Pipe Bursting / Other non-opencut methods for sewers

[cr1973]

I want to replace about 300 feet of old 8" sanitary sewer. I do NOT want to use open cut, as telephone poles and storm sewers are close, if not right on top, of this sanitary line. Plus, it's in a tight corridor with plenty of traffic.

The "sewer cleaning guys" think there is a collapse in the pipe.

Can pipe bursting be used to replace a pipeline even if there is a collapse in it? If not, what about direction drilling?

I don't think directional drilling is an option, because the slope is very low, and directional drilling isn't accurate for slopes of .20%

So, can pipebursting be used on lines even if there is a collapse? Any other ideas?

 

[KRSServices]

You just raised a "red-flag" by indicating the sewer guys "think" it is collapsed. Are the manholes being replaced as well? (I am assuming that the pipe to be replaced currently exists between two manholes)

The directional drill will likely have have a few dips in the mainline. I have trenched and shored very quickly in tight lanes and rights-of way and it is an easy solve. If traffic is a problem, construction in off hours and "half road" widths make it a relatively simple task and serves to minimize disruption to traffic. Backfilling with a fillcrete and quickly resurfacing with ACP is key as well.

I have done several of these projects and can provide seveal different ideas if you wish. Can you scan an overall plan and email it to me? I may have a few suggestions that I haven't considered yet.

KRS Services

http://www.krs-services.com

 

[cr1973]

Thanks for the tips.

I haven't had our techs draw up anything planwise as of yet. The main problem is the proximity of the telephone and power poles, which are literally on top of or a foot or two away from the sewer pipe, horizontally.

I will probably replace the 2 manholes while I am at it. You are right in that drilling would put sags in the line - that definitely won't be an option.

Anyway, can one pipe burst through a sewer collapse? Even though I am not all that familiar with it, I wouldn't think so...?

 

[KRSServices]

Yes, One can burst through a collapse, depending on the severity. The existing pipe is clay, I'm assuming.

With power poles, the telephones are underground?

Power poles are no big deal, they can be supported while excavating near them. Telephones, depending on the numbers of pairs, can be run temporarily and them replaced while backfilling. I'd say that trenching (36" - with shoring) will be your best bet to stay within the tolerance of the grade. How deep is the sewer pipe?

At most you will be looking at a few days, needing a good skid steer, a competent crew, a CAT 315 or 416 size backhoe/loader or equiv., and steady supply of trucks and possibly traffic plates (to cover the trench until ACP) or some firm coldmix. Three to four days would be a bonus as well, but two or three days should suffice.



KRS Services

http://www.krs-services.com

 

[dicksewerrat]

Have you sent a camera down the line? That is the first, cheapest thing you can do. If you can get a jet nozzle through the line to pull the cable, you can burst it. That said, if the line is cleanable and not 'caved-in', you could reline the pipe by the CIPP method.

 

[cr1973]

KRS, the sewer is about 10 feet deep. If power poles are supported, doesn't the power utility have to support them themselves, then back charge?

sewer-rat, the cleaning guys couldn't get the flushing head through. Plus, this line has sags in it, so it is always full of water. I believe they tried to send a camera through once but the pipe was too full of water.

I suppose if we got a vactor truck in, sucked the manhole and sewer out, then quickly got a camera in there, we might be able to see what the deal is. Maybe that's what I'll do. If it is collapsed in just 1 spot, as the case probably is, maybe we could do a spot repair, then burst the line?

 

[cr1973]

Hmmm if you pipe burst an already sagged line, the new line will be sagged aswell huh? Looks like no other choice than to open cut

 

[KRSServices]

You mentioned known sags, while not insurmountable, certainly not desired in a new line. Add to that the fact that the sags have likely had an impact on the bedding itself, I would still recommend open cut. Remember, if done properly, there will not be a huge trench opened and causing chaos with traffic. Ensure the excavation work is well coordinated and organized. After that....no worries!

Regarding your question to supporting the power lines, it's up to the utility. Sometimes they charge, but in other cases the municipality or owner of the right of way can make a convincing arguement that since the underground was in the ground first, it is the responsibility of the owner of the pole to ensure it remains supported. In some cases there are utility agreements in place and therefore they may be obligated to support the poles without charge.

I've made that arguement before and have been successful in some cases.

KRS Services

http://www.krs-services.com

 

[Zambo]

what about sinking a couple of caisson shafts adjacent to the existing manholes then micro-tunneling between them, later you can break into the existing manholes. Directional drilling is not accurate enough for gravity drains, but micro-tunneling will be. At 200mm diameter I think only displacement micro-tunneling equipment is available. Of course open-cut as suggested would be a cheaper option.

Zambo

 

[cr1973]

I am not all too familiar with micro tunneling, how does it work?

Open cut would still be cheaper?

 

[Zambo]

micro-tunneling is in essence pipe jacking but not man entry. Depends on the country but I guess for USA probably about 1.2m diameter and above pipe jacking, below that micro-tunneling. It all depends on the soil conditions but for 300ft, 8 inch diameter you could probably jack from a jacking pit of less than 2.0m diameter.

The costs are high because apart from the specialist sub-contractor services the jacking pipes are also expensive.

Zambo

 

[cr1973]

Ok thanks for the info. It does sound a little on the expensive side, I guess I'll just go with good ol' fashioned open cut.

 

[HB2U]

Just a couple of thoughts....

Would it be possible to move the location of the sewer line since you're replacing the manholes anyway? Then you could get it away from the other utilities?

As I understand it, pipe bursting won't work unless you can backfeed the tow cable through the line and connect it to the bursting head. If your line is collapsed you won't be able to do this.

Have you thought about only open cutting in the area of the collapse? and the utilize pipe bursting for the remainder of the line? You could use the open cut area for a send and receive pit for the pipe bursting activities and then just set an intermediate manhole in that location to tie it all together. That would minimize the open cut and pave restoration that you'll have to do.

 

[cr1973]

Actually I thought about only open cutting to fix the collapse, then pipe burst... but there is a definite sag in this old clay line, and it has a very low pitch on it from invert to invert.

I would like to move it, but there is just too many utilities in the way.