Erosion and Sediment Pollution Control Program Manual.pdf

BENCH - Benches (a.k.a. gradient terraces) are recommended to break up long fill or cut slopes and
convey runoff to one or both sides. For slopes on soils having low shear strength, care should be taken
to prevent saturation of the soil and/or bedrock below the bench.
York County Conservation District
Benches should be constructed to the minimum dimensions shown in Standard Construction
Detail # 6-6. They should have a minimum longitudinal drainage slope of 2% and a maximum slope of
5%.
Wherever soil conditions and/or anticipated flow conditions indicate a significant potential for erosion of
the bench, a suitable protective liner should be provided. Please refer to channel design text or
manufacturer’s recommendations for guidance on selection of protective linings.
Bench lengths should not exceed 800 feet in one flow direction. Where equipment is likely to use the
bench as a travelway, as done at landfills, rock lining is recommended.
Maximum vertical spacing between benches should not exceed those shown in Table 6.12.
Steep Slopes
Long Slopes
North Carolina DENR
TABLE 6.12
Bench Spacing
Slope
Maximum Vertical Spacing
Between Benches (Ft.)
2H:1V 20
3H:1V 35
4H:1V 45
15 - 25% 50
10 - 15% 80
6 - 10 % 125
3 - 6% 200