The Integral Groundwater Investigation Method: Motivation, Principles, and Application

1. Center for Applied GeoscienceApplied Geology The Integral Groundwater Investigation Method: Motivation, Principles, and Application Thomas Ptak Center of Applied Geosciences University of Tübingen Germany Brussels, June 25, 2004

2. Center for Applied GeoscienceApplied Geology Problems of Monitoring • Heterogeneous distribution of aquifer parameters and contaminants • Uncertainty of investigation results • Megasites • Present approaches for site investigation and remediation • either not reliable enough or not cost effective •  How to perform monitoring considering the WFD framework? Approach • New integral investigation based methodology (mass flow rate • and concentrations) • Assessment of the effects of aquifer parameter uncertainty on • the estimates of mass flow rates and concentrations • Assessment of NA potential, assessment of remediation measures • Delimiting of contaminant source zones and of zones absent of source

3. Center for Applied GeoscienceApplied Geology Source Zone and Plume Development • Physical heterogeneity • Hydrogeochemical heterogeneity • Irregular distribution of contaminant release • Complex distribution of contaminants within the subsurface Whittaker et al., 1998

4. Center for Applied GeoscienceApplied Geology Legend landfill site suspected (from history) derelict industrial site known derelict industrial site valley direction of groundwater flow mineral springs Challenges at Megasites • Multiple sources • Multiple plumes • Limited information • Multiple remediation options • Multiple cost-functions •  How to take ´optimal´ decisions?

5. Center for Applied GeoscienceApplied Geology • Megasites • Multiple sources • and plumes • Limited information • Start with an integral receptor perspective by defining control planes (CPs)

6. Center for Applied GeoscienceApplied Geology Plume Detection and Characterisation • How to implement control planes?

7. Center for Applied GeoscienceApplied Geology Problem: Plume Characterisation • Usually high-resolution data required Controlled DNAPL plume at Borden (Rivett, Feenstra and Cherry, JCH (49), 2001)

8. Center for Applied GeoscienceApplied Geology Source zone Individual contributions C Pumping well Isochrone t Superposition of individual contributions C t Integral Approach Plumes and Concentration Time Series in a Pumping Well • Pumping tests offer a possibility of integral investigation  What do local-scale or single concentration measurements mean ?

9. Center for Applied GeoscienceApplied Geology Transient Integral Scale Measurements • Concentrations and mass flow rates obtained

10. Center for Applied GeoscienceApplied Geology Combine concentrations and mass flow-rates in decision making ! Total mass flow-rate Ft (e.g. at site scale) might be a valuable additional decision variable: a) low conductivity, high concentration (e.g. source located in aquitard formation)  resulting mass flow rate Ft = C * Q[M/T] will be low  NO ACTION REQUIRED b) high conductivity, low concentration (e.g. source feeding into major aquifer system)  resulting mass flow rate Ft = C * Q[M/T] will be high  ACTION REQUIRED

11. Center for Applied GeoscienceApplied Geology Multiple Control Planes for NA-Quantification

12. Center for Applied GeoscienceApplied Geology Landfill Site in the Rhine Valley Contamination mainly CHC Aquifer thickness  15 m K  4·10-3 m/s I  0.001 6 pumping wells 2 pumping campaigns (15 days, 3 wells, each 3 l/s) Wells of first pumping campaign Wells of second pumping campaign Control plane, 180 m F F Treatment system Possibly contaminated area Mean flow direction Scale [m] 0 50 100 150 200 Example of Application (Ptak and Teutsch, 2000)

13. Center for Applied GeoscienceApplied Geology Applications in:Stuttgart, Rhine Valley,Bitterfeld, ... (D)Strasbourg (F) Linz (A)Milano (I)Bromberg (P)Borden (Canada)and at many other locations Example of Application  Backtracking from CP to source possible!  Source zone delimiting!

14. Center for Applied GeoscienceApplied Geology Example of Application in Stuttgart Capture Zones (Cycle I) • Concentration-time data of Benzene and ΣCHC from 19 wells • Numerical inversion of C(t) data using the code CSTREAM (Bayer-Raich et al., 2002) Jarsjö et al., 2002

15. Center for Applied GeoscienceApplied Geology Results for Benzene (Cycle I and II) Zones delimiting contaminant source (red) and source absence (green), considering benzene

16. Center for Applied GeoscienceApplied Geology source area of contamination with high gw impact control plane contributes 80 % to detected plume contributes 20 % to detected plume no contribution to detected plume A B C B C A Source Identification (Cycle II) • Development of new investigation methods and tools (direct push methods, multilevel samplers, contaminant fingerprinting, on-site analytical methods, ...)

17. Center for Applied GeoscienceApplied Geology Direct Push Technology Microbiology Hydrochemistry Geology Hydraulics

18. Center for Applied GeoscienceApplied Geology Scenario 1 Scenario 3 Scenario 2 Remediation Strategy (Cycle III) Scenario 1: joint remediation of whole area using one reactive barrier /MNA (plume concept) Scenario 2: remediation of each hot spot / source separately / MNA (source concept) Scenario 3: combined remediation of clusters of related hot spots / MNA Risk assessment, economical evaluation

19. Center for Applied GeoscienceApplied Geology Cyclic Approach • Principle “from large scale to small scale” • Integral investigation at large scale: • Delineation of zones of low and high environmental impact (integral assessment) • Delimiting of source zones using backtracking techniques • Assessment of the NA potential (multi-CP approach) • Assessment of uncertainty • Development of priorities for clean-up and / or further investigations • Cumulative receptor approach • Investigation at small scale (near the source): • Evaluation of individual source zones (integral pumping tests to estimate source • strength and plume backtracking, direct push methods, laboratory and on-site • analytical methods, contaminant fingerprinting etc.) • Development of clean-up priorities and optimized strategies • Polluter pays principle

20. Center for Applied GeoscienceApplied Geology Summary and Outlook  Start with an integral view and consider both concentrations and mass flow rates • Pumping tests and inversion, backtracking • Catchment outflow (rivers, springs, ...) and back calculation • Direct push arrays, horizontal wells, barriers, trenches, ... •  Demonstration and pilot projects are a main key to overcome • barriers for future applications • Development, testing and improvement of methods and tools • under ‘real world‘ conditions • Communication with end-users, problem owners and administrators • Improvement of acceptance, introduction into WFD based rules • => Future projects required

21. Center for Applied GeoscienceApplied Geology Acknowledgements Partners INCORE Jerker Jarsjö Sebastian Bauer Rudolf Liedl Rainer Schwarz Marti Bayer-Raich Georg Teutsch Thomas Holder European Union (EU), FP5 Projekt Wasser Abfall Boden – Baden-Württemberg (PWAB) German Science Foundation (DFG) Federal Ministry for Science and Technology (BMBF)

22. Zentrum für Angewandte Geowissenschaften (ZAG)Lehrstuhl für Angewandte Geologie