Case Study

Seawater disposal caisson


UK Operator


North Sea

AquaTerra was contracted to undertake a critical Seawater Disposal (SWD) Caisson workscope on a North Sea offshore platform. The initial scope involved the installation of restraint rigging onto the SWD caisson. However, during the inspection, unforeseen challenges emerged, leading to the need for a comprehensive solution to address the caisson's worsening damage.
The Challenge

Upon accessing the SWD caisson and conducting a visual inspection, AquaTerra's team discovered that the damage to the caisson had escalated beyond initial expectations.

The integrity of the caisson was compromised, posing potential risks to both the structure and the platform's operations.

The severity of the damage necessitated immediate action and coordination with onshore and offshore management to evaluate the situation and determine the best course of action.

Key Summary
  • The initial scope was to install restraint rigging onto the SWD caisson.
  • During the visual inspection, the caisson's damage was found to be significantly worse.
  • The job was halted to discuss the findings with onshore and offshore management.
  • Temporary restraint rigging was immediately installed as a backup for caisson support until a permanent solution was developed.
  • AquaTerra collaborated with onshore structural engineers to plan the installation of a trunnion into the caisson, utilising previous knowledge.
  • Revised documentation, including lift plans, incorporated the changes required for the trunnion installation.
  • Despite tough working conditions, the team worked extended hours for 7 days to complete the scope on time, ensuring a safe and efficient execution.
"Excellent achievement and another safely executed task by the AquaTerra team."
Platform Maintenance Supervisor
"The team demonstrated unwavering dedication & commitment throughout the project."
Maintenance Supervisor
"Well done, thanks to all for safely completing this work in a very professional manner."
Asset Manager
    The Solution

    Recognising the significance of the caisson's worsening condition, the job was immediately halted. AquaTerra liaised with both onshore and offshore management to discuss the findings, ensuring transparency and effective decision-making. As an interim measure, temporary restraint rigging was promptly installed. This temporary support provided stability to the caisson while allowing AquaTerra to develop a more robust, permanent solution.

    Leveraging their expertise and previous knowledge, AquaTerra collaborated closely with onshore structural engineers to design an effective plan to address the caisson's structural concerns. The team proposed installing a trunnion into the caisson, ensuring enhanced stability and long-term reliability. To accommodate the changes to the scope, AquaTerra generated new lift plans and updated all relevant documentation. These revisions incorporated the installation of the trunnion and support rigging into the project plan.

    Given the SWD caisson's critical role in the platform's operation, AquaTerra had to work within strict time constraints to minimise plant downtime. The team devised a meticulous schedule to expedite the repairs without compromising safety and quality. The worksite conditions presented additional challenges due to cascading water from the SWD caisson continuously raining down on the team. AquaTerra implemented safety measures to ensure the team's well-being while executing the installation. To facilitate the installation process, precise windows were cut at specified locations on the caisson, allowing for easy access during the trunnion and support rigging installation.

    The Result

    AquaTerra's dedicated team worked tirelessly, committing to extended hours for seven consecutive days to meet the challenging deadline.

    Thanks to their expertise, collaboration, and determination, the workscope was completed successfully and safely.

    The trunnion installation and support rigging provided a robust solution, ensuring the caisson's structural integrity.

    As a result, the platform's SWD caisson was restored to full operational capability, minimizing downtime and meeting the client's requirements on time.

    Get in touch

    Contact our expert team to discuss your requirements – we will be happy to help.