Water and Effluent Treatment Magazine
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MAY 2017 WET NEWS 9 Micro-tunnelling resolves flooding issues • Albrighton Flood Alleviation scheme comprised four inter- related projects all combining to overcome severe risk of storm water flooding that had previously affected the town project. In conjunction with Severn Trent, Barhale opened a drop-in centre to provide residents and local businesses with information regarding the project. Barhale looked to minimise disruption to residents where possible and so working hours were restricted to dayshi•s only with no works on a Sunday. The scheme included road, footpath and verge works consisting of four inter-related projects, all combining to overcome severe risk of storm water flooding that had previously affected the town. They were: • Newport Road UID – storm overflow chamber, gravity storm sewer and outfall, 350m of open cut storm water sewer, and a reinforced concrete chamber incorporating a rotating screen • Albrighton Flood Alleviation Foul Sewers – 300m of 1.8m diameter catchment sewer con- structed by micro tunnelling; 700m of 0.6m diameter sewer in microtunnel, 400m of other sewers together with associated manholes • Albrighton Storm Water Scheme – five new storm outfalls to form a stream in open cut, 600m of storm sewer in open cut and guided auger boring • Station Road Clean Water Main – 700m of 250mm diame- ter water main The scheme to upgrade sewerage in the town was extended to include renewal of some water mains, thereby avoiding duplication of construction activity at a later date. All works were undertaken through the narrow town streets involving deep 'open trench top-down construction' and tunnelling between sha•s TECHKNOW • The scheme consisting of four inter-related projects, all combining to overcome severe risk of storm water flooding • A reinforced concrete chamber incorporated a rotating screen • A catchment sewer was constructed by micro tunnelling NEED TO KNOW 1 Albrighton's origins have been traced back to the end of the sixth century 2 The village had experienced substantial flooding in recent years due to lack of capacity in the existing sewerage system 3 Barhale re-used as much of the excavation arisings as possible THE VERDICT • CO2 savings of the pipe jacking element compared to open cut construction were 28% for the 1,800mm diameter drive • The scheme was highlighted as a huge success within the industry and won a number of awards. ONSITE FlOOd AlleviATiOn This scheme resulted in one of the first micro tunnels in the UK to be cut on a curve through rock T he village of Albrighton in Shropshire had experienced substantial flooding in recent years due to lack of capacity in the existing sewerage system, coupled with the volume of surface water flowing into a local brook. Barhale was awarded the £6.4M scheme by Severn Trent Water to upgrade the sewerage system within village, which is steeped in history with its origins having been traced back to the end of the sixth century. Barhale offered an innovative solution to the client through carrying out micro-tunnelling to a curved profile. This was one of the first micro tunnels in the UK to be cut on a curve through rock and provided a £300,000 cost saving to Severn Trent. Benefits of the scheme included: • Adoption of trenchless tech- niques, minimising disruption to local residents • Offered an innovative, cost saving solution through carry- ing out micro-tunnelling operations to a curved profile • Extensive community engage- ment to reduce disruption • Completed to budget and with- out incident Throughout the works, Barhale looked to minimise its environmental impact where possible. Barhale worked hard to re-use as much of the excavation arisings as possible, with dried tunnel slurry being recycled as landfill capping and harder sandstone, sands and tarmac being used as pipe- bedding material. This avoided expensive and environmentally unfriendly transport and special waste- tipping charges. Dayshifts Strong customer relations were also maintained throughout the through ground heavily congested with other utility services. Through-out the works, following pipeline installation and backfilling to open trenches and sha•s, the carriageway was reinstated with full depth pavement construction, and the verge / footpath so• / hard landscaping was reconstructed as applicable. CO2 savings of the pipe jacking element compared to open cut construction were 28% for the 1,800mm diameter drive, and 76% for the 600mm diameter drive. Presentations were held at local schools regarding the importance of being safe around a construction site and Barhale sponsored the village Christmas lights as a gesture of goodwill. Behaviour Due to Barhale's exemplary behaviour during the works and close relationship with the local community, the company was invited to a "Community Party for the Contractor" which was the subject of a BBC Midlands News item. The scheme was highlighted as a huge success within the industry and won a number of awards. It achieved the Gold Award at the Severn Trent Community Awards, and was also awarded the ICE West Midlands Communication Award due to the schemes excellence in communication, PR and media activity. The scheme won a Bronze Award with the Considerate Constructors Scheme and arguably its greatest success was the first prize for new installation of a large project for the UK Society of Trenchless Technology Awards. pROjECT SpECS • Upgrade the sewerage system • Carry out micro-tunnelling operations to a curved profile • Adopt trenchless techniques to minimise disruption