Hinkley Point C: Permanent Dewatering Case Study

Case Study

Hinkley Point C: Permanent Dewatering

Client: NNB BYLOR JV
Location: EDF Hinkley Point C, Somerset
Duration: 2017 – 2020

Project Overview

As part of the permanent design to control porewater pressures to defined values. A series of passive pressure relief wells designed for a functional life of 80 years were installed to discharge into a perimeter drainage galley.

Phased works involved the drilling of 140mo Permanent Pressure Relief Wells upto 60m deep using rotary drilling methods terminating in 200mmØ bore with installation of stainless steel 90mmØ well liner, together with extensive geophysical testing, falling head tests.

Coring & Core Logging

Geobore S coring and subsequent logging was undertaken to determine the boundary between the Lilstock-Westbury Formations. This essential information was used to confirm final drilling depths and comply with specification requirements. All Logging was undertaken by the Stuart Wells Geotechnical Team in accordance with BS5930:2015.

Verticality Testing

To comply with specification requirements on borehole verticality. Verticality Sondes were utilised during the drilling and installation process to determine the deviation and inclination of wells drilled.

Borehole Diameter Calliper Testing

Calliper testing was undertaken to highlight any major fissures in the bedrock any enable adjustment to well design, if necessary. A 3-Arm tool with 600mm max range and +-3mm accuracy has been utilised for the works.

Borehole CCTV

An Axial Colour Camera was used for CCTV investigations and records for each well .

Hydraulic Conductivity Testing

To determine the effectiveness and detail localised permeability of installed wells Falling Head testing were undertaken and interpreted in accordance with BS EN ISO 22282 2012.

Quality & Reporting

An extensive QA procedure was undertaken with detailed records of all parameters and conditions found. Together with site management and recording of the detail of all material used with traceability and allocation to specific wells.