HDD's, streams, groundwater

[LearnerN]

Dumb question about HDD's under streams. Is it almost certain that an HDD would hit groundwater when crossing 20' under a 100-ft wide by 10-ft deep stream? Or is that something that entirely varies from situation to situation, and can only be determined by a soil boring? Thank you.

 

[civilman72]

Yes. Almost certain you are in groundwater.

 

[bimr]

I had an HDD through rock so it is possible to avoid groundwater.

River crossings require information such as a geotechnical study to identify river bed, river bed depth, stability (lateral as well as scour), and width. River crossings are usually installed to a depth of at least 20 feet below river. Soil borings for geotechnical investigation are generally conducted to at least 40 feet below the river bottom.

 

[LittleInch]

30m wide is not often called a "stream".... Yes you will hit ground water, but 20 feet looks a very lw distance to me.

river crossings need good geotech info and to avoid the gravels, cobbles, boulders you often need to go much deeper than you think.

Unless you hit artesian pressure, ground water itself is not normally an issue.

Each crossing is different and to even contemplate an HDD without at least two or three deep boreholes is just asking for trouble and lots of costs.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[civilman72]

Good point bimr - hadn't thought about solid rock. Regardless, borings should be completed.