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Much of the attention on the damage of oil spills is focused on the environment and the repercussions on local industries, but cultural heritage suffers just as much. NCPTT has been researching ways to mitigate the damage done to sites of historic and archaeological significance, such as Fort Livingston. This 19th century coastal fort on Grand Terre Island, Louisiana, was badly contaminated by the 2010 Deepwater Horizon oil spill. This research project concerns the removal of weathered crude oil from historic brick and masonry like that used at Fort Livingston. The goal is to find a cleaning method that effectively strips the oil from the masonry without causing additional harm to either the structure or the environment.
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The Removal of Weathered Crude Oil from Historic BrickKatherine Langdon, Carol Chin, Mary Striegel
Deepwater Horizon Oil Spill
Sources: “Deepwater Horizon Oil: Characteristics and Concerns.” NOAA Office of Response and restoration, Emergency Response Division. May 15, 2010.
“Gulf oil spill, by the numbers.” Los Angeles Times. Sept. 18, 2010. <http://articles.latimes.com/2010/sep/18/nation/la-na-oil-spill-numbers-20100919>
Image: Adapted from “Cultural Resources Potentially affected by Deepwater Horizon Oil Spill.” GeoCommons. <http://geocommons.com/maps/16705>
The Spill◙ 205,800,000 gallons of crude oil spilled
◙ 33,600,000 gallons of oil collected by ships
◙ 11,140,000 gallons of oil removed in controlled burns
◙ 966 miles of coastline contaminated
◙ Impact: • Marine, coastal environment• Health hazard to cleanup workers• Fishing, tourism industries• Coastal historic, archaeological sites
The Oil
◙ The type of oil from this spill is called Mississippi Canyon Block 252 (MS252), a South Louisiana sweet
crude oil. (sweet = low in sulfur)
◙ Crude oil is a toxic mixture of thousands of different compounds
◙ Weathering:• Evaporation of lighter components• Mixture with water to form sticky, semi-solid emulsion called mousse• Mousse breaks apart and solidifies into tarballs, which remain in the environment
Test Brick SelectionAtlanta, Texas, Brick
Atlanta, Texas, bricks were chosen because they were the available brick most similar to those used in the construction of Fort Livingston.
◙ porous but durable (modern bricks are often not porous)◙ high amount of iron concretions◙ similar appearance◙ uses lime-based mortar◙ made in the South
Project OverviewWhy This Research is Important
Much of the attention on the damage of oil spills is focused on the environment and the repercussions on local industries, but cultural heritage suffers just as much. NCPTT has been researching ways to mitigate the damage done to sites of historic and archaeological significance, such as Fort Livingston. This 19th century coastal fort on Grand Terre Island, Louisiana, was badly contaminated by the 2010 Deepwater Horizon oil spill. This research project concerns the removal of weathered crude oil from historic brick and masonry like that used at Fort Livingston. The goal is to find a cleaning method that effectively strips the oil from the masonry without causing additional harm to either the structure or the environment.
Details of Fort Livingston, June 2010.
◙ Product composition analysis (MSDS) • pH compatibility (higher than 7)• Varied mechanism of action• Non-microbial
◙ Solubility tests • Combined 2 g tarry oil, 10 mL deionized water, and 3 mL SWA in test tube• Agitation/mixing• Observations recorded up to two days after agitation• Comparisons made between SWAs and their effectiveness and method
◙ On-site tests • Used test patches• On some, applied clay, clay and sand, or paper poultices with SWA overnight• On others, used direct application and agitation of SWA• Evaluated results
Did You Know?Mortar around bricks should be slightly softer than the bricks themselves so that the mortar will break down first if the wall is damaged or degrades. Mortar can be replaced through the process of repointing. Bricks are much more difficult to replace because they are more expensive and hard to match. Lime mortar is especially important for porous, historic bricks because it channels moisture out from the brick and thus prevents the destructive growth of mold and salt crystals.
Selecting bricks with clean faces. Cutting bricks into tiles for testing.
Cleaning Historic Brick On-Site: Fort LivingstonNCPTT researchers have made several trips to Grand Terre Island to test cleaning methods on the fort walls. A trip this summer produced test patches for comparison with the brick samples being evaluated in the lab.
Products Chosen for Laboratory Testing on Bricks◙ Goo Gone Spray Gel ◙ Goo Gone Spray Gel, followed with Simple Green* (to remove residue)◙ Vulpex Liquid Soap, mixed 1:15 with mineral spirits◙ Vulpex Liquid Soap, mixed 1:7 with deionized water◙ Cytosol*◙ Citrikleen XPC*◙ Marine Green Clean*◙ Shout Advanced Action Gel◙ Dry ice blasting
*listed on the Environmental Protection Agency’s National Contingency Plan Product Schedule
Laboratory testing is ongoing; the final report will be published on the NCPTT website. http://ncptt.nps.gov/
Left: removing dried clay & SWA poultices to reveal cleaner bricks.
Upper right: cleaning with direct application of SWA and agitation.Lower right: wall with course of tested bricks (center).
SWA SelectionIn response to the Deepwater Horizon crisis manufacturers around the country increased development and production of various cleanup chemicals, including surface washing agents (SWAs), which are designed to remove oil from solid surfaces and either disperse it or allow it to be collected. NCPTT is researching SWAs and alternative methods such as dry ice blasting for their use in cleaning historic masonry, as well as archaeological artifacts of stone, bone, and pottery.
Using the Vortex Mixer to agitate mixture forsolubility testing.
Solubility test tubes, two days after agitation. Note variety in color and layers.
