ANDRA wishes to build a new hydrogeological model for the CSA.

Description of expected work:

1) analysis of the hydrogeology of the site:

- analysis of environmental monitoring measures (approximately 140 piezometers, measurements from 1986);

- analysis of the impact of the gradual development works of the center;

2) conceptualization of the model (extension of a few km 2 ) and choice of method for coupling surface, subsurface and underground flows. The objective is to ensure the best possible representativeness for each of the 45 piezometers of the storage platform;

3) construction of the model and verification of correct numerical operation with respect to flow and transport simulations;

4) calibration of the flow model (the objective is to calibrate the piezometers of the platform to less than 30 cm), sensitivity and uncertainty analyzes;

5) carrying out transport simulations. Estimated duration: 24 months. Ref. PLACE: SURRPFADAS210004.

ANDRA wishes to build a new hydrogeological model for the Aube repository. The objective is to review the conceptualization of the model, the adjustment to measurements (flows and levels) and improve the estimation of recharge by a better coupling of surface, subsurface and underground flows. The expected work is broken down into five marcoscopic tasks:

1) analysis of the hydrogeology of the site, including:

- an analysis of the rainfall, flows at the peripheral drains of the site and piezometry (approximately 140 piezometers, data from 1986), in order to identify the phenomena influencing the piezometric response;

- an analysis of the impact of the site development work accompanying the progressive construction of storage structures and galleries of the buried gravity separation network which intercepts the water table in certain areas;

2) conceptualization of the hydrogeological model and choice of the method for coupling surface, subsurface (ZNS) and underground flows: the boundary conditions of the model (extension of about 2 km 2 ) as well as the spatial and temporal variability of the aquifer recharge must be correctly taken into account to ensure good representativeness of the simulation results to the numerous piezometers of the storage platform (approximately 45 piezometers over an area of 30 ha );

3) construction of the hydrogeological model and verification of correct digital operation: correct digital operation should be checked against flow and transport simulations;

4) calibration of the flow model, sensitivity and uncertainty analyzes. The level and flow must be calibrated by using the drawdown measures following the installation of filter tips for the construction of the galleries of the structures (several months of pumping around ten galleries). The calibration process is expected to ensure good representativeness of the model in each piezometer of the storage platform to within about thirty centimeters. The pilot point method is recommended for setting. Uncertainty analysis is to be distinguished from sensitivity analysis;

5) carrying out transport simulations and synthesis of the study. Place: the required services will be performed at the holder's premises. However, a site visit is recommended. Follow-up meetings, in which the incumbent must participate, will be organized regularly. Estimated duration of the entire service: 24 months.