Case studies

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 is within a public park, we also demonstrated high levels of communication and co-operation with stakeholders and site management in order to minimise disruption to the public.

Client Feedback:

We have received extremely positive feedback from the client and stakeholders, with Sean Rielly, Project Manager at Marlborough, praising us for, “A high quality project delivered in a timely and professional manner. We would have no hesitation in recommending PDS as a most Competent and Professional Contractor in these type of works.”

Dave Butcher, Resident Engineer at the London Borough of Haringey, also congratulated us for our, “Quality of work and attention to detail of the highest order, and an approach to Health and Safety that is exemplary. I would have no hesitation in engaging PDS for future works or recommending their work to other organizations.”

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 and hydraulic braces; we carefully core-drilled into the existing sewer and installed the new pre-formed saddle with sika sand and cement.

A single lane closure was agreed with the local authority, which was maintained at all times, plus we were able to suspend parking bays nearby which helped with the storage of materials and waste. Correct compaction and materials must be used within any highway at all times, so we used MOT Type 1 crush compacted in layers, with the correct number of petrol trench rammer to guarantee that the reinstatement will not fail when inspected at a later date.

“I would recommend Premier Drainage Solutions to anyone needing to complete a drainage project. We were impressed with the way the work was carried out, with little fuss and on time, considering there were complex logistical needs in terms of the local authority and Thames Water. We were shielded from these and the job was completed efficiently and effectively, on time.”

Suzanne Petrides, Architect / Director, Larkfield Investments

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 to connect onto the public sewer within the highway in central London, but with the carriageway being a designated Red Route, a standard approach would have meant incurring a very high cost in lane closures and TFL rental scheme daily charges. With this in mind, we decided to propose a timber heading, which actually worked out cheaper than open-cut trenching when the extra costs of road closures were borne in mind. Using a timber heading, our work could be carried out from the site boundary, by tunnelling out to the main public sewer within the highway, keeping all traffic flowing as normal.

After taking level measurements from the existing upstream and downstream manholes within the highway, to give us our excavation depth for the shaft, the timber heading began as a shaft at the site boundary, excavated down to invert level. At the correct depth, the actual process of excavating towards the sewer does change depending on ground conditions, but does not change the way it is installed. Once we reached the existing sewer with the timber heading, we installed pre-formed clay saddle to complete the connection to the public sewer.

Sewer connection made, the back-fill process involved laying the pipe, and dry packing with concrete by hand, until the heading is filled back to the shaft. At this point we used the shaft to construct a new pre-cast concrete boundary manhole, leaving a stub pipe for our client to connect to.

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 correct falls on a stone bed and surround.

For this job, two-way traffic lights enabled us to carry out the connection without closing the road,  by using one lane for our works at any time. Our traffic management solutions always include communication boards for the general public, so that they might contact us if any problems were to occur during our time on site.

It goes without saying that the correct compaction and materials must be used within any highway. In this instance we utilised MOT Type 1 crush compacted in layers, using the correct number of passes with a petrol trench rammer, before all cut edges were cleaned ready to receive bitumen edge sealer and the specified tarmac was used. Once this stage was completed, thermoplastic overbanding tape was used to prevent water ingress. At Premier Drainage Solutions we believe that a temporary reinstate is not good enough, and that a permanent solution is the only way of completing the work – nobody wants to have to return to site and cause further interruption.