GIS processing to support an Hydrogeological Flux and Transport Model in Cecina Plain (LI, PI)

Transcript

1 GIS processing to support an Hydrogeological Flux and Transport Model in Cecina Plain (LI, PI) Riccardo Armellini**, Elena Baldini*, Dario Del Seppia*, Fabrizio Franceschini*, Natacha Gori***, Stefano Menichetti*, Stefano Tessitore* *ARPAT Agenzia Regionale di Protezione Ambientale della Toscana Direzione Tecnica, Dipartimenti Pisa e Livorno. ** Master AA 2011/2012 in Sistemi Informativi Territoriali per la Gestione del territorio UNIFI *** Diploma di Corso di Laurea Triennale in Scienze Ambientali UNIPI - natacha.gori@gmail.com

2 Geographical Setting The study area is located within the provinces of Pisa and Livorno at south of Cecina river, in Montescudaio and Cecina municipalities

3 History of contamination 2004: pollution by tetrachlorethylene (PCE) and trichlorethylene (TCE) in groundwater of Cecina with exceedances of limits for drinking water (total PCE + TCE = 10 µg/l) investigative monitoring: - source area of contamination located in the industrial area of Poggio Gagliardo, east of the town of Cecina - contaminant plume that spreads towards the town of Cecina. in many wells monitored exceedances of CSC for contaminated sites (1.1 µg/l for PCE and 1.5µg/L for TCE) Agreement Program (DPGR 363/04) between RT and territorial authorities to coordinate joint actions for the implementation of emergency safety and remediation of ground water.

4 History of contamination : securing emergency (MISE): hydraulic barrier with installation systems Pump & Treat in the source area, pumping calibration and installation of carbon filters in the wells of the aqueduct. monitoring plume: major boost with the rains characterization and remediation project : monitoring plume assisted by a model of flow and transport start cleaning up: upgrading and reconfiguring hydraulic barrier, sealing or reconditioning wells in the source 2014 => completion of reclamation: removal of free phase DNAPL by SVE and P & T in the source area

5 GIT Geology and Information Technology 9a Riunione del Gruppo di Geologia informatica - Sezione della Società Geologica Italiana Mappe isocone del plume inquinante Ricostruzioni basate sui valori medi annuali dell indicatore chiave somma PCE+TCE.

6 Mappe isocone del plume inquinante Ricostruzioni basate sui valori medi annuali dell indicatore chiave somma PCE+TCE.

7 Mappe isocone del plume inquinante Ricostruzioni basate sui valori medi annuali dell indicatore chiave somma PCE+TCE.

8 1. Conceptual Model 2. GIS processing Modeling Geometry reconstructions Estimation of hydraulic conductivity Calculation of inflows Withdrawals Piezometric reference 3. Model of flow and transport

9 Conceptual Model 1. MULTILAYER AQUIFER in Quaternary marine and continental deposits: single hydrogeological domain bordered by Cecina river, Le Basse creek, the coastline and an elevation, hydrological and geological discontinuity between hills (lower pleistocene) and plain terraces (medium upper pleistocene); 2. AQUIFER RIVER CONNECTION, very strong in Steccaia area; 3. LOCALY MULTILEVEL AQUIFER: in contaminated area a clayey interlayer separates a very contaminated shallow water table; 4. TECTONIC CONTROL: a fault along Linaglia creek interrupts continuity of interlayer. IGG CNR LAMMA (2009) CISS characterization: isobaths 32CT CT030 STECCAIA Benvenuti et alii Tectonic and climatic controls on historical landscape modifications: The avulsion of the lower Cecina River (Tuscany, central Italy)

10 GIS PROCESSING: geometry reconstructions Integration of regional survey database SIRA_DB-GEO: 97 new logs with 1133 layers LITHOLOGICAL interpretation: classification of each layer lithotype as AQUIFER, AQUITARD or AQUICLUDE on the basis of intrinsic permeability (K). GEOLOGICAL interpretation: classification according CARG s synthems and lithofacies

11 Hydrogeological units Hydrogeological interpretation HYDROGEOLOGICAL interpretation: definition of hydrogeological units corresponding to model layer 1 = aquiclude substrate 2 = aquifer undifferentiated 2a = deep aquifer 2b = aquiclude aquitard interlayer 2c = shallow aquifer 3 = aquiclude aquitard cover Surface modeling using the Kriging ArcGIS Geostatistical Analyst extension Geometric corrections, needed especially on the sides of the domain, and calculation of thickness using the Raster Calculator tool Spatial Analyst extension.

12 Hydrostructural maps Modeling products => SURFACES and THICKNESS maps of HYDROGEOLOGICAL UNITS. COVERAGE thickness average thickness ranging from 5 to 8 meters max thickness on hill reliefs tectonic control by Linaglia and other faults that marks several thickness discontinuity

13 Hydrostructural maps Modeling products => SURFACES and THICKNESS maps of HYDROGEOLOGICAL UNITS. INTERLAYER top sloping to the Cecina follows the morphology of the reliefs the source area coincides with an incision sloping towards southwest

14 Hydrostructural maps Modeling products => SURFACES and THICKNESS maps of HYDROGEOLOGICAL UNITS. INTERLAYER thickness Average thickness ranging from 10 to 15 meters Maximum thickness zone downstream of Steccaia Local maximum near the contaminated area of Poggio Gagliardo

15 Hydrostructural maps Modeling products => SURFACES and THICKNESS maps of HYDROGEOLOGICAL UNITS. AQUIFER thickness average thickness of 45 meters minimum thicknesses area in interlayer area max thickness areas at hilly reliefs and town of Cecina appreciable tectonic control by Linaglia and other faults

16 Hydrostructural maps Modeling products => SURFACES and THICKNESS maps of HYDROGEOLOGICAL UNITS. AQUIFER bottom Sloping to the Cecina and the sea with the presence of a northsouth depression Max depth meters s.l.m at Cecina town Min depth meters s.l.m. at hilly reliefs

17 Model of flow and transport Modeling Software: Groundwater Vistas 5 Numerical code MODFLOW: three-dimensional flow equations in a porous medium finite difference method (FDM) Input data => "packages files Boundary Conditions (BCs): imposed conditions which the differential equation must comply with Properties: apply to aquifer cells (elevations, conductivity, storativity, recharge) Analytic Elements (AE): apply at precise location (wells, target with observed heads) Stages of implementation: Rev0 => steady state natural Rev1 => Rev0 + wells withdrawal Rev2 => Rev1 + hills constant flow boundary Rev3 => Rev1 + Cecina River boundary Rev4 => Rev3 divided into 4 layers Simulation of past, actual and forecast scenarios: Rev3.0 => pre 2004 scenario (no MISE) Rev3.1 => 2004 MISE with detail telescopic mesh refinement (Rev3.1.tmr) Rev3.2 => 2012 MISE increase (Rev3.2.tmr) Rev3.3.tmr => forecast scenario for MISE (change in flow rate of activated wells in Rev 3.2) Rev3.4.tmr => forecast scenario for MISE (variable flow) Rev3.5.tmr => forecast scenario for MISE (hypotesis of reinjection well)

18 Steady flow Model: optimization MISE Rev3.2_tmr => MISE Rev3.1 => MISE Rev 3.4_tmr => MISE model designed

19 fair / good correspondence in the trends in the case of Peep and Ladronaia, except for the intensive phase of where DNAPL separate flow may have occurred; differences in the case of St. Vincenzino, probably due to inaccurate reconstruction of concentration as interpolated by discontinuous data in space and time. GIT Geology and Information Technology Model of transient transport (Rev 3) Recharge, Cecina river heads and wells withdrawals modified according to their temporal variation in Ladronaia Peep S. Vincenzino

20 Predictive transport model: hydrological year Rev3.4 version, scenario implemented with the MISE: Q(CD1)>> Q(CD2) = Q(CD3) Initial concentrations = concentration of the third quarter of Peep Ladronaia Forecast scenarios related to hydrological years such as 2008/2009, which scenario of maximum wet year, and the 2005/2006 minimum dry year. Maximum Plume Direction SW with strong increase towards the well Peep of Cecina ; Ladronaia Minimum Plume direction SW But with lateral extent relative to the flow, to Ladronaia Peep

21 Forecast Model : Proposal enhancement of MISE In 2014 Rapida well has been reconditioned and is now filtering the deep aquifer. Model forecast simulation suggest improvement as Rapida Pump & Treat plant moved to CD4 well. Fig. 1 Rev3_4_TT13_TMRmax.gwv. Stress period 1 e Time step 3 - Attuale Scenarios maximum (late autumn hydrological year ) Fig. 3 Rev3_4_TT13_TMRmin.gwv. Stress period 4 e Time step 3. - Attuale Scenarios minimum (end of summer hydrologic year ) Fig. 2 Rev3_5_TT13_TMRmax.gwv. Stress period 1 e Time step 3 - Proposta. Fig. 4 Rev3_5_TT13_TMRmin.gwv. Stress period 4 e Time step 3 - Proposta Heads and particle tracking evaluated with the post-processing program MODPATH.

22 Present model will assist in the coming years monitoring of contaminant plume and remediation interventions by reproducing elapsed hydrological year and providing forecasts for minimum and maximum scenarios GIT Geology and Information Technology Conclusions The present work has increased the knowledge of the hydrogeological system of coastal aquifer of Cecina, with the main purpose of calibrating withdrawal from the wells of the MISE, in order to optimize it, and secondary support monitoring of the water body impacted At first has been defined the conceptual model of the aquifer system need to set the development of the model of flow and transport By GIS processing it was possible to create several layers of information useful to all stages of implementation of the steady state and transient flow and transport model; A preliminary steady-state natural, without withdrawals, simulations have shown the consistency of the data processed Several scenarios were simulated aimed at the optimization of the MISE to confine the plume The subsequent reconstruction in transient seasonal and transient in the period showed a good qualitative agreement between measured and simulated data in the selected targets