LAUSR

We present the first demonstration of hydraulic tomography (HT) to estimate the 3D hydraulic conductivity (K) distribution of a fractured aquifer at high-resolution field scale (HRFS), including the fracture network and connectivity through it. We invert drawdown data collected from packer-isolated borehole intervals during 42 pumping tests in a wellfield at the former Naval Air Warfare Center, West Trenton, New Jersey, in the Newark Basin. Five additional tests were reserved for a quality check of HT results. We used an equivalent porous medium forward model and geostatistical inversion to estimate 3D K at high resolution (K blocks < 1 m3 ), using no strict assumptions about K variability or fracture statistics. The resulting 3D K estimate ranges from ~0.1 (highest-K fractures) to ~10-13 m/s (unfractured mudstone). Important estimated features include: (a) a highly fractured zone (HFZ) consisting of a sequence of high-K bedding-plane fractures; (b) a low-K zone that disrupts the HFZ; (c) several secondary fractures of limited extent; and (d) regions of very low-K rock matrix. The 3D K estimate explains complex drawdown behavior observed in the field. Drawdown tracing and particle tracking simulations reveal a 3D fracture network within the estimated K distribution, and connectivity routes through the network. Model fit is best in the shallower part of the wellfield, with high density of observations and tests. The capabilities of HT demonstrated for 3D fractured aquifer characterization at HRFS may support improved in-situ remediation for contaminant source zones, and applications in mining, repository assessment, or geotechnical engineering. This article is protected by copyright. All rights reserved.