The crossing of surface water streams is a major challenge in any pipeline construction. Each crossing is a unique project in itself and depends on local parameters. The design of the structure, the selection of technology and work management is always preceded by an in-depth study of local hydrology, hydrogeology and topography.

The methodology is chosen strictly according to the findings of the local study.

Pipes need to be laid down so as to protect them against external damage and wash-out by the stream's current and to ensure their stability. Moreover, the pipeline must continue to operate without failure in case the streamway is changed or the bed has sunken.

It was equally important to ensure that the crossings have the least possible environmental impact (e.g. to prevent bank erosion or instability of flood dykes) and do not limit navigability.

Note that any repair work performed on the pipeline over or under a surface stream is inherently complex, labour-intensive and extremely expensive. Hence, the selection of technology and quality of workmanship can never be overestimated.

One of the interesting methods used in the Polish section of the transit pipeline has been microtunneling.

This consists in drilling a microtunnel for the casing followed by the gradual insertion of the pipe welded section by section in a chamber mounted on the bank. This method was successfully applied on the river Warta and Skrwa. Other river crossings involved the use of the traditional open trench method.

The crossing of the Vistula river posed a major engineering challenge. The project was unique in that the trench had to be excavated in a very wide river for a very large pipe diameter (1400 mm). Two lines of the underwater section (primary and back up line) are 1300 m long each. Two overland sections of more than 1200 m are additional pieces of the project.

The extent of the earth moving works is another measure of the project size. Some 1.3 million cubic metres of earth have been removed from the site, of which approximately 0.2 million cubic metres (including rock boulders of more than 1 m across) have been extracted from the river bed. It took more than 30 hours to place the 5,000 t "syphon" (1400 mm pipeline in an 18 cm concrete casing) in the river bed trench.

Specialised equipment was deployed (dredgers and ditchers) to support the method of pulling the syphon into the underwater trench. The work involved the use of scuba divers and military engineers.