Phase 2 Site & Ground Investigations
The Phase 1 Desk study will underline required follow on intrusive investigation works- Phase 2 Site/Ground Investigations. Intrusive works may involve a variety of exploratory techniques
- Intrusive techniques
- 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 / openhole boreholes.
The drilling is 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.
- 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.
Samples from the trial pits or boreholes are sent to a UKAS and MCERTS accredited laboratory for geotechnical testing and contamination analysis.
Laboratory testing and analysis
Typical geotechnical testing and chemical analysis 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 has included:
- 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
Following site works, where boreholes have been installed, a program of groundwater and ground gas / hydrocarbon vapour monitoring will be undertaken.
Upon completion of all site works, laboratory testing/analysis and monitoring a Phase 2 Intrusive Investigation Report will be compiled. This includes a summary of desk study information, all factual information (exploratory hole logs, laboratory results, monitoring results), description of the encountered ground conditions and recommendations for further investigation works where required.
A Phase 2 contamination site investigation will also include a revised conceptual site model, a qualitative contamination risk assessment and recommendations for Phase 3 remediation options where required.
A geotechnical ground investigation will also include recommendations for excavations, slope stability, concrete design, pavement design and preliminary foundation design. Reports may include recommendations for retaining structures and basements.
Contaminated land and geotechnical investigations can be combined into a Phase 2 Geo-environmental intrusive investigation report if required.