The Department of the Interior’s Bureau of Safety and Environmental Enforcement (BSEE) National Oil Spill Response Research and Renewable Energy Test Facility, Ohmsett, plays a critical role in advancing oil spill response capabilities through research, development, testing, and training. Ohmsett’s 10 million liter (l) saltwater wave tank provides an independent venue to conduct research and development with full-size response equipment using real oil, in realistic, repeatable conditions.
This paper will discuss recent research and development conducted at Ohmsett, including: Remote sensing of surface oil by BSEE, the National Oceanic and Atmospheric Administration (NOAA), the United States Army, the United States Coast Guard (USCG), and the United States Environmental Protection Agency (U.S. EPA); using acoustics to measure oil slick thickness; creating large volumes of emulsions for Ohmsett tests; mechanical recovery of chemically treated, undispersed oil; skimmer testing in diminishing slick thickness; a USCG and BSEE test of a skimmer ice management system; and an autonomous skimmer development.
This paper will summarize the setup and methodology used during recent testing, training, and research conducted at Ohmsett. Reports of BSEE funded oil spill response research can be found at https://www.bsee.gov/site-page/master-list-of-oil-spill-response-research.
Ohmsett, located in Leonardo, New Jersey, provides independent and objective performance testing of full-scale oil spill response equipment. Ohmsett helps improve oil spill response through research and development of the tools responders use, as well as supporting full-scale training of response personnel. Ohmsett’s largest asset is its above-ground concrete test tank (Figure 1) which measures 203 meters (m) long by 20 m wide by 3.6 m deep. The tank is filled to a depth of 2.4 m with 9.8 million liters of saltwater that is continuously filtered to maintain clarity, enabling the use of underwater cameras and viewing windows installed in the tank’s concrete walls.
The test tank is spanned by three movable bridges (carriages). The Main Bridge is used to tow full-size oil spill response equipment through the water at speeds up to 3.3 m/s to simulate a vessel towing equipment at sea or deploying equipment in a current. The Main Bridge is equipped with an oil distribution system to dispense test oil on the water in front of the equipment being towed or tested. The Auxiliary Bridge is equipped with multiple open-top tanks to temporarily store test oil/fluid recovered during a test. Two of the modules are partitioned into eight sections, with each section having 946 l capacity, while the other two modules each have four sections, with each section having 2,264 l capacity. All of these calibrated tank sections have control valves to decant free water from the recovered fluids.
The test tank has a wave generator that can generate waves up to one meter in amplitude, and the amplitude, frequency and wave length can be varied. An adjustable beach system is used to attenuate the waves, when desired, and is used to create breaking, non-breaking, and harbor chop waves. In addition, there is an on-site oil/water chemistry laboratory to analyze test oils.
Ohmsett is the largest facility in North America for testing oil spill response equipment. Built in 1974, it has facilitated the testing of a wide variety of spill countermeasures in a controlled, repeatable and safe environment. Initially, the focus was on the testing of containment booms and mechanical recovery skimmers. The facility has since expanded its capabilities to meet the needs of the spill research community and can now perform testing of dispersants, chemical herders, weathering, in-situ burning, pumping and separation devices, simulated pipe discharges, detection of surface slicks, and detection and recovery of suspended oil plumes.
BSEE manages the facility as mandated by the Oil Pollution Act of 1990 (OPA ‘90). In accordance with OPA ‘90, agencies represented on the Interagency Committee are to ensure the long-term use and operation of Ohmsett for oil pollution technology testing and evaluations. More information on the Interagency Committee can be found at www.iccopr.uscg.gov.
Ohmsett is an integral part of BSEE’s oil spill research program and directly supports BSEE’s goal of ensuring the best and safest oil spill detection, containment and removal technologies are available to protect the U.S. Coast and ocean environments.
3 OPERATIONAL TESTING
Ohmsett’s mission is to increase oil spill response capabilities through independent and objective performance testing of equipment, and improve response technologies through research and development. Many of today’s commercially available oil spill cleanup products and services have been tested at Ohmsett, either as off-the-shelf commercially available equipment or as equipment or technology under development.
Ohmsett provides an intermediate step between small scale “bench testing” and open-water testing of equipment. Manufacturers, researchers, and end-users have the opportunity to 1) conduct proof of concept prototype testing; 2) evaluate oil recovery and oil containment capabilities; 3) evaluate sea-keeping abilities; 4) validate the performance of full-scale response equipment in dynamic conditions and; 5) evaluate the logistics of transporting and deploying equipment as well as ease of decontamination cleaning. In addition, operational testing aids response organizations in making well-informed decisions through competitive acceptance testing of response equipment, ensuring that the best equipment is available during a spill response.
While Ohmsett is available to academia and commercial entities on a cost reimbursable basis, the Ohmsett tests discussed in this paper were BSEE funded. BSEE collaborated on many projects with other agencies, including: Remote sensing tests of surface oil with the National Oceanic and Atmospheric Administration (NOAA), the United States Army, the United States Coast Guard (USCG), and the United States Environmental Protection Agency (U.S. EPA); tests using acoustics to measure oil slick thickness; studies to create large volumes of emulsions for Ohmsett tests; testing mechanical recoverability of chemically treated, undispersed oil; skimmer testing in diminishing slick thickness; a USCG and BSEE test of a skimmer ice management system; and an autonomous skimmer development.
Hundreds of tests have been conducted at Ohmsett over the years and those selected for this paper were related to recent testing and research with an emphasis on a system approach to mechanical recovery. One regular comment by Oil Spill Removal Organizations (OSRO) is that if you can’t find the oil, you can’t recover it. This is particularly challenging in low visibility conditions. Another challenge is determining the thickness of oil slicks so skimming operations can concentrate on those slicks. Remote sensing of oil tests conducted at Ohmsett will aid OSROs in not only locating oil, but locating the thickest oil, and one day this technology may be used to relay information to skimmers to autonomously recover oil, even in low light conditions.
Ohmsett seeks to create the most realistic test conditions possible. Oil spilled in open waters not only weathers, but often emulsifies. Creating large volumes of stable emulsions for test purposes has been challenging and BSEE is funding an ongoing project to efficiently create large volumes of stable emulsions. These methods are now being used to create emulsions for Ohmsett testing.
Tests are also conducted at Ohmsett to determine how operating conditions affect recovery efforts. Several years ago, BSEE partnered with the USCG to investigate how the presence of ice floes affected a skimmer’s performance. As a result of those test, BSEE and the USCG collaborated to test an ice cage to improve a skimmer’s performance in the presence of ice floes. This paper also highlights a BSEE funded project to investigate how a skimmer’s performance is affected by an oil slick of diminishing thickness.
While numerous dispersant tests are conducted at Ohmsett, one recent test that is particularly relevant to mechanical recovery was in response to OSROs’ comments that oil that had been treated with dispersant but had not dispersed was more challenging to recover than untreated oil. BSEE funded a test to investigate this and that test is highlighted in this paper.
Privately funded tests are regularly conducted at Ohmsett and while their data is generally proprietary, details of how the tests were conducted are often featured in the bi-annual Ohmsett Gazette, http://www.ohmsett.com/gazette.html
4 REMOTE SENSING
4.1 Calculating Flow Rates in an Undersea Well Blowout
The ability to quickly and accurately determine flow rates of an undersea blowout is critical for an effective oil spill response. A National Energy Technology Laboratory (NETL) research team conducted large-scale tests at Ohmsett to further develop a technique to calculate flow rates of undersea blowouts.
Since flows can be scaled by their Reynolds number, a light viscosity oil was used. Ohmsett staff blended two refined oils, Jet-A and JP5 aviation fuel, to create a test oil with the proper viscosity. To create high speed underwater discharge flow rates, Ohmsett engineering mounted 25 mm and 76 mm nozzles on test fixtures near the bottom of the test tank and used hydraulic pumps to propel test oil through the nozzles (Figure 2). Using this system, they were able to simulate an undersea blowout with oil flow rates from 280 liters per minute (lpm) to 3,330 lpm, roughly equivalent to 2,500 barrels (bbl) per day to 30,000 bbl/day. At these flow rates, they were able to produce jet velocities up to 38 m/s.
NETL’s team used high speed cameras to track the physical features of the plume, such as the formation of transport eddy currents. Using this data and the theory of turbulent jets, they were able to calculate flow rates. They then compared their calculated values to the known flow rates created in Ohmsett’s test tank to verify the accuracy of their model. NETL is developing this technique to use as part of a remotely operated vehicle (ROV) field-ready tool. Further software development may allow the use of less expensive off-the-shelf video cameras, as well as reduce the time to calculate flow rates to a matter of hours. Here’s a link to the project page where a final report will be posted: https://www.bsee.gov/research-record/osrr-1027-development-rov-deployed-video-analysis-tool-rapid-measurement-submerged
4.2 Oil Spill Detection in Low Light Conditions
Detecting and tracking oil spills in low light conditions and at night is especially challenging. Researchers from the U.S. Army Night Vision and Electronic Sensors Directorate (NVESD) conducted tests at Ohmsett as part of their project to develop enhanced oil spill detection sensors for low-light environments. The goal is to enhance real-time methods to remotely detect crude oil in a marine environment in degraded visual environments (DVE), which includes darkness, snow, rain, dust, fog, smoke, and clouds. NVESD’s MARINE SCOUT is a compact, lightweight, motion-compensated, multi-spectral sensor with flash memory data storage. The system is derived from military low-light technology and has full compatibility with small unmanned aerial vehicles (UAV) to remotely detect spilled oil over a wide area.
Night vision instruments rely primarily on infrared (IR) sensors to detect radiation, either emitted or reflected. Since oil and water emit IR differently, the sensors are able to capture the contrast in radiation between the oil and water to detect an oil spill. In general, oil on the water’s surface appears warmer than the surrounding water during daylight hours, while the oil appears cooler than the surrounding water at night.
Low-light testing was conducted at Ohmsett where weathered crude oils were placed in targeted areas and the oil was scanned with long-wave infrared (LWIR), near infrared (NIR), and short-wave infrared (SWIR) cameras. Test were conducted during the afternoon (full sun), sunset, and evening (night conditions, under partial moonlight) to capture data during the thermal crossover period when the water and oil have the same apparent temperature and are indistinguishable. Once the thermal crossover period was over, the sensors were able to detect the oil after dark and in low light conditions (Figure 3). Here’s a link to the project page where a final report will be posted: https://www.bsee.gov/research-record/osrr-1013-enhanced-oil-spill-detection-sensors-low-light-environments
4.3 Creating Stable Water-in-Oil Emulsions
Researchers are developing sensors to remotely detect fresh and weathered/emulsified oil, but creating large volumes of emulsified oil for test purposes has always been challenging. BSEE recently funded a study to create stable emulsions. This on-going project is multi-phase, starting with creating small batches in Ohmsett’s Oil/Water Lab. Following the lab tests, researchers ramped up to mid-scale to produce emulsified oil via artificial means to weather and mix the oil and water in small tanks. With mid-scale tests complete, they were able to produce large quantities of emulsified oil on the surface of Ohmsett’s test tank (Figure 4) by simulating conditions found in the open ocean.
For this study, researchers obtained HOOPS crude oil, a light viscosity Gulf of Mexico (GOM) pipeline crude oil blend. In the lab, different methods were used in controlled and repeatable conditions to create the emulsions. Using these results, larger volumes were created by artificially weathering the oil in 208 liter (55 gallon) drums using air sparging. Once the oil was weathered, industrial mixers were used to introduce saltwater into the oil to create the emulsions. Following these mid-scale tests, researchers intentionally discharged approximately 1500 liters of HOOPS oil onto the surface of Ohmsett’s wave tank. After several days of weathering and photo-oxidation, Ohmsett’s wave generator was used to emulsify the oil through the wave’s shearing energy. By allowing the oil to weather, photo-oxidize and emulsify via wave shearing action in conditions similar to the open ocean, researchers were able to create realistic emulsified oil for use in upcoming tests to remotely detect emulsified oil slicks. A report will be available on BSEE’s website.
4.4 Remote Sensing of Oil Slicks using Multiple Platforms
Remote sensing of oil slicks is a key component of an oil spill response, but even more useful is determining the relative thickness of the oil so responders can be dispatched to the thickest slicks and most recoverable oil. BSEE recently partnered with NOAA, USCG, and EPA to evaluate how well different remote sensing platforms could detect, and determine the relative thickness of, oil slicks on Ohmsett’s test tank (Figure 5) to better understand the capabilities and limitations of each system.
Remote sensing instruments were mounted on Ohmsett’s Main Bridge, on an unmanned aerial system (UAS rotocopter), a fixed wing aircraft, a helicopter, and satellites. During the remote sensing overflights, physical data from the oil slicks was simultaneously obtained to compare with data obtained from the remote sensors. In-situ oil samples were obtained using dip plates, sorbent pads, and manual- and radio-controlled tube samplers for grab sampling at multiple depths.
For these tests, approximately 1500 liters of HOOPS crude oil was emulsified in Ohmsett’s test basin using a recently developed technique of natural weathering, photo-oxidation, and tank-generated waves. This method created emulsions with approximately 80% water-in-oil content.
Once the emulsions were created, the goal was to have the airborne sensors overfly the tank within 30 minutes of the satellites’ overflights. The satellites used synthetic aperture radar (SAR). The fixed wing aircraft used a complement of instruments, including: Side Looking Airborne Radar (SLAR); Laser Fluorosensor (LFS); Microwave Radiometer (MWR); and, Electro Optical Infrared (EO/IR). The manned helicopter and UAS rotocopter collected data using thermal IR, as well as visible red, green, blue (RGB) sensors. Data was collected from multiple angles and altitudes to compare with the satellite imagery and physically collected oil samples. Here’s a link to the project page where a final report will be posted: https://www.bsee.gov/research-record/osrr-1079-deepwater-horizon-lessons-learned-methodology-and-operational-tools-to
4.5 Underwater Acoustic Slick Thickness Measurement
BSEE funded research to detect and measure oil slick thickness from below the water’s surface. This is particularly useful where ice is present and conventional tools have limited effectiveness. It is also a valuable tool for tests conducted at Ohmsett. While a number of methods are used to determine slick thickness during a test, such as mass-balance and a Tactical Rapid Airborne Classification System (TRACS), mass-balance is difficult to perform in real time and TRACS is limited to thin slicks.
Acoustics transducers are able to readily travel through, and detect the difference between, seawater and oil slicks, including thick oil slicks. BSEE awarded a contract to build an acoustic sensor package that was mounted on a remotely operated vehicle (ROV). As the prototype would be used at Ohmsett, the ROV was a heavier than water device that would sink to the bottom of the tank, and it was equipped with motor-drive rubber crawler tracks to maneuver along the bottom of the tank. The underwater rover (Figure 6) was equipped with multiple upward looking acoustic sensors, an upward looking high definition camera, and a forward looking camera to assist while maneuvering.
The system is able to determine oil slick thickness in both calm conditions and moderate wave conditions. The system has been used to verify slick thickness on a number of tests at Ohmsett, particularly ASTM F-2709 Standard Test Method for Determining a Measured Nameplate Recovery Rate of Stationary Oil Skimmer Systems. The system works well with fresh oil as there is a clear demarcation between the oil and water interface. As the oil becomes weathered and oil at the interface takes on water, there is not a clear distinction for where the oil/water interface is and accuracy diminishes. Future software enhancements may mitigate this condition. Here’s a link to the project page where a final report will be posted: https://www.bsee.gov/research-record/osrr-1028-acoustic-tool-measure-oil-slick-thickness-ohmsett
5 MECHANICAL RECOVERY
5.1 Developing an Autonomous Skimmer
Spilled oil is often located on surface water that is difficult to reach or recover using conventional human-operated skimmers. BSEE is funding research to develop skimmers that one day may be able to autonomously maneuver, detect, and collect spilled oil on surface waters. This is a multi-phase project that is investigating components that can measure oil thickness on surface water, develop an autopilot system that will maneuver the skimmer to track with an oil slick, and recover oil without operator input.
Thickness sensing tests were conducted at Ohmsett by using boom to create a channel. Within the channel, four slicks of different thicknesses were created, interspaced with clear water (Figure 7). As the sensor travelled down the channel at various speeds, it encountered the spilled oil and collected data. The first tests were in calm water, followed by tests in moderate waves. The data was later compared with the known slick thickness. Preliminary results indicate that further work is needed with the sensors’ hydrodynamics as moving through the water changes the fluid dynamics in the sensor’s near field, affecting the sensors’ accuracy. Here’s a link to the project page where a final report will be posted: https://www.bsee.gov/research-record/osrr-1037-development-autonomous-oil-skimmer-aos
5.2 Developing a Skimmer Ice Management System
Previous BSEE funded research indicated that one factor detrimental to recovering oil in ice infested water is that ice floes tend to collect around the skimmer, impeding oil flow to the skimmer and reducing oil recoverability. In follow-on research, USCG’s Research and Development Center (RDC) partnered with BSEE to investigate possible solutions. One solution is an ice cage that surrounds a skimmer (Figure 8). An effective cage allows oil to flow to the skimmer while keeping ice floes away from the skimmer. USCG funded a contractor to construct an ice cage that could be used with two different skimmers, and the systems were tested at Ohmsett.
To create a simulated arctic environment, sea ice was grown at the Army Corp of Engineer’s Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire and shipped to Ohmsett. The 1 m × 1 m × 0.2 m thick ice slabs were broken into multiple sizes to create a realistic ice field, and the skimmers were tested in two ice field concentrations: 30% ice coverage and 70% ice coverage. An ice field with 30% ice coverage is the threshold where ice begins to impact recovery efforts, while an ice field with 70% ice coverage is the upper limit where mechanical recovery is feasible.
Once the ice was placed into the test field, Hydrocal 300 test oil was dispensed onto the water surface to create a 25 mm thick slick. To verify the ice concentrations throughout the test series, two methods were used: Overhead digital photographs were taken and pixel counting software was used to differentiate between the ice and the oil; and, a Tactical Rapid Airborne Classification System (TRACS) processed images obtained from its thermal imaging camera to calculate ice coverage.
With the ice and oil in the test area, an oleophilic drum skimmer was rigged in the ice cage and lowered into the test area. The ice cage has a conical lower section to pierce an ice field and push ice away from the skimmer as the cage is lowered into the field. Flotation devices on the ice cage allow it to float independently of the skimmer so it does not impact the skimmer’s freeboard on the water surface.
With all the equipment in place, the skimmer was started and as it was recovering oil, it was moved throughout the ice field to encounter oil. When tests were completed with the oleophilic drum skimmer, it was replaced by an oleophilic brush skimmer and the tests were repeated. The report will be available on BSEE’s website.
5.3 Diminishing Slick Thickness Testing
Ohmsett tests skimmers following the guidelines of ASTM F-631 Standard Guide for Collecting Skimmer Performance Data in Controlled Environments and ASTM F-2709 Standard Test Method for Determining a Measured Nameplate Recovery Rate of Stationary Oil Skimmer Systems. Performance testing is conducted as a skimmer recovers oil in a slick that diminishes from 76 mm (3 inches) to 51 mm (2 inches). It is understood that this provides ideal conditions and are likely maximum values for both oil recovery rate (ORR) and recovery efficiency (RE).
In field operations, skimmers may operate in much thinner slicks. BSEE conducted a series of tests to collect data on skimmer performance as a slick diminished from 76 mm (3 inches) to 13 mm (1/2 inch). Seven different skimmers from Ohmsett and USCG’s inventory were tested: An Elastec TDS 118G Grooved Drum Skimmer; a Crucial C-14d Mop Wringer System; a Lamor LWS 500\GTA50 Weir Skimmer; a Desmi AFTI MI-2HD Disc Skimmer; a Desmi Terminator Weir Skimmer; a Crucial C-13/24 Coated Disc Skimmer; and, a Desmi Dop-Dual Terminator with Helix Circular Brush Skimmer.
Tests were conducted in a boomed section of Ohmsett’s test tank. Per ASTM F-2709 guidelines, the area was three times the length and three times the width of the skimmer. Two different test oils were used: Hydrocal 300, a light viscosity oil; and, Calsol 8240, a medium viscosity oil.
Prior to the (3) qualifying runs, which were then averaged, each skimming system was operated to find its optimum operational settings. To be a valid test, three runs must be performed at identical skimmer settings and each of the three runs must be within 20% of the mean, with each run achieving a minimum RE of 70%. Once the optimum values were obtained, each system was brought to steady-state recovery operation prior to the start of each run. Per F-2709, runs were conducted for a minimum of 30 seconds each, with recovered oil collected in calibrated recovery tanks located approximately 4 m above the water surface.
After each test, the recovery tanks were sounded to determine the gross amount of fluid recovered. The recovered fluid was allowed to settle for 30 minutes, after which the tanks were decanted of free water and a second sounding was taken. The remaining fluid was stirred and a representative sample was obtained and sent to Ohmsett’s Oil/Water Lab to determine the amount of entrained water and solids present in the recovered oil. From the test data, performance values were calculated for Oil Recovery Rate (ORR) and Recovery Efficiency (RE). The formulas for ORR and RE are:
Oil Recovery Rate (ORR):
Recovery Efficiency (RE):
5.4 Mechanical Recovery of Chemically Treated, Undispersed Oil
There have been anecdotal claims that undispersed surface oil that had been chemically treated is more difficult, if not impossible, to recover with conventional containment booms and skimmers. BSEE funded research to investigate whether oil treated with low doses of dispersant that has not dispersed and is floating on the water surface can be collected and recovered with conventional boom and skimmers.
Following initial research in Ohmsett’s oil/water lab, full scale tests were conducted at Ohmsett. For the recovery portion of the tests, two oleophilic skimmers were used: A smooth-drum skimmer and a disc skimmer, fitted with aluminum (uncoated) discs. Following the general guidelines of ASTM F-2709 Standard Test Method for Determining a Measured Nameplate Recovery Rate of Stationary Oil Skimmer Systems, each skimmer was deployed in a test area that was filled with 76 mm of oil floating on top of saltwater. Tests were conducted with HOOPS crude oil, a GOM pipeline blend that had been artificially weathered to simulate oil that had been floating on the surface. Following tests using weathered oil that had not been treated with dispersant, tests were conducted with weathered HOOPS oil that had been treated with various low doses of dispersant, and the ASTM 2709 tests were repeated to determine oil recovery rate (ORR) and recovery efficiency (RE).
The next phase of testing compared collecting treated vs. untreated oil using conventional containment boom in advancing mode following the general guidelines of ASTM F-2084 Standard Guide for Collecting Containment Boom Performance Data in Controlled Environments. A 15 m (50 foot) boom was rigged in a 3:1 U-configuration to Ohmsett’s main bridge so it could be towed through the water, simulating a response vessel towing boom to collect oil at sea. As the boom was towed down the tank at various speeds, HOOPS crude oil was dispensed onto the surface of the tank and allowed to collect in the apex of the boom, simulating oil collected at sea (Figure 9). High definition underwater camera’s recorded the test to determine first loss and gross loss tow speeds. First, HOOPS oil that had not been treated was collected and tow speeds recorded; then the tests were repeated using HOOPS oil that was treated with low doses of dispersant. The report of the skimmer and booms test will be available on BSEE’s website.
Ohmsett supports a wide range of research, development, testing and training to improve oil spill response. BSEE makes Ohmsett available to researchers from around the world and to date, participants from 36 countries have utilized Ohmsett’s unique capabilities.
This paper highlighted some of the recent research and development testing conducted at Ohmsett and while many tests and data are proprietary, BSEE funded test reports are available on BSEE’s website - https://www.bsee.gov/site-page/master-list-of-oil-spill-response-research.