Evaluating risk during the military munitions response program remedial investigation at a formerly used defense site on the Mid-Atlantic Seashore

Abstract

Background From 1944 to 1947, the U.S. Navy and the U.S. Army Air Corps established two rocket ranges on a Formerly Used Defense Site (FUDS) on the Mid-Atlantic Seashore. Rocket Range North (MRS 01 - 3,412.2 acres) and Rocket Range South (MRS 03 - 3,245.5 acres) are comprised of land and water and are open to the public for recreational purposes. A remedial investigation (RI) was performed in the Fall 2017/Spring of 2018 to characterize the nature and extent of potential munitions and explosives of concern (MEC) present at MRS 01 and MRS 03. Remedial Investigation Findings At MRS 01, a total of 336 subsurface anomalies were investigated on land, and 109 in the water. Of the 336 anomalies, 51 anomaly locations contained munitions debris (MD). All MD identified during the RI was located in and around the concentrated munitions use area (CMUA) identified as the target area, this was the only CMUA identified, and the MD here was consistent with MD historically identified at MRS 01. To date, only MD from 2.25-in. practice rockets, 3.25-in. practice rockets, 3.5-in. practice rockets, 5-in. practice rockets, 3-lb Mk 23 practice bombs, 4.5 lb Mk 43 practice bombs, and 20 mm (inert Training Practice [TP] projectile and casing) have been identified at MRS 01. Over nine-nine percent of the MD was from practice rockets. The only explosive component associated with practice rockets is propellant, which is expended when fired. The notable presence of the MD from practice rockets in the target area confirms that they were fired. No MEC has been identified at MRS 01. At MRS 03, a total of 219 subsurface anomalies were investigated on land and 41 anomalies in the water, none of which were attributed to MD. Historically, only two pieces of MD from 5-in. practice rockets were reportedly found at MRS 03. Based on these observations, it is unlikely MRS 03 was used by the Navy as a practice bombing and strafing range. No MEC has been identified at MRS 03. Risk Evaluation Conclusions The FUDS Risk Methodology Tool, currently undergoing a two-year trial period, was applied to assess level of risk to determine if acceptable site conditions exist. This tool helped the PDT focus discussions and apply the decision logic needed to assess MEC risk. This tool clearly identifies the main factors that influence MEC hazards at a site in each of the Matrixes (i.e., likelihood of encounter, severity of incident, and likelihood of detonation) and pulls them together in the final matrix. This facilitates the identification of remedial actions that may be implemented to reduce or eliminate site risks. However, in cases where only MD is found, there seems to be a grey area. At MRS 01, a CMUA was delineated around the target area, but following an extensive RI, only MD was identified at the site. Using the FUDS Risk Methodology it was not immediately clear how the site should be ranked. Although a CMUA was present and MD was identified, using a weight of evidence approach and historical finds, MEC is not suspected to be in the area. Several terms used within Matrix 1, including “MD indicative of MEC” and “evidence of MEC presence” should be more clearly defined within the FUDS Risk Methodology. Reviewing and implementing the new method required additional time, which translated into slightly higher costs. However, as personnel become more familiar with this tool it is not expected to be any more or less time consuming than the MEC Hazard Assessment (MEC HA). Unlike the MEC HA, the new method avoids the “one-size-fits all” approach and requires the PDT to consider how the data affects the conceptual site model and the potential for human exposure. Additionally, the new method assesses MEC risks at sites where only MD has been identified, whereas the MEC HA is not typically completed unless MEC has historically been identified at the site.