A Phase III Detailed Site Investigation would be required on a project where a Phase II site investigation is commissioned, some initial chemical and geotechnical testing is carried out and the results indicate that there is a requirement for further work, such as a site where significant levels of contamination are recorded. Exploratory holes are usually spaced around 25 – 50m apart depending upon the size of the site and any restrictions present. On some sites further investigation is then required to collect information at greater sampling densities & frequencies and at closer spacing between existing holes. This can provide more information about the underlying soils and there chemical contents which can have an effect on the quantities or soils that require removal or remediation at a site. We can ultimately save our client money by conducting a thorough phase III detailed site investigation and potentially reducing removal and remediation costs.
Phase III site investigations are not just limited to sites with significant contamination, but are also used on site where geotechnical information is required. I.e a phase II site investigation is carried out at a site and the ground conditions encountered are very variable and change significantly across the site, we would recommend that further work is carried out to gather more information between the existing exploratory holes. This information can be crucial to any foundation and substructure design. Without it structural engineers can over design foundations to cover all situations which can ultimately cost the client significantly more money. On the other end of the scale if foundations are designed without the correct information, then there can be a risk of total and differential settlement.
