Maximum Contaminant Level Goal or MCLG: The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.

Maximum Contaminant Level or MCL: The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology.

Maximum Residual Disinfectant Level or MRDL: The highest level of disinfectant allowed by the EPA, calculated as a running quarterly average of monthly samples.

Treatment Technique or TT: A required process intended to reduce the level of a contaminant in drinking water.

Action Level or AL: The concentration of a contaminant that, if exceeded, triggers treatment or other requirements that a water system must follow.

ppm = concentration in parts per million, or milligrams per liter (mg/L); this is equivalent to 1¢ in $10,000

ppb = concentration in parts per billion, or micrograms per liter (µg/L); this is equivalent to 1¢ in $10,000,000

ppt = concentration in parts per trillion; this is equivalent to 1¢ in $10,000,000,000

pCi/L = picocuries per liter; a measure of radioactivity

N/A = Not Applicable

NLE = No Level Established

NGE = No Goal Established

NTU = Nephelometric Turbidity Units; units describing how cloudy a water sample appears

< = less than; when seen in a table, it usually refers to below detectable levels

Contaminant: Anything found in water (including microorganisms, minerals, chemicals, radionuclides, etc.) that may be harmful to human health.

Raw Water: Water in its natural state, prior to any treatment for drinking.

Source Water: Water in its natural state, originating from the watershed that supplies a water system with its raw water.

Watershed: The land area from which water drains into a stream, river, or reservoir.

Treated Water: Water to be used by a public water system that has received the application of approved water treatment chemicals.

Drinking Water: Water that has been treated to comply with EPA regulations and is pumped to water customers for their use.