Faced with a challenging programme of more than 950km of pipework cleaning, Affinity Water sought a collaborative team approach and innovative solution to plan and carry out the works, with minimal disruption and environmental impact.
As part of the development of Affinity Water’s Business Plan for 2015-2020, the company asked its customers what was important to them. Two key customer expectations were: supplying high quality water and minimising disruption to them and their community.
Meeting these expectations was the responsibility of Affinity Water’s Mains Flushing Team, managing a programme for the removal of manganese and iron deposits from 958kms of mains pipework within the Ickenham, Harlow, and Epping areas in an 18 month period – one of the largest mains cleaning exercises carried out within the water industry in recent years.
Manganese and iron are naturally occurring minerals present in some groundwater sources, over time sediment can build up in pipework, which can lead to discoloured water.
A programme was developed to begin the controlled removal of these deposits to ensure the highest water quality standards and improve the usability and resilience of the network, with minimal disruption and environmental impact. At the heart of this strategy was developing a project structure that was based around Risk.
A key part of the RISK BASED strategy was to procure the services of specialist contractors directly linked to Affinity Water, rather than through a management contractor.
This allowed informed decisions to be made at all stages of the design and execution process, which was especially important when the work was carried out on the live potable water network.
A number of strategies were implemented on this risk based approach:
• Ice Pigging was selected as a preferred technique for cleaning the mains
• A contract strategy was designed to bring specialist supplier knowledge closer to the client design and planning team
• Cleaning/flushing of certain distribution mains areas first, to reduce the risk of discolouration when taking trunk mains out of supply. This was a departure from the source to tap cleaning process that is traditionally adopted.
• A detailed risk review of each and every trunk main sequence to be cleaned – involving key internal and external suppliers.
Implementation of Ice Pigging
The team was determined to achieve minimum customer and environmental disruption as they reviewed the available flushing techniques and impacts. Traditional methods involve a high number of large excavations for the insertion and retrieval of foam swabs.
An innovative Ice Pigging technique was selected as the method to clean the trunk mains as this offered an effective cleaning solution with minimal environmental impact and disruption to customers and commuters. This was because less excavations would be required as existing hydrants and valves could be used to insert and retrieve the mixture of ice and salt water which formed the ice pig.
The pipe network was reconfigured to allow the ice pig to be inserted and then pushed along the main using network pressure behind it.
The work was carried out at night which further reduced customer impact. Mains supplying around 100,000 properties were cleaned and customers were notified in advance of the activity.
A number of water companies have struggled with the implementation of this technology, as operations are carried out on a live network, the potential network risks involved cannot be underestimated.
The highest risk element of the programme was cleaning the cast iron/coal tar lined mains without adversely effecting water quality when the mains are returned to service. Many water companies have adopted the ‘not able to clean’ approach and have chosen to relay or reline these pipes at significant cost.
However, Affinity Water worked with Ice Pigging Contractor SUEZ and Programme Manager MACE to develop a number of predictive tools and assessments to enable the Ice Pigging technique to be successfully applied to these mains.
The tools that were developed included a PAH calculator, which, in combination with model data, predicts levels of PAHs post cleaning. Using this, a number of strategies could then be adopted to manage these levels post cleaning.
Water Quality Samples were taken before and after each cleaning operation and the data was used to refine the tools developed and ensure continual improvement.
True Collaboration between affinity Water and its suppliers was key
The contract strategy was key and was developed using lessons learnt from the previous AMP period, the cleaning programme strategy was based on the principal of bringing the key skills from the various internal and external suppliers together in to one collaborative team, working towards the common goal of achieving the challenging target, whilst continually maintaining water quality throughout flushing operations.
With specialist contractor SUEZ working directly with Affinity Water this was a different approach than usual both within Affinity Water and the water industry in general. The benefit to them was that a whole year’s programme was agreed in advance and adhered to – over 100 ice pigging operations have been carried out and significant cost savings have been realised by cutting out the “middle man”.
Specialist contractors were able to be involved in the design and planning stage. SUEZ is now advocating this approach with other clients across the water industry.
The strategy to work with specialist contractors brought expertise closer and enabled work to be better planned and executed at significantly lower costs.
Health & Safety
Over the course of the Programme between October 2015 and March 2017, no accidents or lost time injuries occurred with more than 60,000 man hours worked, a significant proportion of those at night.
Affinity Water worked with the supply chain to ensure all activities were risk assessed and safe systems of work implemented. The programme was preceded by a number of workshops involving specialist suppliers. Site based risks were captured during these workshops and appropriate standards implemented to avoid, manage or mitigate the risks as determined.
One such example was the detailed operational method statement for carrying out the Ice pigging, this was overseen by a dedicated Method Statement Administrator who would validate and sign-off that each step had correctly been carried out prior to allowing the site operation to safely move to the next phase.
This resulted in more than 100 ice pigging operations being completed without accident, water quality or network incident.
During the early stages of the programme, the project team took on feedback from the site operatives and invested in a dedicated mobile welfare unit. This improved the site conditions for operatives and this is something that Affinity Water is looking to implement for other programmes of work.
Environment and customer benefits
The programme of mains cleaning was successfully completed in March 2017 with over 950Kms cleaned overall without incident.
Zero complaints were received over the course of the programme and all work was carried out as planned, with no highway overruns occurring, meaning no Section 74 fines.
By choosing the Ice Pigging method, the team significantly reduced the impact on the surrounding environment. The ice pig used for flushing the mains is prepared from a food grade product; it is not a synthetic chemical, so use of these and consumables such as foam swabs was avoided.
Fewer excavations meant less material and energy used transporting waste, approximately 5,000 tonnes of excavated waste material was prevented from going to land fill.
The project has delivered significant cost savings as result of direct contracts with specialist contractors and the contract model will be adopted for similar works going forward.