Case Study: Underwater Structural Investigations & Scour Assessments

Location: Inshore Waterways, Scotland

Client: Confidential Infrastructure Authority

Lead Contractor: UK Diving Services Ltd

Project Overview

UK Diving Services Ltd was commissioned to undertake complex underwater inspections of several deep-water piers across Scotland’s inshore waterways. These structures form critical components of the regional transport and logistics network, necessitating a high-level assurance of their structural integrity and the stability of the riverbeds supporting them.

The primary objective was to provide a dual-layered assessment: a topographical analysis of the riverbed to identify potential scour risks and a granular physical inspection of the submerged pier structures.

The Challenge

Inspecting deep-water piers in Scottish inshore waterways presents several logistical and technical hurdles:

• Low Visibility: Suspended sediment often renders traditional visual photography ineffective.

• Depth & Current: Operating at significant depths requires stringent safety protocols and specialised diving equipment.

• Access: Managing diving operations within active waterways while ensuring minimal disruption to maritime traffic.

Our Technical Approach

1. Sonar Profiling & Scour Analysis

To mitigate the lack of visibility, our team deployed low-resolution sonar to capture accurate acoustic imagery of the riverbed.

• Gradient Mapping: We mapped the riverbed gradients and profiles surrounding the pier bases.

• Scour Assessment: This data provided the essential evidence required for Level 1 scour assessments, identifying any significant depressions or material loss that could compromise the foundation’s stability.

2. Structural Condition Investigations

Our divers conducted comprehensive "hands-on" inspections of the piers to assess the physical condition of the assets.

• Material Integrity: Detailed examination of concrete and masonry for signs of spalling, reinforcement corrosion, or fracturing.

• Submerged Asset Mapping: Identifying the extent of marine growth and its impact on the underlying substrate.

• Compliance: Ensuring all inspections met the rigorous standards required for UK infrastructure maintenance and safety audits.

Results & Deliverables

The project was completed on schedule, providing the client with a robust data set to inform their long-term maintenance strategy.

Key outputs included:

• Detailed Technical Reports: Comprehensive documentation of all structural findings, cross-referenced with sonar data.

• Risk Identification: Early identification of scour patterns, allowing the client to implement preventative measures before structural failure occurred.

• Asset Management Data: Digital profiles and visualisations to assist in the prioritisation of future remedial works.

Contact Us

For further information on our underwater inspection services or to discuss a specific project requirement:

• Website: diving-services.co.uk

• Telephone: +44 7455 123182

• Expertise: Commercial Diving, Marine Civil Engineering, & Sub-surface Inspections.

UK Diving Services Ltd have recently completed on behalf of Mott McDonald a river wall survey on the river Cam in Cambridge. The survey was requested by Architects designing on behalf of a local College. The waterway area was very exposed to the public venturing along the river in punts and canoes and traffic controls and risk assessments were implemented to reduce hazards to both the dive team and members of the public. The area was also environmentally sensitive and care was taken to avoid any negative effects to the surrounding environment.

UKDS have completed several underwater scour surveys with Stantec UK. The inspections were completed on behalf of Lanarkshire council to understand the condition of their structural bridge assets below the water line. 2D sonar was incorporated in the surveys which were in environmental sensitive areas

On instruction from North Norfolk Council and HOP Engineering, UK Diving Services have completed an extensive inspection of the structural steel pile supports beneath the pier head on Cromer Pier. The scour survey included underwater 2D sonar scanning and underwater imagery. The underwater condition assessment included inspection to the pier legs, concrete encasements and steel jackets as well assessing any previous scour measures previously implemented. The severity and extent of damage and or corrosion was recorded accordingly

UK Diving Services Ltd have been awarded the structural inspection contract on behalf of CBRE at Battersea Power Station Coaling Jetty in the heart of central London on the tidal river Thames. The survey and maintenance schedule includes a condition inspection of the Transport For London (TFL) clipper mooring pontoon, fenders and piles.

The inspection of the 150m long structure adjacent the tidal river wall and adjacent the power station outfalls will include an underwater structural condition survey of the submerged timbers identifying any areas where the pier legs may benefit from structural bracing and or repair. An underwater sonar survey will be deployed to better understand the riverbed profiling

UK Diving Services Ltd are a leading UK underwater investigation company specialising in the assessment of assets threatened by scour and or undermining. Our teams work in some of the most challanging underwater environments to locate, assess and repair damaged marine assets. UKDS utilise underwater imagery both conventional and sonar to understand environments where scour and its long term effects are present. Our underwater systems are developed to measure undermined scour voids in deep or fast flowing water and establish methods of repair.

Our dive teams recently provided underwater support to Scotland's highways and infrastructure. UK Diving Services were contracted to provide sonar, topographical surveys and river bed profiling following severe flooding which closed one of Scotland's trunk roads. The water levels were extremely high with fast flowing water threatening the integrity of the structure and making progress difficult. Scour investigations were provided along with structural evaluations of the bridge primary components such as abutments and piers etc. Water levels were above the steel deck beam pictured at the upper left of the picture!

UK Diving Services have provided underwater support services to AECOM infrastructure and engineering company. The purpose of the works was to determine the underwater condition of the concrete structure and better understand the river bed profile including locating any scour holes or undercut and or undermining from scouring issues. Any scour protection measures were to be recorded using digital 2D sonar imagery in nearly zero visibility murky silty water. 

UKDS have secured several bridge inspections within the Scottish Borders contracted to Stantec UK. The surveys include underwater inspections of the submerged structural elements to determine scour and or undermining as well as better understanding of the structural integrity of the bridge piers, abutments and river beds. 

Our surveyors, engineers and environmental experts once again provide the groundwork for UK infrastructure with sustainability focused goals and environmental science woven into all our projects.

UK Diving Services have provided an underwater 3D sonar investigation of an historic masonry arch bridge structure on behalf of WSP and Kier. The sonar survey comprised of 56no x 360 degree individual scans knitted together to form an accurate underwater point cloud image of where the bridge interface's with the riverbed. The underwater sonar images were  knitted with surface laser scanning data to provide a complete data package of the entire both above and below water structure. A detailed topographical survey was also recorded.

Sonar is quickly becoming the tool of choice for aiding the underwater inspection of bridge structures. They have the ability to create detailed high resolution images around bridge footings, piers, cut water's and abutments including other areas such as sea walls, dams, river walls, ports and harbors. Sonar inspections provide valuable information on underwater submerged bridge structures which may include details of damaged components, water depths and structural measurements including undercut and scour measurements. They are ideal for creating detailed scour surveys in difficult water conditions. Underwater subsea assets and infrastructures worldwide need to be surveyed regularly for problems caused by conditions including undercut, scour, impact and or structural damage. Corrosion, debris and other causes can also cause major problems needing regular inspection. Diving surveyors and inspection engineers will provide visual surveys when water conditions are clear allowing easy working. When conditions worsen and visibility becomes impaired due to murky water a more tactile hands on survey is usually required. These underwater environments can present many hazards to working divers and fortunately todays technology gives the option to reduce risk with the aid of modern sonar devices. The detail and accuracy of these sonar devices can create safe working environments for divers prior to water entry by simply understanding what the area looks like prior to getting wet. These sonar systems provide high accuracy 2D and 3D sonar scans of underwater structure and provide environmental data in zero visibility water conditions. 

Our sonar surveys provide high resolution detailed images and video in any water conditions. The sonar services we offer include simple 2D data imagery and live video imagery through to more complex 3D point cloud data. Our sonar transducers can be attached to or deployed from small work vessels, attached to poles, tripods and,ROVs. Each sonar whatever the deployment method can be used for principle and general inspections, environmental and structural evaluations and real time underwater works monitoring.

UK Diving Services have won a tender to inspect 4no x bridge structures on behalf Angus Council. The structures vary in design from modern steel to historic masonry brick arch construction. The assets cross both tidal and non tidal waterways with one being confined space entry.

On inspection of a complex culvert system UK Diving Services confined space team discover extensive damage to a reinforced concrete invert due to scour followed by undermining. Our inspectors measured the voids underneath each area of concern and recommended urgent remedial works to prevent further damage threatening the integrity of the structure. All data was recorded in accordance with the Roads & Bridges Manual BD63/17 and BD 97/12 and a scope for remedial works implemented. UKDS is one of the UK's leading bridge inspection companies for investigation of underwater assets.

UKDS have provided work boats and pontoons for urgent repair and maintenance works at Prudhoe Paper Mill. The recently refurbished sludge/pulp tank required water baffles to be adjusted to allow a more even flow over the circular perimeter of the tank. UKDS provided trained commercial divers and boat skippers to assist with the project which was completed ahead of time.

UK Diving Services Ltd have provided a complete under and above water model of Thrapston Nine Arches Bridge to determine if any structural damage or underwater scour is present. Our diving team and underwater surveyors scanned the structure over a period of 5 days. Deliverable's were laser and sonar data in .pts and .xyz files allowing viewing of a point cloud.

UK Diving Services Ltd are working with Kier WSP on behalf of Northamtonshire Highways providing diving services supported by hi resolution three dimensional sonar surveys on a nine arch masonry stone bridge. The 3D mapping data in .xyz format for point cloud will show undermining and scour holes within the structure and adjacent areas. The invert, piers and abutments are scanned by placing a transducer on a tripod as well as fixing to a vessel using gps. 

UK Diving Services Ltd have recently completed 4no x underwater principle inspections for Kier WSP on behalf of Northamtonshire Highways. The surveys from our dive service identified scouring and undermining to some of the upstream elements of the structure. Repairs included placing of underwater scour packs into voids beneath the masonry structure and placing scour protective rock up to adjacent bed levels. This is a typical example of how important dive services are when protecting underwater structural assets from scour and undermining

UK Diving Services have successfully provided dive surveys to numerous bridge structures across Kent, Sussex, Surrey and Scotland. The surveys were to assess the condition of recent remedial works undertaken at each structure. Written reports were provided including detailed digital photography and video.

For the third consecutive year UK Diving Services have provided underwater services on various Bridge assets throughout Scotland on behalf of Transport Scotland.  UKDS provided a full underwater scour and condition surveys of many of the bridge structures and concluded that urgent repairs were required to several of the structures. Some of the bridge structures exhibited deeper channel piers where sea bed levels had dropped and the supporting Hercules piles had become exposed.  Repairs were undertaken including concrete grouting and the placing of extensive rock armour. Rock is a good fundamental scour protection however by protecting one pier generally tends to pass the scour problem to the next adjacent unprotected pier. We have now introduced sonar backed diving surveys for monitoring a structure's scour protection. 

UK Diving Services Ltd have undertaken a full underwater sonar and diving inspection of the intake screens on behalf of Zenith for Scottish Power. The intake screens  and forebay were at 12m depth and clear of debris. NDT inspection of the steel work was carried out. 2D sonar provides helpful underwater images to back any diving inspection or survey

UK Diving Services Ltd have undertaken an internal inspection of of a decommissioned concrete sewage effluent pipe. the purpose of the survey was to understand the condition within the pipe to determine if the structure is structurally sound to support plant crossing the adjacent access road. The pipe was in a flooded state during inspection.

UK Diving Services recently completed a variety of principle bridge inspections on behalf of ATKINS engineering. The works included underwater inspection and sonar surveys of two large multiple arch bridges spanning the Ladybower reservoir. The structures were built during the second world war prior to damming and flooding of the valley and villages below. An interesting project that demanded extensive planning and skill due to the depth of the bridge piers which met bed level at 31m.

UK Diving Services have been contracted on behalf of CAPITA to provide a river wall condition survey to determine suitability prior to the construction of a new road to link to the new River Wear crossing. The new road bridge will be a two span cable stayed bridge with an A-frame pylon rising to 105m crossing the River Wear between Castletown and and Pallion. The new bridge will have two lanes of traffic in each direction, plus cycleways and footpaths along its full length. Our dive team inspected a variety of structures along the wall from concrete piers and sheet pile walls to areas of timber fenders and rock embankments.

UKDS have secured a river wall inspection in Sunderland north east England. The survey involves underwater inspection of the tidal river wall over several hundred meters. Due to likely poor visibility within the area divers will be using tactile probing methods of inspection backed by 2d sonar images.