Sanitary sewer pipe thru box culvert?

[RickSewerPipe]

Hello Eng-Tips.com community!

I need to cross-under a four lane state highway to get to the township's gravity sewer main on the other side.
In lieu of pneumatic tunnel boring (expensive) the ideal point of cross-under is at an existing state owned box culvert with a low flow stream running thru it (see pic).
Its a 5ft high x 12ft wide box culvert with a 100 year flood design size.
Is it ever permitted to run a sanitary sewer pipe (2" HDPE forced lateral)thru a box culvert of this type? The 2" pipe would be attached to the ceiling of the culvert.

 

[fel3]

Have you talked to the highway department? It's probably their culvert and they would be the ones to decide if it's allowed.

From an engineering perspective, I can envision putting your 2" HPDE pipe inside of a 4" (?) steel carrier pipe that is securely attached to the roof of the culvert, probably near or in an upper corner.

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[RickSewerPipe]

@FEL3
Thanks for your response!
The township sewer engineer is agreeable to this, but said I would have to get PA STATE approval and permit if they allowed this.
...... and other authorities may also want permissions as well (EPA, etc)

 

[bimr]

What are you running, a gravity sewer or a force main?

What is pneumatic tunnel boring?

Why do you state that HDD is expensive? You can construct this within a week?

 

[RickSewerPipe]

@bimr:

What are you running, a gravity sewer or a force main?

Forced lateral (pumped) ...... with siphonic drain function as a back-up.
This 2" lateral is 450ft long!!
The vertical height differential from starting elevation to end discharge into the township's gravity sanitary sewer is 40ft (25ft is of almost a vertical drop straight down .... the remaining pipe is at 1/4" drop per ft)

What is pneumatic tunnel boring?

an air operated cylinder that punches its way horizontally thru the soil ..... leaving a hole to thread your 2" sewer pipe thru

NOTE: Running this 2" pipe across the ceiling of the colvert allows me to transverse the steam without having to do an inverted loop under the stream bed.

 

[bimr]

It may be an easier process to install your piping using HDD instead of the culvert option. 450' of HDD is a run of the mill project, nothing special.

You haven't presented a site plan nor a geotechnical analysis, nor location. Are you concerned with the possibility of freezing?

The culvert option may have more hurdles in so are as permitting the project. You may have to convince somebody that the pipe won't lessen the capacity of the culvert. You may have to put up a maintenance bond as well. If you anchor the pipe to the wall, you may need to prove that a flooded stream scenario won't rip the piping off the wall.

Don't see why you are concerned with the drainage since you are pumping downhill. It is the normal practice to keep force mains full as the capacity will drop if you have air pockets.

 

[RickSewerPipe]

@bimr

Hi bimr! : ) ........ thanks for your input!

I hear ya in all that your saying ........ but you really have to see the aerial topography of the areas in question here.
Basically, its a small motel located in a rural area up on a hillside with a 4 lane major highway in front, surrounded by a vast area of flood zones and small streams. This motel is orphaned (isolated) from pretty much anything else around. There is no sanitary sewer main on this main highway. Homes in this area are over a 1,000 ft away up on the hills in scattered groups of cal-de-sacks. The public gravity sanitary sewers "trace the cal-de-sacs" then are gravity feed to a municipal pump station and forced mained out. This gravity sewer network is on the other side of this highway and none on our side.
When the gravity sewers on the other side encounter the streams, the pipe is embedded (inverted) within the stream bedrock.
It is my contention (proposal) to request PENNDOT to allow me to embed my 2" HDPE forced lateral within the emulated "stream bedrock" atop the existing box culvert floor transversing this highway. The municipal sewer pump station is now only 25ft in front of me for an easy tie-in. There is no attachment nor obstruction to the function of the box culvert itself.

........ your thoughts on this?

 

[bimr]

Where I am located the State DOT has this regulation:

"Utilities should not be permitted to cross under highways in cattle passes, culverts, or other drainage facilities."

 

[RickSewerPipe]

Where I am located the State DOT has this regulation:

"Utilities should not be permitted to cross under highways in cattle passes, culverts, or other drainage facilities

Where I am located the State DOT has this regulation:

"Utilities should not be permitted to cross under highways in cattle passes, culverts, or other drainage facilities."

This township's codes requires the sewer main to be embedded 2 feet under the stream bed or in hard rock areas, 1 foot.
I could meet this criteria easily within the emulated bed stream going thru the culvert.

 

[RickSewerPipe]

I put in a box culvert many years ago to cross a stream to reach an isolated residential land plot. The bottom floor of the culvert was left as bare concrete (I took this project on as I have never did one before! : )

The culvert was 30 tons! The crane was massive and cost $2,500.00 for the 30 minutes he was there. He said I could put my hand under the culvert as he lowered it down to the sand bed as it would only be 11 PSF to my hand. : )

Was an interesting project indeed!

I bring this up because, looking at the picture I posted of the colvert, I thought, look at all the rocks that got washed into this culvert's floor : (

I didn't know that those rocks were put in there intentionally! …… they emulate the natural stream bed as it was before the culvert ever existed.

Now knowing this ……..I'll bet I'll be allowed to bury my 2" pipe within this stream bed as is done throughout the township in this area.

 

[RickSewerPipe]

....... The other requirement was that the pipe be of hard impact duty ...... so if lets say a backhoe drives thru the stream for example, it cant crush the pipe.
Its my contention is that in lieu of this, the 2ft thick reinforced concrete box culvert itself affords an encapsulated protective barrier to such damage.