Warunki hydrogeologiczne na trasie I linii metra w Warszawie

Bronisław Paczyński



Two major water-bearing layers are found in the Quaternary series along the first line of the Warsaw Underground under construction. The first of them is situated close to the terrain surface, usually 2-3 m thick and discontinuous. Therefore, it may be regarded as of limited hazard for both construction works and operation of the underground. The other layer, deeper seated and from a few to over 40 in thick, is related to Masovian Interglacial sands and gravels in southern part of the line, Mid-Polish Glaciation sediments in Śródmieście and northern part. The layer is usually situated below the level of underground tunnels. Moreover, it is partly drained when situated in proximity of an escarpment which (similarly as the Służewiec and Marymont depressions) represents the major zone of underground outflow. Both layers (but especially the upper one) are characterized by an increased mineralization (over 3 g/dm3) and shows of strong pollution.
Mottled Pliocene clays occur at shallow depths or even directly beneath covers in large sections of the line, from Świętokrzyska Str. to the Warsaw steelworks. The hazard of groundwater inflow to the constructions appears the highest in sections passing along the Służewiec and Marymont depressions, Marszałkowska Str., Ogród Saski Park, and southern Żoliborz. In these areas dewatering works may require abstraction rates of 20-150 m3/d. 100 m and zone of influence of these works may be 150-200 m wide (in comparison with the width of less than 50 m in other sections of the line).
Changes in hydrogeological conditions due to construction works may be rather small. They will usually include intensification of groundwater flow from upper layer to the lower, local deterioration of water quality, and some damming against tunnel walls in the Plac Inwalidów Square (which may result in flooding cellars west of the underground line).

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