Erosion and Sediment Pollution Control Program Manual.pdf

Gumbo -----Silty soil that becomes, soapy, sticky, or waxy when wet.
Guy Wire -----A support wire used to keep the stakes of Reinforced Silt fence erect (see Standard
Construction Detail #4-8.
H
Hard Armor -----Non-living erosion protection, such as riprap, concrete, gabions, etc.
Hardness -----A measure of soap-neutralizing ions present in water; predominantly magnesium and
calcium, but other alkali metal ions contribute to the effect.
Hardpan -----Layer of extremely dense, nearly impermeable soil — chiefly clay or organic materials —
beneath a more permeable soil, formed by natural chemical cementation of the soil particles.
Haul Road -----A temporary dirt, gravel, or stoned roadway used during earth disturbance activities to
access a work area.
Hazardous Material -----Any substance, pollutant or contaminant listed as hazardous under the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980.
Head -----1. The difference in elevation between a water elevation and a point in question (e.g. crest of
a riser, outlet barrel elevation, etc.). 2. In culvert pipe calculations:
A) For inlet control, it is the difference in elevation between the highest attainable water
level and the pipe invert.
B) For outlet control, it is the difference in elevation between the highest attainable water
level above the culvert and the level of the water below the culvert.
Head Cut ----- The point at the upstream end of a channel where it grows and lengthens, also called a
“nick point”.
Head Cut Control Structures -----BMPs designed to break up erosive energy at a head cut, often in
the form of stair steps constructed out of logs or rocks in conjunction with erosion control
blanketing.
Head Cutting -----1. Headward erosion of a locally steep channel or gully. 2. The action of an upstream
moving waterfall or locally steep channel bottom with rapidly flowing water through an otherwise
placid stream. These conditions often indicate that a readjustment of a stream’s discharge and
sediment load characteristics is taking place.
Head Gate -----A water control structure. A gate at the entrance to a conduit.
Head Loss -----1. The decrease in total head caused by friction. 2. The effect of obstructions, such as
narrow bridge openings or buildings that limit the area through which water can flow, raising the
surface of the water upstream from the obstruction.
Headwall -----The wall placed around the opening of a culvert, storm sewer, etc.
Headwater -----1. The source and upper reaches of a stream or reservoir. 2. In culverts, it is the depth
of the upstream water surface measured from the invert of the culvert entrance.
Heaving -----The partial lifting of plants out of the ground, frequently breaking their roots, during the
freeze-thaw cycles of winter.
Hectare -----A metric unit of area equal to 10,000 square meters (107,639 square feet).
Herbaceous Plant-----A plant with no persistent woody stem above
ground.
HGIS -----the Pennsylvania Natural Heritage Program database, formerly PNDI, available at
www.naturalheritage.state.pa.us.
High-Density Polyethylene (HDPE) -----A synthetic polymer used for geomembranes and pond liners.
High Quality Waters -----Surface waters having quality which exceeds levels necessary to support
propagation of fish, shellfish, and wildlife and recreation in and on the water by satisfying 25 Pa.
Code § 93.4b(a).
Highwall -----The unexcavated face of exposed overburden and coal, or other mineral being extracted,
in a surface mine or quarry.
Historic Resource -----A building, structure, object, district, place, site, or area significant in the history,
architecture, maritime heritage, archaeology, or culture of this Commonwealth, its communities
or the nation.
Histosols -----Organic soils.
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