Deep drainage structures

[zebco]

Looking for design info. for a catch basin/ drop inlet approx. 30 feet deep, feeding a 42" outlet pipe. This is for a quarry reclaimation plan. What kind of info. or standard drawings are out there? I seem to see that most standards limit the height to 10-12 feet. Also, are there any major issues with a water drop of this distance?
Thanks in advance, Herb

 

[dicksewerrat]

The only thing I see as a problem will be the water hitting the bottom and causing wear in the structure. You will have to reinforce the bottom and construct a sump also.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[zebco]

Thanks for the reply, my thoughts too on reinforcement. Have you got a diagram of the sump you mentioned?

 

[gbam]

Zebco - I think you are in a realm of design where you will need to come up with the design. I know that this configuration is not common in my area. You may be able to put something in the vertical drop to diffuse the water enough to limit the impact at the bottom. I first thought of a device at each pipe joint that would push the water to one side and then back (zigzag). The other thought I had is similar to dick's but use a manhole base with a 3-foot sump filled with 6-12" riprap. Just some thoughts.

 

[Ryb01]

zebco,

Is there another way to drop the water? (i.e could you install a few sections of sewer and manholes to drop the flow 30').

I would have a few things that come to mind with a direct 30' drop.

1) As gbam and dicksewerrat have outlined, scour would be an issue at the botom of the structure. Especially if you require a 42" outlet. I'm not sure a 3' sump would be enough given the drop.

2) Maintenance access. A 30'drop would require (depending on design standards in your area), 1-2 safety platforms within the structure. I would assume that you would want access given the drop. With the flow that would be entering the structure, you would have to provide a safe access for maintenance staff to the bottom of the structure.

3) Custom Structure Design. The structure that you would be looking for would have to be structurally designed and likley not something that could be obtained via a catalouge. Groundwater pressure, soil pressure, internal forces, etc would come into play with a structure like this.

4) Outlet. There would be quite a bit of turbulence at the bottom of the structure, it may also be beneficial to look further at the 42" outlet for erosion and scour d/s.

Hope this helps.

 

[dicksewerrat]

No drawing. But if you put a 3-4 ft sump below the outlet invert and line the bottom with granite paving blocks, it should last until you retire. The water in the sump will slow down the water and the granite will protect the cncrete sump bottom. Do you know the flow depth in the 42"? You may want to have the lip of the sump at or above the flow line in the 42".

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[beej67]

2nd the recommendation for a granite invert.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Ryb01]

had another thought....

I've seen vortex drop structures for sanitary applications, which may work for this. May be something to look into.

 

[zebco]

Thanks guys, since I'm in a quarry, I think I'll create a sump/dissapator pad of granite in the invert.