A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Macropores
Large spaces between the organic or mineral particles in soils which give rise to high permeability.

Maximum Contaminant Level (MCL)
Designation given by the U.S. Environmental Protection Agency (EPA) to water quality standards promulgated under the Safe Drinking Water Act. Based on conservative risk-assessment methodology, the MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.

Metamorphic Rock
A rock type formed from pre-existing rocks/ sediments as a result of heat and/or pressure. Schists, gneiss, quartzite and slate are examples of metamorphic rocks.

MGD
Million gallons per day (alternate meaning, Miller Genuine Draft).

Microdrip Irrigation
An efficient irrigation system that uses tiny holes on plastic pipes to deliver water directly to plants.

Milligram (mg)
One thousandth of a gram.

Milligrams per liter (mg/l)
Unit of the concentration of a constituent in water or wastewater. It represents 0.001 gram of a constituent in 1.000 milliliter (mL) of water. It is approximately equal to one part per million (PPM).

Million gallons per day
A rate of flow of water equal to 133,680.56 cubic feet per day, or 1.5472 cubic feet per second, or 3.0689 acre-feet per day. A flow of one million gallons per day for one year equals 1,120 acre-feet (365 million gallons).

Monitoring Well
A well constructed or used for the purposes of water level or water quality data collection. Monitoring wells are often installed to provide an early warning of contamination occurring down gradient from a landfill or industrial facility. See also Observation wells.

Municipal Water System
A water system that has at least fifteen service connections or which regularly serves 25 individuals for 60 days; also called a public water system. See also Community Water Supply.