Case studies
Manhole construction and sewer connection in Wood Green, Haringey for new public café facilities
- Asset owner: London Borough of Haringey
- Manhole Diameter: 2.4m pre-formed concrete caisson ring
- Depth: 7.5m
- Existing sewer: Connection to a live 525mm diameter Thames Water foul sewer.
- Connection Method: 150mm Pre-formed saddle, The manhole was constructed as a caisson shaft with a 2m heading to make the final sewer connection.
About the project: Working with both Marlborough and the London Borough of Haringey, we carried out a manhole construction and sewer connection for the ROJ Café Kiosk currently being developed within Ducketts’ Common Park. Through the process of early engagement in the pre-construction period, we identified the most cost-effective and efficient method of construction and engaged Thames Water directly on behalf of the client. During the Construction Period we delivered the project according to timescale, budget and QHSE standards. As the site…
Remedial works at Shell’s flagship forecourt
- Asset owner Thames Water
- Depth 4m
- Existing sewer Victorian brick built
- Lateral remedial 225mm
We were asked to provide our specialist expertise during the redevelopment of Shell Fulham into the company’s first ever all-electric forecourt. Our client Toureen Group had discovered an issue on the project where the outgoing drain (interceptor) was blocked with historical debris, which needed unblocking and the old interceptor rat trap removed. After further investigation we had found that the existing interceptor plus four metres of the existing main had be filled with concrete by a previous contractor –…
Foul water sewer connection into Victorian main
- Asset owner Thames Water
- Depth 2.5m
- Existing sewer Victorian brick built 1140mmx790mm
- New Lateral Connection 100mm
- Connection Method Core-drilled saddle
This connection into an existing 1140mm x 790mm Victorian main, at 2.5m depth, involved working within the confines of one lane of the highway, but thanks to our experience and rigorous process it was completed within the timescales given by the client – despite the very tight turnaround required between the order being placed and starting on site, which meant the relevant licences had to be obtained quickly. The dig-and-push method that was used involved two levels of aluminium frames…
Moving a sewer so an extension can be built
- Asset owner Thames Water
- Depth 2m
- Existing sewer 225mm
- Relocation of Manhole 1200mm Pre-cast concrete
- Diversion Length 10.5m
Our client was extending to the rear of their property, and while excavating for the new foundations had found an existing 225mm foul water sewer – this is always a possibility when doing any sort of extension around an existing property. The client produced his own drawings for the application to Thames Water for a minor diversion, which was passed by the authority, and we were awarded the work. The timescale between placement of the order to starting on…
Controlling costs with a timber heading
- Asset owner Thames Water
- Depth 4.5m
- Existing sewer 300mm
- New Lateral Connection 150mm
- Connection Method Saddle
- Tunnel Length 7m
A timber heading is where a tunnel is manually excavated, and supported using timber sets, enabling the installation of sewer pipes where access is limited, and standard methods of sewer connection can’t be employed. This method of trenchless sewer connection dates back centuries, but it is very much still relevant today – it’s regularly used in London and in other large city centres, where space constraints, busy roads, and dense development makes laying sewers in trenches impossible. Our client wanted…
Foul water connection inside a building
- Asset owner Thames Water
- Depth 2.5m
- Existing sewer 150mm
- New Lateral Connection 6 x 100mm
- Connection Method New manhole
Unusually, this public sewer connection took place within an existing building – an old bank, which was being converted into a KFC. Working indoors creates specific challenges around access for plant machinery, the size of plant, ventilation, safety, moving plant, noise, and waste removal, so this was a complex job with many constraints. Only a small plant was used due to the limiting size of the building’s entrance – a 1.5 tonne excavator, with retractable tracks for ease of movement…
Sewer connection into an existing manhole
- Asset owner Anglian water
- Depth 1.50M
- Existing sewer 150mm
- New Lateral Connection 100mm
- Connection Method Existing manhole
Sewer connections into existing manholes can sometimes prove challenging due to the concrete used around the chamber when initially constructed. However, with the correct tools, equipment, and, most importantly, experience, it’s possible to break into the manhole to complete the necessary sewer connection. In this particular instance, once the concrete had been carefully removed, all clay channels and fittings were installed by hand and re-benched to complete the connection. Once the connection process was completed, pipe was laid to the…
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