The Regulatory Implications of PREDicT™ – A Shorter, Less Expensive Path to Regulatory Closure


The Regulatory Implications of PREDicT™ – A Shorter, Less Expensive Path to Regulatory Closure

James Ash, P.E., LSP and Jessica Englehart, P.E. (GEI Consultants, Inc.)


James Ash, P.E., LSP

GEI Consultants, Inc.

Speaker Bio:

James Ash is a senior vice president at GEI Consultants, Inc. He has been assisting utility clients with the investigation, remediation, and regulatory closure of former MGP sites for over 20 years.


The recent breakthrough in DNAPL recoverability evaluations and high resolution mobile NAPL interval measurement, PREDicT™, will greatly reduce the cost of closure for many former MGP sites. Another paper proposed for this conference will focus on the method for calculating the transmissivity of DNAPL at former MGP sites. This paper describes the regulatory implications of this new development. Coal tar DNAPL is frequently present in the subsurface at former MGP sites and poses significant remediation challenges. It is not easily destroyed or treated using in-situ techniques, and can take years – even decades – to remove using mechanical methods. It frequently has high viscosity, resulting in very low transport velocities in the environment. As a result, it is often the last condition remaining at a former MGP site after other potential exposure pathways have been addressed. The new patent pending technique proposed for evaluating the transmissivity of DNAPL, PREDicT™, will allow a direct measurement of the recoverability of DNAPL and is likely to demonstrate that active recovery is not necessary at many former MGP sites – resulting in a shorter, and less expensive path to regulatory closure. In states including Massachusetts, Iowa, Kansas, Michigan, and Virginia, evaluations of LNAPL transmissivity have been used to demonstrate when, and if, active LNAPL recovery is necessary and appropriate to achieve regulatory closure. Using PREDicT™, DNAPL transmissivity evaluations are conducted using the same general hydrogeologic and fluid dynamic principles used in LNAPL transmissivity evaluations. Because the methodologies and principles are consistent, the transmissivity site closure metrics used in existing regulatory LNAPL guidance will be applicable to DNAPL sites. This will allow many former MGP sites to achieve regulatory closure.


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