construct end treatment in the wet, how?

[2civil]

Design calls for a 30" HDPE pipe that outfalls to a storm water pond with a 5:1 side slope. The top of pipe is approximatley 3ft below the control elevation of the pond. The end treatment called for is a cast in place Mitered End Section.

The contractor neglected to install/construct the MES when the pond was dewatered.

Can the MES be installed properly underwater? My biggest concern is not being able to compact the area where the MES will sit.

Any construction suggestions appreciated.

 

[SMIAH]

So the end of the pipe is submerged?

 

[SMIAH]

Sorry, but I'm wondering what this "end treatment" should be there for?

 

[2civil]

Correct the pipe is submerged.

I guess I've gotten into the habit of specifying an end treatment without too much thought to the pipe being submerged or not.

A submerged pipe would not require an end treatment because there would be no erosion issues?

 

[SMIAH]

End treatments are applied to culverts for many purposes, including:
- retention of roadway embankment
- improvement of hydraulic efficiency
- protection of highway embankment
- protection against piping
- control if debris
- traffic safety

I'm going to let someone else answer the need for an end mitered to the slope at the outlet of the culvert under submerged condition.

One would tend to think that this is not needed for a 5:1 slope...

 

[gbam]

2civil,
Is the pond always full? If so, I do not see a need for the end section. If not, then the end section may be warranted and you could wait for dry period and install.

 

[2civil]

Yes. It is always full.

I consulted with the project geotech and he had the same suggestion. If it is always submerged leave as is.

Thanks!

 

[beej67]

Just because it's submerged doesn't mean it won't scour.

If I were you I'd leave it as-is, but inspect it in a year or two for scour around the sides of the pipe. If you notice scour forming, throw rip rap in the scour holes of a nominal size equal to the scour hole itself.

Make the recommendation in a letter to the owner and contractor, so they can have that in hand when it comes time to pay for the inspection and possible maintenance later.

my .02

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