Diving operations at Zeesluis IJmuiden

Max Schellenbach and Jan-Pieter Steunebrink of Boskalis are responsible for the Boskalis diving department and the execution of the work for OpenIJ. They told us about the work of their divers.

Inspect, repair and supervise

The divers carry out underwater work and assist with a variety of other activities, such as concrete pouring, inspecting and - where necessary - repairing diaphragm walls. Max explained, “Our divers recently inspected over 26,000 m2 of diaphragm walls and touched up joints in the walls.” The divers do not only carry out underwater work, they also assist during important phases in the construction. Jan-Pieter added, “The divers were also present when the lock gates were manoeuvred into position in the lock gate chambers. Approximately 8 to 10 divers were working simultaneously when the lock gates were positioned into the gate chambers. The divers were there to assist the underwater process and were in constant contact with the workers above water to tell them whether or not all was going well."

A wide variety of possible underwater work

Professional diving is a very special career. The work is exciting but also very demanding. Max explained, “Every project is different. Our divers are now diving at the new sea lock at IJmuiden, but may be in Denmark, Norway or even Mexico next month. The possibilities of working as a diver are endless.”

Safety under water

Divers have to take into account all kinds of regulations and legislation with regard to safety under water. Each diving team, for example, consists of at least three divers so that they can take turns. Jan-Pieter agreed and added, “The divers arrive at the pontoon in the morning and then start the day with a cup of coffee and the daily ‘toolbox meeting’. During this safety talk, we discuss what kind of activities can be expected and if there are any specific items of concern. Every dive is different. That is why we make a Last-Minute Risk Analysis before we start. This way, we can understand and keep track of any risks during our working day. I have a lot of contact with the divers during the day. All day long, they keep me fully informed of the diving operations they are carrying out.”

Efficient diving

The divers alternate in shifts of three or four divers to work as efficiently as possible. Max explained, “The total diving time a diver can work underwater depends on the working depth. Dive tables indicate how long a diver can safely remain underwater. In the lock, the divers have to dive deeper than usual. Sometimes they dive as deep as 20 metres in the waters outside the lock. Because of this depth, they cannot stay underwater as long as they would otherwise. To extend the diving time, we dive with special air, namely ‘nitrox’. Nitrox is a type of air with more oxygen than in 'normal' compressed air. The divers who are not diving remain on the pontoon. By using special communication devices and by observing the air bubbles, they know approximately the diver’s underwater position. If he needs tools, the divers on the pontoon lower them in the water by means of a rope or by using the crane. On average, each diver works approximately 50 hours a week, based on applicable Labour Legislation.”

Special circumstances

It is very dark underwater, so divers always use head torches and cameras. Jan-Pieter explained, “All diving operations can be followed with cameras and sound equipment. If visibility is very poor, due to dredging for example, then everything has to be done by touch. You have to get used to it, but it actually goes very well.” The average water temperature in winter is 5 degrees Celsius. So the divers take special measures to keep warm. Max added, “To keep warm, the divers dive with a special dry suit. No water gets through and the skin stays dry. Divers wear special thermal clothing under this suit. The thickness of the thermal clothing allows them to dress as warmly as they like. In winter we also install a heater on the pontoon and in summer an air conditioner.”