Minimum Pipe Cover Under Streambed 1

[esass13]

Does anyone know a typical or minimum depth of cover for a 12" waterline to be buried under a streambed? I can't seem to find anything on the internet, other than below the frostline.

 

[sam74]

I don't know where your location is but here in the Southeast US typically streams with a year round base flow don't freeze during winter conditions. I have asked that question before while on a water line inspection job. The answer I recieved was in the best case still maintain 30" of cover (frost depth) over the pipe. However, the stream was about 40 feet wide, four feet deep, with a rock bottom, and it was hard to accurately observe this without the construction of somewhat major temporary water barriers and other misc. construction efforts. Also, the stream was never likely to freeze and I was told to make sure the contractor laid the pipe below the stream bed and get what cover he could. The main reason being to avoid a future line breakage caused by a collision with debris in the stream bed. I'll be curious to see what other responses you get.

 

[esass13]

Thanks Sam74!

We will encounter shallow rock and I was more concerned with streambed erosion. I don't really think we'll have a problem with erosion with 3 feet of cover, but I just couldn't find anything on it.

 

[dicksewerrat]

would it make any sense to HDD the line under creek bed? Then it would be in the rock and protected by the rock. also you may be able to do the job without getting tree huggers upset. then reconnect the pipes 100 to 400 feet away from the water.

 

[esass13]

I looked at directional boring but it was going to be very costly. Other utilities have bored at this location and had problems due to very hard rock and a lot of it. I've checked into the permits for a stream crossing like I've planned and it's relatively easy, at least for our project.

thanks for the reply

 

[cvg]

I doubt that you will find a standard, because it varies too much on a case by case basis. You really need to consider the amount of risk you want to take, and then do a scour analysis. This may include the following analysis: local scour, bend scour, low flow incisement, lateral migration, bed armoring and stable slope analysis. Without this information, you will be just guessing at the potential scour depth. You might be able to estimate it by looking at the scour evaluation reports for any nearby bridges. These would be available from the local county / state road department.