Brighton Marina to River Adur Coastal Defence Scheme

Introduction

Spanning a 9km coastline from Shoreham Port to Brighton Marina, the Brighton Marina to River Adur Coastal Scheme aimed at bolstering coastal defences to mitigate long-term flood and erosion risks in light of predicted sea level rises from climate change. This project underscores a collaborative venture between Concept and its sister company IN-SITU under Phenna Group, tackling complex geotechnical challenges.

Scheme Objective

To develop robust coastal defences to shield residential and commercial areas from rising sea levels, facilitated by comprehensive ground investigations and high-quality data to inform design decisions.

Location

The scheme covers various locations between Shoreham Port (west) and Brighton Marina (east), with ground investigations segmented into five areas (Area 1, 2, 4A, 4B, and 5) based on geographical differences and different coastal defence types.

Project Detail and Description

Concept was entrusted with exhaustive ground investigations to aid in the design of coastal defences, comprising:

• PAS 128 Services Detection and Tracing Survey.
• UXO risk management.
• Geophysical void detection (2m depth over 1880m2).
• Drilling 21 cable percussion boreholes (10-15m depth).
• Excavation of 11 hand-dug pits for wall foundation analysis.
• 5 Service Inspection pits.
• 8 Machine excavated observation pits and trenches to 1m.
• 1 Deep observation pit to 3m.
• 16 Cone (Piezocone with integral magcone) Penetration Tests to 20m depth.
• Standpipe piezometers installation for long-term monitoring.
• Both geotechnical and chemical analysis were executed by Concept’s in-house laboratory and environmental laboratory partners. 

Inter-Company Collaboration

A hallmark of this project was the first-time crane lifting of IN-SITU's CPT crawler rig, and a cable percussive rig onto the beach, showcasing the resource-sharing and collaborative prowess between Phenna Group companies; Concept and IN-SITU.

Challenges and Resolutions

Headlines:

• Busy Hove Beach and Shoreham Port: Coordinated with local authorities to minimise disruptions.
• Uncertain Utility Positions: Strategically relocated boreholes to avoid utility conflicts.
• Tidal Zone Work: Planned intertidal CPT operations meticulously around tidal windows and public access constraints.
• Wildlife Concerns: Ensured operations did not disturb local wildlife, for example a reported seal in the area.
• Equipment Accessibility: Safely transported CPT and cable percussive drilling equipment to site and lifted on and off the beach.
• Liaison with Port Authority: Liaised with the Port of Shoreham Authority to minimise impact on the port operations.

In Detail:

Part of the site was on the very busy Hove Beach with the remainder in and around Shoreham Port. Concept worked alongside BHCC and the Shoreham Port Authority to ensure that ground investigations were conducted in accordance with the programme whilst limiting disruption to the public on the beach and a working port. 

All exploratory hole locations were checked for utilities / buried services using a CAT and Genny and where necessary surface concrete was required to be broken out by handheld electric breakers. A rising water main was located on the site and the actual position could not be fully identified using surveys. Due to this uncertainty, boreholes were relocated using a 6m exclusion zone and a lighter plant was used to avoid overstressing the ground above the areas where the service might be located. 

Planning the CPT works was complicated, as they needed to be coordinated around public access constraints and weather conditions and sufficient time given for each location within the available tidal window. During the investigation, there were reports of a seal occasionally resting on the beach in the vicinity of the works. Prior to working on the beach, the location was examined to ensure that wildlife would not be disturbed. 

Outcome

All of the site works were completed safely, to the programme and to the satisfaction of all parties. The information from the siteworks enabled JBA to progress their designs. 

Concept understand that our expertise in undertaking complex ground investigations in difficult locations is a valuable asset. Our expert knowledge enabled a detailed assessment of tasks and likely contingencies for intertidal work, which led to a robust, practical, and efficient programme of works, undertaken safely and with minimal delays.  We are proud to have helped deliver a successful project for all stakeholders, to work collaboratively, and to play a part in safeguarding the coastal defences for future generations.