Locating Deep (50'+) Cast Iron Pipe?

[kstefanich]

I have recently run into a problem on a project where an MUA CSO line (36" CIP) with a 20' easement is in conflict with my site layout.

The MUA is asking for 3'+/- precision in locating this pipe to establish the correct easement (no plans or records with correct information are available).

The line is approx 50' deep, is cast iron, and is buried under a cruddy fill (large boulders and cobbles throughout). The site is extremely tight (on the top of a cliff) and layout is extremely limited. We have access to upstream and downstream manholes, the upstream manhole is 45'deep, the downstream 15 (sitting at base of cliff).

Does anyone know of any technology that might allow me to locate this line?

Thanks.

 

[CarlB]

Can you sight along pipe between manholes and verify pipe runs in a straight line (as is normally the case for gravity flow)? Then it's a simple matter of surveying the manholes and connecting the dots.

 

[kstefanich]

We know that the pipe has at least two bends in it between these two manholes. (600' run MH to MH ignoring z)

The pipe is 50+ years old, and the only record information that can be found is the proposed easement from the tax map (which we have already concluded is off by at least 25').

Something I guess I failed to mention: the development will be a 5 story residential unit on pile foundations.

The concern is that a) we will place the building within the actual easement, and b) we will drive a pile through the pipe by accident. Therefore the local MUA is asking for the 3'+/- precision.

 

[carlorom]

The Accuracy you require for such a deep pipe and 600' distance between manholes with bends which you are sure exist makes it very difficult. 3' positioning on a 50' deep pipe is tricky. Short of opening the pipe up I can suggest the following:

Use mining survey techniques down each manhole to obtain the direction of the pipe from each manhole. A technique known as WEISBACH triangles comes to mind. Alternatively plumb down two points from the top of manhole to get a direction line at the bottom and then try to measure the direction of the pipe. The problem is that any slight error of direction will magnify the further one moves away from the manhole.

Another way of getting such pipe directions is to use a GYROTHEODOLITE. Again accuracy to 3' over the distances you mentioned is tricky. The pipe is obviously too small to actually crawl through hence visual alignment using laser may be the best you can do.

I know that some electrical conduits can be traced using I presume induction techniques. Maybe trying to run an electrical cable through the pipes between manholes could help but again would that give accuracy required? I am not an electrical engineer so can't help here. Just a thought.

There are recently laser robots (CYRA and CALLIDUS come to mind) These measure "point clouds" as the "robot" moves. If one could send such a laser device remotely through the pipe and it measures common points back and forward as it moves along the pipe one could possibly get pretty high accuracies. It would probably still involve some survey adjustment (like Bowditch Adjustment in a traverse) but the results could be quite accurate.

This is just speculation as I have personally not done such a survey but this is how I would initially investigate the problem.

Lastly I vaguely remember seeing an article where some seismic technique was used to "X-Ray" the soil. This involves techniques similar to Echo sounders used at sea. The position of the recording device etc can be established above ground using normal survey techniques. And then translated below ground from the echo soundings? I somehow doubt if 3' accuracy will be obtained? I believe this has been used for mapping caves.

Let me know if you want more info on this as I will then try to find the articles mentioned. Good Luck

 

[allanhosking]

Hi,

There are small compact inertial navigation systems available that can be used for such applications. They are the size of a small shoe box and can be flushed(using water) down the pipe at a fairly constant speak. They will measure X,Y,Z position along the pipe at user specified interval easily within your accuracy tolerance of 3 feet.

I suggest you contact the manufacturer PHOTONETIC in France who manufacturer the PHINS inertial navigation system who will put you in contact with someone who can rent you one.

They will be expensive to rent though at a few hundred dollars a day.

Good luck

Allan Hosking
allanhosking@hotmail.com

 

[guw]

hi,
I just found your information request - if it is still valid I think I could help you - using a pipeline inspection tool with an inertail measurement unit (navigation unit) on board - further information can be provided on request.
If the problem is solved differently it would be intersting to know how.

 

[pwtem]

Have you considered geophysics? We located an 8ft pipe 45ft below the surface using high-resolution shear-wave reflection. The data looked like radar, and easily had enough resolution for a 3ft pipe. Technique requires a shear-wave micro-vibrator. Like all geophysics, the quality will depend on the soils, site characteristics, etc.

http://www.geovision.com/html/high-resolution_shear_wave.html

 

[bitsculpt]

http://www.radiodetection.com/products/html/ppl2.cfm

We've used this product before and it has proven to be extremely accurate on several different occasions. Hope This may be of some help.

 

[namdac]

I have used a GPR unit to find pipes that were deep 71' on one and 110 on another. (Ground Penetrating Radar) the unit has also work to find potential sink holes too. As to where a person could find one there are quit a few the one that I used went to 60 meters and displayed the information in 3-D on the screen.
Regards,
Namdac

 

[bazaka]

I know this is a less complex idea, have you consider water jetting along the pipe?