Project Introduction
The Southern Strategic Support Main (SSSM) is a 30.5km, of 600mm and 700mm diameter, potable water pipeline, constructed to provide resilience to 280,000 customers across the southern Bristol Water network. It is the largest single pipeline scheme in the history of Bristol Water and the longest new water pipeline anywhere in the UK during AMP6.
The route is designed to allow water to gravitate from reservoirs at Barrow to Cheddar and Banwell, this reduces operational costs and significant long-term energy consumption. The pipe runs through mostly agricultural land; 25km through fields, 2.7km along highway and 2.8km along the Strawberry Line (a dismantled railway line). The route avoids all European- designated statutory nature conservation sites and scheduled monuments.
A series of ecological surveys were completed, the route encountered various protected species such as great crested newts, dormice, bats, badgers and cave spiders.
An approach was taken to minimise the environmental impact of these construction works. Along with considerable savings on quarried aggregate, waste to landfill and vehicle movements, the scheme has also increased local historical knowledge and improved wildlife habitat.
Water Saving Innovation
The commissioning process requires the pipeline to be swabbed (to remove any debris), pressure tested, super-chlorinated and de-chlorinated.
Each of these phases require huge quantities of potable water. All water from these processes goes to waste through dichlorination. In some cases, the water was discharged to storm drainage but where possible it was discharged under agreement directly to selected watercourses.
The pipeline was split into 1km sections to swab and test. A swab catching arrangement was developed to isolate the main and lock-in water so that it could be reused on further sections of pipeline. To make this feasible, careful thought was required regarding the restraining forces on the pipework at test pressures.
%
Water saved (in millions of litres)
Archaeology
A geophysical survey was undertaken of the pipeline to identify potential areas of archaeological interest. These areas were investigated through trial trenches. Two parts of the site developed into full archaeological digs. Evidence of a Romano-British settlement was found at Churchill, including a burial which will undergo further analysis.
The most significant find was a Romano British kiln, which was discovered along with over 400kg of pottery. It has previously been known that there was a Roman pottery industry in this area, although little was understood. This kiln is the second of its type found in the UK and the analysis of the pottery will add to the knowledge of trading networks in North Somerset and the wider region.
Compound Management and Material deliveries
Kier worked very closely with the pipeline supplier on a strategy to supply and distribute the materials as effectively as possible from manufacturing plant to site. Over 6200 pipes and fittings were required for construction, these were manufactured in France. The logistical challenge was to determine the best way to distribute these materials across the 30.5km scheme.
20nr delivery sites were constructed where articulated vehicles brought specifically selected materials to these sites to ensure pipes and fittings got to the location where they were needed. This significantly reduced the number of times materials were handled and the distance of transportation around the site using heavy plant and machinery.
Hedgerows
A total of 191 hedgerows have been crossed along the pipeline route. Typically, our working width is 30m, however to reduce the impact on hedgerows, we narrowed our working area to 7m at hedgerow crossings.
24 no. dormice hedgerows were identified. Innovative dormouse tunnels were created by using the material from the hedgerow clearance. These were designed to be light enough to be lifted by hand for ease of maintaining a continuous dormouse habitat and still allowing access. Over 40 key hedgerows were maintained for bat navigation.
%
Kilometres of hedgerow saved
Re-used Backfill Material
Over 80% of the scheme was across fields. The pipe needed to be bedded and surrounded with suitable material. To guarantee quality, imported
quarried aggregate is typically used. However as-dug material can be utilised if it meets specific criteria. Efforts were made to reuse excavated material across the site, including an in-situ screening process. Quantity of as‐dug material re‐used as pipe bed and surround: 12,700 tonnes.
Waste Management
Consideration has been given to every waste stream.
- 100% of ‘as-dug’ material has either been selected to be used as backfill in field areas, or recycled off site.
- Vegetative waste was shredded and spread within site during initial clearance works.
- We are currently liaising with local farmers, developers and other Kier projects to re-use the aggregate generated when clearing compounds at the end of the project instead of being sent to landfill.
Wildlife Habitat
Pre-construction habitat surveys were carried out, this identified an ecological baseline, risks and constraints and further works that were
required during construction. These included:
- 5km of newt fencing with trapping and translocation plus fence monitoring throughout construction.
- Shute Shelve Tunnel works were planned to avoid bat roosting times.
- Cave spiders were protected in the Shute Shelve Tunnel.
- Badger setts required monitoring throughout construction
- Great crested newt fencing at Congresbury
- Use of a riddling bucket to process as dug material
- Nesting bird checks were carried out when undertaking vegetation clearance during the breeding season.
Biodiversity Enhancements
Substantial work has been put into improving biodiversity along the pipeline route and in the local region with co-operation from several
inner-city schools and councils. For example:
- 1110 trees planted, additional to reinstatement requirements.
- 520 children/ students engaged with the project.
- 500 elvers (juvenile eels) released into the wild.
- 100 bee orchids temporarily translocated.
- 40 owl and kestrel boxes installed along the pipeline route.
- 35 landowners benefitted from ecological enhancements.
- 3 ponds subjected to habitat improvement.
Local Labour Agreement
Of the £11.25m total small/medium-enterprise spend, £9.71m was spent within 40 miles of Cheddar on subcontractors, outlining our commitment to utilising and training local resources as agreed with Sedgemoor District Council as part of the LLA that we committed to. This resulted in a Social Impact Amount Return on Investment of 1.56.