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Harrow Manorway Flyover


Description of Works

Working in partnership with the London Borough of Bexley, FM Conway’s civil engineering team was commissioned to deliver an exciting £8.7 million public realm refurbishment project to the areas in and around Abbey Wood Station and the Harrow Manorway Flyover. Improvements included redesigning the public space and flyover to create better pedestrian, cycling and vehicle access to the new Elizabeth line station construction Crossrail programme.

Utilising their self-delivery promise across the project, FM Conway was able to deliver an array of services throughout - including civil engineering, structural engineering, surfacing, street lighting, consultancy services, traffic management and in-house material supply from their Aggregate and Asphalt division – maximising the delivery of the scheme, whilst achieving significant savings for the client.

Delivering Innovation 

The project was issued to FM Conway as two distinct work packages, this study highlights the work on the Harrow Manorway Corridor, which included:

  • Widening of the existing road to provide a dual carriageway with a cycleway and footway on each side
  • Remodelling of two existing roundabouts
  • 925 metres of linear drainage and 1,365 metres of drainage pipework
  • 1,500 metres of ducting
  • 3,700 metres of conservation kerb
  • 10,000m2 of precast concrete paving
  • 3,000m2 of multi-coloured granite sett paving to carriageway with high strength mortar
  • Construction of boundary wall consisting of 50,000 bricks
  • 14,500m2 of carriageway surfacing including anti-skid and road markings
  • Installation of StrataCell modules for tree planting (by others)
  • Monolithic granite tables with high performance mortar to BS7533
  • Installation of new street furniture, traffic signs and posts
  • Construction of new bus shelters
  • 60 new street lighting columns

Originally constructed in the 1970’s, the Harrow Manorway Highway was developed as one wide expanse of road with no existing footway. Anticipating an increase in footfall because of the wider regeneration scheme at Abbey Wood station, attention was highlighted towards the development of a more pedestrian friendly area. FM Conway installed new footways along the flyover, with a bespoke waterproof mechanism sprayed underneath the footways to maximise performance and durability for the years ahead. 

To retain strength around wall structures within the flyover, FM Conway’s structure’s division installed a new concrete rap around the existing parapets. Through a hydro demolition technique, FM Conway was able to remove one section of the existing parapet using high pressure water equipment, causing virtually no dust and greatly mitigating noise pollution. This then led to undertaking an expansion joint renewal scheme, implementing new expansion and asphaltic plug joints within the redeveloped structure to confirm strength and durability.

FM Conway’s in-house surfacing team concluded the project with the installation of HitexPrint. HitexPrint is a specialist installation imprinted into the asphalt, designed to mimic the appearance of traditional brick setts, cobbles or paving without the associated maintenance costs, proving excellent long-term cost effectiveness for the client.

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Our paving team utilised our self-supplied concrete and materials to put together the scheme supported by our surfacing division who laid the final asphalt layer in the carriageway.

Paul Williams - Contracts Manager at FM Conway

Challenges and Solutions

Due to the highly congested nature of Abbey Wood station, one major challenge for FM Conway was to maintain a safe, yet efficient two-way traffic flow across the flyover to ensure that the works ran smoothly with minimal disruption to the public. This was achieved through phased working, alleviated by the support of FM Conway’s in-house Traffic Management division.

Contraflow traffic lanes were designed and implemented to keep the traffic moving. As the project was designed to widen the existing carriageway, TM arrangements maintained the daily traffic flows. Temporary signals were used to manage traffic at roundabouts, during key phases of work and to provide pedestrians with safe crossing locations. All TM was designed by our in-house team and approved by one of FM Conway’s in-house Traffic Safety and Control Officers (TSCO). Installation was undertaken by FM Conway’s specialist TM division who are all Lantra certified and all on site changes were in accordance with Chapter 8 of the Traffic Signs Manual.

Dedicated TM site meetings with TfL, Bexley, Greenwich, Peabody, Thistlebrook, TfL Buses and third-party contractors were utilised to review arrangements, future plans and provided an opportunity to identify improvements and address potential risks. Through site meetings we were able to improve access and egress to third party works, in addition to rephasing our TM to accommodate changes to the programme and sequencing of the works. Our site team was responsible for undertaking three daily inspections, any improvements were implemented immediately, and issues rectified.

Our TM design process incorporated route plans for deliveries and collections which were circulated to drivers on a daily basis. Site access and egress was carefully planned to minimise disruptions on the network by including site vehicle movements into the works area, in a controlled manner. Site entrances were clearly and visibly signed to prevent unauthorised access.

An additional challenge was managing the concrete works on an elevated deck, which saw the development of a bespoke cantilever scaffolding design to support the team. The access scaffold was three boards wide, drilled into the outside of the existing parapet. From these platforms, the new parapet access was used to construct the new concrete rap around the existing parapet, allowing the replacement of the existing expansion joints. This was established using cherry pickers and alloy towers, allowing the team to effectively and safely set up at an appropriate height.

As the footways and carriageways were constructed on an existing bridge deck, depth was restricted to achieve new finished levels. Therefore, drainage was incorporated into bespoke iron channel kerbs to ensure the successful installation of a modernised drainage system. The bridge deck’s depth restrictions proved further challenges for the team when installing new columns for street lighting and signage. The overall depth of the bridge deck was less than 300mm to the new paved surface level, therefore FM Conway installed shallow NAL socket foundations – 245mm deep – in a concrete base, directly behind the kerb drains to install the new columns.

Due to the limited construction depth on the flyover, FM Conway’s technical team worked in collaboration with the Council to introduce our proprietary single layer surfacing solution, SureLayer, which incorporates a chemically engineered polymer modified bitumen to provide enhanced durability and greater resistance to common failure mechanisms such as rutting and cracking. The elimination of a horizontal joint also improves compaction and minimises water ingress to retain the structural integrity of the road pavement. SureLayer was laid at a depth of 70mm in lieu of the traditional 100mm dual layer specification. In addition to realising a direct cost saving of 8.7% on the surfacing works at Harrow Manorway, this material innovation reduced time on the network by 43% and congestion by 27%.

 

Outcomes

Thanks to FM Conway utilising a number of safe and innovative working practices on this project, combined with our self-delivery promise, the team ensured a high-quality public realm project was achieved.

Paul Williams, Contracts Manager at FM Conway, highlights:

“Our civil engineering divisions were tasked with widening footways and creating areas of soft landscaping. Our paving team utilised our self-supplied concrete and materials to put together the scheme supported by our surfacing division who laid the final asphalt layer in the carriageway. Finally, our lighting team worked closely with the support from our consultancy arm, who supplied advice on the use of energy-saving LEDs which maximise light levels whilst being energy efficient.”