Geotechnical & Geoenvironmental Ground Investigations
Applied Geology has extensive experience in the design and execution of both single purpose and combined geotechnical and geoenvironmental ground investigations. The extent of individual projects undertaken ranges from a single trial pit, to complex multi-phased investigations utilising conventional and innovative techniques on both greenfield and brownfield sites.
In many cases, ground investigations are designed by Applied Geology and are based on the initial Phase I Desk Study previously undertaken, though Applied Geology is also commissioned to undertake investigation works by other consultants and specialists to their specifications, using its in-house drilling and testing resources.
Applied Geology was approached by a developer who planned to erect an industrial unit on a site he had purchased in Gloucester. He was aware that the site was a former landfill but had been asked by the Local Authority to provide them with evidence that he knew the risks he was taking on and that he knew how to mitigate them.
Applied Geology was initially asked to prepare a Phase I Conceptual Model for the site based on the plentiful data that existed from previous investigations on and around the main landfill site. The Conceptual Model identified a number of pollutant linkages, these being:
- End users of the site were at risk from hazardous gases generated both on and off the site.
- End users were also at risk from contaminants.
- It was clear that similar gas producing soils existed across the former landfill site. It was assumed that any surrounding properties had been constructed with gas protection measures to mitigate any risk of landfill gas migrating from the known source on this site.
- An adjacent small water course and an underlying minor aquifer were identified as sensitive groundwater targets that were at risk and hence a groundwater risk assessment was needed.
A physical investigation of the site was then undertaken to confirm the soil profile and to allow the installation of monitoring probes. Shallow samples were taken and tested for potential contaminants (total and leachate) along with deeper samples from pits and boreholes. The boreholes yielded data for a pile design and the monitoring of the soil gas and groundwater within the probes yielded valuable data to allow a detailed risk assessment to be undertaken. Following this assessment the following works were undertaken:
- A contractor installed and commissioned gas control measures within the unit based on a Low Energy Clean Air Blanket solution.
- Applied Geology confirmed that prior to piling and construction work the site was raised from the level where the boreholes were sunk. Three hand-dug trial pits were excavated and proved a cover of 300 to 400mm of granular fill overlying an imported clay fill which was proved to a depth of at least 150mm. The clay fill was sampled and tested and the results used in a subsequent groundwater risk assessment. The cover also effectively cut off the pathway to the end user of the site.
- Discussions with a member of the design team involved in the construction of the unit directly to the west confirmed that gas control measures were indeed undertaken.
- The architect for the project produced an ‘As Built’ drawing showing the areas of hardstanding and their make up and these conformed to the assumptions made in the P20 Groundwater Risk Assessment undertaken during the investigation phase. This was accepted by the Environment Agency.
Following production of a validation report the Local Authority and Environment Agency were happy to sign the site off. The developer has since returned to Applied Geology to undergo the investigation of a larger adjacent plot.