Bilge slick detail

PERKASA Caught Bilge-Dumping?

Possible Bilge Dumping by Indonesian Cement Carrier in the Strait of Malacca

By Lucy Meyer

On February 15, 2019, a vessel that appeared to be releasing oily waste was captured by satellite almost 10 kilometers offshore Peureulak, a small town in Aceh Province, on the northern tip of the Indonesian island of Sumatra. Radar imagery from the European Space Agency’s Sentinel-1 satellite shows an 18-kilometer slick trailing a northbound ship, visible as a bright spot at the end of the dark slick.

Bilge slick detail
Figure 1. Sentinel-1 radar satellite image showing suspected bilge-dumping (dark, linear slick) off Sumatra on February 15, 2019.

The ship is traveling through the Strait of Malacca, a narrow strip of water between Sumatra and the Malay Peninsula. The Strait is one of the world’s busiest shipping lanes as it is both the shortest and most convenient path between the Indian and Pacific Oceans. Due to the Strait’s high density of marine traffic of all types, oil spills — accidental and intentional — are likely to occur. Figure 1 illustrates suspected bilge dumping, a typically intentional discharge of oily waste from ships to reduce ballast water or free up space in the cargo holds. Typically, bilge-dumps form distinctive linear slicks visible on satellite imagery.

While radar satellite images are very useful tools for detecting slicks, they are typically not detailed enough to allow identification of the responsible vessel. However, many vessels broadcast their identity and other information using the radio-frequency Automatic Identification System (AIS). AIS use is required for all large cargo vessels and tankers. By studying the AIS broadcasts in this area using exactEarth’s ShipView service, which collects the signals using satellites and ground-based receivers, SkyTruth analyst Bjorn Bergman determined the Indonesian cement carrier PERKASA (Figure 2) was at this location when the Sentinel-1 radar image was acquired. Formerly known as KOEI MARU NO 7, the vessel was built in 1981 by Ube Industries, Ltd., a Japanese chemical manufacturing company. Today, the ship is operated by PT Indobaruna Bulk Transport (IBT), an Indonesian shipping company based in Jakarta.

Figure 2. MV PERKASA [source: IBT].
Figure 3. PERKASA’s AIS broadcast track overlain on Sentinel-1 image.

Figure 3 shows the PERKASA’s  AIS-derived track overlain on the Sentinel-1 image, revealing a very close match between the vessel’s path and the suspected bilge slick. The AIS signal immediately to the south of the vessel location on the image indicates it was traveling 11 knots (~20.4 km/h) at 11:17 UTC;  the signal immediately following at 12:10 UTC indicate the vessel was traveling 10.8 knots (~20.0 km/h). Using the location data encoded with these AIS signals, we calculated the likely position of PERKASA at the instant the image was acquired (11:43 UTC). The ship’s predicted location closely matches the vessel’s position in the Sentinel-1 image, and no other vessels broadcasting AIS were likely candidates for a match. This leads us to infer that PERKASA is the vessel seen apparently discharging oily bilge waste in the satellite image.

Slicks to the south
Figure 4. Zoomed-out view of Sentinel-1 image showing a series of patchy slicks along the coast of Aceh Province, Indonesia. Dark, linear slick at upper left is the suspected bilge slick from PERKASA shown in Figures 1 and 3.

To the south, a chain of less-distinctive slicks along the coast are roughly aligned with PERKASA’s track (Figure 4). These slicks are broad and striated as opposed to the slender 18-kilometer long slick, which could be a result of wind and current blowing apart what had originally been a series of discharges from the vessel. The AIS transmissions from PERKASA are infrequent in this region (Figure 5), making us somewhat less confident that this vessel was also the source of these patchy slicks.

Slicks to the south + AIS
Figure 5. PERKASA’s AIS-derived track overlain on Figure 4.

The operator of PERKASA, IBT, claims “we put high priority in safety by adhering to policies, practices, and procedures in our Safety Management System to ensure the safety of crews, staffs, cargoes, vessels, as well as environment.” In addition nearly all of IBT’s fleet is registered with classification societies. According to The International Association of Classification Societies (IACS), the purpose of a classification society is “to provide classification and statutory services and assistance to the maritime industry and regulatory bodies as regards maritime safety and pollution prevention.” IACS is a non-governmental organization composed of twelve classification societies.  PERKASA is registered with Biro Klasifikasi Indonesia (BKI) and Nippon Kaiji Kyokai (ClassNK), which is a member of IACS.  

One of the certification services provided by ClassNK is the Verification for Clean Shipping Index (CSI). The objective of CSI is to verify the environmental performance of a vessel’s operations in five areas, including water and wastes. Ballast water, sewage/black water, garbage, sludge oils, and bilge water are covered under this category.

Bilge dumping — intentional or otherwise — would seem to violate the principles touted by the vessel operator, and call into question the effectiveness of the classification societies.  


Possible Bilge-dumping Offshore Indonesia

Near the northern tip of Indonesia’s Bangka Belitung Islands (located directly below the yellow box within the inset map of image 1), I spotted a slick that resembles clock hands pointing to the hours 4 and 11. Captured by radar satellite, Sentinel-1, on the evening of January 8, 2019 (22:40 GMT), the slick stretches at least 117 kilometers. Due to the slick’s narrowness and distinct sharp turn in track, it is likely a bilge dump. To the right, the slick trails beyond the edge of available imagery. Though we cannot see the responsible vessel on this image, the sharp linear impression of the slick indicates that it probably passed through the area within 24 hours of the scene’s capture.

Image 1. Sentinel-1 scene of slick approximately 50 km north of Bangka Belitung Islands. See text for explanation.

SkyTruth analyst Bjorn Bergman verified this presumption. To look for similarities in timing and trajectory, Bergman used ExactEarth’s ShipView, a web-based platform that provides access to automatic identification system broadcasts (a global vessel tracking system commonly abbreviated to ‘AIS’), and identified the Indonesian crude oil tanker GAMSUNORO as a possible source.

Image 2. ExactEarth ShipView displaying AIS signal of tanker GAMSUNORO.
Credit: Includes material © 2019 exactEarth Ltd. All Rights Reserved.

Image 3 juxtaposes the slick and GAMSUNORO’s AIS signal. Traversing southeast, the ship’s first signal was recorded at 12:59 GMT. Close to 14:00 GMT, the vessel encountered the area with the slick. From this information, we know the tanker’s predicted track occurred approximately 8 ½ hours before the scene was captured. In addition, the vessel’s path imitates the shape of the slick. However, the ship’s track is slightly displaced to the northeast. It is possible that the slick may have drifted due to steady winds blowing from the NE (~6-13 knots) at least seven hours prior to the image’s capture. There appears to be a strong correlation in the temporal and spatial attributes of slick and ship, indicating that the GAMSUNORO is a likely source. To corroborate our findings, we followed the ship as it sailed southbound.

Image 3. GAMSUNORO’s AIS signal superimposed onto the Sentinel-1 scene

Initially, we anticipated the ship would journey to Jakarta; however, image 2 displays the vessel’s latest position (January 14, 2019 at 10:55 GMT) anchored about 6 miles offshore near the town of Indramayu. With an updated version of the vessel’s track, we may be able to find evidence of a continued slick either on their way south or at their current anchorage. Whether or not we are able to positively ID the perpetrator, this is one of many examples displaying the temporal challenges of using satellite imagery to capture not just illegal activity but any short-lived phenomena.

The remnants of a likely bilge dump (dark streak) possibly from a vessel traveling north to a tanker “parking lot” (the cluster of dozens of bright spots, each representing a vessel at anchor) off the coast of United Arab Emirates.

From Monitoring for Bilge-Dumping to Analyzing Coal Mining Activity and Mapping a Proposed Pipeline Expansion, My Year in Review

International Projects

This summer, SkyTruth began monitoring bilge dumping “hotspots.” I focused my monitoring efforts in the coastal waters surrounding the United Arab Emirates and Oman or the “tip” of the Arabian Peninsula. I began by visiting the European Space Agency’s datahub (and USGS) daily and downloading tons of imagery. The downloading of imagery was tedious and time-consuming. Using Google Earth Engine, we created scripts to input an AOI and automatically queue up all the imagery in a specified date range, which is easy. But Earth Engine has a lag time ingesting new imagery from various satellites, so I still need to manually download from ESA’s data hub to obtain the most recent imagery. I customized different versions of the script with different AOIs covering the coastal waters I wanted to monitor.

The remnants of a likely bilge dump (dark streak) possibly from a vessel traveling north to a tanker “parking lot” (the cluster of dozens of bright spots, each representing a vessel at anchor) off the coast of United Arab Emirates.

The remnants of a likely bilge dump (dark streak) possibly from a vessel traveling north to a tanker “parking lot” (the cluster of dozens of bright spots, each representing a vessel at anchor) off the coast of United Arab Emirates.

Bilge is an oily liquid that accumulates in the bottom of the hull, and vessel operators will sometimes just dump it overboard. If the vessel is moving while bilge dumping, then the slick appears on radar satellite imagery as a long, skinny, black line. But if a vessel releases the fluid while anchored then the slick can appear as an irregular black patch. There are examples of both above and below. Sometimes the vessel would still be in the range of its environmental “gift.” Then we could report on that vessel as the likely culprit evidenced by satellite imagery. Satellites don’t lie.

The Nordic Jupiter, a crude oil tanker, anchored offshore Fujairah in the United Arab Emirates, and located at the likely source of an apparent oil slick, suggesting a leak or possibly intentional bilge dumping.

The Nordic Jupiter, a crude oil tanker, anchored offshore Fujairah in the United Arab Emirates, and located at the likely source of an apparent oil slick, suggesting a leak or possibly intentional bilge dumping.

Domestic Projects

Much of my time was spent on the Google Earth Engine surface mining identification process, which involved using Landsat satellite imagery to create a composite of only the greenest pixels from each year’s summer months and creating a NDVI band from that composite. The purpose was to identify bare rock and soil typical of active strip-mining operations, like mountaintop removal mining (MTR) to extract coal.

The Normalized Difference Vegetation Index (NDVI) is a ratio of a pixel’s red value to its near-infrared value. Vegetation absorbs most visible light but reflects the infrared, while bare surfaces reflect both. A low NDVI value indicates a bare surface and a high NDVI value indicates healthy vegetation. By masking out all urban areas, streets, railroads, etc., the only large bare surfaces left in our Appalachia study area are large-scale coal mining operations.

This process requires a lot of satellite imagery. To accomplish this, I used Google Earth Engine, a cloud-based platform with access to satellite imagery collections and various geospatial datasets, including the entire archive of Landsat images going back into the early 1970s.

In central Appalachian states like West Virginia, mountaintop removal is the process of removing the several top layers of rock to expose coal seams. It is a resource-intensive process that results in massive landscape change.  As much as 85% of federal coal comes from Wyoming and Montana, specifically the Powder River Basin. My job was to attempt to adapt our process designed around Appalachia to the flat, dry shrublands of Wyoming and document the results.

The first step was creating a new area of interest (AOI). In Wyoming, the Powder River Basin spans two counties in Wyoming (Converse and Campbell), and those county boundaries formed the study area. The next step was creating the mask to eliminate areas that we didn’t want to analyze. That process involved downloading GIS shapefiles for hydrology (lakes/ponds, rivers/streams), urbanized areas, roads, railways, and oil & gas drilling sites. Shapefiles are georeferenced to represent these features on a map accurately. To create the mask, these shapefiles were merged and converted to a binary image. We could exclude these elements from the analysis because some were misidentified as active mining.

Coal mining in Black Thunder coal mine, WY from 1985 (in green) to 2015 (in red) overlain on 2015 aerial survey photography (NAIP).

Annual progress of landscape disruption caused by coal mining at the Black Thunder coal mine, WY, from 1985 (green) to 2015  red) overlain on 2015 aerial survey photography (NAIP).

I also worked with Tracy Cannon of Eastern Panhandle Protectors on Mountaineer Gas Company’s proposed pipeline across the Eastern Panhandle of West Virginia. A very rough, general path for the pipeline had been published, but the particular route is not being shared by the company or state regulators. To give the public a more precise view of the pipeline’s likely route, Tracy visited county courthouses and gathered publicly available information about easements purchased by the gas company on dozens of properties in the area. She shared that information with us. We combined it with a public GIS layer for tax parcels that includes the outlines of residential and commercial properties. By using Google Earth to view all of the properties that had sold easements to the gas company, a more detailed pipeline path began to take shape through Morgan, Berkeley, and Jefferson counties. I discussed some assumptions about pipeline construction with the Protectors (to minimize construction costs a pipeline will take the shortest route between two points, but will also avoid sharp turns and steep slopes, excessive road and stream crossings, and when possible will keep clear of homes and other structures. With that in mind, I analyzed the Google Earth imagery and manually traced what I considered to be the likely pipeline path through our own Eastern Panhandle. The map shown below is our “best guess” based on the easement information provided by Tracy, and the very crude maps made public by Mountaineer.

The hypothetical Mountaineer pipeline path (dashed red line) overlain in Google street-view. The proposed pipeline enters Morgan County at upper left across the Potomac River and continues through Berkeley and Jefferson County.

The hypothetical Mountaineer pipeline path (dashed red line) overlain in Google street-view. The proposed pipeline enters Morgan County at upper left across the Potomac River and continues through Berkeley and Jefferson County.

My time as a SkyTruth intern was divided among a diverse set of projects, and it was certainly well spent. I’ve garnered an in-depth understanding of GIS and satellite imagery processing, map-editing, and worked in a team environment to accomplish complex tasks. Satellite images offer so much more than their beauty. I conclude my time at SkyTruth a true believer in the power of satellite imagery for environmental conservation. If you can see it, you can change it!


Bilge Dumping Proving to be a Persistent Issue for the UAE

15 kilometers (about 9 miles), off the coast of Fujairah and Khor Fakkan in the United Arab Emirates is a popular tanker parking lot.

Tankers anchored offshore of Fujairah and Khor Fakkan in the UAE.

There is no issue with this, until you consider the fact that it appears to be the cause of persistent pollution problems for the UAE. There have been 4 spills in the past 3 months and local communities are getting fed up as these spills impact both local businesses and the environment.
This image, collected on May 24, by the European Space Agency’s Sentinel 2 satellite shows the Nordic Jupiter, one vessel which was anchored offshore as well as oil slicks visible on the surface of the water. While we don’t know if the Nordic Jupiter is the source of this slick, it seems likely based on this image.

The Nordic Jupiter and oil slicks off the coast of the UAE.

Occasional overflights by enforcement agents would be more than sufficient to police this parking lot, to deter future dumping, and to catch violators.

Bilge Dump? in Gulf of Mexico

Probable oil slicks on this Sentinel-1 radar satellite image, taken over the Taylor Energy site in the Gulf of Mexico at about 7:30 pm local time on February 14, caught our eye:

Sentinel-1 satellite radar image of the northern Gulf of Mexico, taken about 7:30 pm local time on February 14, 2017. Oil slicks are dark streaks. Ships and oil/gas platforms are bright spots. South Pass of the Mississippi Delta is at left. Image courtesy European Space Agency.

As usual, we can see a 9-mile-long slick emanating from that chronic oil leak that has been spilling oil continuously since 2004. The Taylor slick is drifting straight to the northeast away from the leak source on the seafloor.  But the image is dominated by a thicker-looking 28-mile-long slick closer to shore. It seems to almost hook up with the Taylor slick on it’s east end, suggesting it could be a major continuation of the Taylor slick.  This would make it one of the biggest slicks at Taylor we’ve ever observed; and if it is the Taylor slick, it makes a very unusual 180 degree turn.  That’s possible, given the complex currents:  outflow from the Mississippi River meets eddies spinning off the Gulf Stream, creating strong horizontal “shears” where the current on one side can be moving in a very different direction than on the other.  But there may be a simpler explanation: this could be an oily slick caused by intentional bilge dumping from a moving vessel.  Based on how the slick appears to be more pushed around by wind and current as you follow it back to the east, I’m guessing the vessel was moving from east to west, working its way around the tip of the Mississippi Delta parallel to shore.

Image above, labeled to identify oil slicks and the location of the chronic Taylor Energy leak. Possible vessel near west end of bilge slick marked by yellow circle. Sentinel-1 satellite radar image courtesy European Space Agency.

Dumping oily bilge is illegal in US waters, and we don’t often see this here — although it is a big problem elsewhere.  In this case, checking against our daily stream of Automatic Identification System (AIS) ship-tracking data, we haven’t been able to identify a possible culprit. There is a small bright spot near the west end of the slick that is probably a small vessel — there are no platforms or other structures at this location. This could be the culprit.  But it wasn’t broadcasting an AIS signal.

Detail from above, showing probable vessel located near west end of bilge slick. Is this the culprit? Sentinel-1 satellite radar image courtesy European Space Agency.