Remedial Investigation and Feasibility Study (RI/FS), Munitions Response Site (MRS), Site UXO3, Naval Weapons Station Seal Beach (NWSSB), Detachment Fallbrook, Fallbrook, CA.

This task order includes the preparation of Planning Documents, performance of associated Remedial Investigation field work, and preparation of the Remedial Investigation/Feasibility Study Reports for UXO3.

GCE performed a Remedial Investigation to define the nature and extent of Munitions and Explosive Concerns (MEC)/Munitions Constituents (MC) in shallow soil, to provide the data to update the human health and ecological risk assessments, and prepare a Remedial Investigation Report and Feasibility Study for the site at Naval Weapons Station Seal Beach Detachment Fallbrook, CA.

MRP Site UXO 3 was used for disposal and burial of MEC and non-MEC related debris. The non-MEC debris included metal banding, canisters, drums, car parts and other scrap metal; construction debris that included asphalt, concrete, and metal pipes; and other debris that included wood, glass, and batteries. Visible MEC-related materials at MRP Site UXO 3 are located primarily in the northern portion of the site, including small arms ammunition and cartridge casings (5.56-millimeter (mm), 7.62-mm, .30-caliber, and .50-caliber rounds), 20-mm cartridges, inert rocket motors and practice bombs (misidentified as Mark 79 Mod 1 1,000-poundfire bombs with Mk 257 Mod 0 electric fuses and igniters in the Site Inspection Report). Planning documents included preparation of Remedial Investigation Work Plan and Sampling Analysis Plan, Accident Prevention Plan/Site Safety and Health Plan, an Explosive Safety Submittal (ESS) to define the safety procedures to be implemented during site activities for potential hazard/threat presented by MEC and MC, and a Biological Avoidance and Minimization Plan to identify sensitive habitat exclusion areas within MRP Site UXO 3.

In order to define buried metallic anomalies, a Digital Geophysical Mapping (DGM) survey was performed to identify likely locations that may be MEC. Based on the DGM survey, eleven exploration trenches were advanced at selected locations within MRP Site UXO 3 to evaluate the buried anomalies detected in the DGM survey and to collect soil samples. The MEC encountered was removed, classified, and disposed of as required by the ESS. Additionally, four large unidentifiable bomb cannisters, believed to be practice bombs for aerial deployment, and four missile motors were encountered during field activities required demilitarization due to the uncertainty of the bomb types and the potential for residual missile fuel prior to disposal.

GCE also collected an additional 20 soil samples from locations surrounding two areas that contain elevated metals concentrations. Following the completion of field activities, GCE prepared a Remedial Investigation Report, updated the Human Health and Ecological Risk Assessments, performed Ammunitions Hazard Assessments, and conducted a Focused Feasibility Study.