1. Rock Chute Mike Cox State Conservation Engineer Contractor Certification Training March 2008

2. Purpose: Stabilize the grade and control erosion in channels. Prevent the formation or advance of gullies. Grade Stabilization Structure (410) Rock Chutes are commonly used to control grade in Indiana

3. Rock Chute-Advantages Most of the construction can be done with a backhoe or excavator Economical compared with poured concrete

4. Rock Chute - Disadvantages Rock can move during large storms Hard to find larger rock sizes in certain areas High overfalls require long chutes Small rock size increases width and length of chute

5. Rock Size vs Velocity

6. What is a d50? Expressed as D50 size (50% maximum passing by weight) RIPRAP GRADATION d50 =7INCHES SIZE% PASSING 14100% 750% 2.333315%

7. Example: p1 = 24” p2 = 19.2” D50 = (24” + 19.2”)/8 = 5.4 inches

8. Bedding Minimum Thickness = 6” INDOT Sizes Specified

9. Geotextile

10. Riprap Thickness Minimum of 1’ thickness Must be 2 times D50 size Example: If using D50 Size = 7” Riprap Minimum Riprap Thickness = 2 * 7” = 14” 2xD50 min.

11. Installation Report http://www.in.nrcs.usda.gov/ technical/engineering/engine ering.html

13. Construction Tolerances-Rock Chute Depth at Centerline:Grade to 0.1 foot below Width:10% wider not to exceed 1.0 foot Top of Levee:Grade or above Side Slopes: +0.1 ft./ft.

14. Helping People Help the Land