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Site characterisation Assessment of risk Determination/validation of remediation Define the context an Identify remedialReview data set the objectives objectives to mitigate unacceptable risks Carry out phase one desk study Identify feasible Is data reliable? No remedial options (eg appropriate response Develop initial conceptual site zones, variable/ Undertake model and undertake preliminary unrepresentative further risk assessment groundwater levels) intrusive investigations Yes No Undertake Has development of furtherNomodel included site Has sufficient dataintrusive specific factors that Has monitoring been investigations been obtained to allow No may influence gas/ carried out under and/or the selection/design of vapour regime? varying conditions monitoring appropriate remedial likely to influence the and sampling solutions? gas vapour regime? Yes Yes Yes Detailed evaluation of remedial options No Have these factors identified the potential Results sufficiently No presence of consistent/reliable Develop a remedial strategy gases/vapour Yes Design, implementation Yes and verification of remedial measures Source(s) of gas(es)/ No Review No vapour(s) identified? remedialamendAre there potential unacceptable risks? strategy No Is post installation/ Yes construction monitoring required? Yes Extent of source(s) No Identify further actions to clar- established? Yes ify potential unacceptable risks Undertake post installation/ Yes construction monitoring Establish objectives of any Refine conceptual site model further investigations No Is the monitoring Consider odour and toxicity and incorporate data acceptable? Carry out further investigation into risk assessment as appropriate (desk based/intrusive/monitoring Undertake appropriate risk assessment Yes modelling. Define gas regime Completion/ validation report Green Amber Red No Does risk assessment demonstrate corrective action required? No further action No further action No further action required required Yes required Figure 2 The process of managing risks related to hazardous ground gases (from Wilson et al, 2007) 21


evolutionwinter2012
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