Natural deposits of asbestos can be found in certain types of bedrock in Virginia. These rock types are locally known as greenstone since they can have a green or blue-green hue. Greenstone is found in about 11 square miles of Fairfax County and the City of Fairfax. It is likely there are other areas of this rock in surrounding jurisdictions. Certain soil types form on greenstone, thus the county soil maps have been used for many years to determine the approximate extent of potential asbestos. The full soil maps are available through the Digital Map Viewer. Areas of greenstone-derived soil are displayed as a colored overlay on the maps, with the most recent soil mapping displaying the most up-to-date information. The Health Department website features a less detailed map that highlights all tax grids in which greenstone soils occur. For information about the location of potential asbestos soils in the City of Fairfax, please contact the city's Code Administration division at 703-385-7830.
Construction Safety in Areas of Naturally Occurring Asbestos
In areas of greenstone bedrock, the asbestos fibers are locked up in the rock and separated from the surface by several feet of soil. Construction is not prohibited in these areas. However, during the major earth moving that accompanies new construction, large additions, or redevelopment, excavations may be deep enough to reach the deep subsoil or the bedrock itself. Due to the health risks associated with breathing asbestos fibers, proper precautions should be taken to control the risk of releasing airborne fibers.
Construction safety is regulated by the Virginia Department of Labor and Industry, which administers the federal Occupational Safety and Health Administration’s (OSHA) asbestos regulations. While many of the specific practices within the regulations are geared towards controlling asbestos from human-made materials, all worksites are bound by OSHA’s General Duty Clause, which requires that employers provide a workplace which is free of hazards which could cause death or serious harm. The regulations also mandate permissible exposure limits (PELs, described below) for airborne asbestos fibers, and regulatory interpretations by OSHA have stated that PELs must be adhered to regardless of the source of asbestos. For this reason, the OSHA regulations provide guidance on precautions for safe construction activities in areas of naturally occurring asbestos.
Evaluation of air monitoring data has found that construction in greenstone bedrock can be made safer with proper precautions. Based on these findings and the existing federal regulations, the Fairfax County Health Department developed recommendations to minimize the presence of airborne asbestos fibers during construction.
General Recommendations
1) Develop a construction plan – Before construction (or even design) commences, the site can be evaluated to determine how far the bedrock is from the surface. Asbestos is found within the rock itself, and may potentially be found in the deep subsoil above the rock, but it is not thought to be found in the clayey surface soil. Exceptions to this are for previously developed sites, where past construction may have mixed bedrock and subsoil material with the surface soils.
The greatest threat of exposure comes from aggressive rock disturbing operations such as drilling, blasting and chipping. Such disturbances without proper precautions should be avoided or limited. If excavation does not reach the depth of the bedrock or deep subsoil, the chance of asbestos exposure is greatly reduced.
2) Keep the Site Moist to Control Dust - If no dust is created at a work site, asbestos fibers that may exist in the rock or soil are unlikely to become airborne. Water is the key to controlling fugitive dust. Keeping the site damp, but not wet, will prevent dust from forming. It is especially important to apply water directly to any activities that aggressively disturb the bedrock. All exposed and excavated material, especially bedrock and deep subsoil, should also be kept damp.
An excessively wet site may result in soil sticking to the shoes and clothes of workers, who can track potentially contaminated soil back into their cars and homes after a work shift. If the site is kept damp enough to prevent visible dust emissions, airborne asbestos fibers will be limited.
3) Monitor the air – To protect workers, OSHA regulations have established air concentrations of asbestos fibers--called Permissible Exposure Limits (PELs)--of 0.1 fibers/cubic centimeter averaged over an eight hour work shift and 1 fiber/cubic centimeter averaged over a 30-minute span. Compliance with PELs can be determined by sampling the air around workers’ breathing zones during the 8-hour-duration of a typical work shift and during a 30-minute-duration while performing work that is most likely to create asbestos exposures (deep excavation, bedrock disturbance, etc.). Sampling equipment placed at the perimeter of the work site can monitor the asbestos fiber concentration leaving the site. While the recommended control practices in this document help to reduce airborne asbestos concentrations, only air monitoring can definitively tell what the airborne asbestos fiber level is at a work site.
4) Provide protection for your workers – Controlling visible dust with water and avoiding disturbance of the bedrock will greatly reduce the risks of airborne asbestos exposure. However, there can still be asbestos within the exposed soil and rock on the work site. During construction, it is inevitable that workers will get dirty. Dust released from dirty clothes and shoes after a work shift can contaminate workers’ cars or homes with asbestos. Personal protective equipment can prevent this. For workers who simply walk on exposed soil at the site, wearing rubber boots that are washed off at the end of a work shift (or before entering a vehicle) can prevent asbestos from being tracked into workers’ cars or homes. Tools and vehicles that are covered in dirt should also be hosed off before leaving the site. For workers who operate within trenches or excavations and are surrounded by exposed soil (foundation work, laying utilities, etc.), an inexpensive coverall (Tyvek© or similar material) can be worn to keep soil from smearing onto clothes and shoes. The coverall can then be properly disposed of or laundered at the end of each work shift.
If air monitoring shows that PELs are being exceeded, an approved respirator that is properly fitted and maintained can protect a worker. OSHA regulations provide guidance for proper selection and fit testing of respirators.
5) Properly dispose of asbestos-contaminated spoils and secure the site – Whether removed or not removed from the construction site, a safe disposal site should be used to dispose of any asbestos-contaminated rock or subsoil brought to the surface. All final disposal areas and the finished grade of the developed land can then be covered with six inches of clean material and planted to trap any asbestos underground. If asbestos spoils are removed from the site, water or other wetting or binding agents should be applied to prevent dust emissions during transport and disposal.
Who Can Help?
Asbestos Safety Consultants:There are local firms that specialize in outdoor asbestos safety consulting and may be able to provide all of the assistance you will need, including air monitoring and the creation of a complete asbestos safety plan for your worksite. A list of such firms is available from the Northern Virginia Soil and Water Conservation District. Industrial Hygienists may also perform this work, and a list of licensed hygienists can be found on the American Industrial Hygiene Association’s website. These listings are not exhaustive and the companies are in no way endorsed by any government entity. Other asbestos specialty firms can be found by searching for Industrial Hygiene or Environmental Health and Safety companies on the internet on in the telephone directory.
Individual Services
Because asbestos is generally an indoor air quality concern, it can sometimes be hard to find companies that will perform all aspects of outdoor asbestos safety consulting. This is especially true of testing bedrock depth: most asbestos safety consultants will not have the equipment to perform this service themselves. The types of companies listed below provide individual services that are part of overall outdoor asbestos safety. They can be contacted directly or serve as a subcontractors to an asbestos safety consulting firm.
Taking Soil Samples: Geotechnical engineering firms or soil science firms can conduct site evaluations to determine the depth to bedrock. A list of local firms is available from the Northern Virginia Soil and Water Conservation District.
Air Monitoring: Air monitoring can be performed by many of the asbestos safety consultants, or it can be overseen by Certified Industrial Hygienists, although not all hygienists perform or are licensed to perform outdoor air monitoring. A list of Industrial Hygiene companies can be found here: www.aiha.org, click on the “Find an IH” link.
Air monitoring samples should be analyzed in a lab licensed by the Virginia Department of Professional and Occupational Regulation (DPOR). A list of labs licensed by DPOR to test materials for asbestos can be found here: http://www.dpor.virginia.gov/LicenseLookup/. Use the search term “Asbestos Analytical Laboratory.” Each licensed lab will have a list of specialties: PCM indicates the lab performs air sample testing. This list will include many companies located outside of Northern Virginia.
Guide to Regulations
The OSHA regulations concerning asbestos safety for the construction industry can be found in the Code of Federal Regulations: 29 CFR 1926.1101. The full text of these regulations can be found on the OSHA website: https://www.osha.gov/law-regs.html. Click on the “Construction” tab and scroll down to section 1926.1101.
The text of OSHA’s General Duty Clause can be found in the United States Code, 29 U.S.C. § 654, available here: http://www.law.cornell.edu/uscode/text/29/654
Questions about OSHA regulations can be directed to the Northern Virginia (Manassas) Office of the Department of Labor and Industry, Virginia Occupational Safety and Health: 703-392-0900, TTY 711.
Conclusion
Areas in and around Fairfax County overlie bedrock which can contain naturally occurring asbestos. This material is only considered a hazard when it is disturbed, which is possible during major construction. The risks of harmful asbestos exposure during construction in greenstone areas can be greatly reduced if proper precautions are taken. Under the General Duty Clause of the OSHA regulations, it is the responsibility of all employers to provide a safe workplace for employees. The work practices outlined in the “General Recommendations” section above can greatly decrease the chances of any harmful exposures. You should contact a consultant to assist you in planning your project and protecting people from harmful airborne levels of asbestos fibers.
General Questions
If proper precautions are taken, construction work can be done safely in areas of greenstone bedrock. While naturally occurring asbestos is not regulated by the local governments, if you have general questions about greenstone bedrock, you may contact the Fairfax County Health Department, Environmental Health Division (703-246-2444, TTY 711, hdehd@fairfaxcounty.gov) or the Northern Virginia Soil and Water Conservation District. For naturally occuring asbestos within the City of Fairfax, you may also contact the city's Code Administration division at 703-385-7830.