THE ROLE OF 3-D GEOLOGIC MODELING AND DATABASE SOLUTIONS IN THE VIRTTAANKANGAS ARTIFICIAL RECHARGE PROJECT, SOUTHWESTERN FINLAND

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1 THE ROLE OF 3-D GEOLOGIC MODELING AND DATABASE SOLUTIONS IN THE VIRTTAANKANGAS ARTIFICIAL RECHARGE PROJECT, SOUTHWESTERN FINLAND Artimo, A. 1, S. Saraperä 2, and I. Ylander 1 1 Turku Region Water Ltd., Maariankatu 1, FIN Turku, Finland; 2 Department of Geology, FIN-20014, University of Turku, Finland; Aki Artimo at aki.artimo@turunseudunvesi.fi

2 INTRODUCTION The artificial recharge project of the Virttaankangas Aquifer was launched to provide the 285,000 inhabitants of the Turku area in southwestern Finland with good quality potable water by the end of this decade. The total budget of this project is about 100 million euros. The planning and building of the 100 km pipeline and affiliated construction constitute the largest items of expenditure in the water supply project. However, the research and geological understanding of the Virttaankangas Aquifer will be the decisive factors for its success.

3 STUDY AREA The artificial recharge will be conducted in the Quaternary esker aquifer called the Virttaankangas aquifer, located 66 km north of Turku. The water for the infiltration will be extracted from the River Kokemäenjoki, located 28 km north of Virttaankangas. The residence time of the water in the aquifer should be at least 3 months to ensure that natural purification can occur. The location of the Virttaankangas Aquifer.

4 IMPLEMENTATION Artificial recharge (Figure) is a process that requires control and understanding of various fields of geology including, hydrogeology, sedimentology, geochemistry, and geophysics. Commonly, the studies conducted in one of these fields of geology do not significantly overlap with the other fields, which has also been the case in previous investigations for the Virttaankangas area. Therefore, a tailor-made database was required to assemble all of the available data into a commensurable form. This allows the users of the database to analyze and compare data from different sources simultaneously. Testing of an infiltration area by the sprinkling method, July The location of the infiltration area was determined on the basis of the drilling data, 3-D geological model, and ground penetrating radar data. Presently, only natural groundwater from the Virttaankangas Aquifer is used in the infiltration tests.

5 IMPLEMENTATION The described approach to integrate and control the data became essential when the first 3-D geologic modeling study was conducted. The 3-D model data was not unambiguously integrated with other data, and the updating of the model ended up being a timeconsuming task. To overcome these difficulties, the database and the 3-D model were integrated. The database is either automatically or manually updated with field data from several sources. Littoral sand Silt and clay Glaciofluvial fine Glaciofluvial coarse Till Bedrock Hydrogeologic units of the Virttaankangas 3-D model.

6 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results

7 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results

8 DATA SOURCES P 568 Grain size distribution 0 % 50 % 100 % 1 Data from the following sources have been included into the database: >2.0 mm Drill logs: Original and interpreted results Soil samples: Location and sieving results mm <0.2 mm

9 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results Hydraulic Head (automatic / manual)

10 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results Hydraulic Head (automatic / manual) Hydrochemical data: ph, DO, EC, Temp

11 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results Hydraulic Head (automatic / manual) Hydrochemical data: ph, DO, EC, Temp Isotope data δd and δ18o

12 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results Hydraulic Head (automatic / manual) Hydrochemical data: ph, DO, EC, Temp Isotope data δd and δ18o Geophysical data (GPR, Gravimetric data)

13 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results Hydraulic Head (automatic / manual) Hydrochemical data: ph, DO, EC, Temp Isotope data δd and δ18o Geophysical data (GPR, Gravimetric data) Pumping and Infiltration test data

14 DATA SOURCES Data from the following sources have been included into the database: Drill logs: Original and interpreted results Soil samples: Location and sieving results Hydraulic Head (automatic / manual) Hydrochemical data: ph, DO, EC, Temp Isotope data δd and δ18o Geophysical data (GPR, Gravimetric data) Pumping and Infiltration test data Geochemical data: Ctot Groundwater monitoring well technical data These will be used to add the interpretations of the 3-D hydrogeologic units into the database.

15 None of the data sources alone can depict the conditions of hydrogeologic sub-regions of Virttaankangas aquifer. In order to efficiently apply the study results for the use of the Artificial Recharge Project, they must be contemplated simultaneously with several types of data and the existing version of the 3-D hydrogeologic model.

16 Depth (m) Syvyys (m) P 568 Grain size distribution 0 % 50 % 100 % 1 >2.0 mm mm <0.2 mm Ctot (p-%) 0,00 0,10 0,20 0,30 0,40 1 C tot organic soil material 3-D model units (Artimo et al. 2003) Littoral sand Upwards coarsening sets, almost no traces of silt and clay Silt and clay Glaciofluvial fine Glaciofluvial coarse Bedrock (87 m below the land surface) GW ph ph 9 9.2

17 IMPLEMENTATION All the new data affecting the extent and structure of the hydrogeological units will be first interpreted by a geologist and then added into the database. This information is processed with the help of tailor-made programs that link the database with other software. Presently, these programs for modeling work and data management include Surfer, PMWIN Pro and ArcGIS / Arcview.

18 Artificial Recharge Control System Graphical logs Traditional GIS On-line hydraulic head (points, curves, animations) Aquifer vulnerability map 3-D model Semi Automated Tasks Flow model DATABASE 3-D hydrogeological units Semi Automated Quality Assurance / Quality Control Drill hole data Geochemical data Geophysical data Groundwater data (automatic measurements) Groundwater data (manual measurements)

19 RESULTS Programs included into the database can create internally consistent 3-D hydrogeological units and slice the resulting 3-D model at a given z- surface. Littoral sand Silt and clay Glaciofluvial fine The 3-D model units are then used to produce the 3-D architecture of the Virttaankangas groundwater flow model. Glaciofluvial coarse Till Bedrock Hydrogeologic units of the Virttaankangas 3-D model.

20 RESULTS The programs can also be used to produce animations of the hydraulic head changes during pumping and infiltration tests. Using the animations, it is possible to inspect the hydraulic head changes during recharge or pumping tests conducted in the past, and use the up-to-date 3-D hydrogeologic model to contemplate the results. The data is prepared for the animation by filling the temporal gaps between observations. This is done by extrapolating and interpolating the actual measurements. The first day of the animation is used as a baseline. The contour spacing is 5 cm (about 2 inches).

21 RESULTS The database is used on a daily basis in the Turku Region Water Ltd: Constantly up-to-date hydraulic head measurements are available. New field work can be planned and guided with the support of the previously obtained study results. The use of the database ensures that everyone has access to the most recently updated data and study results. The programs integrated with the database help to avoid time consuming routine tasks. New study results can be contemplated with all the existing data, without having to browse through several paper reports. The same tools will be used in the full-scale phase of the artificial recharge project.

22 CONCLUSIONS The nature of the 3-D geologic modeling effort has changed during the course of the Virttaankangas artificial recharge project; the model has become a dynamic, constantly updating part of a larger research entity. The 3-D model not only consists of the data obtained from the sedimentological studies, drill hole logs, and geophysical studies, but is also closely connected with hydrogeological and geochemical data with the help of the flexible database solutions.

23 CONCLUSIONS The 3-D model has become an important tool for planning and building of the facilities connected with the artificial recharge. For example, the 3-D model has been used for finding suitable locations for water intake wells and infiltration areas. Therefore, the database solutions and modeling tools are not only serving the needs of scientific research, but also contributing to the progress of the artificial recharge project in its present stage, and later on, during the actual groundwater production phase. Building of the new water supply well, March The location of the well was determined on the basis of the data obtained from the 3-D geological model. The well has a stainless steel casing and the screen consists of a slotted PVC pipe. The depth of the well is 26 meters and the diameter of the screen is 500 mm. The measured yield of this well is 7500 m 3 /d (265,000 ft 3 /d).

24 Sami Saraperä s work has been funded by the Maj and Tor Nessling Foundation.