Curvilinear Sanitary Sewer

[MarshfieldTimC]

I am considering installation of a curvilinear sewer for a sanitary 'relief' sewer project. The pipe would be approx. 10-inch (HDPE or fusible PVC), installed via directional drilling, approx. 600 lf, no lateral connections, and good slope (more than minimum required slope). The two end locations are fixed (one existing and one proposed manhole). I also want a manhole in the middle, however the location is somewhat flexible. The reason for a 'curved' sewer would be to save a few dollars utilizing only one set-up of the drill rig. The middle manhole would be installed after the curved line is in-place.
Has anyone done something similar to this?
What are the disadvantages/potential problems of a curvilinear sewer?
What is the minimum recommended horizontal radius?
All comments welcome.

 

[bimr]

Sewers are installed in a straight line to facilitate cleaning.

Should a wire rope be used to pull a pipe cleaning device through the sewer, the wire rope will probably cut the PVC at the bend.

 

[dicksewerrat]

600 feet is not a long drill. Why does there have to have a curve in the line? What is in the way of a straight shot?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[coloeng]

I have yet to see a directional drilling operation that can maintain the close tolerences necessary for the slope requirement of most sewer installations. But then again, I haven't been involved in a lot of dd sewer installations, I've mostly seen water line installations.

 

[dicksewerrat]

HDD has come a long way in the past 15 years. If they have the room for more than minimum slopes there shoud be no problems.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[francesca]

In an informal settlement upgrade on the side of the mountain in South Africa (here)we curved the sewers to cut down on manholes. The contractor was cleaning out blockages every week before hand-over. Of course the blockages were often related to people using manholes and toilets as trash cans, places to stash the dog you killed before the dog catcher found him.

How deep is your sewer? I wouldn't think that the cost saving is worth it for you.

 

[MarshfieldTimC]

Thanks for all of the replies.
Regarding the need for a curve or 'kink'in the horizontal alignment, the sewer will be installed across private property, in easement. The property owner has imposed restrictions regarding locations of these sewer segments and manholes.
The angle between the segments is approximately 150-degrees (i.e. 30-degree pipe bend/fitting).
The depth of the sewer varies between 12-feet at the upstream manhole and 22-feet deep at the downstream manhole.
Another possibility is to drill such that the curve is as tight (short radius) as possible and then excavate at this location, straighetn the pipe segments and install a manhole at the intersection of these straight segments. Due to the easement constraints, I have a limited area for this excavation (approx. 60-feet max.).

 

[dicksewerrat]

Bring a couple HDD contractors to the site and ask for reccomendations. With a 60 ft. easement, they can probably drill it in in one pass for you.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

The radius of the curvature is determined by the rig. The minimum radius of curvature of the HDD path should be approximately 1200 times the diameter if the pipe. That would be about 1000 feet. If you are drilling in rock, it may be as low as 750 feet.

You may be limited by the radius of curvature.

You also have to contend with the entry angle. You will probably have considerable setback for the the drilling equipment because of the pipe depth.

Before you bid this project, you shoudl review the project with an experienced contractor.

 

[Ted3884]

Line and grade is now possible using existing HDD equipment. There is a process developed by a company called Trenchless Flowline, Inc. that works with existing HDD equipment. I recommend Google searching Ted Dimitroff the owners name for more info.

 

[dicksewerrat]

You could also attend the trade show in Houston starting Jan 25.

http://www.uctonline.com.

Every HDD manufacturer and many contractors will be there

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com