Weeping tile design

[cht13er]

Been asked to conceptually design a weeping tile around a large (1000x750' or 325x230m) warehouse. Any suggestions as to where I should start?

Thanks in advance!
Chris

 

[dik]

What is the condition of the groundwater? Draining a lake or a desert? Typically use 300' as a max run with laterals at 100' max... works fine in our environs but, we don't have much groundwater.

I'll post my notes for drainage, later.

Dik

 

[cht13er]

Building is founded on several metres of compacted fill consisting primarily of silty sand. GWT approx 10m below the building.

 

[Ron]

For groundwater that low, why do you need it? Is it only to handle building runoff? If so, I agree with dik; except that I would cut the length of runs even lower.

If this is for roof runoff from collectors or downspouts, I'm not a fan of "hiding" the runoff. If an underdrain becomes clogged (and with silty sand surrounding it, there's a good chance of that), the water will backup and cause damage to the downspouts, the roof, or the structure.

I would create a series of "dry wells" lined with filter fabric and filled with gravel at or near each outlet and let the water drop into there.

 

[cht13er]

Ron, thanks for your comments. The weeper is just to ensure the long-term performance of the foundation - the thought being that if they're sitting in a wet trench something could happen. Roof drains, as you suggest, will be directed to infiltration areas far away from the building.

My ignorance comes to the fore: dik said "300' max run with laterals at 100' max": what is a lateral? I cannot connect the weepers to the on-site storm sewers, as I'm designing parking lot storage: there's no free outlet. "300' max run" means that I could go 600' between sump pumps??

Thanks again!
Chris

 

[dik]

Added info, I usually run perf pipe a max 300' before it changes direction of slope... this varies and for residential const, I usually use 40' to 50'. For a large warehouse without lots of ground water, 300' is OK.

Laterals are the drain tiles connecting the perf pipes to the sump (or, free drainage).

I usually determine the number of sump pumps from the water condition and/or the size. If problem water, then I often use 2 for redundancy, even for a small area.

The longer the run, the deeper the trench excavation and you should keep this above the lowest point of discharge <<++G++>>.

The attached are part of my General Notes (now over 300k in size). They are modified for each project and, depending on the use, have been upgraded for [Imperial | Metric]

Good luck...

Dik