Open Sump Pumping Method of Dewatering Excavations
This is the most common and economical method of dewatering as gravity is the main playing force. Sump is created in the excavated area into which the surrounding water converges and accumulates facilitating easy discharge of water through robust solid handling pumps.
Its application is however confined to the areas where soil is either gravelly or sandy. Since the bottom of the sump is situated at a level lower than that of the excavation bottom, it will abridge the seepage way along which groundwater from outside seeps into the excavation zone and as a result the exit gradient of the sump bottom will be larger than that on the excavation surface.
If the excavation area is large, several sumps may be placed along the longer side or simply use a long narrow sump which is called a ditch.