Groundwater Standards

Groundwater quality standards are established by 15A NCAC 02L .0202 as the lowest of the following six criteria:

1. A concentration protective of the non-cancer or systemic effects of a contaminant. 
2. A concentration which corresponds to an incremental lifetime cancer risk of one-in-a-million;
3. The taste threshold limit value;
4. The odor threshold limit value;
5. The National Drinking Water Maximum Contaminant Level; or
6. The National Secondary Drinking Water Standard.

After public notice and opportunity for hearing on the matter, the Commission may also establish groundwater standards less stringent than the existing maximum contaminant levels (MCL) or national secondary drinking water standards noted above.  In making this decision, the Commission will assure that the standard remains protective of public health and assures that the aesthetic quality of the water is maintained.  Where the groundwater standard for a substance is established at a level greater than the MCL, the Director shall apply the MCL as the groundwater standard at any private drinking water well or public water system well that may be impacted.  Currently only one adopted groundwater standard 1,1 Dichloroethylene (1, 1 DCE), is established above the federal MCL. 

In addition to the standards listed in Section .0200 of the 02L rule, the DWR Director may establish an interim maximum allow concentration (IMAC) for substances for which a standard has not been established.

Every three years the State is required to review its groundwater water quality standards and interim maximum allowable concentrations to determine if changes are needed and, if necessary, to make those changes. This review process is referred to as the “triennial review.” Revision of standards is sometimes needed to incorporate the most recent health and toxicological information. The most recent modifications to the 15A NCAC 02L groundwater standards become effective April 1, 2013. 

Any person may petition the Division of Water Resources Director to establish an interim maximum allowable concentration (IMAC) for a substance for which a standard has not been established under the rules. The petitioner is required to submit relevant toxicological and epidemiological data, study results, and calculations necessary to establish a standard in accordance with the groundwater rules in 15A NCAC 2L .0202. If the information submitted is adequate, the Director may establish an enforceable IMAC.

If there is not enough information available to establish a standard or interim maximum allowable concentration for a substance, then that substance is not permitted in groundwater above detectable concentrations. A detectable concentration is defined as a detection of that substance at or above the practical quantitation limit. The practical quantitation limit is the lowest concentration of a substance that can be reliably achieved by a laboratory. Note that the practical quantitation limit may vary slightly from lab to lab due to sample matrix interference, dilution and other factors.

As outline in the regulations at 15A NCAC 02L .0112, tests or analytical procedures used to determine compliance or noncompliance with the standards should be in accordance with:

1. The most senistive of the following methods or procedures for substances where the standard is at or above the method detection limit value: 

• The most recent version of Standard Methods for the Examination of Water and Wastewater, published jointly by American Public Health Association, American Water Works Association and Water Pollution Control Federation;
• Methods for Chemical Analysis of Water and Waste, 1979, U.S. Environmental Protection Agency publication number EPA?600/4-79-020, as revised March 1983;
• Test Methods for Evaluating Solid Wastes: Physical/Chemical Methods, 3rd Edition, 1986, U.S. Environmental Protection Agency publication number SW-846;
• Test Procedures for the Analysis of Pollutants Under the Clean Water Act, Federal Register Vol. 49, No. 209, 40 CFR Part 136, October 26, 1984;
• Methods or procedures approved by letter from the Director upon application by the regulated source; or

2. A method or procedure approved by the Director for substances where the standard is less than the method detection limit value. 

Where the standard for a substance is less than the practical quantitation limit, the detection of that substance at or above the practical quantitation limit constitutes a violation of the standard.

Where naturally occurring substances exceed the established standard, the standard shall be the naturally occurring concentration as determined by the Division of Water Resources Director.

Where groundwater quality has been degraded, the goal of any required corrective action is restoration to the level of the standards or as closely thereto as is economically and technologically feasible.

The Division of Water Resources' Groundwater Resources Section is responsible for protecting and preserving NC’s groundwater resources through its pollution prevention strategies, monitoring programs, permitting activities and enforcement actions. For more information on the Groundwater Resources Section please visit their webpage.

The Division of Waste Management, which regulates solid waste disposal, hazardous waste management, underground storage tanks and Superfund cleanups, also enforces the groundwater standards. For more information on the Division of Waste Management please visit their webpage.

You can contact your county or local health department for a list of laboratories in your area that do water testing. The cost will vary, depending on the laboratory and the test(s). More information can be found on the Division of Public Health webpage. 

The Environmental Protection Agency (EPA) Office of Groundwater and Drinking Water webpage connects you to fact sheets for many contaminants..

In addition, the federal Agency for Toxic Substances and Disease Registry (ATSDR) provides toxicological profiles for a number of contaminants.