Main replacement slashes leakage
Over 2,000km of failing Victorian mains have been restored across London, cutting leakage by nearly a quarter. J Murphy & Sons' programme delivery manager for North London, Kieran Starr, reports
More than 60% of London's water mains are between 100 and 150 years old, and its water resources are being put under increasing pressure from the effects of climate change, population growth and rising demand for water. Although the original cast-iron mains have served Londoners well, the increase in road traffic, corrosive soil conditions and ground movement mean they are now more likely to leak, or even burst.
Thames has invested heavily in replacing the original Victorian mains with more durable and flexible PE pipes, and this programme of works, called the Victorian Mains Renewal (VMR) programme, is the highest rate of water mains renewal ever undertaken worldwide. Within London, Thames Water has approximately 16,600km of distribution network, of which 2,500km will have been replaced under the VMR programme by the end of AMP5.
Across all its London zones, its AMP framework contractors have replaced more than 2,000km of mains. An entire network or district metered area (DMA) is replaced under each project from the inlet district meter up to the boundary box and domestic meter for every customer in the area, covering 300,000 homes.
J Murphy & Sons was appointed in 2002 as Thames Water's AMP framework contractor for the mains renewal works in its north London zones. With the programme in its eighth year, Murphy has to date replaced approximately 580km of mains and installed 90,000 communication pipes and domestic meters.
Pipe diameters range from 150mm up 450mm in diameter for water mains replacement and 150mm diameter and below for the networked mains. This has focused on the West End and St James, Tachbrook, Warwick and Churchill wards, taking in popular tourist areas and heavily populated residential areas including Westminster, St John's Wood, Pimlico, Hampstead and Maida Vale.
Iconic buildings in these areas include Middlesex Hospital, the National Portrait Gallery, Royal Courts of Justice, the Savoy Hotel, Somerset House, the Ivy restaurant and the British Museum. For AMP5, Optimise, the joint venture (JV) between Murphy, Barhale Construction, Clancy Docwra and MWH, was awarded the prestigious contract by Thames Water, valued at potentially £500M over five years.
The project employs 250 staff, including 45 mains replacement teams, 25 service laying teams and 12 reinstatement teams. The work to date has been carried out in the most challenging of street works environments, both above and below ground, requiring proactive stakeholder management and planning skills by the project team.
To facilitate this, in the areas where pipework needs to be replaced, Murphy undertakes detailed investigations using the latest computer modelling techniques to find the best way of renewing the pipe network. While open cut techniques formed the greater part of the works - 149.7km on networked mains under 150mm diameter and 74.2km in water mains under 300mm - to minimise disruption, trenchless technology was used wherever possible. On the networked mains alone, this included over 40km of pipe insertion and slip lining techniques, over 90km of pipe bursting and 14.5km directional drilling.
The VMR programme has presented many challenges, including busy thoroughfares, complicated junctions with intricate connections, schools, hospitals, underground and railway stations, plus the maze of large and small utility services. The greatest thus far has been the traffic management in London's West End, due to the constrained road network and high vehicular and pedestrian traffic levels, in locations such as Soho, Covent Garden, Chinatown, Trafalgar and Leicester Square, Charing Cross Road, Oxford Street, Shaftesbury Avenue, The Strand and Piccadilly Circus.
During the three-and-a-half-year programme, the team has had to contend with events including the Tour de France, film premieres in Leicester Square, the London Marathon, demonstrations, Christmas moratoriums, Chinese New Year, Gay Pride and state visits. The area takes in major Transport for London (TfL) routes: New Oxford Street, where the bus lane was closed for six weeks; The Strand, with 40 major connections to trunk mains; Shaftesbury Avenue, where a Bailey bridge was constructed over ventilation grills to enable two way traffic, and the removal of traffic islands and traffic signals to maintain traffic flows, and their reinstatement when the works were complete. Traffic disruption was minimised by using Chapter 8 traffic management.
The area contains many different types of high value paving, often chosen for its aesthetic appearance rather than practicality. This made it difficult to source replacements and required a high level of skill to relay.
The planning process was the key element to delivering the programme of works; to minimise and alleviate traffic issues, to avoid saturation of work streams, but still maintain productive outputs. The planning team worked tirelessly to facilitate the works, respond to changing circumstances and reacting speedily to mitigate impacts on stakeholders.
This was achieved with the full support, commitment and backing from Thames Water and buy in and support from local authorities, TfL, bus operators, the police and emergency services. A thorough, well thought out and comprehensive communications process engaged all relevant parties. As many as 25 teams were involved in laying the new water mains. Their knowledge and skills cannot be underestimated in the delivery of this project.
These West End projects accounted for about 20% of Murphy's VMR programme delivered in this period. Due to their complexity and sensitive location they took up 40% of the planning and management team's time and effort. The final connections were completed in June 2010 and involved two night closures of the eastbound carriageway on The Strand.
The scale of this section of the programme involved 80km of new mains, over 600 fire main connections, 10,000 customer connections, hundreds of replaced fire hydrants and 150km of trenches excavated.
In July 2010, the Murphy VMR team turned its attention to the Heath Street/Hampstead High Street area of the scheme. This has involved close collaboration with London Borough of Camden's principal network coordinator for Public Realm & Sustainability, and stakeholders along the route including local councillors, the police, TfL, London Ambulance Service, residents associations and local retailers.
The scope of works for this area involved renewing 1,200m of old cast iron mains and 150 customer supplies in a high amenity area that is also a major traffic route. The same traffic management would also be used to facilitate a number of Camden schemes including gulley cleansing, street lighting upgrades, footway reinstatement works and, on completion of the VMR works, the complete carriageway resurfacing and relining.
Advanced planning meetings with all major stakeholders months in advance of works enabled a one-way system of traffic flow to be introduced through the area with buses allocated defined diversions during the works. Advance warning signs were placed at 29 key locations on traffic networks to advise about potential delays prior to work commencing. The close working relationship with key stakeholders, the ability for Murphy to upsize the level of resources on site as works progressed, coupled with the skill and knowledge of the team involved on the scheme, ultimately resulted in the project being delivered nearly three weeks early.
Historically in the area, water mains have been laid, pressure tested, chlorinated and surfaces reinstated prior to relaying the service pipes. As part of its mains laying operation, Murphy introduced the installation of the service pipe between the new main and the footway, where it is connected to the new main and capped at the boundary box in the footway.
This allows for the service pipe to be tested in conjunction with the new main thus negating the requirement for a second visit and further disruption to that particular section of carriageway. Murphy has completed VMR activities in more than 40 DMA projects in the boroughs of Camden, Islington, Haringey, Hackney, Tower Hamlets, Brent, Barnet and the City of Westminster. Murphy continues this work into AMP5 for Thames Water, working now as part of the Optimise JV. This essential work has helped cut leakage by 24% in the past four years. It is expected that when the work is completed, typical savings of approximately 1Ml/d for each zone in which the work is completed will have be achieved.