Remedial Investigation/Feasibility Study (RI/FS) Culebra Island, Puerto Rico

Contract: USAESCH Munitions Response Services (MRS) Worldwide

This $6.3M project, which begun in 2009 and scheduled to be completed in February 2016, has been performed by USA as prime contractor under our USAESCH Munitions Response Services (MRS) Worldwide contract. Culebra is a remote island situated 23 miles offshore from the main island of Puerto Rico, and was used extensively for military training from 1914 until 1975.

USA successfully investigated six Munitions Response Sites covering 3,746 acres, of which 678 acres were conducted underwater. The multiple MRSs contained dense vegetation and steep terrain, with a significant number of critical habitat areas and threatened or endangered species, both on land and underwater.

On land, field work started with vegetation removal to provide access for terrestrial DGM surveys within 236 acres of transects and grids. Geophysical mapping was conducted and selected anomalies were intrusively investigated. A biologist was on site to ensure protection of endangered species and critical habitats.

Field data was captured within a project Geographical Information System (GIS) database. The RI field efforts were presented in two separate RI reports for the terrestrial and the underwater investigations. MC sampling was conducted with USA collecting a total of 90 soil, sediment, and surface water samples during the terrestrial RI.

Following assessment of the DGM data, dig lists were created and approved by the USAESCH for intrusively investigating anomalies in each MRS. USA obtained approval to implement “Analog and Dig” methods along shorelines and beach areas due to migration of anomalies through continually shifting sands in tidal zones. A total of 1,882 anomalies were investigated and associated data was accurately collected and recorded. While no UXO items were recovered, two demolition events to address recovered Material Potentially Presenting an Explosive Hazard (MPPEH) were successfully completed.

During the underwater RI, USA collected 44 marine sediment samples. USA also collected groundwater samples from existing wells on Culebra and from two monitoring wells installed by USA. Detection Technologies used during the terrestrial RI included EM61 and analog sensor technologies.

To investigate the underwater acres, USA effectively employed a combination of technologies in a multi-phase approach. USA completed the underwater Environmental Baseline Survey consisting of an International Hydrographic Organization Order I survey, with both visual and side-scan sonar, utilizing our Remotely Operated Vehicle with video cameras and side-scan sonar capabilities. Underwater DGM was performed covering 19.34 miles of transects utilizing the underwater EM-61. USA performed underwater intrusive investigations, utilizing UXO divers with underwater EM-61 and underwater analog detectors, to reacquire and investigate geophysical anomalies.

As Culebra is a small island within the Spanish Virgin Island chain, USA was presented with unique logistical challenges working there. USA overcame these challenges by developing an effective logistics network to successfully maintain the flow of equipment and project supplies in order to avoid delays in field production.

USA installing a groundwater well

Result of the excavation of a DGM Anomaly in MRS 13 (MK45 Mod 0 Projectile)

Diver is measuring the Length, Width, and Depth of the excavation site to record the impact to the Manatee Seagrass prior to pushing the spoils back into the hole