Water Quality Data
Definition of Terms
Action Level (AL): The concentration of a contaminant that, if exceeded, triggers treatment or other requirements that a water system must follow.
Maximum Contaminant Level (MCL): The highest level of a contaminant that is allowed in drinking water. Primary MCLs are set as close to the PHGs or MCLGs as is economically or technologically feasible. Secondary MCLs are set to protect the odor, taste and appearance of drinking water
Maximum Contaminant Level Goal (MCLG): The level of a contaminant in drinking water, below which there is no known or expected health risk. MCLGs are set by the U.S. EPA.
Maximum Residual Disinfectant Level (MRDL): The level of a disinfectant added for water treatment that may not be exceeded at the consumer's tap.
Maximum Residual Disinfectant Level Goal (MRDLG): The level of a disinfectant added for water treatment below, which there is no known or expected health risk. MRDLGs are set by the U.S. EPA.
Notification Level: Health-based advisory levels established by CDPH for chemicals in drinking water that lack maximum contaminant levels (MCLs). When chemicals are found at concentrations greater than their notification levels, certain requirements and recommendations apply.
Public Health Goal (PHG): The level of a contaminant in drinking water below, which there is no known or expected health risk. PHGs are set by the California EPA.
Primary Drinking Water Standard (PDWS): MCLs and MRDLs for contaminants that affect health along with their monitoring and reporting requirements, and water treatment requirements.
Abbreviations
A: absent
CA SMCL: California secondary maximum contaminant level
CDPH: California Department of Public Health
CSD MDL (City of San Diego Water Quality Lab method detection limit):
lowest quantifiable concentration of a measured analyte detectable by the lab
CU: color units
DLR: detection limit for reporting
gr/Gal: grains per gallon
ml: milliliter
MWD: Metropolitan Water District of Southern California
n/a: not applicable
ND: not detected (less than DLR, where applicable)
NTU: nephelonmetric turbidity units
OU: odor units
pCi/L: picocuries per liter (a measure of radiation)
ppb: parts per billion or micrograms per liter (μg/L) - [1 ppb = 0.001 ppm]
ppm: parts per million or milligrams per liter (mg/L) - [1 ppm = 1,000 ppb]
TT (treatment technique): a required process intended to reduce the level of a
contaminant in drinking water
μS/CM: micro-siemens/cm
< less than
> greater than