Washoe County Department of Water Resources
2009 Water Quality Report - Glossary of Terms
In this report you may find terms or abbreviations that may not be familiar. To help you better understand these terms we have provided the following definitions:
Action Level (AL) – the concentration of a contaminant that, if exceeded, triggers requirements that a water system must follow.
Color Unit (CU) – is the standard unit of measure for water color.
Maximum Contaminant Level (MCL) – is the highest level of a contaminant allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology. Most often, MCLs are defined in parts per million or parts per billion.
One part per million equals:
- One inch in 16 miles
- One minute in two years
- One cent in $10,000
Maximum Contaminant Level Goal (MCLG) – the "Goal" is the level of a contaminant in drinking water below which there is no known or expected risk to human health. MCLGs allow for a margin of safety.
Nephelometric Turbidity Unit (NTU) - is a measure of the clarify of water. Turbidity in excess of 5 NTU is just noticeable to the average person.
pH – is a measure of acidity. A pH value of less than 7 is acidic, values greater than 7 are alkaline.
Parts per Billion (ppb) - or micrograms per liter (ug/L).
Parts per Million (ppm) - or milligrams per liter (mg/L).
Picocuries per Liter (pCi/L) – is a measure of radioactivity in water.
Running Annual Average (RAA) - is calculated by averaging the four (4) most recent quarters of readings.
Total Odor Number (TON) - is the unit of measure of the detectible odor of water.