Sanitary Sewer Rehab 1

[LarryStruct]

I have a client with cast iron (4" & 6&quot interior sanitary and storm sewers under a corridor of a mid rise apartment complex. The 20 year old sewers have corroded due to salt ground water (next to a salt water bay).

A contractor has proposed pipe bursting to replace the existing truck line. The laterals will be excavated at the mains and CIPP would be installed until the lateral is above grade.

I would like to know if any one has had any experience in piping breaking in type of application.

 

[KRSServices]

I have pipe burst 6" and 8" ductile and cast water main. Recovery of the broken pipe is key. Also, I'm assuming that under the corridor that there are not any tie-ins to worry about because they will have to be dealt with (excavation?). The other problem was the length the new pipe had to be "pushed". The longer the distance and depending on the material type surrounding the old pipe, it became harder to push without the assistance of mechanical devices. I do not like the mechanical pushing because it is very tricky to ensure that too much pushing force is not excerted on the pipe resulting in split joints. Sewer pipe is thinner and more suseptible to failure than the C-900 we were using, so be careful. If the existing pipe is surrounded by native gravels or gravelly soils, it will get incredibly complicated if the pushing of new pipe gets too far behind the bursting tool because of the high probability of the pipe cavity collapsing.

KRS Services

http://www.krs-services.com

 

[EricC]

To add to the discussion, pipe bursting can cause heaving above the pipe if there isn't sufficient cover. That sounds like it could be a concern in your case.

 

[ivanlocke]

I have a related question about pipe bursting. We have an 8" ductile water main running under a high school track that has been recently redone with that eraser like surface. The line has a history of leaks, so we are looking at replacing it. The options are to lay a line around the track or to pipe burst the existing line. We've run some numbers and the pipe bursting seems to have a bit of cost savings, but we have no experience. We would be bursting the 8" ductile and pulling behind same sized HDPE. The main probably has 42" of cover. As the whole point of the project is to avoid damage to the track we are worried about heave. Any experiences would be appreciated.

Thanks

 

[KRSServices]

Ivanlocke, assuming of course that the soils are conducive to that type of work, I wouldn't pipe burst, I would core it instead. The reason would be due to the fact that there would be more room (either side of the track) to auger in a new line. It will also save some money because you won't have to spend so much time removing the old pipe and hauling it to a disposal area. The tie-ins can be easily accomodated and the job on the whole will be much easier (and cheaper).

KRS Services

http://www.krs-services.com

 

[ivanlocke]

This would be a winch and hydraulic line fed through the existing pipe. Bursting head connected to lines and HDPE pipe attached behind. The bursting head is pulled through with the HDPE following along behind - all one pull. The existing pipe is supposedly burst into the surrounding soils.

 

[KRSServices]

Ivanlocke, assuming of course that the soils are conducive to that type of work, I wouldn't pipe burst, I would core it instead. The reason would be due to the fact that there would be more room (either side of the track) to auger in a new line. It will also save some money because you won't have to spend so much time removing the old pipe and hauling it to a disposal area. The tie-ins can be easily accomodated and the job on the whole will be much easier (and cheaper).

KRS Services

http://www.krs-services.com

 

[KRSServices]

I would not even worry about bursting the old line. Abandon it. Core the new line beside it and effect the tie-ins accordingly. It is extremely accurate. That is of course assuming the soils are non gravelly, then aguering may be an option, but it gets a little pricy. I prefer the burst to remove the old pipe as well. Moving into the surrounding soils sounds wonderful, but think about it, would you specify placing new pipe on broken pieces of cast pipe? It does not make the best bedding in the world, and HDPE will swell and shrink due to pressure flucuation. Over time, the pipe will pop due to rubbing. If pipe bursting, remove the old pipe as well. But then again, I advise abandonment and coring a new line.



KRS Services

http://www.krs-services.com

 

[cvg]

KRSServices - by "coring" do you mean horizontal directional drilling?

 

[KRSServices]

cvg,

I believe the definitions that are used may be somewhat different but essentially mean the same. I know that I have seen the term horizonal directional drilling in these threads before and have assumed they mean the same as the terms I use. I think we are essentially speaking about the same techniques.

Coring - Hydraulically pulling a plug and pipe through soils.

Pit and core - coring over smaller distances and hand pushing pipe. Usually completed to rehab water mains and the "pits" are opened up at each service location. Very efficient replacement methodology when asphalts are in good shape and not in need of replacement.

Augering - Horizonally augering (drilling) through soils and pulling pipe behind. Simple, straight runs.

Directional drilling - Similar to augering but more expensive due to the equipment used. I've used directional drilling to install HDPE pipe within escarpment areas (under rivers and stream basins).



KRS Services

http://www.krs-services.com

 

[gtrainor]

KRSS, I am envisioning a burst under a road 6 ft deep, 80 feet in length; How do you remove the pieces of the old pipe?

 

[KRSServices]

Gtrainor,

It is a two fold process. The pits are excavated on each side of the job. On one end the bursting tool is fed through the pipe and the pipe is minimally fractured. Once the tool is through, a special attachment is connected and the tool is pulled back and the new pipe is pushed with it. In this process, the old pipe is also "pushed" and it essentially extruded into a hopper. It is a slow process, but very effective. I have seen the process on a couple of jobs where the pipe was under a major arterial road and open cut was not an option.

KRS Services

http://www.krs-services.com

 

[dicksewerrat]

I would talk to a couple of pipe-bursting contractors before I decided on one method over the other. There are more than one. I think the best way to put a pipe under the track would be Hor. Dir. Drilling. the roadway could be crossed with either of the pipe- bursting methods. For a better expanation, email me at contact info in profile.