Investigation Techniques

The scope of the Phase II Intrusive Investigation depends on the findings of the Phase I Investigation and may simply involve trial holes with chemical analysis through to boreholes with installation of monitoring wells for assessment of gasses and groundwater. The report refines the CSM and determines if risks are present which require further assessment or remediation. The most common techniques employed by Worms Eye are:

• Trial Holes, usually shallow excavations, by machine or hand dug, to inspect the shallow soils and collect samples for analysis.
• Dynamic window/windowless sampling, when deeper inspection of the ground and deeper samples are required, typically up to about 10 metres deep (depending on conditions), when monitors are needed, where access with larger equipment is difficult or to limit disturbance at the surface.
• Cable percussion (shell and auger) where deep boreholes, up to about 30 metres, and deeper samples are needed.
• Rotary boreholes (open hole or rotary cored) where drilling through bedrock is required.

Each technique has advantages and limitations which will be determined by your requirements, the Phase I Investigation, proposed development, potential contamination sources and risks, site restrictions and geology.

Laboratory Testing

Various gases might be present in the ground from natural sources (e.g. peat and coal) or from landfill sites and filled ground (e.g. quarries and reservoirs). These can migrate into buildings and confined spaces at levels which are toxic, asphyxiating or explosive.

Where potential on and off-site sources of landfill or ground gas are identified, we would typically install monitoring points and return to site to take regular readings, allowing the potential risks to be assessed. We generally recommend installing a minimum of three gas monitoring points, with monitoring for methane, carbon dioxide, oxygen and gas outflow over an agreed period of time. The findings form an assessment of the gas risk and determine whether protection measures are required, in accordance with BS8485:2015 + A1:2019, NHBC or CIRIA guidelines.

If no viable gas sources are identified in the Preliminary Risk Assessment, or the development is very small, the site may be assessed in accordance with CL:AIRE RB17 A Pragmatic Approach to Ground Gas Risk Assessment, and may be designed in-lieu of testing, under the right conditions. This is site specific and the risk may need to be re-assessed as the investigation proceeds.

Landfill Gas/Ground Gas Monitoring

Various gases might be present in the ground from natural sources (e.g. peat and coal) or from landfill sites and filled ground (e.g. quarries and reservoirs). These can migrate into buildings and confined spaces at levels which are toxic, asphyxiating or explosive.

Where potential on and off-site sources of landfill or ground gas are identified, we would typically install monitoring points and return to site to take regular readings, allowing the potential risks to be assessed. We generally recommend installing a minimum of three gas monitoring points, with monitoring for methane, carbon dioxide, oxygen and gas outflow over an agreed period of time. The findings form an assessment of the gas risk and determine whether protection measures are required, in accordance with BS8485:2015 + A1:2019, NHBC or CIRIA guidelines.

If no viable gas sources are identified in the Preliminary Risk Assessment, or the development is very small, the site may be assessed in accordance with CL:AIRE RB17 A Pragmatic Approach to Ground Gas Risk Assessment, and may be designed in-lieu of testing, under the right conditions. This is site specific and the risk may need to be re-assessed as the investigation proceeds.



Waste Classification

Moving waste soil to landfill can be expensive, therefore correct classification is important. Waste Classification and WAC Testing is required to satisfy the landfill operator that the waste soils are acceptable and a staged approach is recommended.

• Waste Classification based on contamination soil test results to determine if the soil is hazardous or non-hazardous.
• Decide where you want to send the soils and determine if WAC Testing is required. 
• Carry out WAC Tests to determine leachate levels and how the soils will behave in the landfill. This will establish if non-hazardous soil can be disposed at inert landfill or if hazardous soil can be disposed at hazardous landfill without treatment.
• Issue the Waste Classification Report and WAC Test results to the receiving landfill.

Waste Acceptance Criteria (WAC) tests on their own do not classify soils as non-hazardous or hazardous. They enable hazardous waste soils to be moved to the appropriate landfill or non-hazardous wastes to inert landfill. 

Drinking Water Pipes

If a new water supply is required, a risk assessment may be requested by the Local Water Authority to ensure correct materials are used for water pipes, and there is no risk to drinking water.. Worms Eye can undertake analysis and risk assessments to satisfy Water Authority requirements.

To prevent delays at a late stage, Worms Eye recommend, and routinely carry out, testing as part of the Phase II Intrusive Investigation.