Department Force Cherryhill Township SR 1008 Section 450
Bridge Indiana County Over Tributary to Crooked Creek
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References: PENNDOT Design Manual, Part 4 – Chapter 7
PENNDOT BD-632M (January 21, 2003) Bridge Design Standards
No scour analysis for pipe or box culvert is required.
Refer to BD-632M for scour protection details for box culverts (DM-4, 7.2.1).
From BD-632M (January 21, 2003)
 Minimum 600 mm (2’ – 0”) thick rock protection, Class R-6 minimum [sec. 850.2 (a)]
(each end), 1500 mm (5’ – 0”) from end of apron or wingwall.
Determine size of rip-rap based on DM-4, 7.2.5
DM-4, 7.2.5 states:
 Rip-rap should be sized based on the velocity of the flow of the Q
100
storm or whichever

 storm velocity is the greatest. For piers, V is 1.5 times the average upstream velocity.
For abutments, V is 1.8 times the flow velocity.
Since culverts do not require scour calculations, the velocity will not be multiplied by a safety factor. The velocity will not be factored for the stream bank, either. The velocities were taken from the first cross-section directly upstream of the culvert.
V
10
= 5.08 ft/sec
V
100
= 4.51 ft/sec
Therefore, use V
10
because it is the greatest velocity.
From table: For V up to 12 ft/sec, use R-6 or larger.