SOCOTEC offers Ground Investigation Services at River Medway: Overcoming Access Challenges and Delivering Essential Data for Structural Design

SOCOTEC’S Direct Client: J.T. Mackley & Co Ltd

Client Info: Construction company specialising in civil engineering projects in the UK. Founded in 1927, specialising in coastal, fluvial, ports, harbours, water industry, flood defence schemes and water sector infrastructure maintenance. Client's Designer: JBA Consulting Ltd Designer Info: Environmental, engineering and risk management company that specialises in climate resilience, flood risk management and sustainable development. Client's Needs: Ground investigation to the southern and northern banks of the River Medway and within the river itself at East Farleigh, just west of the medieval East Farleigh Bridge, requiring the use of pontoon structures to facilitate overwater borehole drilling. They needed a contractor willing to undertake the works that entailed somewhat difficult access constraints.

Project objectives - The works were requested to obtain information to facilitate further detailed design of any necessary remedial works to the earthwork/retaining wall structure to the south bank and to help understand design and construction of the existing sluice gate foundations.

Scope of works - 6no. dynamic sampler with rotary follow on boreholes (BH1 to BH6) to a minimum of 15m depth or a minimum of 2.0m penetration into competent bedrock. These were located as follows: BH5 & BH6 on the south bank. BH3 & BH4 on the river and BH1 & BH2 to the north bank. 2no. hand excavated pits to 1.2m depth on the south bank of the river against the existing retaining wall to establish the ground conditions and to establish the design of the structure.

Timeline - Work commenced on 1st October and ran to 1st November. Work began on the south bank, which ran for a week. We then had to wait on the arrival of the pontoon structure at Allington Lock to load our single comacchio 205 rig and equipment onto the pontoon structure. This was then floated on the River Medway from Allington to East Farleigh on 23rd of October. The two overwater positions were then undertaken and completed within three days. Concurrently the north bank positions were also undertaken.

Challenges - Mackleys undertook the design of the pontoon that required detailed weights and volumes of equipment that we would use. We had to use a Comacchio 205 due to both its capabilities but more importantly due to its dimensions that would allow it to float on the pontoon and not endanger the many bridges between the loading point of Allington Lock and East Farleigh. Floating up river required careful and constant monitoring of the Environment Agency river flow rates. Heavy rainfall in October caused significant delays until a window of opportunity arose. We remained at a constant state of readiness from our Maidstone office for several days, our drilling crew and engineers ready to jump in their vehicles and mobilise to Allington Lock within 25 minutes. We also had to maintain high standards of ecological protection whilst operating on and near the River Medway. Both, Aquifer protection methods and silt capture and storage methods were employed throughout the project to protect the local environment. Another risk that had to be mitigated was the unexploded bomb risk to the area from World War 2. To mitigate this risk SOCOTEC employed a specialist contractor (UXO Operative) during the works to clear positions and to undertake down-borehole scans incrementally during the drilling works, to check positions were clear of magnetic anomalies (i.e possible bombs) The north bank also had difficult access. East Farleigh Bridge is a medieval structure that has little head clearance and thus most drilling rigs would not be able to transit underneath it. Even walking under it on the footpath requires you to slightly duck your head. In order to obtain information on the north bank, the first plan was to offload the rig from the pontoon structure from the river onto the footpath. This was later changed to tracking (some 2 hours) from the east at the only viable vehicle access position with a tracked dynamic windowless sampler rig along the footpath, to undertake BH1 and BH2.

Our Approach - We used multiple ground investigation techniques with multiple teams, often on standby in a state of readiness to react to the Client’s needs. Collaboration with the Client, design team and the Environment Agency was required to successfully complete the works. Experience, preparedness and attention to detail were essential to the project’s success.

Results - All of the required positions were successfully completed to depth. The works had been in the planning stage for some time due to the difficulty of access. Whilst other ground investigation companies may have looked at the task at hand and walked away, our collaborative attitude and expertise successfully delivered the project. Our drilling team and engineer's willingness to go the extra mile for the Client shone through.

Client testimonial - ‘SOCOTEC supported JT Mackley throughout all phases of the East Farleigh GI Project. Mackley was responsible for organising the floating plant, SOCOTEC in turn provided expert advice regarding drilling kit and methodology, to enable Mackley to suitably design the temporary works & plan the operation. The permitting process for this project was particularly arduous and delayed the start date several times, SOCOTEC kept their workforce & rig availability elastic throughout.

Once we finally made it to site, SOCOTECs performance was admirable as a subcontractor. SOCOTEC acted in mutual good faith when the works were delayed due to strong river flows. Flows varied on a day by day basis, sometimes with less than 6 hourswarning due to unpredictable and remarkably wet weather. SOCOTEC kept flexible throughout, ensuring that as soon as the window of opportunity opened up we could proceed with the works as planned. SOCOTEC adapted well when faced with change at short notice, carrying out their work diligently. That includes rapid response to methodology alteration to reduce risk to programme & works performance.

Their site team was professional throughout and back end support was also very good. High level advice was available when required which contributed to the GI works running as smoothly as site conditions would allow.’

Technical details - SOCOTEC Equipment Used: BH3, BH3, BH5 & BH6 - Comacchio Geo 205 Dynamic Sampler and Rotary drilling rig BH1 & BH2 - Dando Terrier Dynamic Window Sampler Rig Misc Equipment: TRL Dynamic Cone Penetrometer Equipment (to undertake probing of the retaining wall inspection pits). 3.5tonne trailer, 4x4 trucks. UXO operative’s magnetometer probe. Client Equipment: NATO Pontoon structures, commercial river work boat, mobile crane to load and off-load our equipment.

"This project demonstrated our impact and presence across the UK, showcasing our network of experts across different teams. We added significant value through partnership in this project, highlighting our collaborative approach. Throughout multiple project stages, we delivered a variety of solutions, demonstrating our comprehensive approach throughout the project lifecycle. We provided support throughout the project, going above and beyond for the client.  Safety was our top priority, and we consistently acted reliably throughout the project."

Worked collaboratively with the Client and the various subcontractors, to safely deliver the project successfully. Our expertise and knowledge during the planning stages assisted the Client with designing the mobilisation of the rig safely to the required positions. Protection of the public and the environment during the work allowed the positions to be completed with no incidents occurring, we undertook the works and left site with as little disturbance to the local community and ecology as possible.