Calibration and Reliability in Groundwater Modelling: Credibility of Modelling

(Proceedings of ModelCARE 2007 Conference, held in Denmark, September 2007). IAHS Publ. 320, 2008, 197-202.

Modelling the source zone depletion and plume development of a coal-tar contaminated site

FERNANDO MAZO D’AFFONSECA¹, PHILIPP BLUM¹, MICHAEL FINKEL¹, REINER MELZER² & PETER GRATHWOHL¹

1 Center for Applied Geosciences (ZAG), University of Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany

fernando.mazo-daffonseca@uni-tuebingen.de

2 URS Deutschland GmbH, Sutelstraße 2, D-30659 Hannover, Germany

Abstract The studied site is a former wood impregnation plant situated in northern Germany, at which the subsurface was contaminated with coal-tar DNAPL. The use of monitored natural attenuation as the site groundwater remediation strategy was evaluated by mathematical modelling. Consistency with reality and reliability of the modelling framework could be assured by combining innovative investigation methods, data interpretation methods and numerical modelling codes. Hydraulic conductivity distribution was estimated using MODFLOW and PEST. The DNAPL depletion and the respective contaminant emission were estimated according to Raoult’s law using the hydrogeochemical model MIN3P. The contaminant propagation further downgradient was quantified using the reactive transport package MT3DMS. Given the results of site characterisation and model predictions, there are significant indications supporting the effectiveness of monitored natural attenuation as a remediation strategy at the site.

Keywords groundwater contamination; modelling; remediation; monitored natural attenuation; DNAPL; coal-tar