The location and cleanup of buried unexploded ordnance (UXO) has been identified as a high priority, mission-related environmental requirement of the Department of Defense (DoD). In 2003, the Defense Science Board (DSB) Task Force on UXO estimated that there are 1,400 sites suspected of containing UXO contamination covering approximately 10 million acres in the continental United States. By some estimates, as much as 80% of this acreage is quite likely not contaminated with UXO at all. Technologies that can accurately and rapidly delineate the areas within each site that are contaminated from those that are not contaminated would lead to an immediate payback in terms of reducing the acreage that must be carefully examined and potentially cleaned.
The prototypical Wide Area Assessment (WAA) site is a large area (10,000s of acres) that may contain isolated areas of concentrated UXO, such as aiming points. The ESTCP WAA Pilot Project fields a layered suite of technologies to evaluate potential WAA strategies. The top layer consists of (relatively) high-flying sensors (and aircraft) (orthorectified photography and Light Detection and Ranging [LiDAR]), designed to detect “munitions-related features” such as target rings and craters. The next layer is a helicopter-borne magnetometer array designed to detect subsurface ferrous metal directly. The magnetometer data can be used to locate and define boundaries for targets, aim points, and open burning/open detonation (OB/OD) sites. The final layer is a survey of portions of the site using ground-based sensor arrays. In conjunction with statistical transect planning, the ground survey aids in defining target locations and boundaries. The project team has demonstrated several such final-layer systems using ground-based (a) towed-array magnetometer system, (b) towed-array electromagnetic (EM) system, and (c) man-portable (MP) EM systems.
The objective of the project was to demonstrate a suite of data collection and analysis methodologies to support the rapid delineation of UXO contamination within a site. Transect plans were developed by Pacific Northwest National Laboratory (PNNL) and Sandia National Laboratories (SNL) in cooperation with the ESTCP Program Office. The transect plans were based on available archive information and designed to allow the efficient sampling of the demonstration sites for areas of interest (AOI) while maintaining a statistically defensible probability of traversing the types of AOIs within the site that match the criteria developed from the available archive data and collected in the conceptual site models (CSM). These transect plans were implemented and data were collected at each demonstration site. Anomaly location and a measure of anomaly magnitude were extracted from these data using an automated anomaly detection methodology. This information was provided to PNNL/SNL for analysis to rapidly delineate AOIs. With this rapid pace, it was possible to interactively plan and execute additional transects to further resolve potential AOIs while the survey team was still deployed in the field.
Total coverage surveys were also conducted in small areas (1-90 acres per area) to better characterize the overall site and to support later validation efforts. The goals of the total coverage surveys were (a) to characterize background anomaly densities in areas found to be quiet (low anomaly density) in the transect survey results, (b) to characterize the falloff behavior of the anomaly density as a function of distance from known AOIs within the demonstration site, and (c) to gather further information on AOIs identified either from the transect data or from other sources such as the high airborne results.
As part of the ESTCP WAA Pilot Project, Nova Research, Inc. conducted a series of vehicular and MP geophysical surveys at three of the ESTCP WAA Pilot Project demonstration sites. Data were collected at the Pueblo Precision Bombing and Pattern Gunnery Range #2 (Precision Bombing Range [PBR] #2), the Victorville PBRs Y and 15, and the Former Camp Beale, located near La Junta, Colorado; Victorville, California; and Marysville, California, respectively. Towed-array transect surveys were conducted using the Naval Research Laboratory (NRL) Multi-Sensor Towed Array Detection System (MTADS) magnetometer and EM61 MkII arrays. A MP EM adjunct was also used in areas of the Victorville and Former Camp Beale demonstration sites that were inaccessible to the towed arrays. Approximately 1-2% of each site was surveyed using transect plans developed by the ESTCP Program Office, PNNL, and SNL. Known AOIs (BT3 at Pueblo PBR #2, for example) were identified at each site, and additional AOIs were identified for further evaluation.
Terrain and other site access issues presented more of a challenge to both survey rate and to site coverage than had been initially expected. Significant portions of the Former Camp Beale and Victorville, California, demonstration sites could not be accessed with the tow vehicle. In the case of the Victorville demonstration site, the geological properties of the northern portion of the site also limited the effectiveness of the magnetometer system. In these cases, the MP EM system was deployed to survey some or all of these areas at the cost of a significantly slower survey rate. For the Former Camp Beale demonstration, all assigned transects were surveyed using a combination of the two systems. Initial site visits can help to contain the effects of terrain by providing the necessary information to plan survey strategies in advance.