The Department of Defense (DoD) uses over two million rounds of high-explosive (HE) munitions per year ( Defense Science Board Task Force, 2003 ). A small percentage does not explode, thus generating unexploded ordnance (UXO) in current range areas at a substantial rate. As these ranges are closed, the DoD becomes responsible for the environmental restoration of the affected properties. Current methods of UXO remediation are costly because of high false alarm rates. Our current research is to develop a complementary technology that will alleviate false alarm rate by detecting, classifying, and locating UXO in near real time (less than 1 minute) as a munition impacts the range. This technology will utilize an array of buried seismic sensors in a calibrated range area, along with a set of algorithms based on theoretical and applied seismology and statistical analysis. Initial field tests at three sites focused on developing concepts of the seismic and acoustic location of ordnance impacts. Our research program developed from these initial field tests has four primary objectives: 1) fully implement a wired seismic-acoustic ordnance impact location system for live fire ranges; 2) develop a system capability to discriminate high-order (HE), low-order (partially exploded), and zero-order (UXO) events; 3) reduce location error to a stringent program metric of 1–2 m; and 4) investigate the feasibility of developing a wireless implementation of the technology. This paper describes the procedures and results from follow-on tests that were conducted in two locations at the U.S. Army Aberdeen Proving Ground (APG), Maryland. These tests were used to evaluate potential seismic-acoustic methods and system configurations for a Seismic-Acoustic Impact Monitoring Assessment (SAIMA) system for mitigating UXO hazards. Significant results from this work include: 1) seismic impulses from low-order impacts were detected at distances up to 1,000 meters; 2) classification features based on measurements of the amplitude of acoustic and seismic phases produce clear discrimination between HE and UXO impacts; 3) calculated location solutions for HE and UXO impacts yield an average location error of 10–20 meters; and 4) empirical observation and waveform modeling demonstrated that surface waves dominate the signal at all distances and therefore should be the primary phase used for all components of analysis. Furthermore, these tests demonstrated the current system design, allowing further enhancements, is capable of meeting the initial research objectives (1) and (2). Future research will focus on improving system performance with refinement of the sensor-layout geometry and the detection and location algorithms through system error analyses and follow-on field testing.

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For the past several years, Quantum Technology Sciences (QTSI) and U.S. Army Engineering Research and Development Center (ERDC) have been developing a system to actively sustain present and future artillery ranges at zero unexploded ordnance (UXO) gains. With the Department of Defense (DoD) using over two million high-explosive (HE) munitions per year with a significant fraction as UXO, reducing costly range remediation and environmental restoration efforts will offer significant savings. The developed Seismic Acoustic Impact Monitoring Assessment (SAIMA) system is not designed for past ranges, but as a complementary technology to detect, locate within two meters, and classify UXO in near real-time to aid existing cleanup technologies. Feasibility and descriptions of system components have been previously provided ( VanDeMark et al., 2009 , 2010 , 2013 ). The current system is composed of multiple buried seismic arrays encircling a mortar or artillery impact area, communications from the arrays to a central processing station, and a processing unit that employs an algorithm suite based in the seismology and statistical analysis disciplines to detect, locate, and classify the HE or UXO impact. Recent deployments of the SAIMA system have demonstrated hardware maturity and algorithm refinements to nearly enable the goal of locations within two meters. A field deployment at Ft. Sill, Oklahoma, in June 2012 demonstrated acoustic locations at a large range ( QTSI, 2012 ). Subsequent systems tests with five arrays using a synthetic UXO source (kinetic source only; no acoustic phases) on a small field (80 m by 80 m) resolved locations within 0.5 m of ground truth with coverage ellipses at 0.1 m2 (time and azimuth). On a small mortar field, approximately 365 m by 480 m, simulated UXO (inert rounds) were located within an average mislocation distance of 4.1 m and confidence ellipses on the order of 5.8 m by 3.8 m. Scheduled field testing in the near future will validate the system.

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