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#### INFORMATION

Per Loose RipRap Protection Minnesota

G. Allowable Side Slopes. The stability of the riprap on the side slope of a channel
is dependent on the angularity of the rock. The more angular the rock, the higher the
angle of repose. The maximum (steepest) slope for riprap is recommended to be 2:1
(that is, two feet horizontally for every foot of vertical height). For small areas, such as
around existing culverts or transitions where slopes steeper than 2:1 cannot be avoided,
slopes up to 1:1 can be tolerated, provided the riprap thickness and size are increased.
Very angular rock must be used and carefully installed. The thickness shall be
increased by 10% for 1.5:1 side slopes and by 20% for 1:1 side slopes. The minimum
D50 that can be used on slopes steeper than 2:1 is 4 inches. This must be angular rock,
not rounded.

———RipRap pile angle calculation————–

—From Slope foto #01—

x1,y1 = 1400,1600

x2,y2 = 4100,0

Slope = (1600-0) / 4100-1400   = 1600/2700 = 31     using bottom less sloped

x1,y1 = 3200,700

x2,y2 = 4100,0

Slope2 = 700 / 900 = 0.78   Absolute maximum slope of pile  => 38 degrees

—From Slope foto #02—

x1,y1 = 2500,1300

x2,y2 = 4100,0

Slope1 = 1300 / 1600 = 0.81   Absolute maximum slope of pile  => 39 degrees

—From Slope foto #03 & 4—

x1,y1 = 0,0

x2,y2 = 2900,1700

Slope1 = 1700 / 2900 = 0.58   Absolute maximum slope of pile  => 30 degrees

Current Cut Slope = 3/4 = 0.75  => 37 degrees  — Essentially at max slope here.

Modifying creek slope to 3/5 = 0.60  => 31 degrees => 1ft delta at top of cut

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