Erosion and Sediment Pollution Control Program Manual.pdf

Critical Area -----That part of a disturbed area which poses the greatest threat of sediment pollution to a
receiving water
Stream Channel: Within the floodway
Wetland: Within 50 feet
Steep Slopes: Any slope 3H:1V or steeper directly above a surface water.
Erodible Soils: Any slope 3H:1V or steeper directly above a surface water.
Critical Depth -----The flow depth at which the specific energy for a given discharge rate is a minimum.
Since water passes through this depth, it is hard to find in nature. Flow is critical when the Froude
number is equal to one.
Critical Flow -----The flow conditions at which the discharge is a maximum for a given specific energy, or
at which the specific energy is a minimum and the Froude number is equal to 1.0 for a given
discharge.
Critical Slope -----The slope that will sustain a given discharge at uniform, Critical Depth in a given
channel.
Critical Velocity -----The velocity that minimizes specific energy. A wave caused by a disturbance cannot
move upstream in a channel where flow is at critical velocity.
Cross Drain -----A structure, usually a culvert pipe, used to convey runoff from a roadside ditch to a
discharge point below the roadway.
Cross Vanes -----Rock structures that extend across a stream channel from bank to bank; they are keyed
into the bankfull elevation in order to control the channel carving flow.
Cross-section -----A section formed by a plane cutting an area, usually at right angles to an axis.
Cross-sectional Area -----The surface area of a form or structure formed by a plane cutting it at right
angles to an axis.
Crown -----The inside top elevation of a conduit.
Crowned Roadway -----A roadway graded so as to be higher in the center of the roadway than at either
side. This is to promote drainage of runoff from the roadway into a roadside ditch or to an adjacent
vegetated area.
Crows Foot -----Marked survey stake, which shows the cut/fill needed during grading operations.
Crust -----A dry surface layer on soils that is much more compact, hard, and brittle than the material
immediately beneath it.
CSL -----Pennsylvania Clean Streams Law (35 P.S. §§ 691.1—691.1001).
C-TRM -----Composite turf reinforcement mat.
Cubic Foot Per Second -----A unit expressing rate of discharge, typically used in measuring pipe or
channel flow. One cubic foot per second is equal to the discharge of a pipe or channel having a
cross-section of 1 square foot and flowing at an average velocity of 1 foot per second. It is
equivalent to 7.48 gallons per second, 448.83 gallons per minute, 1.9835 acre-feet per day, or
723.97 acre-feet per year.
Cul-de-sac -----Street that is closed at one end with a circular turnaround area and only one outlet.
Cultural Resource Notice -----A notice given by the project applicant to PHMC regarding the intended
activity for which the applicant needs DEP’s permit or plan approval.
Culvert -----A pipe or box used to convey runoff or stream flow under a roadway or embankment to a
discharge point on the downslope side. (See Standard Construction Detail # 3-10, 3-13, and 3-14)
Curb -----Raised concrete border constructed along a street or sidewalk.
Curb Inlet Sediment Barrier -----A temporary barrier, such as concrete block and gravel, constructed
around curb storm sewer inlets to reduce sediment discharge to the storm sewer. See Standard
Construction Detail #s 4-15, 4-17, 4-19, and 4-22.
Curb Stake -----Survey stake used to locate the curb grade that is to be cut.
Curled Wood Matting -----A type of erosion control blanket used to minimize erosion on cut slopes or fill
slopes or in constructed channels until a protective vegetative cover can be established.
Curlex -----A brand name often used to signify curled wood matting.
Current Meter -----A device that is lowered into a stream in order to record the rate at which the current is
moving.
Cut -----1. An area from which earth material has been or will be removed by excavation. 2. The depth
from original ground surface to the excavated surface.
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