What Is A Phase 2 Site Investigation?

A Phase 2 Site Investigation may be recommended following the findings of The Phase 1 Desk study.  A Phase 2 Site Investigation provides further information regarding the risks posed by development site or surroundings. It can assist in further definition of ground risks and allows you to identify and quantify these risks. It allows for refinement of the Conceptual Site Model (a preliminary of which was produced as part of the Phase 1 Desk Study).

It 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.

Phase 2 Ground or Site Investigations require intrusive investigations and may involve a variety and combination of exploratory techniques.

What Is Involved In A Phase 2 Site Investigation?

A Phase 2 Site Investigation will be commissioned to physically inspect potential contamination sources and/or geotechnical hazards that have been identified in the Phase 1 Desk Study.

The condition of the soil, groundwater and surface water will be inspected through a variety of methods. These methods are site specific and are generally dependent on the Phase 1 Desk study.

What Intrusive Techniques May Be Used?

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.

Any drilling required as part of the Phase 2 Site Investigation will be undertaken by specialist sub-contractors under the close direction and supervision of an EMS Geo-Environmental Engineer.

Where necessary, monitoring standpipes are installed in the boreholes to allow subsequent groundwater or ground gas monitoring or sampling.

Soils are logged in accordance with British Standard BS5930:2015 and Eurocode EC7 by EMS’s trained and experienced Geo-Environmental Engineers.

In-Situ Testing Techniques

  • Standard Penetration Tests (SPTs) / Cone Penetration Tests (CPTs)
  • Dynamic probes/CPTs;
  • Hand Shear Vanes;
  • Indicative CBRs using DCP TRL Probe and/or Mexicone; and
  • CBRs using Plate load tests.

All samples taken from trial pits or boreholes are sent to a UKAS and MCERTS accredited laboratory for geotechnical testing and contamination analysis.

Laboratory Testing & Analysis

Typical geotechnical testing and chemical analysis relating to Phase 2 Investigations are outlined below, however, this list is not exhaustive:

Geotechnical soil and rock tests:

Moisture Content;

Atterberg limit (liquid limit, plastic limit, plasticity index);

Particle Size Distribution determination;

Triaxial shear strength / shear box;

Consolidation tests;

Bulk density, dry density, chalk density;

Uniaxial Compressive Strength;

Point load test;

BRE SD1 (pH, water soluble sulphate, total sulphate, total sulphur).

Contamination analysis for soil and water:

Heavy metals (arsenic, cadmium, chromium, hexavalent chromium, copper, lead, mercury, nickel, selenium, zinc)

Inorganic compounds (phenols, total cyanide, total sulphate, water soluble sulphate, total Sulphur & pH);

soil organic matter;

Organic compounds (speciated Polycyclic Aromatic Hydrocarbons (PAH), Total Petroleum Hydrocarbons (TPH) CWG or Banded, BTEX and MTBE;

Asbestos in soils and quantification; and

Ground gas and hydrocarbon vapours.

More specialist contamination analysis can include:

Explosives – Picric Acid (2,4,6 – trinitrophenol), Trinitrotoluene and Ammonium Nitrate;

Chemical warfare agents – Mustard Gas (2, 4, 6 – Dichloroethyl sulphide);

Phosphates in soil and leachable

Monitoring

Following site works, where boreholes have been installed, a program of groundwater and ground gas or hydrocarbon vapour monitoring will be undertaken.

Completion of the Phase 2 Site Investigation

Upon completion of the Phase 2 Site Investigation a report will be compiled with detailed information and findings from the investigation. This will include information such as soil analysis, water, gas monitoring and geotechnical data.

The Conceptual Site Model formed in Phase 1 will be updated to further refine pollutant linkages. A risk assessment will be produced based on the data compiled as part of the investigation (quantitative risk assessment). This will also include an interpretative report.

The interpretative report will present the findings of the site investigation and associated risk assessment relating to the specific requirements of the site.

How EMS Geotech Can Help

EMS Geotech’s experienced team of highly qualified consultants are competent in designing both cost effective and compliant investigations that target contamination.

All site investigations are undertaken in accordance with current guidance such as the recommended approach set out in the Environment Agency’s Model Procedures for the Management of Land Contamination (CLR11) and the British Standard Code of Practice Investigation of Potentially Contaminated Sites (BS 10175: 2011).

We have assisted a huge variety of different clients gain planning permissions and discharge planning constraints placed on development sites due to contamination.

 

phase 2 site ground investigations