Wells to Glastonbury Trunk Main Installation

Bristol Water 8km Trunk Main Installation – Environmental Management (2020 – 2022).

Bristol Water commissioned a new water tank trunk main to protect water supplies in Glastonbury and its surrounding areas to ensure a supply to over 32,000 residents can be maintained. The proposal was to install a new 450mm diameter pipe that will run from the 12-inch watermain on Henley Hill to Windmill Hill Reservoir in Glastonbury.

The contract to provide Environmental Management for the installation of this 8km pipeline was awarded to NPT Engineering & Environmental Ltd under the strategic partnership that NPT Engineering & Environmental Ltd have in place with Bristol Water.

Due to the size of the project (ca.24 ha.), the works were considered as an Environmental Impact Assessment (EIA) ‘Schedule 2’ type development, and therefore an EIA Screening Opinion request was required and submitted to Mendip District Council to confirm the works are not an EIA development and could proceed in line with Bristol Water’s permitted development rights.

The Somerset levels are made up of delicate habitats and special ecological requirements dictated that directional drilling was the only solution through some of the sections. The drill shots reached up to 375m in length through the fragile peat levels to ensure the habitats and ecosystems could be protected as much as possible.

There were a number of designated sites including Site of Special Scientific Interest (SSSI), Special Area of Concern (SAC), National Nature Reserve (NNR) and Local Wildlife Site (LWS) within 200m of the works, however, Assent from Natural England was not required on this occasion, provided the designated sites could be avoided.

NPT Engineering & Environmental Ltd engaged with the County Archaeologist and a local archaeological contractor to determine the suitable areas that required supervision and manage the appropriate input during the course of the construction programme. This included identifying nearby listed buildings to ensure these could be avoided during the works.

The 450mm diameter High Density Polyethylene (HDPE) pipe ran 8km in total which included crossing three main rivers (The River Axe, The Hartlake River and The River Sheppey) where an Environment Agency (EA) Flood Risk Activity Permit Exemption was required from the EA for each main river. Additionally the pipeline route crossed seven ditches and rhynes and land drainage consent was obtained from The Somerset Drainage Board.

The works included the removal of 35 x 5m sections of hedgerow where and application for consent was submitted to Mendip District Council for approval as well as redirecting the pipeline route to avoid impacting 57 mature trees.

Himalayan balsam, an invasive species, was present along section of The Hartlake River and recommendations on suitable preventative and control measures were provided during the construction works.

9 public rights of way (PRoW) was crossed as a result of installing the new pipeline and an application for the temporary closure of the PRoW was submitted to Somerset Council. Following the grant of the PRoW application, this included providing the construction teams with the suitable signage and plans to display on the PRoW during the works.

On completion of the works, NPT Engineering & Environmental Ltd assisted with improving the local biodiversity through the selection of native hedgerow species, recommending the installation of bat and bird boxes and specifying the suitable seeding for reinstatement to enhance the local ecosystem.

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