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Directional Boring under canal/railroad

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rharashi

rharashi

Civil/Environmental
Jul 19, 2007
8
I have a client asking me to stamp a drawing for a directional bore underneath a railroad and a 50' wide x 10' deep canal which is not concrete lined. The boring company will be pulling a 10" dia. steel casing through and then a 4" pvc conduit inside of it. The bore would be 10' below the bottom of the canal; thus, 20' below the railroad.

Any suggestions? I'm concerned about water intrusion and possibly the pressure from the railroad. What are the standard procedures for this type of job?

Thanks.
 
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See if the railroad has specifications for this kind of application - I know CSX has a 40+ page document concerning utility crossings under the tracks. They are very specific about pipe wall thicknesses, installation methods, etc. Unless you extend your casing pipe above the water table on each end and then seal it well, water will likely get in there and accumulate. It is a judgement call based on whether or not water in the casing pipe is a bad thing.
 
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The Norfolk Southern document looks pretty good but railroad crossings should always be reviewed by the particular RR involved for their approval prior to stamping your client's drawing. For standard procedures you should refer to Practical Guide to Railway Engineering published by AREMA (The American Railway Engineering and Maintenance-of-Way Association)


 
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Do you mean a thrust bored cased pipeline, or that the pipelines will be directionally drilled and pulled through the hole (without any casing)?

If they are not cased, there is nowhere for any ingressed water to go. If cased, the casing will normally have vents for water removal or for filling the casing with paraffin or some other water displacing compound.

There doesn't appear to be any danger that is evident from your description so far. 20 feet below the railway and 10 feet below the canal should be more than adequate for any loading condition, if the pipeline is directionally drilled and pulled through or if it is a thrust bored cased crossing.

As was already stated above, the railroad will require their approval (as will probably also the canal owner) and it will be beneficial to you to have both of their approved drawings in your hand before you stamp it just to be sure that everybody's requirements are squared up beforehand and that there will be no confusion as to who approved what and when later on.

 
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As BigInch pointed out, loadings will not be an issue.

The standard installation procedures will be quite different depending on if it is a directional drill or a horizontal thrust bore.

If you need more information on the actual installation procedures, advise as to which of the 2 methods it is and there is plenty of informaiton available.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
 
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You may have water breakthrough during the directional drilling and prior to insertion of the casing.

You may be better off pushing the casing through rather than directional drilling. You won't have to worry about the water breakthrough.

You probably need a bigger casing than 12" too. I think the rule of thumb is 6" larger on each side of the pipe.

 
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bimr

It depends on the length of the bore. If it is short, then thrust boring will be a better option, if it is a longer bore, then ditrectional is the way to go.

Roads are not typically cased anymore due to the horrendous problems they cause, but with a pvc carrier pipe, casing is fine. Rule of thumb back in the casing heh-day was 4" larger, i.e. with a 4" carrier, 8" casing would be used. But that again will be dependent on the length. It's hard to control 8" or 10" bore pipe much over 60'-90', if it's a thrust bore and over 80' long, I would go with a 12" casing.

The design of crossings (road or railroad) need to comply with 49 CFR Part 192.111.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:
 
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Actually, the boring is for an electrical run. The wires will be in a 4" PVC conduit.
 
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To everyone who's already replied to this: thank you very much. You've all given me a lot of useful leads.
 
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