The mandatory cleanup of accidental releases of petroleum into the environment costs the Department of Defense (DoD) millions of dollars annually. DoD is responsible for the cleanup of thousands of barrels (bbl) of petroleum hydrocarbons (POL) spilled into the marine environment each year. The total volume of accidental POL releases at Navy facilities alone has exceeded 3.4 million gallons over the past decade. Estimates of the associated economic costs—including cleanup, disposal, lost product, and fines—range from a low of $2,000/bbl to as high as $18,000/bbl. Other, non-economic costs associated with major spill occurrences include irreversible harm to ecologically sensitive areas as well as damage to local community relations arising from a perception of negligent environmental stewardship within DoD.

Current spill detection and response strategies rely solely upon the use of human observation to visually detect the presence of a surface sheen indicative of a petroleum spill. Once an oily sheen is spotted, a response team is alerted to contend with the spill. The response team will first seek to isolate and stop the source if a leak is still occurring, then use any combination of skimmers, absorbents, and booms to contain and remove the spilled material. Early identification of a leak or spill, enabling responders to take immediate corrective action, is an important means of preventing large volume releases and reducing the associated environmental damage and economic cost. Early spill identification can only be achieved through diligent continuous monitoring.

The U.S. Navy has developed an automated oil spill detection technology, Spill Sentry, to improve the accuracy and timeliness of spill reporting. The system detects petroleum contamination in aquatic systems with an upward-looking underwater multispectral fluorometer that is designed to float just below the water’s surface. The optical system utilizes the germicidal effects of ultraviolet light to prevent biofouling, thereby enabling underwater deployment for indefinite periods of time, even in high fouling environments. Data are transferred in one of two ways: through a hard-wired umbilical or via a wireless data link. The wireless sensors utilize a solar cell for onboard power requirements to simplify deployment.

The objectives of this demonstration were to test and validate Spill Sentry under real-world conditions and to promote rapid transition to DoD users by facilitating commercialization, user awareness, and regulatory acceptance. To meet these objectives, year-long field demonstrations were conducted at Puget Sound Naval Shipyard, Bremerton, Washington; Langley Air Force Base, Hampton, Virginia; Norfolk Naval Station, Norfolk, Virginia; and Pearl Harbor Naval Station, Pearl Harbor, Hawaii. Additionally, in order to validate the system under controlled conditions and to verify performance parameters, wave-tank testing was conducted at the Ohmsett National Oil Spill Response Test Facility in Leonardo, New Jersey. Ultimately, the goal in demonstrating the effectiveness of utilizing an automated oil spill monitoring system is to provide users with the means to eliminate the need for 100% reliance on human visual observation to detect oil spills.

Overall, the Spill Sentry met or exceeded expectations in most key performance objectives, including the ability to detect petroleum, performance in choppy seas, freedom from spectral interference, ease of use, and effective use of ultraviolet light to prevent biofouling. However, the system significantly underperformed in two critical areas: reliability and false alarm rate. Though missing demonstration objectives, the relatively high false alarm rate is not a worrying concern; it can be substantially improved by adjusting the alarm threshold to meet site conditions and user needs. The reliability of the system, as measured by uptime during the demonstrations, is a more significant shortcoming. Uptime averaged just 47% at the four demonstration sites. This is largely attributable to the uncertainty and learning involved with first time use of prototype systems. Important lessons learned during the demonstrations as well as engineering improvements made to production systems will certainly improve future performance in this area.

The Spill Sentry demonstration serves to establish user confidence in the new oil spill detection technology. This is especially important as automated spill detection represents a completely new approach to pier-side monitoring. End-users had expressed initial concern over issues including the potential for generating false positives, the importance of data security, overall ease of use, low cost, durability (including the ability to withstand severe storms), and effectiveness in detecting oil. Information and network security also represents a broader user concern when linking the oil spill sensors’ real-time web-based data capability to local networks.

End users can now obtain Spill Sentry systems, system service, and support directly through Applied Microsystems Ltd. (AML). The technology currently being marketed by AML has benefited significantly from the lessons learned from the ESTCP demonstrations. The newest generation of sensors has been significantly improved to be more durable, less expensive, and easier to deploy.