Crude oil is a complex mixture of hydrocarbons of various molecular weights. An oil well normally produces a variety of products, together considered to be crude oil, that include the range of components from gases and lighter liquids to highly viscous tar-like materials. The lighter, more volatile components tend to evaporate more quickly if they are on the sea surface. Some of the gases and other aromatic components are relatively soluble in water compared to other hydrocarbons, and will disperse more readily in the water leaving the heavier fractions that remain on the surface to be carried to shorelines.
Crude oil contains alkanes which can be decomposed by microbes; hazardous air pollutants (HAPs) such as benzene (a known carcinogen), toluene, and xylene; and polyaromatic hydrocarbons (PAHs) which are highly toxic and tend to persist in the environment, particularly once the crude oil has penetrated shorelines and building materials.
What are potential threats to historic structures?
Threats to an historic structure vary depending on the material of which it is constructed and its amount of exposure to crude oil.
Toxicity: Hazardous air pollutants (HAPs) such as benzene, toluene, and xylene can be found in the oil/water mixture or emulsion called “mousse” as well as in fresh oil. They evaporate over time, but some take much longer than others. HAPs are acutely toxic and can be a potential inhalation hazard of fresh or emulsified oil. Though they are volatile, they take time to dissipate. Contamination of a structure could require evacuation until levels of HAPs are considered safe. Crude oil also contains polyaromatic hydrocarbons (PAHs) that are highly toxic and, if they have penetrated building materials, can persist for long periods of time. Some cleaning methods can hasten the volatilization of these toxic substances.
Porous structures and building materials have the potential to absorb significant quantities of oil. Staining and disfiguration could range from black or brown staining to subtle darkening of the building materials. Even after cleaning, this visual disfiguration can persist. Some cleaning methods have the potential to enhance differences between materials exposed to oil and unexposed materials. Other cleaning methods can force oil farther into a substrate. Sticky material will act as an adhesive for wind-born sand.
Acceleration of decay: The complex chemical mixture that makes up crude oil has the potential to accelerate decay of materials. In particular, unusual microorganisms that live in oil have the ability to digest the oil and produce acidic waste. Nitrifying organisms that produce nitric acid are commonly found around oil, as are sulfur-reducing organisms that produce sulfuric acid. These microorganisms can be beneficial in the breakdown of the oil, but their acidic byproducts can chemically attack sensitive materials such as lime-based materials (mortars, stuccoes, limewash), some stones, and metals.
What are some important factors to consider?
All deterioration of historic materials resulting from exposure to crude oil will be dependent on the rate of reaction of the oil with the resource. Some effects will happen quickly. For example, soiling and staining will be readily observed. Other effects to the historic structure may not be evident until time passes. Oil may penetrate into composite materials like concrete and the resulting growth of microorganisms may cause deterioration only observed at a later date.
In choosing an intervention for an historic structure, several factors must be considered. First, the risks and benefits of any action should be considered. Interventions must do no harm. Second, the historic structure must be considered as part of a larger environment. Impacts on the surroundings must be considered. Third, preventing contact with the oil is better that cleaning up the aftermath. Responders will likely need to use materials that are readily available to protect structures. Fourth, the size and shape of the structure as well as the materials that it is made from will influence the actions taken.
What types are materials are susceptible to injury?
Stone is a porous material (like a sponge) and is capable of absorbing crude oil. If chemical dispersants are used on the oil spill, they may actually allow the crude oil to penetrate farther into the stone. Crude oil may stain and visually impair stone. Asphalt-like tars have PAHs that are highly toxic chemicals that can persist in the environment for long periods of time. Contamination in stone pores may significantly influence the use of the structure or object.
Concrete is made up of aggregate and lime and/or Portland cement and may contain additives. Aggregate used in historic concrete can contain crushed rock, sand, or even shell. Like stone, historic concrete is porous. Since concrete is a composite material, it may be more susceptible to injury than other materials. Staining, visual disfiguration, and contamination by toxic chemicals are possible from exposure to crude oil.
Brick, such as low fired historic brick, tends to have a soft, porous interior beneath the protective fire skin. Brick structures may be affected by crude oil in the following ways. Heavy asphalt-like products in the crude oil may adhere to the brick surface and clog or seal the surface. When this occurs, moisture and salts that may be trapped within the porous interior can build up, creating pressure and eventually damaging the protective outer skin. The damaged brick is more vulnerable to deterioration. In addition to aesthetic issues, lime mortars may be chemically attacked by sulfur containing chemicals in the crude oil, leading to decay.
Metals, such as steel, stainless steel, and copper alloys may be affected by exposure to crude oil. The presence of sulfides in water from the crude oil can cause stress corrosion cracking and pitting in metals.
Additionally, nitrifying and sulfur-reducing bacteria can digest the crude and produce acids leading to microbially-induced corrosion.
Wood: The effect of crude oil on wood has not been widely researched by the historic preservation community. The most likely problem will be staining or discoloration of wood that comes into contact with crude oil. Crude oil will likely be removable from a well painted surface by cleaning with a solution of mild detergent and warm water. Removing oil from poorly maintained, lightly finished wood or raw wood (no paint or stain was applied), may require cleaning with an alcohol-based solution or mineral spirits, and a light sanding before refinishing or leaving unfinished. This cleaning method should be tested on a small area to see if the cleaning is effective before attempting to clean all of the affected wood. If the wood is painted, appropriate methods for lead based paint must be used to contain and dispose of any waste, and for personal protection.
While it is common practice to refer to impacts on cultural resources as “damage,” in this document an impact will be referred to as “injury”. The term “damage” in this case will be associated with the monetary value of the injury.
What are things we can do to protect historic structures?
Prevent contact with the oil. If the crude oil has not come into contact with historic structures, some type of barrier could be used. There are two main types of barriers: physical barriers that serve to obstruct the oil from coming into contact with the surface and chemical barriers that are applied to the structure to prevent penetration of crude oil.
Physical barriers include, but are not limited to, sand bags or berms, booms, and portable dams. Each oil spill is unique and the type(s) of barrier selected will be determined by potential resource impacts, characteristics of the oil, location, weather, and other variables.
Physical barriers are most effective under normal weather conditions and in minor flooding situations. Their use should be re-evaluated in the event of a forecast hurricane or significant storm.
Physical barriers protect cultural resources by eliminating or at least minimizing the amount of oil that comes into direct contact with the resource by providing a physical means of collecting oil or separating the oil from the resource. Some barriers may be more appropriate for short periods of time while others are more useful for long term protection. However, wind, waves, currents, and other environmental conditions impact the effectiveness of physical barriers.
Sandbags and Berms are proven tools for fighting storm waters. According to the Corps of Engineers, “Sandbagging is one of the most versatile of flood fighting tools and is a simple, effective way to prevent or reduce flood water damage.” Although sandbags do not guarantee a watertight seal, they are readily available and can be deployed with relative ease. If sand is being collected from the site for filling bags or for creating berms, the threat to archaeological and natural resources must be considered. Likewise the placement of sand structures should be thoughtfully considered to avoid negative impacts on archaeological and natural resources.
Booms come in many different shapes, sizes, and styles. They are used for concentrating oil so that it is thick enough to be skimmed, for keeping oil out of sensitive areas, or for diverting oil into accessible or desirable collection areas. The success of booming as a strategy is largely dependent on currents, wind, and waves. Currents can draw the oil under the booms; waves may cause oil splash-over; wind and currents may cause the booms to sink or plane off the surface of the water; and currents or debris may damage the boom.  Placement of booms should be thoughtfully considered to avoid negative impacts on archaeological and natural resources.
Portable Dams are a consideration for cultural resources. There are a number of portable and quickly deployable dams for emergency flood control that could be used to provide barrier protection. There are varieties of portable dams that can be used on land or in water. Placement of portable dams should be thoughtfully considered to avoid negative impacts on archaeological and natural resources.
Film/Sheet barriers may be considered as an apron or physical barrier for some structures. Main considerations for film or sheet barriers include chemical composition and attachment to the structure. Some plastics, such as polypropylene, actually absorb and swell in oils and are not recommended for use. High Density Polyethylene (HDPE) may be considered and is produced in a variety of widths and thicknesses and may be useful as a barrier.
Sorbents are materials or mixtures of materials that take up liquids through adsorption (taking up liquids onto the surface or into the pores of a material) or absorption (taking up liquids into the material’s molecular structure). Most of the materials that are likely to be useful for oil spills are adsorbents.
Sorbents could be used to reinforce another physical barrier, such as a sand berm or boom. Using a sorbent in conjunction with another physical barrier would reinforce the main barrier and help to prevent the oil from penetrating the main barrier. Sorbent material can also be applied directly to a structure. Ideally, the sorbent would take up any oil that reaches the structure before the oil makes contact with the structure.
Sorbents may include organic, inorganic, and synthetic materials. Natural organic sorbents include peat moss, straw, hay, sawdust, ground corncobs, feathers, and other readily available carbon-based products. Natural inorganic sorbents consist of clay, perlite, vermiculite, glass wool, sand, or volcanic ash. Synthetic sorbents include man-made materials that are similar to plastics, such as polyurethane, polyethylene, and polypropylene and are designed to adsorb liquids onto their surfaces.
Chemical barriers are chemicals applied to the surface of the historic structure to serve as a protective or a sacrificial coating. Protective chemical barriers include film forming and penetrating oil-resistant or oil-repelling chemical treatments. Penetrating treatments are generally preferred as they allow for the transmission of water vapor. These “breatheable” treatments do not trap moisture within the substrate.
Few, if any, chemical protectants have been tested for long-term behavior on historic materials exposed to crude oil. Most chemical protectants are irreversible and may influence future treatments and repairs. Chemical protectants need time to dry and cure. The cure rate of the protectant is influenced by conditions of the historic structure and the environmental conditions. Chemical protectants cannot be applied below water lines or in wet conditions. In addition to treatment application and curing issues, these chemical treatments may pose environmental issues. For these reasons, one should always consult an architectural conservator or preservation professional prior to application of any chemical barrier.
Use of sacrificial coatings has been suggested for historic structures. Any sacrificial coating should be easy to apply, repel oil, and be easy to remove. Limewash has been suggested as a sacrificial coating for brick masonry structures. However, limewash must be applied in multiple coats (probably five or more) and may cure slowly. Latex paint is not recommended as a sacrificial coating because it may react with chemicals in the oil. Additionally, latex paint is not easy to remove from brick structures.
Do nothing. Sometimes, the best course of action may be no action. If the benefits of preventing oil from reaching historic structures outweigh the liabilities, preventive measures should be taken. If not, no action may be the best choice, and attention turned to clean-up.
What should we do once oil has come into contact with historic structures?
Once oil has impacted an historic structure, it is critical to document the injury. This information will be used to record effects of the oil contamination and hold responsible parties accountable for any damages. Additionally, documentation serves as an historical record of the conditions of the structure after oiling. Photograph the overview of the structure and details of oil injuries. Record the location of the structure, including Global Positioning System (GPS) coordinates. (The National Park Service (NPS) and the Fish and Wildlife Service (FWS) have adopted a survey form, a GPS data dictionary, and a set of standards and a supporting Cultural Resource Geodatabase Template that integrates descriptive and spatial data. This information is available through a National Park Service protocol, “GIS data collection standards.”)
Cleaning up after the fact
Clean up alternatives are best considered after the threat of additional oil contamination is over. Decisions on oil removal should not be rushed. If possible, suppress the urge to act quickly, and consult a conservator or a preservation professional prior to undertaking cleanup efforts. Any cleaning should be undertaken with the mildest, least abrasive method available that removes the crude oil. Keep in mind that it is important to do no harm in response to the oil contamination. Some cleaning methods to consider include:
Pressure washing: Care must be taken with the use of pressure washers on historic stone, brick, or concrete. Excessive pressures used on historic materials can result in the removal of surface material and scarring of the surface of historic structures. Power washing includes a variety of variables that influence the performance, including pressure, volume, temperature, nozzle pattern, attitude or angle of delivery, water quality, operator skill, and chemical additives. Depending on the condition of the structure’s surface, washing with low to medium jet pressure (200-500 pounds per square inch (psi) at 4-6 gallons per minute (gpm) using a 45 degree fan type nozzle) may help remove the crude oil. Pressures of 200-500 psi may be excessive for some materials and a small test patch (36 inches by 36 inches) in a less conspicuous area is advisable before large scale cleaning. It is important not to work too close to the surface, maintaining a distance of 18 inches or more. Note that most commercial pressure washing systems operate at significantly higher pressures than those recommended here. Use of a pressure regulator to reduce pressures may be needed. Heated water at 150-180°F (65-82°C) may improve cleaning efficiency. One major disadvantage of using power washing to remove oil contamination is that it may drive the chemicals farther into the surface of the material.
Steam Cleaning is a water-based cleaning method that may be considered for removal of crude oil from historic structures. In this method steam is generated in a boiler and directed against the masonry with the use of a very low pressure nozzle (10-30 psi). The heat of the steam swells and softens the oil waste which must be removed and collected from the surface. Before overall cleaning, create a small test patch (6 inches by 6 inches) in a less conspicuous area to see how the steam cleaning method will work. An advantage of this method is that it does not involve chemicals which pose an environmental risk. Disadvantages include potential hazards to the operator from heat and PAHs, as well as the potential to damage the material surface from thermal shock.
Cleaning by compresses or poultices: Crude oil deposits can be removed from surfaces using poultices made of cellulosic material such as paper pulp. If large surfaces are to be cleaned, cleaning agents can be mixed into the pulp, then sprayed on with special equipment. Some testing will be needed to find a solvent or solvent mixture to incorporate into the poultice. Solvents such as acetone, methylene chloride, mineral spirits, and naptha have been used in poultices. Please check state and federal EPA regulations prior to using a solvent and use all recommended personal protection equipment. As the pulp dries, it will pull the waste products into the poultice. After the poultice dries, it must be removed carefully by brushing it from the surface by hand or using a soft brush, collected, and disposed of. Clay poultices can also be used for cleaning. Test the cleaning method on a small test patch in a less conspicuous area before proceeding. One advantage of the technique is that the crude oil can be collected in the poultice for disposal. Disadvantages of the method include the amount of labor needed to complete clean-up. The amount of contamination, and the environmental risks posed by the chemical agents will be critical considerations.
Dry Ice cleaning: Mild forms of abrasive cleaning may be considered, such as dry ice dusting. Dry ice particles vaporize and leave no secondary waste as they lift contaminants from the surface. Make sure that any company planning to use dry ice for removal of crude oil has some experience with historic materials. A small test patch (6 inches by 6 inches) in a less conspicuous area is advisable to see how the dry ice method will work. Once the treatment is chosen and operation conditions are selected, make sure to collect the waste materials on drop cloths or other devices so that the ground or water is not re-contaminated. This technique should be carefully tested before being used on brittle or friable surfaces. Harsher abrasive methods, such as sandblasting, should be avoided.
Chemical Cleaning: Most chemical methods pose environmental risks. Detergents and soaps may be able to dissolve some of the chemicals in the crude oil and remove them from the surface. Products containing surfactants and solvents may run the risk of making it easier for the oil to penetrate to greater depths into the structure. These methods require saturating the surface with water prior to the application of chemicals (which may be impossible due to the oil), and subsequent rinsing of the chemical residue with plain water. These steps insure the elimination of potentially harmful chemical residues from the structure’s surface. Major concerns with chemical cleaning are the nature of the chemicals, the run-off of chemicals and crude from the surface, and the potential to contaminate the ground and waterways. Always consult Material Safety Data Sheets (MSDSs) and product data sheets, available from the manufacturer, to learn how to handle, apply, and dispose of the chemical cleaners.
Power tools: Abrasive methods include sandblasting, grinding, and power sanding and are not recommended. The use of abrasive methods will damage surfaces of historic structures, remove original material, and accelerate deterioration of the surface.
Grimmer, Anne, Keeping it Clean: Removal of Exterior Dirt, Paint, Stains and Graffiti from Historic Masonry Buildings, National Park Service, 1992. http://books.google.com/books?id=JmiHY-8ZRhoC&printsec=frontcover&dq=nne+Grimmer’s+Keeping+it+Clean&cd=1#v=onepage&q&f=false
Dry ice dusting uses smaller particle sizes (sugar-sized granules) than the traditional dry ice blasting and has been used to clean soot from library collections that have been in a fire. See Randy Silverman and Seth Irwin, “Fire and Ice revisited: A Comparison of Two Soot Removal Techniques for Book,” International Preservation News, No. 49, December 2009, p 31-35, http://www.ifla.org/files/pac/ipn/49-december-2009.pdf.
Where do we get more information?
Inclusion of a product or service in this section should not be construed as endorsement by the National Park Service. Additional resources and information on some products:
National Center for Preservation Technology and Training
Sandbagging Techniques pamphlet by the Corps of Engineers
MECHANICAL CONTAINMENT AND RECOVERY OF SPILLED OIL by the Region IV Regional Response Team, U.S. Coast Guard and U.S. EPA
Alaska Oil Spill Response and Cultural Resources
Heritage Documentation Programs, Cultural Resources Geographical Information System Guidelines
US EPA information on sorbents
A temporary, portable cofferdam, water diversion or fluid retention
A water inflatable flexible emergency flood control dam
Absorbent booms for oil collection
Bentonite blanket used for lining waste ponds
Geomembranes that may be useful for film/sheet protection
Oil response products such as booms and shoreline barriers
Cleaning methods for historic masonry buildings
Preservation Brief 1: Assessing Cleaning and Water Repellent Treatments for Historic Masonry Buildings (http://books.google.com/books?id=6t8VA3onDgIC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false)
Oil Spill Rapid Building and Site Condition Assessment Instructions
This form (attached Oiled Building and Site Assessment Form, FileMaker Pro) was developed by the NPS National Center for Preservation Technology and Training for oil spill response. The form is intended to provide public officials with a tool to rapidly assess the condition of buildings and sites within the oil spill area and is designed to be completed in 10 minutes or less. Ideally, the information fields defined in this form can be used as a guide for a Global Positioning System (GPS) data dictionary. Surveys then can be conducted electronically using a GPS instrument operating at +/- 3 meter or better resolution. The form will serve as a hard copy backup to the electronic data. If it is not possible to collect data with a GPS instrument, then the form will serve as the primary survey document. In this case, plot the location of the resource on a 1:24,000 scale USGS quadrangle map to be submitted with the form.
This form is derived from a Rapid Building and Site Condition assessment developed for FEMA in response to Hurricanes Katrina and Rita in 2005.
Several assumptions guided the design of this form:
- the built environment is the focus of the assessment effort;
- inspectors may have minimal preservation skills;
- assessments may be conducted from the street, and access to interior inspection may be limited; and
- a second tier of inspection may follow at a later date based upon the initial rapid inspection;
Step 1 — Preparation:
Before using this condition assessment form, inspectors should gather existing data. A large amount of information exists that can be used to identify historic properties and cultural resources before inspectors ever enter the field:
- State Historic Preservation Office maps:
- National Historic Landmarks, National Register Individual Listings, National Register Districts, Eligible Properties, including:
- historic buildings
- archaeological sites
- Landmark/Historic Commission maps:
- Locally regulated historic Properties and Districts
- National Historic Landmarks, National Register Individual Listings, National Register Districts, Eligible Properties, including:
Recommended or preferred equipment needed for the condition assessment includes (1) a GPS instrument, such as a Trimble Model GeoXT, GeoXM or GeoXH, (2) clip board, (3) 100 ft. tape measure, (4) pencil or permanent ink pen, and a (5) digital camera
Inspectors should be briefed on each section of the Assessment Form and associated definitions (see attached Definitions Page). Safety issues must be addressed, including appropriate gear and supplies needed to ensure personal safety.
Step 2 — How to use this form:
The condition assessment form is designed to be completed by inspectors with limited training in historic preservation. Ideally, an assessment team should draw on historical architects, conservators, archaeologists, engineers, and others. If a limited number of trained personnel are available, especially historical architects, their assessment efforts should be targeted at the known historic resources. Inspectors should make every attempt to fill out the form in its entirety to the best of their ability. When in doubt, a second more detailed evaluation should be recommended.
The form is divided into seven major sections:
- Inspection – basic information about the inspection team, any attachments available, photographs, documents, sketches, etc.;
- Property description – basic information on location of the site, type of construction, primary occupancy, and ownership;
- Property Location Data – when at all possible, provide global positioning system (GPS) data for the site.
- Characteristics – information needed to assess the historic significance of the structure or site;
- Oil data – information specific to oil spill injury;
- Evaluation – information on the contamination of the structure or site;
- Further actions – recommendations on further actions including detailed evaluations, barricades, etc.; and
- Posting – documentation and instructions for safety and further actions.
Step 3 – Location Data:
Field teams should:
- Use Global Positioning System (GPS) units that have an accuracy of +/- 3 meters or better.
- Record GPS information in decimal degrees, using the NAD83 datum.
- Have GPS post processing capability of exporting GPS data into GIS shapefiles
- At a minimum map each site or standing structure as a point; however, whenever possible map the property as a boundary or building footprint.
- If mapping as a point be sure to note if the point represents the center of the site or building, a random point within the site boundary, the corner of a building, or the entrance of the building.
Map each contributing site, building, or structure that contributes to an historic district or historic landscape. If a GPS instrument is not available, then the assessment will serve as the primary survey document. Plot the location of the resource on a 1:24,000 scale USGS quadrangle map to be submitted with the form.
Step 4—Archive Data:
Data may be collected manually using printed versions of the form. Alternately, electronic data can be captured by installing Filemaker Pro ver. 7 or higher software on a PC-based device such as a tablet, laptop, or palmtop and using the programmed version of the form. If forms are completed manually, data should be entered into a database file regularly for further analysis at a later date.
Step 5—Action Recommendations:
Inspectors will make strategic recommendations in the Further Actions section of the form. Issues of public health and safety are the first priority. Further recommendations may include remediation. When possible to observe interior conditions, note any visible signs of collections (artifacts, historic furnishings, etc.).
Each site or structure should be posted upon completion of inspection. This posting serves as notice to the public regarding the safety of the structure or site. In addition, postings that reflect “historic designation” or “detailed evaluation needed” will assist in further inspection of the property by specialist teams including professionals with expertise in health and safety, structural engineering, archeology, historic preservation or collections care.
For More Information:
National Center for Preservation Technology and Training
Oil Spill Rapid Building and Site Condition Assessment Definitions
Residential Units: the # of times a structure has been divided for a family living unit. (e.g., a common house is 1 unit, a duplex is 2 units, and apartment buildings may be divided into any number).
Foundation: what connects a structure to the ground; this can be done in many different ways. For Example:
Historic designation: when a structure or site is deemed important by a governing body because of its place in history or culture (may be an individual landmark or “background” in a district).
Depth of water measured from the main floor: defined as the level that waters, if any, rise in relation to the main living or business level of the structure (may be a positive or negative number).
Sediment deposited: mud, sediment, or chemical sludge left by the oil spill.
GPS: Global Positioning System, using NAD83 Datum (in decimal degrees)
NAD83 Datum: The North American Datum for 1983. A set of constants specifying the coordinate system used for geodetic control.
Decimal Degrees: latitude and longitude geographic coordinates expressed as degrees with decimal fractions and used in many Geographic Information Systems (GIS).
Location: The GPS coordinate expressed in decimal degrees for a specific point on the historic property. The form allows for up to five locations to be recorded.
Description: A written or verbal account, representation, or explanation of the location.
Nat’l Hist. Landmark(s): (NHL)nationally significant historic places designated by the Secretary of the Interior because they possess exceptional value or quality in illustrating or interpreting the heritage of the United States.
Nat’l Reg / District: (NR) the National Register of Historic Places is the nation’s official list of cultural resources (individual sites or whole districts) worthy of preservation.
State Historic Preservation Office: (SHPO) State government office that carries out responsibilities in historic preservation within the state.
Detailed evaluations recommended:
Structural: there is some question as to the overall stability of the building due to oil exposure; this could include the deterioration of the structural material.
Environmental: there is concern about the safety or condition of the structure due to oil exposure, or overwhelming environmental conditions. This may include chemical or waste spills, broken or leaking sewage or gas lines, or large amounts of decaying materials.
Archeological: survey needs to be done if there is evidence of artifact deposits that have been contaminated or could deteriorate due to exposure or recovery efforts.
Historic Significance: refers to the importance of a structure due to its age, unique style, or as a place of importance to history.
Collections: gatherings of historic materials. This may include libraries, museums, or archives (records). Evaluation must be done if obvious collections are present.