[M-GI25] Near Surface Investigation and Modeling for Groundwater Resources Assessment and Conservation

[MGI25-P06] Characterization of a contaminated aquifer using hydraulic tomography and a Fiber Grating Multilevel Monitoring System

*Jui-Pin Tsai¹, YU-LI WANG¹, YEN-TE HO¹ (1.National Taiwan University, Taiwan)

Keywords:Aquifer heterogeneity, Optical sensor, Contaminated site remediation

Understanding the hydraulic heterogeneity of the contaminated aquifer is crucial to predict the flow paths of the plume and remediation agents. However, traditional pumping tests can only estimate the average hydraulic properties, resulting in difficulty in accurately predicting the transient groundwater flow fields. Hydraulic tomography (HT) is a new hydraulic test method for characterizing heterogeneous aquifer properties. For the HT test, we need to perform sequential pumping/injection tests using a group of wells and simultaneously measure the groundwater pressure variations during the HT test. The pressure variations are then transformed into hydraulic heterogeneity using the geostatistics approach. The conventional wells often open screens at the single target depth to collect pressure data for the traditional HT test. In other words, a single well can only measure the pressure data in one depth range. On the contrary, a multilevel well monitoring system (MLMS) has several open-screen at the target depths. The packer separates each monitoring zone to interrupt the connection of vertical flow inside the well. Thus, the amount of pressure data from an MLMS can be several times more than those from a traditional well. Accordingly, this study employed a new multilevel well system, developed by fiber Bragg grating technology, to conduct HT at a contaminated site in Taiwan. We then compare the image profile of hydraulic conductivity with that of electrical resistivity to validate the practice of using FBG MLMS to conduct HT. Results reveal that HT with an FBG multilevel well system is reliable and practical.