Elbląg made safe thanks to the Gravity Drilling Rig – renovation of damaged sewerage

A Gravity installation rig is a device used in trenchless technologies for repairing and replacing sections of sewer pipes. In simple terms, the device allows new pipe elements (e.g. modular PP sections) to be inserted with minimal disturbance to the ground and surface — often using existing manholes and access points as the start and end locations. The term “gravity” refers to installing pipes with a gravity fall (typical for sanitary sewers), and the technology itself enables precise positioning and joining of elements in confined conditions without the need for deep excavations. This method is particularly useful in built-up urban areas where access is limited and minimizing disruption to residents is important.

The process usually includes several key stages: (1) technical assessment — CCTV inspection and measurement of the damaged section's diameter and length; (2) bypass preparation — temporary diversion of wastewater to a pumping system to allow work in a dry section; (3) site and access preparation — use of existing manholes or enlargement of an access opening; (4) removal of the damaged section and installation of the new modular PP pipe — components are sealed together in confined spaces; (5) tightness tests and acceptance — quality control, TV inspection and any necessary adjustments; (6) restoration of the surface and site cleanup. By using modular pipes and working from existing start manholes, execution time can be significantly reduced, but each stage requires careful supervision and testing.

A polypropylene (PP) pipe is commonly used in sewer rehabilitation due to its high chemical resistance, smooth internal surface that limits sediment buildup, and long service life (when installed correctly the works can provide several decades of use). In addition, modular PP pipes are lightweight and allow sealed connections to be made in tight spaces. It is important, however, that the work is carried out according to installation rules: good quality seals, correct seating in the existing manhole, control of gradients and performance of tightness tests. Differences in mechanical strength compared to some other materials and the need for additional protection on very heavily loaded routes should also be taken into account.

The “one day” execution time refers to a specific, short section and the particular conditions of the described location (available manholes, short damaged segment, quick site preparation, use of prefabricated modular elements). It is not a universal standard — the duration of works depends on the length of the section, the condition of the existing infrastructure, the need for surveys, the quality of existing manholes, ground conditions, the need to obtain permits and the complexity of the bypass pumping. In practice, works can take from a few hours for simple, short repairs to several days or weeks for larger rehabilitations.

Temporary diversion to a pumping system (bypass pumping) involves conveying wastewater around the work area using pumps and temporary discharge piping so that the work section remains dry. This requires selecting pumps with appropriate capacity, correctly sized and secured discharge pipes, monitoring pump operation, securing the site against spills, and ensuring power supply and an emergency pumping plan. In addition, environmental protection measures and notifications to relevant authorities are often required, especially when there is a risk of leakage or when works are carried out in a sensitive area.

In the center of Elbląg, on Stefana Okrzei Street, the MIDO team faced a task that required both precision and a rapid response. A damaged 200 mm vitrified clay sanitary sewer posed a real threat – its poor technical condition threatened not only interruptions in the system's operation but even ground subsidence under nearby buildings.

Renovation under pressure – without shutting down the city

We worked in the area of the WIK back facilities, where continuity of the network's operation was crucial. Long-term closures or excavations were out of the question. To ensure safety and maintain flow, the existing sewer was temporarily switched to a pumping system – which allowed us to carry out the work smoothly without interruptions in wastewater collection.

Modern modular pipe replacing the old vitrified clay pipe

The damaged 200 mm vitrified clay section was replaced with a 200 mm PP modular pipe. The modular technology enables quick and watertight connection of elements in confined spaces, minimizing disturbance to the surroundings. We didn't need to construct any new launch chambers – we used existing manholes, which shortened the work time and reduced costs.

Narrow conditions, difficult access – we solved it in one day

The biggest challenge turned out to be an undersized manhole cover that prevented the introduction of standard equipment. It was necessary to remove the paving stones and enlarge the access accordingly. We carried out the whole operation with full site protection, and after completing the work we restored the surface to its original condition – as if we had never been there.

Ecology and safety above all

  • no need for deep excavations → less environmental impact,
  • no traffic shutdowns → time savings for residents,
  • rapid response → minimized risk to nearby buildings.

The entire renovation, including site preparation, took one day.

 

Why is this so important?

In places where underground infrastructure is decades old, failures can occur suddenly and pose a threat to residents' safety. Trenchless technology using our Gravity Drilling Rig allows for immediate and effective response without creating chaos in the city, without interfering with existing infrastructure, and in a way that does not disrupt the peace and daily life of the city's residents.

 Location: Elbląg, Stefana Okrzei Street
 Pipe diameter: 200 mm PP
 Duration: 1 day
 Technology: Gravity Drilling Rig

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