ASI Group

A Record-Breaking Underwater Inspection

Paijanne Tunnel Inspection

In a bustling Helsinki district, home to a million residents, a critical challenge arose: differential pressure measurements signaled a significant blockage within a potable water supply tunnel. The following project demonstrates how the precise location and severity of the obstruction was identified by a comprehensive underwater inspection and survey.

In 1998, ASI Group was tasked with identifying and addressing a severe blockage in a section of the 120+ km of the Päijänne Water Tunnel in located in Finland. Using a remotely operated vehicle (ROV) equipped with sonar and underwater video and operated using a 10 km long umbilical, the location of the blockage was located and identified at a rockfall that was completely obstructing the tunnel. Only a limited amount of water was getting past the rock rubble, putting Helsinki’s drinking water supply at risk.

ASI team mobilizing the Mantaro ROV

ASI identified the location and extent of the main blockage and upon the request of the client, extended the inspection to cover the full length of the 120 km long tunnel. This provided them the opportunity to make plans and complete repairs to other locations that may only have become known when the tunnel was dewatered for the main repairs. ASI Group managed all aspects of the project, from coordinating local support services to conducting the inspections and producing a comprehensive report. Two world records were set on this project: multiple excursions to 10 km from a single access point and the inspection of a 120 km of submerged tunnel. ASI has since repeated and exceeded that ground-breaking 10 km excursion on multiple projects since then.

These points highlight ASI’s expertise in underwater inspection and maintenance, their ability to manage complex projects efficiently, and the importance of their work in maintaining critical infrastructure.

Click HERE to learn more about ASI’s services and extensive array of customizable ROVs which can facilitate the inspection of flooded tunnels and pipelines, thereby saving valuable time and resources while mitigating the hazards associated with de-watering such structures.