Clean fill dump site slippage (NEED HELP!)

[BirdmanJ]

I have a commercial construction business and at one of my properties I own a small clean fill dump site that we use to dump clean soil, concrete, rock, etc. The dump site is on a hillside that leads to a river. At the base of the hill, between our dump site, and the river, there's a 21" aerial sewer line owned by our local sanitation department. We recently discovered that the sewer line is broke, because one of the piers it's set on has shifted. I want to know if it's possible that the weight of the fill that I've dumped on the hillside could cause the peering below it to move.

Some additional facts:

The sewer pipe at the bottom of the hill is in a waterway that often floods. The river was over the sewer line about 2 weeks before we noticed the break in the pipe.

The closest fill to the sewer line is approximately 40 feet away. There has not been any rocks/debris fall on to the sewer line.

There is no sign of slippage between the sewer line and the fill site. There are trees between the sewer line and the fill site that are standing straight up.

The area that this sewer line is in is known for slipping. There is some kind of fault line that runs through our fill area.

 

[dik]

You need to advise your insurance company to go forward, and, a good geotechnical consultant with a background in slope stability. Without detailed information we are likely unable to assist you, and with the potential for litigation, many geotekkies might be reluctant.

Dik

 

[fattdad]

I agree with dik.

That said, you could go to the trouble of installing a slope inclinometer at the property line and obtaining measurements of ground movement (or lack thereof). If there is nothing to record, that'll tell you something.

If you do; however, record movement, you'd have to come clean and own up to the problem, eh?

f-d

ípapß gordo ainÆt no madre flaca!

 

[oldestguy]

In te process, perhaps some property surveying may be in order, especially if that pipe is not on your land. As to easements,etc, an attorney with expertise on real estate may be needed. Sometimes in situations similar to this the owner of the facility has to protect themselves against actions of the neighbor.

 

[dik]

Should also note with bank instabilities, they can go from bad to worse in a short period of time. You might look into this ASAP.
Fatdad: Never encountered a slope inclinometer... had to look it up.

OG: Hadn't thought of survey stuff...

part of my learning process... thanks, Dik

 

[GeoPaveTraffic]

Based on your post, it appears that you placed fill on a hill that caused a slope failure that in turn damaged a sewer pipe.

Call your insurance and get ready for bad news.

Best of luck.

Mike Lambert

 

[BirdmanJ]

I have notified my attorney and my insurance company of the issues. At this point it's a waiting game to see if the Sanitation Dept. is going to point the finger at us. I just want to get out ahead of it as much as possible. I appreciate all of your feedback and ideas.

-B

 

[oldestguy]

I'd add that any photos you can get of the pipe and the area may help. If this gets to court or similar, that won't be for a long time and memories fade. Photos don't. In particular get photos of the ground up hill from the pipe with an occasional prop in the picture for size, such as a yard stick. A plumb bob in the picture shot from the same elevation contour may help, If needed get someone to hold it. That will serve as a"measurement" of slope angle. Date every photo.

 

[dik]

OP... I'd engage a good geotekkie ASAP, too. As OG suggested you cannot take too many pictures. Make sure your digital camera is set to the current date and time and most cameras will date stamp photos... Something for scale, as OG noted, is also very good.

Just thought of it... is some soil has subsided, do NOT backfill the portion that has gone down...

What area are you in?

Dik

 

[oldestguy]

As to a geotech, if this gets into a legal hassle, the more he (she)has in experience the better. Preferably he has had jobs as expert witness also, because sometimes the lawyers try to "buffalo the expert" and that experience makes the difference when a lawyer tries to affect how you are seen.

 

[oldestguy]

More from OG. Once you get the geotech on line, I'd suggest that he do some installation of reference markers or use a surveyor. The purpose of the markers would be to check on possible continuing, or if any, movements of the slope happen. The likelihood of a slip or just bulk movement most likely will be noticed at the surface. Thus, you set up a few measuring lines, if you will, at spacings on the slope, perpendicular to the slope, roughly on contours of equal elevation. Set two basic reference points, one on either side of the possible movement area. These can be sturdy stakes set so you can set surveying instrument on one and see the other. Then, on each of these measuring lines, drive in stakes that then will be periodically checked to see if and how much they may move horiz9ontally. I'd drive a nail in each stake so measurements to a fraction of an inch can be measured to see how far from the main line (between the two references) the stak may have moved. Something more than a cheap transit is required to be able to note movements of as small as 1/4". Of course compete records are needed, including such things as weather conditions, river stage, etc. I'd flag each stake and take what ever precautions you can to preserve all of the points being observed from time to time.

 

[Mad Mike]

This is interesting and a basic sketch section through the site might help.

If you have managed to induce movement of the pipe at a distance of 40 feet from the toe of your fill embankment, it would require a deep circular slip surface with high volumes of movement.

In most instances, a movement of this scale would require a deep clay soil profile at the toe of your fill. Usually, one would expect to see a very clear bulge in the ground where the deep failure surface "kicks out" below your slope. If there is no evidence of any such feature, there is no clear reason to believe the failed pipe pier is landslip-associated. Check your waterway and see if any rock outcrop is present- if so, I doubt your fill on the slope is the root of the problem.

All of the advice for monitoring movement would be the best way forward, but until you have clear reason to believe your land has slipped, don't look too guilty...but do employ a geotech. in the future!

All the best,
Mike

 

[dik]

but do employ a geotech. in the future!

Should have happened, yesterday... all the information above is pretty sound; if your lawyer allows it, can you advise of any outcome?

Dik

 

[EireChch]

As Mad Mike said, a cross section would help a lot. Could you upload a sketch with dimension and angles?

 

[oldestguy]

Considering what we know, I'd bet the pipe lost its support due to erosion or debris from that stream. Any info related to that, such as history of flooding, etc. might be needed in case of a claim. However, the info so far, vertical trees, submerged pipe (it may have floated) (erosion of support) may well have occurred. For instance, how many times do municipalities set a sewage lime up on supports where a stream may have affected it? And it frequently gets submerged without anyone concerned that it is broken? Sounds like poor management by the municipality.