Rapid response gets large retail and leisure re-development moving

3rd April 2024

Geoenvironmental • Geotechnical • Specialist Services

Ground & Water was invited to scope a Site Investigation for the re-development of a large site in west Surrey that has been home to a petting zoo, wildlife park and garden centre for many years. Given the underlying geology, infiltration testing was the priority and following a rapid response, the client was able to proceed to the design stage.

Our Client

Our client was working on behalf of a major leisure and retail business in Surrey.


A Desk-based review indicated the site is located on Head Deposits overlying Gault Formation.

An initial site investigation on other parts of the site revealed shallow Head Deposits, which comprised a gravelly sandy clay were noted across the area, with dark grey clays of the Gault Formation at depth. Given the potential for drainage issues it was decided to prioritise infiltration testing.


Our Challenge

Due to the fact the site is open to the public and very busy, the Site Investigation needed careful coordination with the client’s operations team; and it was becoming apparent the full scale of the SI needed for the full design of the scheme was too extensive without disrupting the businesses. The SI needed to be broken down into stages.

The Ground & Water Approach

The project team broke down what was required, along with timescales and put together an adjusted scope so that we could provide the infiltration data, which was the most pressing part of the design.

Soakaway testing

The engineering team attended site with a digger and water tanker to carry out BRE365 soakaway testing at varying depths to understand if conventional soakaways would work or if shallow permeable paving could be utilised. We also carried out PAK spraying of the existing car park to determine if any coal tar was present, as this was required as part of the waste costing exercise of the build.

The PAK spray testing showed no evidence of coal tar, meaning traditional waste budgeting could be utilised. The soakaway testing was found to be unsuccessful to BRE365 standards, meaning other drainage solutions needed to be designed.


The Outcome

A quick turnaround in prioritising site works, completing the most pressing work, and reporting, meant that in the early stages of the project design, the structural team could make informed decisions about a new drainage scheme and move forward with their design. All this was completed with minimal disruption to the client’s business.

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