Mean High Water (MHW): The average height of all the high tides.

Mean Higher High Water (MHHW): The average height of the higher of the two daily high tides.

Mean Low Water (MLW): The average height of all low water heights.

Mean Lower Low Water (MLLW): The average height of the lower of the two daily low tides.

Mean Sea Level (MSL): A datum, or “plane of zero elevation,” established by averaging all stages of oceanic tides over a 19-year tidal cycle or “epoch.” This plane is corrected for curvature of the earth and is the standard reference for elevations on the earth's surface. The correct term for mean sea level is the National Geodetic Vertical Datum (NGVD). For purposes of the National Flood Insurance Program, the NGVD of 1929 or other datum, to which base flood elevations shown on a community's flood insurance rate map are referenced.

Mineral Resource: A mineral resource is a concentration (or occurrence) of material of economic interest in or on the earth's crust in such form, quality, and quantity that there are reasonable and realistic prospects for eventual economic extraction.

Mitigate: To ameliorate, alleviate, or avoid to the extent feasible.

Mitigation: Actions which address an adverse environmental impact by either (1) avoiding the impact; (2) reducing or minimizing the magnitude, scope, or intensity of the impact; or (3) compensating for the impact by replacing or substituting for the [natural] resource, or ecological functions, which are impaired, suspended, or eliminated.

Mixed Use Development: Different types of complementary land uses located in close proximity within one or more buildings and/or developments within the same development, planned and constructed to function as a unified complementary and integrated whole.

Mobile Sources: Sources of air pollution such as automobiles, motorcycles, trucks, offroad vehicles, boats and airplanes that move as they generate pollutants.

Modified Mercalli Intensity Scale: A scale used for measuring the intensity of the physical effects of an earthquake on the earth’s surface, humans, objects of nature, and man made structures on a scale of I through XII, with I denoting not felt, and XII one that causes almost complete destruction. The values will differ based on the distance to the earthquake, with the highest intensities being around the epicenter.

Multi-Modal: The utilization of various modes of travel that enhance the movement of people and goods, including, but not limited to, highway, transit, non-motorized, and demand management strategies including, but not limited to, telecommuting.