Works at the Queensway Tunnel, Liverpool, included planing, waterproofing and resurfacing on all four lanes. The tunnel is part of a key commuter route from central Liverpool to Birkenhead under the River Mersey and the project required extensive logistical planning to ensure that the tunnel was handed back by 6:30am each morning.
On this £1.9m scheme we used 6,600 tonnes of HRA Binder Course together with 2,500 tonnes of Polymer Modified Binder (PMB) surface course along the 2 mile length of the tunnel. All of the material was supplied from our local North West production units based at Bootle, Liverpool and Weaste, Manchester.
We worked with Merseytravel and URS during the design phase to develop value engineered solutions. Upon contract award and following full analysis of the requirements it was discovered that instead of the anticipated planing depths of 75mm we had to plane out material to 105mm. This increased the cost by an additional £380,000 taking the potential overall contract value to £2.18m.
Through consultation and liaison with the Client we were able to value engineer the scheme through the use of innovative technologies and solutions including:
Vogele Feeder & Conveyor System
Due to the profile of the tunnel our fleet of insulated tipper vehicles was unable to tip into the paving machine in the outside lanes of the tunnel. We overcame this issue through utilisation of the Vogele Feeder Conveyor Belt System.
Our tipper vehicle fed the material into the Vogele Feeder Machine which in turn uses a conveyor to discharge the asphalt directly into the hopper of our paving machine. This system substantially reduced both cost and the overall contract period when compared to utilising the traditional methods of feeding a paver in a confined space; loading shovel and dumpers. The cost of hiring the Vogele equipment was approximately £2,500 a week which, when compared to traditional methods, saved circa £1,500 a night. Overall this realised savings across the contract period of £19,500.
The tendered scheme included waterproofing in the tunnel for the first 300m in length from each portal. Due to the restricted working window of night time working a waterproofing product that is widely utilised in France on bridge decks was proposed; although this product had only been used on a limited basis thus far in the UK. This rubberised product was tanker-spray applied to a fine milled surface and covered with a single size aggregate protection layer.
Upon contract commencement the condition of the concrete decks after initial milling were found to be poor, and any further fine milling of the surface may have compromised the cover to the reinforcement; resulting in exposed steel. Without fine milling the surface was not acceptable as suitable to receive the French system. We therefore proposed that, following concrete repairs, we would apply a bituminous membrane through our integrated spray-jet paver and Tanker-mounted sprayer that would act as a barrier for the ingress of water. Permeability Tests were carried out to prove the validity of our proposals and the Client instructed the change, thus saving the Client approximately £150,000.
Environmental and Sustainability Considerations
Due to the nature of the works there were increased environmental considerations. Both noise and dust levels increased due to working within a confined space. We ensured that all operatives wore mandatory ear protection and that dust was removed quickly by increasing ventilation via the extractor fans within the tunnel.
All planings were stockpiled and collected by a local recycling contractor and has been processed for reuse on other construction schemes within the local area. This saved the contract the potential cost of tipping at a local landfill location.
For the scheme we utilised key members of our local supply chain including:
• Planing – Tripod Crest
• Concrete Repairs – Volker Laser
• Roadmarking – L&R Roadlines
• Tackcoat Spraying – Recomac
• Waste Transfer – JC Balls and Brookes Haulage
Prior to commencement we worked with Merseytravel to develop the construction and possession programme. Time-line planning was essential due to the limited hours available for work to ensure that the tunnel was handed back at 05:30 for re-opening at 06:30. Each night there were up to 50 members of the Site Team and numerous items of the construction plant in the tunnel at any one time; this required significant programming to avoid congestion and health and safety incidents (No Lost Time Injuries).