Marlborough Highways
Sewer connection, backdrop manholes & connection to an existing Thames Water chamber
Sewer connection, backdrop manholes & connection to an existing Thames Water chamber
Marlborough Highways
- Service Provided: Connection into an existing Thames Water manhole with external backdrop, install new 1200mm concrete chamber with external backdrop, and install additional 600mm GRP manholes.
- Client: Marlborough Highways
- Asset Owner: Thames Water
- Location: Freeling Street, Kings Cross
- Depth: 5m, 3.5m & 2m
- Existing Sewer: 1100mm diameter
- New Diversion Pipe: 100mm diameter
- Connection Method: Existing manhole
- Licence: London Borough of Islington
Overview/scope of works
We completed a surface water sewer connection in Kings Cross, connecting via an existing manhole built over a 1100mm culvert in Freeling Street for Thames Water. The project involved excavation to a depth of 5 metres, a road closure, and reinstatement to strict highway standards — all delivered in accordance with sewer adoption standards and specifications.
Key Requirements & Challenges:
- Highway location & traffic management: The connection point was located within a live carriageway, and due to the depth and layout, a full road closure was required for the work to commence.
- Depth of excavation (5m): Excavated using an 8-tonne machine with safety and protection measures in place to ensure stability and protection to the existing infrastructure, this machinery can only be operated by a fully qualified plant operator experienced in deep drainage.
- Precise connection method: The existing surface water manhole was carefully cored drilled into the brickwork, removing two sections, one at the soffit off the 1100mm main and one at the agreed backdrop level. Once cored, we installed the new 100mm clay pipe, sealing it with sand, cement, and Sika 4a water stop.
- Shaft excavation for new 1200mm chamber: With the correct temporary works drawings in place for the shoring, we excavated and installed a 1200mm pre-cast concrete chamber with a secondary backdrop. With the design of having two backdrops, it means our client can work at a much safer depth when connecting up the site drainage.
- Reinstatement to Specification:
- Compacted MOT Type 1 in layers using a mechanical trench rammer/forward-reverse diesel wacker plate.
- Finished with a final jet down.
At Premier Drainage Solutions, we do not rely on temporary reinstatements. We believe in completing work permanently and to the highest standard, preventing future disruption and repeat visits.
Outcome:
- Sewer connection completed to Thames Water standards
- Full reinstatement carried out to specification
- Project delivered safely with approved plan and programme for works
- Client received a permanent, long-term solution