In February 2020, EMS Geotech were commissioned by a local planning company on behalf of their client to undertake a Phase 2 Intrusive Ground Investigation in rural Herefordshire.
A Phase 2 Site Investigation can often be recommended following the findings a Phase 1 Desk Study. The purpose of a Phase 2 Site Investigation is to provide further information regarding the risks posed by development site or surroundings. In addition, Phase 2 investigations can also assist in further definition of ground risks. A Phase 2 Ground Investigation is very often the second stage of a phased contaminated land investigation which is often required to discharge planning conditions or remove objections, once planning permission has been granted.
Intrusive investigations can involve a variety and combination of exploratory techniques. Some of the most common methods of intrusive investigation used during a Phase 2 Site Investigation include:
• Hand dug pits, i.e. foundation inspection pits, shallow contamination samples;
• Trial pits, i.e. general investigation works, soakaway tests;
• Handheld window sample boreholes;
• Dynamic windowless samples boreholes;
• Dynamic cable percussion boreholes; and
• Rotary core / open-hole boreholes.
The aim of the investigation in Herefordshire was to provide advice on safe allowable bearing pressures to aid in foundation design. The proposed development was a two-storey house with associated gardens and parking on an area of land previously known to be an orchard.
This intrusive Phase 2 Investigation comprised of five windowless sample boreholes drilled within the footprint of the proposed development. Standard Penetration Tests (SPTs) were undertaken in all boreholes to compare soil strength across the site. The boreholes were logged, and geotechnical samples were taken in general accordance with BS5930:2015 and BS EN ISO 14688 by one of EMS Geotech’s Geo-Environmental Engineers.
The samples obtained on site were sent to various laboratories for geotechnical testing, including soil classification and BRE analysis to aid in the foundation concrete selection.
An interpretive Ground Investigation report was provided to the client which included the foundation recommendations necessary for the next stage of the development. The Phase 2 Investigation was completed on time and to budget and the house was subsequently built in the latter part of the year.