Erosion and Sediment Pollution Control Program Manual.pdf

Mesic -----Refers to environmental conditions that have medium moisture supplies as compared to wet
conditions — Hydric — or dry conditions — Xeric.
Mesophyte -----A plant that grows under medium conditions of moisture supply.
MHW -----Mean High Water
Micron -----A unit of length equal to 1 millionth of a meter and usually denoted by the symbol .
Microphytes -----Microorganisms found in soil.
Microscopic Soil Particles -----Clay and silt; particles that cannot be observed individually by the
unaided human eye.
Mineral Soil -----Soil that is mainly mineral material and low in organic material. Its bulk density is
more than that of organic soil.
Minimum Tailwater -----The flow condition at a pipe outfall where the depth of water below the pipe
reaches an elevation below ½ the diameter of the pipe.
Minor Amendment to NPDES Permit -----A change to the permit that does not require the permit to be
re-advertised in the Pennsylvania Bulletin. For example, the addition of another rock
construction entrance to the E&S Plans).
Minor Drainage System -----The drainage system consisting of street gutters, storm sewers, small
open channels, and swales, etc.
Minor Fill in Wetland -----A permanent or temporary fill which is an integral part of the construction of a
residence and driveway located in wetlands with the total surface of disturbed area not
exceeding 0.1 acre.
Minor Road Crossing -----1. A small roadway across a wetland that individually impacts < 0.10 acre of
wetland or cumulatively impacts < 0.25 acre of wetland. 2. A small stream crossing having a
watershed drainage area < 1.0 square mile. A GP-7 is required.
Mitered End (a.k.a. beveled end) -----A culvert end, the face of which conforms roughly with the face
of the embankment slope.
Mitigation Plan -----1. Measures taken to reduce adverse effects on the environment. 2. A plan that
decreases the severity of adverse effects on the site of historic resources.
MLW -----Mean Low Water.
MOA -----Memorandum of Agreement, a legal agreement between two agencies regarding certain
duties or responsibilities.
Moraine -----An accumulation of earth, stones, and other debris deposited by a glacier. Some types
are terminal, lateral, medial, and ground.
Mottled -----A soil characteristic denoting spots or blotches of different color.
MOU -----Memorandum of Understanding, essentially the same as an MOA.
MS4 -----Municipal separate storm sewer system.
Muck -----Dark colored, finely divided, well-decomposed organic soil material.
Mud Line -----The lower surface of an excavation or braced cut.
Mulch -----A natural or artificial layer of plant residue or other materials placed on the soil surface to
protect seeds, prevent blowing, retain soil moisture, curtail erosion, aid in establishing plant
cover, and minimize soil temperature fluctuations.
Mulch Binder -----A substance sprayed over a mulched surface to hold the mulch in place, and often
used on steep slopes or in areas subject to wind gusts.
Municipal Notification -----A written notice (required by Acts 67, 68, and 127) to local governments
informing them of planned land development activities and providing them an opportunity to
identify any land use planning or zoning ordinance conflicts associated with the proposed
project before the Department or county conservation district completes its review of the
application.
Municipal Separate Storm Sewer System (MS4)----- A publically owned conveyance or system of
conveyances that discharge to waters of the US and is designed or used for collecting or
conveying stormwater, is not a combined sewer, and is not part of a publically owned treatment
works (POTW).
Municipality -----A county, city, borough, town, township, school district, institution or authority or
another public body created by or pursuant to state law. For purposes of this definition, town
includes an incorporated town.
Munsell Chart -----A standardized listing of soil colors according to hue, value, and chroma.
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