Groundwater Management Plan
The Groundwater Management Plan combines and summarises the results of integral modelling and measures necessary to ensure good groundwater conditions in Stuttgart. It includes a forecast of how contaminant loads and migrations in the groundwater in the future will develop. The plan consists of reports, maps, databases and the visualisation tool MAG-IS. The Environmental Authority is provided with an important basis for future efforts in reducing CHC contaminants in the mineral springs, and in the limestone aquifer “Upper Muschelkalk”. To achieve the restoration goal which is the natural purity of the mineral springs in the foreseeable future, priorities in processing groundwater remediation as well as contaminated site remediation are suggested.
The Stuttgart City Council acknowledged the implementation and financing of the groundwater management plan developed in MAGPlan on 1st July 2015.
The groundwater management plan consists of:
A conceptual model of groundwater flow and contamination processes,
A 3D numerical flow and transport model,
An IT-visualisation tool for numerical modelling results,
A groundwater remediation concept for the inner city of Stuttgart.
Further project results:
The „Vitreous aquifer“ for public relations including a strata model for 3D visualisation of the underground conditions,
Two project films
Guidance document for integral contmainated site management,
Guidance document for proportionality review of long-term pump-and-treat measures,
Guidance document for detection and evaluation of isotopic fingerprints.
Procedure during the modeling of the contaminant distribution and transport:
Contaminated load and transport processes (2012)
Conceptual contaminant and numerical groundwater transport model enabled a spatial overview and rough delineation of major contaminant plumes. Indications for vertical exchange processes between aquifers were derived from spatial distribution of hydro chemical parameters. An interpretation of possible biodegradation processes was done on base of isotope fingerprinting data in context with hydro chemical conditions and distribution of CHC compounds. The numerical model plausibly reproduced the overall contaminant input and release. Furthermore, results showed a satisfactory compliance to recorded mass reductions of performed remediation measures. Nevertheless some remarkable inconsistencies remained for small scale detail modelling of selected sites; therefore a further adjustment was necessary.
Contaminant degradation and retention processes (2013)
Evaluation of the new drillings MAG 8 to MAG 12 and performed integral pumping tests enabled the localization of tectonic structures and fault zones, as well as the basis for understanding the spatial contaminant distribution and preferential transport pathways.
Three key contamination areas, presumed to have a predominant influence on the overall contamination in the project area, could be described in their present conceptual understanding, raising further open questions and knowledge gaps. Based on current working hypothesis, a further investigation need was defined.
The numerical transport model provided new results of a simulation of biologic degradation processes. Modelling was based on a mapping of different biodegradation zones in the conceptual model, elaborated by interpreting isotope fingerprinting results.
Some inconsistencies remained between conceptual and numerical model concerning important contaminant transport pathways, therefore, a further adjustment was necessary.
Remediation concepts and management plan (2014)
The actual state of knowledge enabled the evaluation of a reproduction quality of transport processes in the numerical groundwater model. A comparison of single sites’ key data with numerical modelling output showed remaining knowledge gaps.
After these corrections, the model was available as a prognosis tool for different remediation scenarios.
Based on this, the comprehensive conceptual understanding and its textual and graphical presentation in the final project documentation could be developed. Discussion focussed on a description of driving factors in the contaminant plumes and an allocation of contaminant sources to effective systems. Finally the single contaminant sources could be summarized to three main systems: one system between Stuttgart Southwest and Stuttgart City center and two systems in the direct upstream of high and low concentrated mineral springs respectively.
The numerical model determines the impact of each individual system by means of mass balance, subdividing between groundwater aquifers of “Keuper” and “Upper Muschelkalk”, and describes the leading processes.