Overcoming Groundwater Challenges: Richter's Temporary Works Solution for a Southampton Development

Published: 05/04/2023 09:55

Inland Homes are developing a residential development in a waterside location at Chapel Riverside, Southampton. The project involved the construction of a circular tank; 25 m diameter, 15 m deep shaft for storm water flows. Richter’s role was to develop temporary works measures to deal with groundwater problems to allow the shaft to be built to its final depth.

The geology of the surrounding area was very challenging due to the shaft sinking occurring through saturated fine sands of the Wittering Formation. This material is difficult to work with due to the risk of running sand conditions that are likely to occur if groundwater is not adequately controlled. The risks were heightened due to the groundwater level being close to ground level and tidal due to the influence of the nearby River Itchen.

To develop a temporary works solution to overcome these challenges, Richter carried out a desk study of the geology and reviewed records of nearby projects in similar ground conditions. An outline dewatering design was developed based on an array of pumped wells, with the design refined using data from field pumping tests, carried out during the initial stages of dewatering. A key constructability problem was the concern that the borehole used to form the dewatering wells would be unstable making it difficult to install effective filters. Richter addressed this problem by specifying specialist preformed filters that were manufactured in Holland and could provide effective filtration even in unstable conditions. To reduce the impact of dewatering on local groundwater conditions, the pumped dewatering water was returned to the ground via recharge wells.

Richter's detailed understanding of the ground conditions and experience dealing with such challenging fine sands, and the approach of using field data to refine and confirm the dewatering design allowed the contractors to complete the shaft to its design depth in dry and stable conditions. This successful construction allowed the storm water system in the area to be upgraded ready for the new development to be completed.

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