Deepwells at Lapps Quay
Ground conditions and installation
- Client
- Howard Holdings plc
- Main contractor
- PJ Hegarty & Sons
- Consultants
- Walsh Goodfellow
- Dewatering subcontractor
- WJ Groundwater Ltd
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The site is 100 m by 60 m in plan adjacent to the River Lee. This mixed use hotel and office development had a requirement for a double basement car park with a formation level at 7.5 m depth. Ground conditions comprised gravels with tidally influenced groundwater levels reaching up to ground level. Sheet pile side support was installed to 17 m depth, not sufficient to reach the base of the gravels. WJ designed and installed a deepwell dewatering system comprising 24 wells to 15 m depth. The performance of the system was monitored using vibrating wire transducers installed in piezometers located both inside and outside the sheet piles and in the adjacent river to monitor tidal response. The extraction flows of 200 l/s were monitored using electro-magnetic flow-meters.
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Key words
- property development, gravels, deepwells