Existing pipeline and contingencies for settlement

[KxKy]

We are looking at options for a large stockpile embankment on a large property. However, there is an existing pipeline that is located outside of the property line running parallel to the slope face. We have noted that settlements beyond the property line are to be expected and that the pipeline will need to be monitored over the course of construction. The total settlements are on the order of 200 mm to 400 mm and will be relatively uniform along the pipe alignment as the soil profile is pretty uniform.

We noted that the client have a back up plan in place with the pipeline owner if movements are not acceptable to them. However, the client is nervous and does not want to damage the pipe. What sort of contingency measures can be taken? Would exposing the pipe and developing temporary supports work? Considered relocating the pipeline, but I feel that would be extremely expensive as well. Anyone in the community have some insight as to a reasonable contingency measure to address future pipeline settlement?

 

[oldestguy]

First of all what are your laws? In my area, any damage beyond the property line for a case like this is not usually the responsibility of the owner of the fill pile. If I was the owner of the pipe in this sort of case, I'd abandon the pipe and replace it after all settlement is done.

 

[r13]

I don't know how you able to monitor the settlement of a pipeline, but you either limit the location of the stockpile out of the influence/susceptible zoom, or mechanically provide barrier between the two. I think someone has done an analysis with onsite soil data (so the number 200mm - 400mm), can you provide the profile indicating the pipeline and the proposed stockpile? I think someone here should be able to provide you with good insights.

 

[oldestguy]

An a dded factor: When the time comes to either replace it or do excavations within the zone of influence from that pile, shear failure as well as settlements need considerations. This is somewhat in the field of legal responsibilities of excavations near the property line, but in reverse. In our state it is pretty clear on excavations depending on depth, such as depth of a neighboring basement. For loads on the nearby property that is less common and ther emay not be any current legal history to work with.

 

[miningman]

I think that knowledge of the material moving in the pipe would extremely important in developing a risk analysis. Sour gas ?? Sewoge ??? Potable water?? What might be order of magnitude estimate for repair costs if settlement induced a leak??? Sour gas in a semi residential area?? How good is the clients insurance???

 

[r13]

Is the pipeline above grade, or buried? If the former, please ignore my comments, but provide us with useful information.

 

[oldestguy]

Another point. Moving too fast with actual work, before all legal challenges are covered can bite you petty hard. Costs eventually can be much higher if any legal step is skipped now. Treat all situations like this that it may end up in court. Thus all phone calls, emails, etc must be documented for possible use later in court. Keep a daily written log also.

 

[oldestguy]

While standing by I would comment on this point in the post. "What sort of contingency measures can be taken?". I'd caution that any measures to minimize or prevent effects on that neighboring pipe should again go through approval by your legal advisers. These measures might backfire, such as a failure that then causes damage to the neighbor above that by doing nothing. Who knows. Keep us informed on progress.

 

[KxKy]

Thank you for everyone’s input. Yes, even though it is on an adjacent property, the legal aspects has everyone treading carefully. The current direction from our client is to adjust the stockpile height and distance from the property line to minimize the settlement. The adjacent property is a municipal owned water line. The client doesn’t want to deal with their engineers or legal team. We need to adjust so that the estimated differential movements are small.

With respect to monitoring, our plan to monitor would have been to hydro excavate at regular intervals to top of pipe and survey the line as a courtesy as part of the monitoring program.

I’m still curious if anyone has attempted or know of a more direct intervention? Is there any way to relevel a line to address settlement issues if monitoring trends are unfavorable? Or is it simply dig and replace as the need arise? I assume both scenarios will end up costing about the same in the end.

 

[oldestguy]

While your thoughts are fine, we can't give meaningful answers as it sits. You, for your own plans,should have test borings and sufficient lab tests to do a stability analysis, at least to get a rough idea as to what might happen. No way would I go so far as to measure where that pipe is unless my legal team would OK it. It's like opening a can of worms. I'd stay on my own property and not venture across it for any reason.

 

[r13]

For legal concerns, consult the lawyers that familiar with the local's law on property disputes. For engineering concerns, you should provide some tangible information, so people here can provide their insights/suggestions.

 

[oldestguy]

A possible happening: Good intentions (such as monitoring the pipe location) and your filling doesn't follow your predictions and slight lateral movement opens a joint causing water saturation. The area then has much more saturation and away goes your fill ripping out the pipe under pressure. Water can't be shut off for an hour and many nearby areas get damage from this flooding. Now your good intentions will really backfire with many now starting claims against you. It could happen! Stay on your side of the property line.

 

[r13]

Let me try ask these:

- The pipe line is buried underground, what is the depth?
- How far it is off the property line?
- Where is the end of the stockpile when the settlement study was conducted?
- Do you have soil log and profile (I assume you do)?

 

[oldestguy]

I differ from the NEXT above questions. No way will we here be able to fully know the details there and so trying to solve any questions now IS OPENING THAT CAN OF WORMS. NOTHING ANYWHERE SHOULD BE AVAILABLE FOR THE PIPE OWNER IN CASE OF LEGAL ACTIONS SOMEDAY. THESE STATEMENTS AREN'T HELPING THE POSTER. WAIT FOR THAT LEGAL ADVICE BEFORE DOING ANYTHING MORE HERE.