Intrusive Investigations & Risk Assessment

To accord with CLR11, PPS23, NHBC 4.1, and other relevant guidance, the findings of the desk study and site walkover, together with an appreciation of the proposed future land use, are used to design the intrusive ground investigation.

 Intrusive ground investigations typically comprise excavating trial pits and/or drilling boreholes so that the underlying ground conditions can be inspected and samples retrieved for chemical and/or geotechnical testing.

All our investigations are supervised by experienced geo-environmental and/or geotechnical engineers in order to maximise the data collected, and record the ground conditions exposed by the exploratory holes.

The range of investigation techniques that JOMAS offer include:

• Inspection pits - Shallow hand dug holes to inspect near surface soils or existing foundations.
• Mechanically excavated trial pits – for deeper trial holes.
• Window/windowless sampling - Narrow diameter boreholes that can be undertaken in confined spaces, and used to drill shallow boreholes.
• Cable percussive boreholes - The drilling method for deep boreholes in soils and soft rocks.
• Rotary core boreholes - Method for drilling in hard rock.
• Dynamic probing - A method of measuring the penetration resistance of the soil.
• California Bearing Ratio (CBR) testing - An in-situ test undertaken to assist in the design of road construction.
• Laboratory analysis - Chemical and geotechnical testing of samples.
• Groundwater monitoring - Measuring water levels and retrieving samples for laboratory testing.
• Gas monitoring - Portable analyser is used to measure ground gases such as methane, carbon dioxide and oxygen.
• Soakage tests - A soil permeability test used to provide infiltration parameters for the design of soakaways for surface water disposal.

The ground investigation and laboratory analysis is followed by generic quantitative risk assessments (GQRA) and/or detailed quantitative risk assessments (DQRA), for soil quality appraisal.

The groundwater impact assessment is undertaken in accordance with the EA Hydrogeological Risk Assessment for Land Contamination.

Data from the intrusive investigation enables the conceptual model developed in Phase 1 to be updated. Potential pollutant linkages are identified, and the need for further works (if any), highlighted.

JOMAS are pragmatic in our approach. We carefully manage our scope to prevent unnecessary works.