Case study: Setting new best practice and finding 36% cost saving

VAC UK APPROACH TO TRIAL HOLES EXCAVATION AT HEBDEN BRIDGE YIELDS 36% COST SAVING AND SETS NEW BEST PRACTICE FOR CIVIL ENGINEERING GIANT


Project: Radcliffe & Redvales Flood Risk Management Scheme
Client: Environment Agency
Principal Contractor: BAM Nuttall
Contract: Hebden Bridge Flood Alleviation

Hebden Bridge Case study

PROJECT BACKGROUND AND REQUIREMENT

The Environment Agency-led Hebden Bridge Flood Alleviation Scheme is a vital project to improve the West Yorkshire town’s flood defences and is itself part of the wider Radcliffe & Redvales Flood Risk Management Scheme.
The Surface Water Design across the streets of Hebden Bridge required:

  • Over 1400m of drainage varying in depth to invert level from 1m to 6m with over 50 nr manholes varying in size from 1.2m to 1.5m diameter
  • Over 450m of interceptor sewer tunnel detailed at 1.5m diameter varying in depth to invert level from 5.5m to 8.0m with 5 nr shafts varying in size from 3.0m to 7.5m diameter
Hebden Bridge Case study

CHALLENGES

The tight urban environment presented numerous challenges including:

  • Overhanging Branches
  •  Very tight working space
  • No planning permission in place to cut trees
  • Limited time to find services
  • Narrow Streets
  • On street Resident Parking
  • Local Business impact
  • Visitors to Hebden

APPROACH

The Vac UK team’s expertise in operating in highly constrained urban conditions was called on from the outset – and paid an immediate dividend.
The most frequently encountered problem was presented by difficult access to the trial holes’ sites. To overcome this, the Vac UK team was able to advise BAM Nuttall on the use of extension hoses combined with a small 5T excavator which could operate beneath the trees and meant the vacuum excavator did not need to be immediately adjacent to the digging. Using this approach ensured all of the trial holes were excavated with a minimum of disruption and without causing any damage to the fauna.

Using vacuum excavators reduced the necessary footprint of each site when compared with conventional plant. They could also be much more quickly deployed which meant there was less time spent at each location, lessening impact on traffic and residents and reducing the project’s carbon footprint.

A good illustration of how using vac ex and extension hoses was able to reduce the site’s encroachment into the road and allow traffic to keep flowing
A key element of the approach was collaboration between BAM Nuttall and Vac UK. Working together, the teams were able to “batch” the trial holes and so reduce the need for road/lane closures across Hebden Bridge.

This was augmented by BAM Nuttall issuing a weekly lookahead programme. It gave full visibility of the proposed excavations so that resources could be co-ordinated between the two businesses.

This was better for traffic and residents because it reduced overall disruption and meant that the vac ex machines were maximally utilised with little or no stand down time.
Vacuum excavation practically eliminates the chance of a service strike so not only was the process of excavating each trial hole quicker, there was also almost no chance of a requirement for post-strike reinstatement which in turn meant that the schedule was consistently maintained or even accelerated.

RESULT

Using Vac UK’s plant and expertise delivered an 18% saving in resource costs when compared with using a gang for hand excavation and, through overall project efficiencies and economies, realised a 36% saving on total costs.

Vac UK adopted a highly collaborative approach which led to the two business adopting common principles – now enshrined as best practice at BAA Nuttall. In particular, Vac UK maintained a philosophy of flexibility throughout to support batching and resource management throughout.

There was easy integration between BAM Nuttall and Vac UK. BAM Nuttall’s expectation that there should always be two fully trained operatives to use vacuum excavation kit (CPCS card category A78F with relevant endorsements) entirely conforms to Vac UK’s standard operating practice.

On average, the Vac UK team was exposing 50% more utilities than were charted in every trial hole. The elimination the potential strikes provided a huge reduction in the risk profile over conventional hand digging methods and avoided cost, HS&E, reputational damage and impact on the local community.

No. of Trial Holes Completed: 28
Charted Services Identified 56
Uncharted Services Identified 28
Services damaged 0

 

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