Engineers map the drainage system around the M275 motorway

Lanes for Drains engineers have turned super sleuths to help progress a motorway construction project vital to major plans to regenerate a large part of Portsmouth.

Innovative survey work was needed to allow Lanes’ client, Colas, to finalise plans for a new motorway junction required as part of a £130m regeneration scheme for Tipner promoted by Portsmouth City Council.

A team from the company worked for three months with some assistance from a local Colas team and consultant engineers Halcrow, to find and map the drainage system around the M275 motorway prior to the building of a new junction at Tipner, a suburb of Portsmouth, Hampshire.

With little more to go on than an out-of-date map, they scoured the land, through six feet high brambles, using metal detectors and the skill built up through many years of drainage experience to track down more than 200 manholes.

The work continued, night and day, for three months, to the point where an up-to-date plan now exists, to within an accuracy of a few centimetres, showing a drainage system with 7,500 metres of pipework for the two mile long M275 through Portsmouth.

Keith Oldbury, Sales Manager for Lanes for Drains’ South Central Depot, in Portsmouth, said: “This is an example of a creative approach combining with the right technology and expertise, plus a downright dogged determination, to solve a difficult problem.”

The Tipner regeneration scheme involves plans to build 1,600 new homes, create 1,500 new jobs, a park and ride hub and new public open space on the waterfront.  Colas, in a joint venture with Volker Fitzpatrick, will start the scheme with the installation of a new motorway interchange on the M275.

Keith Oldbury said: “Our brief was to survey and clean the drainage system along the M275 to prepare for the new junction to be built.

“The only drawings we had were from the early 1970s, showing the line of the motorway across the houses that would be demolished to make way for it. So, it was very out of date. The motorway, itself, opened in 1976.

“We realised that, to carry out the lines survey systematically, we first had to establish the scale of the drainage system, which involved going out and physically searching for every manhole. It was a real piece of detective work.”

The work was coordinated by Tony Cutajar, South Central Regional Manager for Lanes for Drains, the UK’s largest independent drainage specialist.

He said: “We worked in a 200 metre corridor either side of the M275 from the M27 down to the sea. When we located a block of 20 manholes, we sent in a surveillance team and a jetting team to survey and map the local system.

“Then we moved on to the next block. But in places it wasn’t that simple. Some of the manholes had been buried. We found one under a 20 metre earth embankment. So we also had an excavation team regularly working on the job. Some outfalls were also in tidal waters, which we could only access at certain times of the day. A couple of them were left un-surveyed due to access issues.”

The Lanes teams often had to work at night, searching for manholes by torchlight, to minimise disruption to traffic, though, in some cases, traffic restrictions and road closures were required. The final manhole was located in August 2012.

All the manholes were plotted by hand on plan drawings. Then, each one was recorded using a GPS positioning device, and the data sent to Colas and consultant engineers Halcrow to carry out drainage calculations and provide an electronic map.

As each block of manholes was identified, they were surveyed using Lanes sophisticated remote-controlled Rovver robot cameras and cleaned using powerful jet vac tankers and recycling tankers. The pipework discovered and cleaned included, storm drains, gully connections and outfalls.

The work was coordinated through weekly project meetings with Colas, which has a 25 year contract with Portsmouth City Council to manage the road system in the city.

Keith Oldbury said: “From the start, we decided that the key to the project was to find all the manholes rather than start survey and cleaning work straight away.

“At the time it felt a little like we weren’t making huge progress, but it’s an approach that paid dividends because it meant the work could be planned effectively. In the long-run it meant the objective was achieved more quickly and cost-effectively for the client.”

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