Project Name: Lower Green West

Scheme background: Lower Green Collaborative Scheme – Thames Water & SGN
The Lower Green Scheme represented a successful example of multi-utility collaboration between Thames Water (TW) and SGN, aimed at reducing disruption to residents, road users, and local businesses within the London Borough of Merton. The works were located in a predominantly residential area, requiring careful coordination, detailed planning, and proactive stakeholder engagement to ensure efficient delivery and minimal community impact.
Background and Planning
This scheme involved Thames Water, supported by Morrison Water Services (MWS), and SGN, supported by Forefront Utilities (FFU), working collaboratively within the same geographical area. The objective was to align both organisations planned mains replacement works to take place under a single road closure.
The project had been under discussion for over two years prior to commencement, with the London Borough of Merton expressing a strong preference for the road to be closed only once, and during the school summer holidays to minimise disruption. Extensive planning and coordination meetings were held between the parties, including joint sessions with the Greater London Authority (GLA), to define roles and responsibilities such as cost sharing, traffic management (TM) planning, excavation and reinstatement responsibilities, and scheduling.
Stakeholder Engagement
Given the impact of the required road closure, engagement with key stakeholders was critical. In addition to the GLA, Merton Council, and the utility partners, discussions were held with Transport for London (TfL) Buses to arrange a temporary shuttle bus service during the closure. The collaborative approach extended to other local services, as the Local Authority used the opportunity to carry out gutter and drain cleaning, while MWS installed a Sustainable Urban Drainage System (SuDS) designed by Merton.
Scope of Works
Thames Water undertook mains replacement as part of its Conditional Allowance Works in Mitcham.
SGN carried out gas mains replacement under a collaboration permit aligned with Thames Water’s programme. SGN replaced approximately 580 metres of old cast iron gas main using live/dead insertion techniques and Open Cut. SGN also replaced 20+ customer services with new PE (polyethylene) mains.
The work included:
387m of 180mm PE, 183m of 125mm PE, and 15m of 90mm PE installed.
192m of 8” CI, 387m of 6” CI, and 15m of 4” CI mains abandoned.
In addition, SGN assisted Thames Water by diverting a section of gas main to facilitate their water connection works.
Delivery and Duration
The project commenced on 14th July 2025 and was completed over a period of 61 days. Despite the complexity of the works and the confined residential setting, the project was delivered successfully within the planned timeframe. Collaboration between the two utility providers and their contractors played a pivotal role in maintaining progress and resolving on-site engineering challenges efficiently. Following on SGN and TW works, FM Conway utilised the road closure to carry our resurfacing works on this section of road
Collaboration and Communication
Regular joint meetings and progress calls between SGN, Thames Water, MWS, and FFU ensured clear communication and rapid decision-making throughout the project. Between formal sessions, additional meetings were held to maintain momentum and address emerging issues promptly. This cooperative working approach helped avoid duplicated excavations, reduced public inconvenience, and maximised the efficiency of the road closure period.
Conclusion
The Lower Green Scheme stands as a strong example of how early planning, open communication, and inter-utility collaboration can significantly reduce disruption to the public and deliver essential infrastructure upgrades efficiently. By aligning programmes and sharing resources, SGN and Thames Water successfully achieved their respective objectives while supporting the broader goals of the London Borough of Merton and the Greater London Authority.

Key Stakeholders

• Greater London Authority (GLA)
• London Borough of Merton
• SGN
• Forefront Utilities (FFU)
• Thames Water (TW)
• Morrison Water Services (MWS)
• Transport for London (TfL) Buses
• FM Conway
• Local Businesses

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