Detailed Quantitative Risk Assessment

Chalk Core
Chalk Core Showing Tar Contamination
Rotary Rig Lorry
Rotary Core Drilling Rig

The site in Hertfordshire is currently used as a storage and logistics yard sited on land which was formerly a gas works.  Near surface soils remediation had been undertaken at the site.  However during geotechnical investigations (undertaken by others) for a proposed building extension, deeper soils were found to be contaminated with various hydrocarbons (PAH, BTEX and TPH) and tarry materials.  These were found through monitoring work to be having an adverse impact on water quality in the underlying Principal Chalk aquifer.

Discovery CE was then commissioned to undertake a detailed quantitative risk assessment for impacts of hydrocarbons on controlled waters in order to define the degree of contamination and what remedial measures might be required.  Discovery CE agreed a scope of investigation works with the Environment Agency (EA) to sample and assess deep chalk cores (up to 21 m bgl) for contamination and subsequently monitor, test and assess contamination in the groundwater in accordance with the EA’s Remedial Targets Methodology.

RTM Example

Modelling parameters were agreed with the EA for use in calculating remedial targets.  The work is ongoing and is expected to be concluded by the middle of 2016.