quality incident management; to maintain a cost-effective water supply. to ensure a course of action for timely network intervention (Capex and/or opex) to maintain statutory obligations and customer satisfaction. Responsibility The responsibility for adoption and implementation of all DOMS procedures and work instructions rest with Scottish Water General Managers and senior managers of external organisations. It is the responsibility of all Scottish Water employees and those of external organisations to comply with DOMS procedures and work instructions. Document Control This document is a CONTROLLED DOCUMENT when viewed on Wavelength. The document becomes UNCONTROLLED if printed or downloaded from Wavelength or any other source. Refer to the Wavelength site for the latest version of this document. Change Request A change to this document can be requested by completing a Change Request Form - refer to document DISTRIBUTION OPERATION and MAINTENANCE STRATEGY GOVERNANCE (DOM- WN-GOV-00000001) for change request procedure. Page i
Copyright Copyright of this document is owned by Scottish Water. The document may not be copied or reproduced in any way. Legal Notice Copyright of this document is owned by Scottish Water. The document may not be copied or reproduced in any way. This document and the intellectual property rights in it belong to Scottish Water and except where you are specifically licensed to use this document, you have no right to re-use it. Disclosure of this document under freedom of information does not change the position on (i) ownership and (ii) reuse. Page ii
CONTENTS FOREWORD... i CONTENTS... iii 1 PREAMBLE.. 1 1.1 Procedure Objectives... 1 1.2 Related Parent Documents.. 1 1.3 Related External Controlled Documents... 1 1.4 Related Internal Controlled Documents... 2 2 PROCEDURE SWIMLANES. 2 2.1 Maintenance Schedule Tasks (MST s).... 3 2.2 Mains Repairs & Network Interventions.... 4 2.3 Boundary Valve Operation... 5 2.4 Mains Rehab (Pipe Bursting etc). 6 2.5 Mains Rehab Flushing Program... 7 2.6 Cleanliness Index (CI Sampling)... 8 2.7 Flushing Design & Uni Directional Flushing... 9 2.8 Commissioning New Mains......10 2.9 Overland Supplies..11 2.10 Tankering Operations (Filling).... 12 2.11 Tankering Operations (Discharge)..13 2.12 Emergency Flushing (incidents).....14 3 DESCRIPTION DOMS Training Guidelines.....15 3.1 Health & Safety Risk Assessment....17 3.2 DOMS Impact Assessment Form. 17 3.3 Assess the Impact of the Flushing.....17 3.4 Obtain Team Leader Approval....19 3.5 Update Operations Log.....20 3.6 Traffic and Pedestrian Barriers... 20 3.7 Hydrant & Stand Pipe Operation.. 20 3.8 Opening Hydrant, Washout or Scour-valve..... 21 3.9 Flush Duration & Volumes....22 3.10 Inspections for Flood Damage..22 3.11 Close Hydrant. 23 3.12 Remove Debris from Flushing..23 3.13 Water Sampling.. 24 3.14 Ops Log Updates...25 4. Network Authorisation & Control for Cleaning Index & Design Flushing....26 4.1 Cleanliness Index (Non Steady State Sampling Method statement).... 27-30 5 Flushing Design / Uni Directional Mains Flushing....30-34 6 DSOU Distribution System Operational Usage...35 7 Hydrant stand pipes... 36-38 Page iii
1. PREAMBLE 1.1 Procedure Objectives Mains flushing is an important operational activity which is required for a number of activities while working on the water distribution network. These include re-charging the existing mains after any intervention on the water distribution network and as part of any regular mains flushing program for maintaining the quality of water supplied. This procedure details the issues, which must be considered, and the actions, which must be taken when flushing is being undertaken for the following activities, to minimise discolouration within the water network and or preventing additional burst mains or apparatus elsewhere on the water network. When do I need to flush the main? Mains flushing is required as per Scottish Waters HCOP appendix 1 and DOMS for (a) All new water mains (b) Any rehabilitated water mains (including replacement by pipe bursting/slip lining, swaging or Re-lining). (c) All water main tie-ins (d) Water mains repair carried out under pressure. Only, if after recharging and flushing the main, the Responsible Person is confident the main has remained under pressure throughout the repair and if an impact assessment form (IAF) has been completed and the excavation has remained free from contamination, there is no need to take samples for bacteriological examination. If there is any doubt that the main has remained under pressure during the repair bacteriological samples must be taken. Samples need not be taken from repairs on service pipes below 50 mm diameter. (e) All water main repairs requiring water to be turned off. (f) And for any suspected contamination of the water supply main including an emergency flushing programme as part of any incidents. (g) All tankering operations (either prior to filling a tanker or before directly pumping a supply of water back into the water network for any operational issues i.e. Interruption To Supply.) (h) Boundary valve operations (any BV operations for either planned or emergency work on the water network) (i) Cleaning Index & Non steady state mains flushing (j) Mains flushing programme to improve water quality. 1.2 Related Parent Documents None 1.3 Related External Controlled Documents Scottish Water s Water Supply Hygiene Code of Practice (HCOP1) WRc Removing Loose Deposits From Water Mains: Operational Guidelines, 1989 Page 1 of 38
1.4 Related Internal Controlled Documents (DOM-WN-WIN-00000303) Work Instruction Hydrant Operation (DOM-WN-WIN-00000306) Work Instruction Valve Operation (DOM-WN-PRC-00000319) Work Procedure Hydrant Standpipe Hire Procedure (DOM-WN-PRC-00000332) Sampling From A Hydrant (DOM-WN-TBT-00000011) Tool Box Talk Potable Water Sampling and sampling details, sample registration (DOM-WN-TBT-00000014) Tool Box Talk 14 DOMS IAF Guidance for the completion for access to Working on SW water Network (DOM-WN-TBT-00000015) Tool Box Talk Sampling repairs and New Mains Information for those taking samples (DOM-WN-TBT-00000016) Tool Box Talk Mains Flushing DOMS Impact Assessment Form (DOM-WN-TBT-0000023) Impact Assessment Form 2. PROCEDURE SWIMLANES Operational Swim lanes refer to following. Page Number Maintenance Schedule Tasks (MST s).. 3 Mains Repairs & Network Interventions..... 4 Boundary Valve Operation....... 5 Mains Rehab (Pipe Bursting etc)...... 6 Mains Rehab Flushing Program.......... 7 Cleanliness Index (CI Sampling)... 8 Uni Directional Flushing......... 9 Commissioning New Mains....... 10 Overland Supplies... 11 Tankering Operations (Filling).... 12 Tankering Operations (Discharge)... 13 Emergency Flushing (incidents).... 14 Page 2 of 38
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3. DESCRIPTION DOMS TRAINING GUIDELINES EVIDENCE OF DOMS TRAINING In 2007, Scottish Water set the goal that all staff working on the water network receives the relevant DOMS training by the end of the year. The result - over 9,000 people have currently completed DOMS training to support their network activities since it has been introduced within SW. All staff, both internal and external, who works on the water network, MUST complete the relevant Distribution, Operation and Maintenance Strategy (DOMS) training associated with their specific network activities and as a result MUST carry two cards which confirm their training. DOMS training is available through a number of approved Training Providers and the registration of the training units taken by individuals is administered through EU Skills. The first card relates to training given around the Hygiene Code of Practice (HCoP) and the card usually coloured light blue, confirms the cardholder has completed this element, which includes a health screening questionnaire. The second card, usually coloured white, relates to training given around DOMS and the training units shown on the back of the card detail the type of DOMS related site activities that the cardholder can undertake. Both cards detail the name of the cardholder, along with their picture, which will allow confirmation that the cardholder is the person holding the card. Scottish Water staff may and will challenge all internal and external staff working on the water network at anytime to produce both their cards to ensure that cardholder has the relevant training and understanding of DOMS Procedures and Work Instruction for the specific task that they are undertaking. The following guidelines should be followed for deciding the course of action to take when either internal of external staff were found to be working on the water network, or any infrastructure that will be connected to our network, without the requisite HCoP/DOMS cards confirming training 1) New starts - expectation that they will have their necessary HCoP/DOMS training organised by their employer within the first 4 weeks of them joining their company. They will not be allowed to work on the water network without the HCoP/DOMS training, even though they are being supervised by a person who has gone through the training. There is a minimal health risk here, which the health questionnaire, completed during the HCoP training, will confirm as acceptable or unacceptable. 2) Completed HCoP/DOMS Training but no card issued by EU Skills - staff in this situation can work on the water network as long as they can demonstrate that they have a 'cover note' issued by training providers. If a 'cover note' is produced, then the person challenging can Page 15 of 38
ensure that 'cover note' refers to the actual person by checking the EU Skills web site against name or reference number. This will be done in conjunction with the relevant DOMS Working Group representative. 3) Person challenged on site and person has no HCoP/DOMS relevant training - if this scenario occurs then the person who has made the challenge will remove the person from working on the water network and contact the relevant business unit DOMS Working Group representative as the first point of contact. Together, the site contact and the DOMS Working Group representative will make the decision on whether work can or cannot continue after discussions with the employee s relevant organisation. 4) Person challenged on site and cannot produce HCoP/DOMS relevant training cards, but claims to have undergone training - if no cards can be produced, then the person challenging can not confirm that the person has had the relevant training by checking the EU Skills web site against name or reference number. This will be done in conjunction with the relevant DOMS Working Group representative. 5) Person challenged on site; DOMS CARD EXPIRED. If a DOMS card has expired and the person is waiting to attend a SW DOMS training course, a signed and dated cover note, with the course reference confirmation number and Registration Status clearly shown, must be issued by the person s line manager, in order to allow access to the network. The person must present this cover note on site. (Failure to provide cover note will result in the individual being removed from working on the network until a cover note is issued, or the individual is retrained and re-registered with EUSR) The cover note will only be valid for 3 months after the original card expiry date. After 3 months has elapsed, if the person has not re-registered and is NOT in possession of a new card or a cover note stating the person is awaiting delivery of a new card, then access to work on the network will be refused. All internal and external staff working on the water network must have completed the relevant training. If the site challenges are made by SW staff (and on occasions the DWQR) for all those working on the network, the message will be sent clearly that 'IF YOU HAVEN T HAD THE TRAINING YOU CANNOT WORK ON OUR NETWORK OR ANY INFRASTRUCTURE THAT WILL BE CONNECTED TO OUR NETWORK. While we all want to balanced and professional in our company approach to this matter, water quality and customer satisfaction in our product is our paramount concern. Finally, can all Scottish Water staff note that for out-of-hours advice on public health issues, a representative from the Public Health Team can be contacted 24/7 through the ICC. Page 16 of 38
3.1 Complete a Health &Safety Risk Assessment All staff working on the water distribution network has a duty to ensure that they undertake their work in a way that protects against the risk of contamination. Where practicable there should be multiple barriers to contamination to reduce the risk of a failure in any single system leading to a breach. Supervisors must ensure that the appropriate safeguards are rigorously applied to each situation. They should also provide equipment and materials, in good condition, necessary to achieve the required hygiene standards. Prior to all mains flushing from any fire hydrant either supervised or unsupervised the operational activity must be properly risk assessed for the following. The potential for the flushing activity / point to cause or experience low or negative pressure during the course of the operation. Slips, trips and falls Flooding Freezing over depending on weather conditions The locations of the hydrant being used for the flushing should take into account the potential for vandalism and theft. Traffic and pedestrian access and egress Any detrimental impacts to the environment e.g. discharge of chlorinated or Chloraminated water into a water course or damage to any water course embankment. 3.2 Complete a DOMS impact assessment form (IAF). Any DOMS IAF completed must now also be Risk Assessed for Maintaining Supplies to include any alternative supplies overland requirements, or tankering operations etc to mitigate any risk to both Water Quality and prevent any unnecessary Interruptions To Supply which will or may affect SW OPA Score. All Authorised DOMS IAF are now required to be sent to the operation log for situational awareness with a proposed or planned start date. Cleaning Index and Flushing designs for Uni directional flushing shall require the weekly or daily whereabouts sheets to be submitted to Operations log and ICC for situational awareness. 3.3 Assess the Impact of the Flushing All mains flushing required from a hydrant must be done using a hydrant stand pipe fitted with a double check valve. The only exceptions are Uni-directional flushing operations / Flow and Pressure tests and Maintaining supply operations at the hydrant point which is directly supplying the water network either from an overland supply or from a tanker. An Air gap must be maintained while carrying out any Uni-directional flushing operations Or Flow and Pressure tests to minimise and prevent back syphoned water entering the water network. Unattended flushing from all hydrants should be avoided wherever possible. Page 17 of 38
For any unattended flushing required from a fire hydrant you must have a special hydrant attachment which incorporates a double check valve to prevent back flow into the water distribution network. (DOM-WN-TBT-00000016) Tool Box Talk Mains Flushing Assess the duration and volumes of water required for the flushing activity to be undertaken and the Impact to the water distribution network both water supply and water quality. Is there a risk of causing interruptions to supplies and or poor pressures? If there is a high risk of discolouration, consider night-time flushing, customer notification. Assess both the concentration of chlorine residuals levels within the water being flushed and the volumes of water required for the flushing activity being undertaken against the Impact to any water course or the local environment. I.e. the volume of chlorinated water entering a water course and damage to any water course embankment (flows & volumes). Even in low concentrations chlorinated / chloraminated water can kill fish and cause environmental pollution, if discharged to watercourses. It is therefore essential to plan how best to dispose of chlorinated / chloraminated water to the environment. SEPA licences often indicate a chlorinated discharge of no greater than 0.05mg/l will be permitted, so individual licences may need to be reviewed, or the local SEPA offices consulted, to determine any limits for discharge. Consideration should also be given to any likely chemical content in sedimentation settled on the floor of an SR/CWT, which would then be flushed out into a receiving watercourse. If an onsite assessment confirms a risk of causing either environmental damage to ecosystem or an environmental Impact to aquatic life in the water course, the local SEPA office should be contacted to determine what control measures may be required prior to SEPA allowing the task to proceed, thereafter the SW EPI Team must be notified. Contact SW Environmental Pollution Incident (EPI) Team. Update SW EPI admin team (planned / confirmed start dates and when work is complete) EPI Helpline: 0845 600 8495 remember to report, update & close all EPI events. CSD staff Water Ops to inform and notify SW EPI reporting line of planned flushing activities 7 days prior to flushing preferably earlier to inform SEPA of any EPI & operational events EPI helpline: 0845 600 8495 office hours (Out of hours standby personnel should inform SEPA - 0800 80 70 60) Contractors should contact & inform SEPA directly. Information required when reporting to the EPI reporting line, asset number / fire hydrant location including. postcode, planned time of flushing / volumes of water & duration / watercourse affected, cause (what, why, etc planned tank clean i.e. change in discharge conditions from a WTW (even if still compliant), Overflow operating from a CWT or SR (if direct to a watercourse), Effect or impact (e.g., discharge, reduced operation or possibly No Impact ), Action taken (e.g., Passed to E&M, Clean Up etc) If updating an EPI please quote EPI CDR number, if known Where a current network model is available, model the proposed exercise to estimate the impact of the flushing. Estimate the flushing volumes, duration and the likely impact on the Treated Water storage point, which supplies the target flushing area. When calculating the amount of water to be flushed, allow twice the nominal volume of the section of pipe being cleaned (the debris moves more slowly than the water). Check the GIS for details of the network, including positions of line valves, scour-valves, washouts and hydrants. Page 18 of 38
Consider the operating pressure at the flushing point taking into account possibility of any recent interventions if there is the potential for the flushing point to experience negative or low pressure during the flushing exercise and particularly if the flushing point is left unattended, a back flow prevention device must be applied to the hydrant outlet. Visually check gullies and drains, watercourses, etc, especially those in rural areas which are to receive the discharge water from flushing operations. Set up appropriate environmental protection. Where super-chlorinated water is being discharged from a recently disinfected section of main, refer to SW HCoP & DOMS work instruction / work procedures. Prevent unnecessary hydrant / scour damage to water course embankments. Identify affected customers, including dialysis patients, key and sensitive customers. Please refer to the Environmental Event Categories list below. SW Environmental Event Categories 3.4 Obtain Team Leader Approval to Proceed For all planned flushing, affected customers are to be given the requisite SW notice period. For larger populations or larger areas, consider press notices and posters. Page 19 of 38
Sensitive customers, e.g. dialysis patients, should be consulted directly and an appropriate time frame agreed for the work, where possible. Where key customers will be affected, liaise with the appropriate SW key account manager and Licence Provider as per SW policy with 22 day licence provider notification. Advice & update team leader for authorisation if flushing point is to be left unattended. Unsupervised flushing should be avoided at all times. 3.5 Update the Ops log All flushing on the live distribution network must be updated into the operations log pre and post hydrant operation with the location of the fire hydrant and the proposed length of time the hydrant will be left flushing and a contact number to help with any complaints from the general public. Note: Any mains flushing as part of any Maintenance Schedule Task (MST) does NOT require an IAF but should be updated onto the operation log pre & post flushing. 3.6 Establish Appropriate Traffic and Pedestrian Barriers. Set up correct traffic management, sign lighting and guarding and pedestrian barriers for the following, Protecting SW staff both internal and external staff from both traffic and pedestrians. Protecting pedestrians from the actual flushing activity and the immediate traffic. Protecting all vehicles and traffic from the actual flushing activity and pedestrians encroaching onto the road. Additional sign lighting and guarding may also be required or extended due to areas becoming flooded as a result of the flushing operation. 3.7 Hydrant and Stand Pipe Operation Check hydrant chamber for any signs of contamination Consideration should be given to environmental conditions e.g. heavy rain, oil in the hydrant chamber etc. Staff should be aware of potential risks and dangers associated with the nature and type of debris that may accumulate in hydrant boxes (for example the presence of sharp or dangerous objects). Staff should, therefore, take appropriate precautions and wear appropriate personal protective equipment (PPE), where required. All possible contamination should be removed from the outside of the hydrant, before connection of the standpipe and any debris present in the area surrounding or in proximity to the connection (the hydrant bowl) should be cleared away and disposed of appropriately. This includes water in the hydrant pot or bowl before connecting the standpipe Remove the hydrant box lid and any debris from the area of the connection, bailing out any accumulated water to well below the bottom of the screw threads, using an appropriate container e.g. a clean plastic beaker. Page 20 of 38
SHARP KIT special care shall be taken in the removal of syringes and other hazardous materials. Use a SHARP KIT for the removal of any syringes found within hydrant chamber and dispose of in the correct manner. Only ever use SW approved standpipes. Anyone using a standpipe on our network must have an SW approved stand pipe hired from SW. The only exceptions are SW staff (and our contractors specifically authorised to carry out flushing activities as detailed in this document and the Scottish Fire and Rescue Service. The only hydrant operations which allow the use of stand pipes without double check valves to be used are Uni-directional flushing operations / Flow and Pressure tests and during Maintaining supply operations at the hydrant point which is directly supplying the water network either from an overland supply or from a tanker. An Air gap must be maintained while carrying out any Uni-directional flushing operations or Flow and Pressure tests to minimise and prevent back syphoned water entering the network. All standpipes to be used as part of any drain down and re-charge or flushing or filling operation for tankers or bowsers must be disinfected with a 250 mg/l chlorine solution (see Scottish Water HCoP). This should be carried out prior to arrival on site and the standpipe should be stored and transported wrapped in a new plastic bag or similar, to ensure that it is clean before use. Unwrap the standpipe, which has been transported in a clean bag, and connect it to the hydrant. Direct the standpipe away from the hydrant box towards a suitable drainage location or alternatively attach a suitable length of lay flat hose. Standpipes used for microbiological sampling should not be used for other purpose. Any unsupervised flushing should be notified to the operations log with the location of the fire hydrant and the proposed length of time the hydrant will be left flushing and a contact number to help with any complaints from the general public. 3.8 Open the hydrant, washout or scour-valve slowly. Direct the standpipe away from the hydrant box towards a suitable drainage location or alternatively attach a suitable length of lay flat hose. Open the hydrant / standpipe tap slowly, as rapid opening may cause turbulence in the main and stir up sediment. Flush water through the standpipe until the water runs visibly clear and constant e.g. for a minimum of 5 minutes Open all hydrant(s) scours and valves in a slow controlled manner. Closing valves or hydrants too quickly will result in transient pressures within the network leading to possible burst mains or water quality issues. Where multiple hydrants, etc are being flushed this must be done in a controlled manner REMEMBER C.A.L.M!! Check. Actuate. Listen. Monitor WHEN WORKING ON SCOTTISH WATERS DISTRIBUTION WATER NETWORK Refer to Work Instruction Hydrant Operation (DOM-WN-WIN-00000303) Page 21 of 38
Refer to Work instruction Valve Operation (DOM-WN-WIN-00000306) Refer to Work Instruction Sampling From A Hydrant (DOM-WN-PRC-00000332) 3.9 Flushing Duration and Volumes Flush mains for the required duration using the relevant volume of water required as per activity being undertaken on site i.e. commissioning new mains / non steady State flushing / cleanliness Index flushing or operational interventions etc. The hydrant flow should run clear and constant before being slowly shut off preventing discolouration elsewhere on the network. When re-charging any mains repairs or interventions the main should only be thoroughly flushed once all the air has been dispelled and there is a continuous and even flow of water, open up the hydrant slightly more and flush until the flow is clear and constant, taking due regard of the possible risk of discoloured water elsewhere on the network. Refer to relevant swim lanes as per the network activity being undertaken for the required flushing volumes and duration page? Refer to volumes of water required for flushing within MCL 2633 DISINFECTION AND DE- CHLORINATION CHARTS. Complete Distribution System Operational Usage (DSOU) proforma when applicable. 3.10 Inspections for Flood Damage during flushing, Carry out visual inspections for flood damage. Visually check gullies and drains, watercourses, etc., especially those in rural areas which are to receive the discharge water from flushing operations. Monitor flows and pressures and any changes in discolouration Monitor any water quality customer contacts or issues up and down stream during flushing especially for any main already in supply. After any mains repairs or mains tie ins are completed the main should be slowly re-charged and flushed clear or flushed for up to an hour and the sample should then be taken if required. If the main is still discoloured at this time still take the sample and then follow this up with another sample up to 24 hours later. After the sample has been taken continue to flush the main until clear. Flushing a hydrant without a standpipe should be avoided wherever possible. For any unattended flushing from a fire hydrant you must have a special hydrant attachment which incorporates a double check valve to prevent back flow into the water distribution network. Refer to Mains Flushing TBT DOM-WN-TBT-00000016 The lid must be replaced from H&S perspective and the operations log updated accordingly. For further guidance please refer to DOM-WN-TBT-00000016 DOMS tool box talk Mains Flushing Page 22 of 38
The attachment shown above is of a standard specification and size which fits onto the hydrant outlet which is within the specification of Scottish Waters standard hydrant box. The attachment is fitted on the hydrant outlet and will permit flushing with the fire hydrant lid replaced to prevent any slips trips and falls. It should fit into most hydrant chambers. If the device cannot be fitted, and it is not appropriate to leave a standpipe in position, the hydrant can not be left unattended and an alternative will need to be found. 3.11 Close Hydrant(s) Scour(s) and Valve(s) Close all hydrants, scours and valves in a slow controlled manner. Closing valves or hydrants too quickly will result in transient pressures within the network leading to possible burst mains or water quality issues. Where multiple hydrants, etc are being flushed this must be done in a controlled manner. REMEMBER C.A.L.M!! Check. Actuate. Listen. Monitor WHEN WORKING ON SCOTTISH WATERS DISTRIBUTION WATER NETWORK Visually check that there is no discolouration and flush until the water is visually running clear before closing hydrant. Cleanliness index flushing / Non steady state sampling require the use of turbidity meters to confirm the quality of water within the water network is 0.4 NTU or below before the hydrant can be shut off. Complete Distribution System Operational Usage (DSOU) proforma if required. 3.12 Remove any debris arising from the flushing Page 23 of 38
Special care shall be taken in the removal of syringes and other hazardous materials Use a SHARP KIT for the removal of any syringes found within hydrant chamber and dispose of in the correct manner. Mains rehabilitation epoxy lining requires a sediment tank to capture and remove debris from cleaning and flushing. 3.13 Water Sampling After mains repairs or mains tie ins are completed the main should be flushed clear or for up to an hour and the sample should then be taken. If the main is still discoloured at this time still take the sample and then follow this up with another sample up to 24 hours later. Bacteriological sampling must be carried out for all mains' interventions. Unless after recharging and flushing the main, if the responsible person is confident the main has remained under pressure throughout the repair and if a DOMS impact assessment form has been completed and the excavation has remained free from contamination, there is no need to take samples for bacteriological examination. If there is any doubt that the main has remained under pressure during the repair bacteriological samples must be taken. Samples need not be taken from repairs on service pipes below 50 mm diameter. All staff who take samples of potable water from any part of the treatment or distribution processes must receive training to take samples and this tool box talk as a reminder of procedures. The information included must also be used by any line managers of the above staff and would be useful to anyone working on drinking water systems. Samples will be monitored by Scientific Services to ensure that the sampler is on a list of trained staff. Where this is not the case the sampler s line management will be informed. All initial sampling training must be complete by 1 st July 2009.Training for SW staff can be requested by contacting People Connect for booking Course DOMS SWD308 or external staff use EU SKILLS Web site for the list of accredited DOMS training providers http://www.eusr.co.uk/provider Samples taken by untrained staff after this date will be analysed but may need to be resampled to validate the result. In order to assess your training status Scottish Water staff will have training records on Quest and non Scottish Water staff will require getting their EURS card updated after training and will need to supply their card number when they submit a sample. This can be put onto the sample registration form. Any audit of the repair / sampling process will regard samples taken by untrained staff as a major non-compliance. For any sampling required from a hydrant please refer to DOM-WN-PRC-00000332 Sampling From A Hydrant. Note: Sampling from hydrants should be a last resort and clearly recorded on the sample proforma. Page 24 of 38
3.14 Update Ops Log Update operation log pre & post valve operations or hydrant operation with any known water quality issues and or the start / stop time of ITS event and populate ITS proforma on IMS device or manual proforma and submit into Corporate Data Repository CDR. Check and monitor Customer contacts for water quality complaints near to flushing activity. Page 25 of 38
Network Authorisation & Control for Cleaning Index & Design Flushing 4 Flushing Method Statement The methodology involves taking non-steady state samples from hydrants, during the night, at 1 minute intervals for 10 minutes. The flow rates are 0.5m/sec. The colour grade of each bottle is assessed using a colour chart. After 10 minutes, the flow rate is reduced and ran until the colour grade is reported as being 0. A turbidity reading is also taken with the aim being the water is no greater than 4 NTU under these non-steady state conditions when the flushing is stopped. The final bottle (along with the first 1 minute bottle) is taken to the lab for testing. We are also planning to take customer tap samples the next day to confirm that water quality has returned to acceptable levels. For Cleanliness Assessment (sampling involves flushing at 0.5m/sec flow) no 22-day LPN is required. For Planned Flushing Activities (flushing at 1.0m/sec flow) we will always follow the 22- day LPN process. Page 26 of 38
Non steady state sampling METHOD STATEMENT A. List of Key Documents: i) SW Standards and Specifications Ref SSP-SP-GUI V 0.1 July 2010 (Water Mains Rehabilitation Guidance) ii) SW Impact Assessment Form & Guidance for Completion for Access to working on SW Network DOM-WN-TBT- 0000014 iii) Work Instruction Hydrant Operation (DOM-WN-WIN-00000303) iv) DOM-WN-TBT-000014a (May 2014) B. Initial Planning Confirm hydraulic asset structure for Treated Water Storage feeding DMA s, Pumps and PRV s, that might impact on planned sampling. Confirm network available for sampling (generally < 9 /225mm). Produce network plans for each sampling area and identify the need for enabling works i.e. additional valves/hydrants. Identify DMA s fed from TWS tanks and risk assess tank capacity/water availability to support downstream sampling needs. Develop initial outline programme. Submit LPN notification. C. Prepare NSS Sampling Design Produce an initial design proposal for area to be sampled showing hydrants to be sample together with any alternates. This is used as a base design for the site survey. Raise site survey work on ops log. Site survey on all hydrants as defined in sampling schedule, clean/clear chambers as appropriate and also checks operability on existing Mark all hydrant surface boxes that are to be operated with high visible marker paint prior to sampling. Refine design to take account of site surveys. Identify alternative hydrants for use where possible. Identify any enabling works required to allow sampling to proceed (or hydrant repairs/installations). Identify any other operational risks planned works etc. Arrange hand over pack for PM/contractor/local Ops and liaise with all stakeholders Complete all necessary DOMS Impact Assessment Forms to comply with DOM-WN-TBT- 000014a (May 2014) Liaise with SW to obtain approval and sign off for access to network via Network Control Forum D. Equipment List for Two Man Field Team and Van Valve Keys. Lifting keys. Small Tools. Stand Pipe with NRV. Page 27 of 38
Vernon Morris Flow Meter. Signing, lighting and guarding in accordance with current Streetworks ACOP (October 2014) Flood lights (Battery Operated) PDA with work mobile White back board and standard colour chart for referencing and photographing of sample jars. Turbidity Meter. Samples jars. Chlorine residual field meter for measurement of free and total chlorine. E. Key General Issues An equipment check must be carried out to make sure all the necessary equipment is present and working correctly. Hydrants must be sampled in numerical order as detailed in the DMA plan and site location drawings, i.e. from the DMA inlet down to the extremities of the DMA Sampling will be undertaken during the night from 23:00 to 05:00 hours Update SW Operations Log before beginning, and after completion of sampling activities in each DMA / Phone SW ICC prior to commencement of works & on completion. Daily email update will be provided to local Water Operations/Leakage Delivery staff of work completed/planned for forthcoming nights. Cleanliness Index results, including pre and post pressure at each hydrant will be forwarded to Water Operations/Leakage Delivery for DSOU reconciliation. F. Site Activities ALL HYDRANT OPERATIONS TO BE CARRIED OUT IN ACCORDANCE WITH SCOTTISH WATER CALM NETWORK PHILOSOPHY 1. Locate the Hydrant to be sampled. 2. If unable to locate or operate the hydrant then use an alternative hydrant and mark the location on the DMA plan drawing. 3. Perform an on-site Risk Assessment. 4. Conduct a thorough (visual) site specific Risk Assessment with regards to Water discharge impact. 5. Follow the DOMS procedure for Hydrant Operation to open the hydrant, using fresh Chlorus spray to disinfect both the hydrant & standpipe. 6. Attach the Standpipe to the hydrant. 7. Direct the flow out of the standpipe to either a drain or gutter wherever possible. 8. Prior to sampling from hydrant, attach pressure gauge to hydrant and record pressure reading. 9. Open the hydrant until the recommended flow rate has been reached (not the maximum possible flow rate) and note the actual flow achieved if unable to achieve design flow. The table below contains the typical recommended flow rates to be achieved for different mains diameters. Page 28 of 38
Pipe Diameter Flow rate (Litres per Second)* 1¼" and 1½" 0.5 2" (50 mm) 1.0 2.5" (63mm) 1.6 3" (75mm) + 80mm 2.2 4" (100mm) 3.9 5" (125mm) 6.1 6" (150mm) 8.8 7" (175mm) 12.0 8" (200 mm) 15.7 9" (225 mm) 19.9 * Flow rates designed to achieve water velocity of approx. 0.5 m/sec 10. Start a 10 minute countdown. 11. After 1 minute, fill a 500ml Jar Sample to be used for sediment colour grading. 12. After 1 minute, fill 1 Chemical sample bottle and 1 Metal sample bottle 13. At each further minute interval, for 10 minutes, take 500ml Jar Samples for sediment colour grading. 14. If after 10 minutes the colour grade is 0, then follow the DOMS procedure to close hydrant. 15. If after 10 minutes the colour grade is greater than 0 then reduce flow to 25% of the recommended flow and continue to flush until colour grade is 0. 16. Upon completion of sampling, attach pressure gauge to hydrant and record pressure reading. 17. Follow DOMS procedure to close hydrant. 18. Record volume of water discharged from hydrant. This information will be passed to Leakage Delivery. 19. Allocate a colour grade to each jar sample and take photograph of the jar samples, with smart phone and field camera Page 29 of 38
20. If the air temperature is less than 5oC, apply grit to the area surrounding the hydrant. 21. Enter all details into the Work Mobile system on the smart phone. G. Incident Reporting When issue is identified, contact call centre / ICC. Full details, timelines, SR numbers of any issue, has to be passed to Supervisor prior to rest period. If required team to stay on site until local NSO turns up for handover or assistance if required. 5 Flushing Method Statements List of Key Documents: 1. SW Standards and Specifications Ref SSP-SP-GUI V 0.1 July 2010 (Water Mains Rehabilitation Guidance) 2. SW Impact Assessment Form & Guidance for Completion for Access to working on SW Network DOM-WN-TBT- 0000014 3. Practical Guidelines for Mains Flushing UKWIR Report Ref No.00/DW/03/16 4. Water Mains Cleaning Handbook WRc UM 1429 March 1994 5. Removing Loose Deposits From Water Mains: Operational Guidance 6. Work Instruction Hydrant Operation (DOM-WN-WIN-00000303) 7. Work Instruction Valve Operation (DOM-WN-WIN-00000306) The methodology to be followed for flushing the distribution network is as follows: A. Initial Planning Confirm hydraulic asset structure for Treated Water Storage feeding DMA s, Pumps and PRV s, that might impact on planned flushing. Confirm network available for flushing (generally < 9 /225mm). Page 30 of 38
Produce network plans for each flushing area and identify the need for enabling works i.e. additional valves/hydrants. Identify DMA s fed from TWS tanks and risk assess tank capacity/water availability to support downstream flushing needs. Develop initial outline programme. Submit LPN notification B Prepare Initial Flushing Design Produce an initial Strumap design proposal for area to be flushed. This is used as a base design for the site survey. Use the Strumap Flushing Tool to design flushing operations and TAG valves and hydrants to be operated. The sequence of the flushing design will enable clean water to be carried forward into each downstream section. Outputs will consist of initial network flushing design and a flushing schedule with all relevant valves and hydrants identified and tagged, together with need for additional hydrants/valves. Raise site survey work on ops log. Site survey on all hydrants and valve locations as defined in flushing schedule, clean/clear chambers as appropriate and also check operability on existing hydrants and status of valves and direction of closing. Submit Workmobile proforma with all details as requested, including picture of valve/hydrant key attached to spindle to confirm fitting check has been completed appropriately. Mark all hydrant/sv surface boxes that are to be operated with high visible marker paint prior to flushing. C. Review and Prepare Final Flushing Design Refine flushing design to take account of site surveys. Identify alternative valves or hydrants for use where possible. Identify any enabling works required to allow flushing to proceed (valve or hydrant repairs/installations. Identify locations of air valve and inspect for faulty valves and flooded chambers as they may present a contamination risk. Identify any other operational risks planned works etc. D. Pre-Flushing Check List Complete all necessary DOMS Impact Assessment Forms to comply with DOM-WN-TBT- 0000014a (May 2014) Liaise with SW to obtain approval and sign off for access to network Review and agree proposed design. Review risk issues and mitigations with regards to: 1. Sensitive and critical customers. 2. Water Availability. 3. Environmental issues relating to dirty water/chlorinated water discharges to surface water drains, sewers, and surface water features. Liaise with SEPA/SW as appropriate. 4. Condition of upstream storage tanks i.e. sediment deposits on floor of tank. Page 31 of 38
Action all enabling works and snagging list. Prepare & Confirm programme of works. D. Flushing Programme Planning Process Finalise Strumap design with details from completed snagging list, site survey details, and local operations input Produce Flushing Method Statement for approval of relevant SW Network Control Liaise and agree with SW on customer notification process Complete all necessary DOMS Impact Assessment Forms to comply with DOM-WN-TBT-000014a (May 2014) for submission & Network Control Authorisation. Forward all Design Detail to relevant Network Control Forum DOMS IAF / Method Statement & Schedule of Works (Strumap Design) Ideally 2 weeks prior to commencement. SW Team Leader, RPS Project manager or allocated Designer to discuss proposal with Network Control prior to Authorisation (In person / via conference call, or by Web-Ex) Ideally week prior to start date. E Equipment List for Two Man Field Team and Van Valve Keys. Lifting keys. Small Tools. Stand Pipe with NRV. Vernon Morris Flow Meter. Signing, lighting and guarding in accordance with current Streetworks ACOP (October 2014) Flood lights (Battery Operated) PDA with work mobile White back board and standard colour chart for referencing and photographing of sample jars. Turbidity Meter. Samples jars. Chlorine residual field meter for measurement of free and total chlorine. Hydrant cap and hose Pressure logger. F. Flushing Activity ALL VALVE & HYDRANT OPERATIONS TO BE CARRIED OUT IN ACCORDANCE WITH SCOTTISH WATER CALM NETWORK PHILOSOPHY Agree with Operations staff that all systems and procedures are satisfied to carry out the planned flushing programme for each night. Conduct a Risk Assessment Conduct a thorough (visual) site specific Risk Assessment with regards to Water discharge impact. Page 32 of 38
Flushing will be undertaken during the night from 23:00 to 05:00 hours *(Valve Operations from 22:00) Undertake Customer Notification specific responsibility to be agreed with SW. Load flushing schedule on to work mobile. Raise flushing work on ops log / Call SW ICC & make aware of imminent Works. Install a pressure logger at a hydrant within the DMA as close to the CMP as possible. Notify SW Operations Control of work commencement prior to commencing work on site. Set up 2 pressure loggers; one at the DMA CMP (recording at 1 minute intervals) and one upstream of the current nights work (recording at 3 sec. intervals). Install a pressure logger at a hydrant within the area to be flushed (Omit). Close valves identified in flushing schedule to isolate section to be flushed. Note Number of turns to close and also direction of operation i.e. CC-Clock Close or CO Clock Open and enter in flushing record in flushing schedule. Record the pressure at the hydrant to be flushed prior to commencing the flush. Open hydrant to take initial sample in jar after 1 minute Open hydrant further to achieve designed discharge velocity as stated on the flushing schedule using VM flow meter and flush. Record and log actual flow in flushing schedule. Pipe Diameter (mm) Re-suspension Velocity (m/s) Industry Standard Required Flow Rate (litres per second) 50 0.7 3 75 0.8 4 100 0.9 10 150 1.1 20.0 200 1.3 42.0 Fill sample jars at one minute intervals up to a maximum of 10 jars. Hydrants must be flushed for the minimum duration stated on the flushing schedule, even if sample runs clear before this time has elapsed. Take a final sample (note time to clearance flush) enter time on flushing schedule and reduce discharge rate until turbidity is < 4 NTU. If after 30 minutes it has not reached 4 NTU, the hydrant can only be closed after it s reached < 10 NTU Close hydrant Record the pressure at the hydrant once flushing has been completed. Take photograph of all sample jars for comparative record. Page 33 of 38
Using standard colour chart note colour grade of each jar and record on flushing schedule. Using turbidity meter record turbidity of water in final sample jar and enter result in flushing schedule, also test for free and total chlorine. Open valves as detailed in flushing schedule. Repeat above process for each planned flushing section as detailed in the nightly schedule. When complete notify SW Operations Control. Complete Issues Log as appropriate. Complete flushing documentation sample results, photographic evidence etc. Record flushing volumes and provide to SW Leakage Delivery for DSOU reconciliation. Close work on ops log / Call SW ICC & make aware of completion of works. G. Reporting Download completed flushing sheets and photographs from work mobile Produce final project report. H. Incident Reporting When issue is identified, contact call centre / ICC Ask for SR Number to be raised & take note of. Full details, timelines, SR numbers of any issue, has to be passed to Supervisor prior to rest period. If required team to stay on site until local NSO turns up for handover or assistance if required. Page 34 of 38
6 DSOU The definition of DSOU as provided by the Water Industry Commission for Scotland is: Distribution System Operational Use; Water knowingly used by a company to meet its statutory obligations, particularly those relating to water quality. This includes, amongst other things: service reservoir cleaning; mains flushing/air scouring; swabbing; draining networks; discharges to control ph or other chemical parameters. Please email completed spreadsheet to SWLPwaterbalanceteam@scottishwater.co.uk On the first Monday of the month. All fields must be completed to provide a full audit trail for each event and to allow any queries to be followed up with the relevant person. Various DSOU sub-types are reported to the WIC by the Water Balance More detailed guidance is available at F:\Leakage\DSOU\DSOU guidance AR13 update.doc Page 35 of 38
Offical Scottish Water Licenced Hire Stand pipe. Standpipes allow customersand SW staff direct access to our water supply network and represent a potential risk to the continuity of supply and water quality. There are many occasions where external Customers and Public Bodies require access to a temporary supply of water. It is Scottish Water s policy to allow such access for approved use by means of the issue of a 25mm dia. Scottish Water Hydrant standpipe. This is the only acceptable method and the use of any other standpipe or means of access is illegal and may result in prosecution. The 25mm standpipes, for hire, will be distinctively coloured (purple and turquoise spiral with a purple plate (SW Corporate Colours)) for ease of identification. The stand pipe is hired by third parties requiring water from SW water network.ie Developers requirig building water. A telephone call to the Standpipe Licence Controller will confirm the standpipe slegitimacy, using the alpha numeric code on the standpipe. If the standpipe does not have such a code it is illegal. Please refer to DOMS document DOM-WN-PRC-00000319 Work Procedure Hydrant Standpipe Hire Procedure. Page 36 of 38
The above stand pipes are the only exceptions for SW staff and its contractors specifically authorised to carry out network activities, flushing etc and the Scottish Fire and Rescue Service. The standpipe must incorporate Double Check Valve to prevent back siphoning. These stand pipe shall be used for all of the following activities on the water network, MST Mains Flushing Mains Repairs & Network Interventions including the drain down and re-charge. Boundary valve operations and required flushing. Mains Re-hab programs to either provided an overland supplies during Pipe bursting etc Overland Supplies. Tankering Operations. Commissioning mains. Page 37 of 38