Vulnerability assessments of the potential for asbestos contamination in public water supplies provide a basis for states to grant waivers from compliance monitoring requirements of public water supply systems if they can demonstrate they are not vulnerable under final U.S. Environmental Protection Agency (EPA) rulings published in the Federal Register.

Land area of geologic units of North Carolina as represented on the 1:500,000-scale state geologic map in digital format and published geologic maps provide the technical basis for waivers for compliance monitoring and associated expensive analytical laboratory testing. These data show that only 3.68% of North Carolina’s land area of 18,790 square km (48,666 square mi) is underlain by rocks that are potentially hosts for asbestiform minerals. We assumed the EPA would follow the initiative of the Occupational Safety and Health Administration (OSHA) and remove nonasbestiform anthophyllite, tremolite, and actinolite from inclusion in the definition of asbestos. We concluded that the portion of North Carolina likely to contain any chrysotile asbestos would be reduced to 0.77% of land area. Ultramafic rocks that have a higher probability of chrysotile occurrences comprise only 0.07%, or 33.8 square mi of land surface in North Carolina.

With additional investigation to delineate watersheds in which chrysotile susceptible rocks occur, the regulatory agency exempted 73 of North Carolina’s 100 counties from asbestos testing of surface water supply intakes. Sixty-eight percent (3,493) of the state’s surface water supply intakes were exempted from unnecessary testing, saving taxpayers at least $368,000; this is about one-third of the North Carolina Geological Survey’s annual appropriated budget. Author staff time to perform the work leading to the conclusion was about two person-weeks at a taxpayer cost of about $2,000.