Evaluation of Airborne and Ground Geophysical Data Collected at Target N-10, Pueblo of Laguna, New Mexico

Target N-10 on the Pueblo of Laguna was used for practice bombing during WWII. Current surface features include earthen berms, bomb scraps, and many ordnance related items. Two magnetometer urveys were conducted over the site as part of ESTCP system evaluation studies. The Naval Research Laboratory (NRL) initially collected MTADS data over ~70 acres with 100% coverage over the target center. Over 16,000 anomalies were selected from these data. Limited ground truthing excavated 1003 anomalies between two mag-and-flag sites and another 431 anomalies were excavated from the MTADS data. Oak Ridge National Laboratory (ORNL) subsequently conducted airborne surveys over ~1100 acres with 100% coverage over the center and 25% coverage over the remaining area. Their survey identified 171 anomalies (DAS category 1 & 2) were selected for investigation. The NRL data exhibits very high-resolution and while the ORNL data shows lower resolution but covers a much larger area. Data collected by NRL and ORNL represents a larger sample set than is typical for most ordnance site investigations. In this case, the NRL data were used to evaluate ordnance density and ORNL data were used to estimate extent of contamination. Coupled with soil sampling for chemical constituents, the site, overall, was characterized with a higher degree of confidence and at a lower cost. Results of this characterization indicated minimal risk to ecology and humans from explosives residue, debris or chemical releases. No intact HE items were found. Intact spotting charges were found in less than 1% of ordnance-related debris. These data have been used to estimate costs for four remedial alternatives that are being negotiated with the Pueblo of Laguna at this time.