Sampling and Testing Stations
Samples of oil/mousse, oiled sand, and water with an oil sheen were collected from locations around the fort. Cleaning tests were done in two locations, on both brick and granite surfaces. GPS coordinates for each of these sites were recorded by Sara Clowery.
Station 1 – poultice tests and exposure of soft bricks for testing in the laboratory.
Station 2 – collection of samples of mousse and mousse + sand.
Station 3 – collection of oil/water samples.
Station 4 – test cleaning, discussed below.
Station 5 – collection of oil/water samples. Station 6 – collection of oil/sand samples, water with oil sheen, and oiled shells that had weathered and fallen from the tabby.
The Louisiana Office of State Parks staff requested advice on the removal of oil contamination from Fort Livingston. The initial advice from NCPTT was not to undertake multiple cleanings. The State Parks staff were particularly interested in a product made by VeruTEK.
Cleaning products and methods need to be tested to determine efficacy, effects on materials, and potential environmental issues. Multiple cleanings are not advised as each cleaning has the potential to remove some of the original material, or to otherwise damage the structure, and additional oil is sure to arrive and re- contaminate the site.
Two cleaning methods were tested on the structure: poulticing and surface washing agents. Surface washing agents are typically surfactants, and VeruTEK products were tested here. Another surfactant, Volpex, was available for testing but time constraints precluded testing this product in the field.
VeruTEK products. The following VeruTEK products were tested: VeruSOLVE, VeruSOLVE-Marine, and VeruSOL Green- Marine. The “Marine” designation indicates that the product has been adjusted to approximate the salinity of seawater. Both VeruSOLVE and VeruSOLVE- Marine include hydrogen peroxide as an oxidant to break down the emulsified oil.
Poultice. A poultice of agapultite clay and mineral spirits was tested. Normally a poultice would be applied and allowed to remain for a minimum of 24 hours, but because of limited time, the poultice was applied at the beginning of work at the site and removed just before departure that same day.
Initial testing of VeruTEK products on brick indicated that they are effective as surface washing agents. However, because of the short time in the field, it was not possible to observe the surfaces after they had dried or, as would be preferable, after a few days to determine how effective these products were at removing oil that had penetrated the materials and whether there were any undesirable consequences from cleaning. VeruTEK products are in the process of being added to the NCP Product Schedule but do not appear on the schedule dated 6/3/2010.
The poultice was effective at lifting/removing the surface soiling from both brick and granite. Because of the short time for the poultice to “cure,” some staining remained from oil that had penetrated deeper into the material. A poultice applied over a longer period would be more effective at removing such a stain. It should also be noted that large area application of a poultice is not practical, and that poultices are normally used for small areas and more stubborn stains.
Preliminary recommendations are to wait until the threat of contamination with additional oil has passed before beginning large-scale cleaning. Use a product that complies with federal, state, and local requirements. Surface washing agents, which are made up of surfactants, should be formulated so as not to cause damage to the materials or surfaces being cleaned. The lime mortar, bricks, and shells that make up the tabby will be sensitive to products with a low pH (more acidic). A test should be conducted on a small, inconspicuous area before large- scale cleaning is undertaken. Damage to the surface might not be obvious immediately, so test patches should be observed after cleaning, after drying, and after some time (days to weeks) to be sure that damage has not occurred.
Before application of a surface washing agent, surrounding, uncontaminated areas should be wet so that the product remains on the surface of the material. In general, a surface washing agent should be applied and allowed to dwell on the surface for approximately 20 minutes to penetrate and react with the oil. Depending on the product, additional time might provide better results. Additional product can then be applied before agitating with a soft bristle brush. A brush that is soft enough not to scratch the finish on a vehicle is soft enough to use for this purpose. Agitate to make sure the surface washing agent comes in contact with the surface being cleaned, but avoid scrubbing. Rinse and reapply the surface washing agent again as necessary.
NCPTT will continue to test products that are currently included in the National Contingency Plan (NCP) Product Schedule to determine which products could be used on historic structures and cultural materials. Results and further guidance will be provided as the research proceeds. In addition to standard cleaning methods, products will be tested for their efficacy in “pre-cleaning” or interim cleaning of structures that have been contaminated with oil but are expected to be exposed to additional oil.
It should be noted that the National Oil and Hazardous Substances Pollution Contingency Plan, more commonly called the National Contingency Plan (NCP), is the federal government’s blueprint for responding to both oil spills and hazardous substance releases. The Environmental Protection Agency (EPA) maintains a schedule of products that may be authorized for use on oil discharges (NCP Product Schedule). Use of products that results in a release of those products to a navigable waterway must be approved in advance by the Regional Response Team (RRT). Louisiana and Texas are part of Federal Region VI. Mississippi, Alabama, and Florida are part of Federal Region IV. For more information see: http://www.epa.gov/ osweroe1/content/partners/nrsrrt.htm.