When Exxon’s Pegasus oil pipeline ruptured in Mayflower, Arkansas on March 29, it flooded streets and homes in a pretty suburban subdivision with dilbit — that’s “diluted bitumen.” Bitumen is a sticky, heavy precursor to oil; it’s the stuff that is being extracted from the vast tar sands mining operations up in Alberta, Canada.  The bitumen is diluted with lighter hydrocarbon liquids that essentially act as solvents so it can flow through the pipeline.

A similar pipeline rupture in Michigan in 2010 flooded the Kalamazoo River with dilbit, a substance that — unlike crude oil — sinks rather than floats, making the cleanup significantly more difficult and expensive.

The Mayflower cleanup has also been a prolonged and contentious operation, with local residents reporting illnesses in the aftermath, and disagreement about exactly what areas have been impacted.

This series of before-and-after pairs of high-resolution images of the Mayflower area yields some clues.  The “before” imagery is aerial survey photography from Google Earth that was taken on September 4, 2010.  The “after” imagery (provided to us courtesy of Sierra Club Arkansas Chapter) was shot from DigitalGlobe’s Worldview-2 satellite on July 31, 2013, four months after the spill. Some changes are easy to see: large light brown areas of bare soil show where excavation and soil removal occurred; and a notable loss of aquatic vegetation in a cove that empties into Lake Conway.

Overview showing area of March 2013 pipeline spill in Mayflower, Arkansas. Left/Before – September 2010 : Right/After – July 2013. Images courtesy of Sierra Club Arkansas Chapter.

Detail 1: In the lower-left (next to SkyTruth logo) is the subdivision that was flooded with dilbit during the March 2013 spill. The Pegasus pipeline right-of-way cuts diagonally across the left (west) side of the image; two long driveways at the end of the cul-de-sac at the northwest corner of the subdivision lie directly on top of the pipeline. In the July image (right), light brown patches on north side of the subdivision probably shows area of soil that were excavated and removed as part of the cleanup operations. Oil flowed from west to east, toward Lake Conway. Left/Before – September 2010 : Right/After – July 2013 Images courtesy of Sierra Club Arkansas Chapter.

Detail 2: West end of the cove and wetlands where the spill apparently entered Lake Conway. In the after image (right) floating booms (thin, pale light lines) are strung across the cove in attempt to intercept the dilbit. Turbid, open water and very pale green area (newly planted grass?) suggest impact to wetlands and aquatic vegetation in this area. Left/Before – September 2010 : Right/After – July 2013. Images courtesy of Sierra Club Arkansas Chapter.