Slope stability question

[shobroco]

I'm a structural guy who didn't mind soils in school 30 years ago but has mostly dealt with them since for foundation bearing. A project that I'm involved in has a problem that's not mine, but I am uncomfortably close to it. A house was torn down & a new one is being built 75' from the top of a 100' high bank with a lake at the bottom. There was an existing foundation & storm drain system that connected to a cast-in-place tank in the rear yard, which outletted to another cast-in-place structure 20' or 25' down the bank, & the outfall from that was rip-rapped & well-grown in with mature trees down the bank to the water. This performed well for 75 years, the depth works, & we said connect the new foundation drain to the existing tank. (my involvement is structural design for the landscaper: pool, canopy, gazebo, etc. not the house, landscape budget is $1M just for reference). The house builder decided to be clever & dug a trench from the basement out the bank with a 5' excavator bucket & laid pvc pipe for the foundation drain outlet. The bank has slumped 6' wide each side of his 10' deep backfilled trench & is threatening to slide further. It's clay soil. How do you stop it now and for the future?

 

[GeoPaveTraffic]

I suggest that you get a local experienced geotechnical engineer involved to determine why the slope failed and how to best stabilize the slope.

Without a site visit, or a whole lot more information, there is no way to tell what is going on.

Good luck.

Mike Lambert

http://www.shannonwilson.com

 

[shobroco]

Thanks, I have already given the house builder the name & number of the guy that I depend on for geotech & told him he has to get someone qualified involved.