Kiel Canal has been used as a shipping lane for national and international navigation for over 100 years and represents the second gate to the Baltic Sea. In this regard, it directly competes with the Skagen route and is a competitive and eco-friendly transportation route for handling expanding trade flows in Europe by the increased use of short-distance sea traffic in parallel to the coast in the future. Together with the Small (Old) Locks, the Large (New) Locks of Kiel Canal in Kiel-Holtenau are the focus of operation and traffic.

Due to their age, the lock structures require refurbishing. It is planned to refurbish the Small (Old) Locks first, so that they are then available as bypass locks during the general refurbishment of the Large (New) Locks. The Small (Old) Lock is to be refurbished in two stages.

Stage A Protection work on Old Locks
In the course of investigations regarding protection work, IRS inspected the existing hydro-mechanical structures.  
As a result, it was determined that the hydro-mechanical structures and the drive technology no longer comply with the state of the art and show irreparable damage in some parts. For this reason, it is not possible to refurbish the existing hydro-mechanical structures and drive units in order to ensure continued, long-term use, and an appropriate new design and renewal is required in the form of complete refurbishment.

Stage B: Complete refurbishment of Old Locks
Complete refurbishment options were to be defined for the chamber system of the Old Lock and examined with regard to feasibility. In this regard, the hydro-mechanical structures as well as the mechanical and technical equipment had to be considered.
In a first step, IRS analysed possible gate variants in a feasibility/variant study, subjected these variants to a technical/economic assessment and identified the optimum solution as the target variant for the complete refurbishment of the Old Lock in Kiel-Holtenau.
This was the basis for a more detailed, more differentiated technical investigation of the target variant. The inverted mitre gate was identified to be the best solution and most innovative gate type for the complete refurbishment of the Old Locks; this type is capable of discharging loads from the backwater from both directions.

IRS provided engineering services for the hydro-mechanical structures as member of a joint venture with their partner WTM and DriveCon as subcontractor.

Scope of planning:
- Feasibility study and variant analysis regarding the lock gates, drive units and technical equipment
- Feasibility study regarding adapter designs for the existing floatable inspection gates
- Feasibility study regarding floatable walkways

Technical data:
- Chamber width: 25.00 m
- Highest backwater differential head: ~3.00 m
- Gate height (mitre gate): ~13.50 m