Penstone Underbridge Replacement

This project formed part of the Western Package 2 works for Network Rail and comprised of the replacement of Penstone Underbridge, a 3-span underbridge, located within 2 miles of the North Devon Line (NDN). The existing structure comprised of two decks of longitudinal main girders, cross girders, longitudinal timbers, and a timber deck bearing onto brick abutments and piers. The structure carries a single bi-directional line with a redundant deck to one side over a public road.

The scheme was carried out in conjunction with two other projects, Battesford Bridge removal and Infill works and Eggesford Station Platform Extensions, under the same blockade.

We provided Network Rail with the assurance of our technical capability, implementing an hour-by-hour programme working on a 24/7 9-day blockade period. Our project team including our rail planners attended the T35-week possession-planning meetings and high-level briefings to de-conflict our works, it was an extremely busy blockade with the three schemes taking place concurrently. Through detailed planning and coordination with our specialist subcontractors, we were able to effectively complete the demolition and track reinstatement phase ahead of time, successfully completing the works 10 hours earlier than scheduled without incident. The works included:

• Setting up the compound, stripping the topsoil and sealing the compound area
• Track work blockade and track removal
• Piled foundations (prior to the blockade from on track plant)
• Demolition of the existing deck
• Deck replacement including construction of the deck on site with waterproofing and concrete infill
• Substructure repairs
  • Installation of a safe access scaffold walkway - our in-house temporary works design team ensured that the scaffold designs met the DPE requirements

A cluster of 15 piles behind each existing pier were required. To de-risk the blockade we installed these with on track plant during weekend possessions prior to the blockade. This created a challenge for the bulk excavation as the piles were then in the way. The correct equipment was planned to execute this excavation and no issues to programme were encountered.

Penstone is a remote hamlet in Devon situated on narrow country roads. The 25m deck had to transported to site in three sections with its concrete infill due to length, width and weight restrictions. The 3 component parts were then spliced together and concrete infilled adjacent to the existing bridge and set up on trestles in preparation for the blockade.

As a result of the construction/splicing of the bridge along with the concrete deck infilling, the bridge weighed almost 300t. The restricted nature of the site meant there was nowhere to site a crane large enough to lift this 25m long structure into place, so we opted to use an SPMT (Self Propelled Mobile Transporter), its 40 wheels each bearing five tonnes, to jack the bridge up and slot it into place.

The works involved working in a live environment to a restrictive programme. The structure was sandwiched between two major Network Rail track renewal projects with several engineering trains and tampers required to transit through our sites for access and egress. This resulted in us being required to work to a strict programme and a complex train plan, which set us with a challenge from the outset. We ensured our activities were planned with extreme precision which resulted in no delays being encountered to the time critical track renewal projects being undertaken concurrently with our works.

 

CLIENT: Network Rail
PROJECT VALUE: £2.5m 
START DATE: February 2020
COMPLETION DATE: April 2021 
FORM OF CONTRACT: NR12