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Introduction and background
The understanding of the fate and transport of contaminant plumes from contaminated sites in limestone aquifers is important because they are a major drinking water resource. This is challenging because they are often heavily fractured and contain chert layers and nodules, resulting in a complex flow and transport behavior. Modeling can help with the interpretation of measurements and the prediction of the contaminant behavior in the aquifer. It can be used as a tool to advance the conceptual understanding and for decision support for risk assessment and the planning of remedial actions.
Several fracture flow and transport models are available for the modeling of contaminant transport in fractured media. This wiki aims at giving an overview of modeling tools that can be used for the interpretation and prediction of flow and transport processes in fractured limestone aquifers. The different concepts will be presented in the chapter Model concepts. They will be compared for their suitability to simulate field data and to represent typical features of fracture flow and transport using a field example (Example Akacievej).
This work is based on a collaboration project between DTU Environment and the Capital Region of Denmark (Region H).
Overview
Available model concepts for flow and transport in fractured aquifers
Model concepts
Model setup for fracture flow and transport in limestone aquifers
Example: Setup of models for a field site (Akacievej, Hedehusene) The models are compared for a contaminated site in Denmark, where a plume of dissolved PCE has migrated through a fractured limestone aquifer. Numerical modeling was integrated in the planning of field tests and in the update of the conceptual model. Field data includes information on spill history, distribution of the contaminant (multilevel sampling), geology and hydrogeology. To describe the geology and fracture system, data from borehole logs, packer tests, optical televiewers and cores was combined with an analysis of local heterogeneities and data from analogue sites. A pump and tracer test with contaminant sampling was performed at the site to determine flow and transport parameters of the fractures and matrix and to quantify the contaminant distribution in the aquifer. Different models were used for the planning and interpretation of the pump and tracer test.
