Using building foundation wall as part of stormwater retention pond

[cfrits]

I am designing a stormwater retention/detention system for a commerical site in Florida. I need to retain a large volume of water and the project area is very restricted. I want the foundation engineer to build me a 5 ft foundation wall on two sides of the building that I can use as part of the retention pond. The foundation engineer claims it can't be done but I don't believe him. Has anyone ever designed something like this or know where I can find information on this design solution?

 

[CTW]

What was the reason given by the foundation engineer that it couldn't be done?

 

[MiketheEngineer]

Done it but don't recommend it. Water always does nasty things to footing, foundations, etc. over time.

 

[oneintheeye]

why cant it be designed as a water retaining structure? Dont see how it will affect the design life if done properly. Never done it or seen it done though. The building foundation would need to be the same level as the bottom of the pond though I would suggest. You post implies the pond is adjacent and deeper.

 

[msquared48]

I have never seen this done as it can affect the bearing calacity of the foundation causing cracking and failure. This is the same reason why we install foundation drains and install downspouts to channel the water away from the foundation. For me, the liability would be far too great. Look to another solution here.

The only time I have seen detention tanks used in a building structure was internally in a high rise where the tank was completely enclosed and sealed from the footings.

Mike McCann
MMC Engineering

 

[kslee1000]

It is possible to get design done by engineers with experience on submerged structures (or coastal/water front structures), but the solution could be costly. Depending on the soil/groundwater conditions, you may need to install piles, seepage cut-off walls...to prevent soil movement under the foundation.

 

[CTSeng]

As mentioned it can be done for a price. The one time I've done it we basically designed the pond as a pool using ACI 350 with a lot more reinforcement, zypex in the concrete and a membrane on the pond. Can’t let the water under the structure or you are asking for problems. Also had the geotech provide bearing capacity for saturated soil and sent a nice release of liability letter to the architect for any future water problems. Turned out to be a pretty cool though, had some nice water side seating for a restaurant.

 

[msquared48]

Assuming that the water retention wall is not one of an occupied basement, I agree that piling would be a very acceptable option here.

Mike McCann
MMC Engineering

 

[JLNJ]

We just had this come up. The civil guy wants the pond elevation to be several feet higher than the finish floor. Me no like!

 

[DonPhillips]

I inspected a house once in Kentucky where a cistern to capture rain from the gutters was not only part of the building foundation, it was under the garage slab. It was entirely under the garage, 3 walls reatained earth on the outside and water on the inside, and the four wall was the basement foundation wall. I think the base of the cistern was about 7' below the bottom of the garage slab - I do remember at least a foot free above my head and I an 6'.

The issue Florida typically has is a high water table and keeping your basin from uplifting could be challenging.

As I tell people, with enough money, nothing is impossible.

Don Phillips

http://worthingtonengineering.com

 

[cfrits]

Thanks for the responses. The foundation guy admitted that this idea was outside his experience base and he didn't want the liability. From the comments here it looks like a last resort type design solution anyway. He scared the client so bad with the cost to implement that when I spoke to the client later about a different but more costly approach to my stormwater retention problem the client gave me the go ahead no questions asked and said he appreciated me saving him money. I tell you sometimes it pays to get up in the morning.