Erosion and Sediment Pollution Control Program Manual.pdf

Slope Protection -----A layer or facing of sound, durable rock or similar material (natural or manmade),
insoluble in water, selectively placed by hand or machine and sized to resist transport by flowing
water.
Slope Stability -----The resistance of any inclined surface to failure due to sliding, collapsing, or
sloughing.
Slotted Inlets -----A section of pipe cut along the longitudinal axis with transverse bars spaced to form
slots.
Sloughing -----Movement of a mass of soil down a bank.
Slow Percolation -----Permeability rate of < 0.2 inches/hour.
Sluice -----An artificial channel for conducting water with a valve or gate to regulate the flow.
Slump -----A type of landslide in which the material rotates along a slip surface. In this type of
movement, the top — head — of the slide usually moves down, while the bottom, — toe —
moves up and outward.
Small MS4 -----Municipal separate storm sewer system that is not regulated under Phase I of the
NPDES program.
Social or Economic Justification (SEJ) -----For earth disturbance activities where discharges to
surface waters classified as HQ cannot be avoided and ABACT cannot demonstrably protect
existing water quality, the applicant must demonstrate that the degrading discharge is
necessary to accommodate important economic or social development in the areas in which the
waters are located. This must be done according to the procedure identified in Chapter 10 of
the Water Quality Antidegradation Implementation Guidance, Document #391-0300-002 as a
separate permit application.
Sod -----Plugs, squares, or strips of turf with the adhering soil.
Soil -----1. The earth materials which have been so modified and acted upon by physical, chemical, and
biological agents that it will support rooted plants. 2. Earthen materials — down to bedrock —
affected by an earthmoving project.
Soil Aggregation -----The cementing or binding together of several soil particles into a secondary unit,
aggregate, or granule for purposes of minimizing erosion potential.
Soil Amendments -----Lime, fertilizer, or organic matter added to topsoil to enhance vegetative growth.
Soil Cement -----A designed mixture of soil and Portland cement compacted at a proper water content
to form a veneer or structure that can prevent streambank erosion.
Soil Classification -----The systematic arrangement of soils into groups or categories on the basis of
their characteristics.
Soil Conservation -----The use of land, within the limits of economic practicality, according to its
capabilities and its needs to keep it permanently productive.
Soil Creep -----The slow mass movement of soil materials down slopes primarily under the influence of
gravity, but facilitated by saturation with water and/or freezing and thawing.
Soil Erodibility -----An indicator of a soil’s susceptibility to raindrop impact, runoff, and other erosive
processes. See K-factor.
Soil Horizon -----One of the layers of the soil profile (i.e. A - uppermost layer containing organic
material, B - layer where material leached from layer A accumulates, C - parent material from
which overlying layers were formed) that has developed characteristics distinct from those of the
layers above and below.
Soil Liquefaction -----Loss of strength of a soil resulting from the combined effects of vibrations and
hydraulic forces, thereby causing the material to flow.
Soil Loss Tolerance (T)-----The maximum amount of soil loss, in tons/acre/year, that a given soil type
can tolerate and still permit a high level of crop production to be sustained economically and
indefinitely. T values for various soil types may be obtained from the Pennsylvania Soil and
Water Conservation Technical Guide, USDA NRCS, 1991, as amended and updated.
Soil Map -----A map showing soil boundaries, such as those in the Soil Survey.
Soil Moisture -----Water in the soil either held by capillary attraction or in the process of movement
toward the water table.
Soil Permeability -----The ability of soil to allow water or air to move through it. It is usually expressed
in inches/hour or inches/day.
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