Infiltration under an underground parking lot? 1

[brandonbw]

We are working on a mixed use development, and the city has a couple of different options with how to handle the water for their requirements. The first one they prefer is to capture to the 3/4" storm and infiltrate. This particular project takes up the entire site and has 2 levels of underground parking. Is it possible to infiltrate under a building?

On a side note what are the best ways to get water out of an infiltration tank system if you can't bubble out of the outlet. We try to stay away from infiltration whenever possible, but it looks like this will slowly be the only method we can use in certain cities.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

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http://bwstructuralengineer.com

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http://bwcivilengineer.com

 

[msquared48]

Asd for infiltrating under a bulding, unless it was 100% on pile, I would never even consider it.

As for bubbling up from the outlet, If it will not flow by gravity and you cannot infiltrate, then pumping is the only option left, an option not allowed by many municipalities. Some have allowed it with a backup emergency generator in the case of an extended power outage - an additional cost.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[cvg]

generally infiltration is the preferred method, drywells second best and gravity bleedoff or pumped out is the last option. use a dry well drilled deep enough to intercept a free draining sand or gravel layer. do not put an infiltration system under a building, this would be ill advised for a number of reasons.

 

[brandonbw]

That's what I figured. Thanks. I didn't think it made sense to infiltrate under any building, but that was brought up when I was talking to a few different plan checkers.

And we try to stay far away from pumps as possible. Those lately have been a nightmare to deal with. I keep hearing it doesn't rain in California the last few weeks from way too many contractors and Architects.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

|

http://bwstructuralengineer.com

|

http://bwcivilengineer.com

 

[Ron]

I agree with Mike. If pile supported, it can be done...otherwise no. An exfiltration system does not charge the surrounding soil uniformly and in times of high rainfall, a deluge effect will occur at certain points in the system. This can cause non-uniform settlement in a shallow foundation system.

Keep it under the parking lot...that works with proper design and construction.

 

[Ron]

Oops! Need to make clear that it should be under a surface parking lot, not an underground parking lot as proposed!

 

[msquared48]

Absolutely Ron...

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[brandonbw]

We have done infiltration under surface parking lots. The fact I was told by a few people at different cities that we could infiltrate under a building made me ask the question.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

|

http://bwstructuralengineer.com

|

http://bwcivilengineer.com

 

[msquared48]

You have to pick and choose whom you listen to...

I don't care who says it's OK. As a licensed structural engineer, I would never stake my reputation on it, let alone the lives of others.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com