Enabling dry excavations near Coventry with wellpoint dewatering

Project Summary

The project involved excavations below the groundwater level to construct four new culverts. The total perimeter of the excavation was 300 meters, extending to a depth of 3 meters below ground level (mbgl). Ground investigation information indicated that the excavation would be in Alluvium (SAND and gravelly CLAY) with the groundwater level encountered at 0.4 mbgl. Considerable dewatering was required to bring the groundwater level down to below the excavation level. This was necessary to provide dry and safe working conditions and to prohibit slope instability.

The Dewatering Strategy

Project Dewatering Limited collaborated closely with a specialist in designing dewatering systems to ensure the success of the project. The primary goal of the dewatering system was to lower groundwater levels in the permeable Alluvium. The required drawdown was 3.1 meters, ensuring the groundwater level remained 0.5 meters below the deepest excavations. The proposed system consisted of an array of wellpoints positioned external to the perimeter of the excavation. These wellpoints were spaced at 2-meter intervals and reached a maximum depth of 6 meters. The wellpoints were pumped on by 2 no. vacuum wellpoint pumps.

Outcome

This section of the project has concluded without any delays. The wellpoint dewatering system performed as expected, successfully lowering the groundwater level below the excavation formation level. After the culverts were constructed, the wellpoint system was switched off and decommissioned.