Repair Stormwater Outfall at top of steep slope

[wnceng]

Working on a stream restoration/enhancement project in an urban setting. Part of the project involves stabilizing two gullies that were created by stormwater outfalls at the top of a steep 20-foot high slope. One situation is a 24" RCP that outfalls at the top of a slope and discharges down a 35% wooded slope for approximately 55-feet to a flatter terrace above a creek. This has created a large gully. The slope of the terrace is approximately 15%.
The other situation is similar but with a 30" RCP.


What are some options to convey this stormwater from the existing outfall down to the terrace and ultimately the receiving creek?

Junction box at existing outfall (connect to existing pipe with fernco coupling?) --> pipe stormwater down the slope to another junction box --> discharge to large plunge pool or some other energy dissipation device?

I would appreciate any thoughts or suggestions.

 

[cvg]

a) pipe drop to an impact energy dissipater or b)chute with a stilling basin on the end. c)Third option is a stepped chute which may reduce the size of the stilling basin and might be safer.

not sure a Fernco is up to the task...

you can find details in here, Sections IIe and IIf:

http://www.usbr.gov/pmts/hydraulics_lab/pubs/manuals/SmallCanals.pdf

 

[wnceng]

Thanks for the tips. What is the best way to connect to an existing RCP to a junction box or similar structure?

 

[wnceng]

Is the USBR Type VI an appropriate impact energy dissipator?

 

[cvg]

that was my first recommendation