artificial turf

[darthsoilsguy2]

what would you expect the time of concentration be for a high-performance artificial turf football field? i figured less than 5 minutes.

turf over 10" washed drainage stone. stone over geotextile and compacter earth. slopes 1% from center of field to 4 corners. laterals at 15 feet o.c.

i'm most concerned with a fast downpour that could float the low parts of the field

Somebody told me almost an hour for the time of concentration. i don't see it.

 

[civilman72]

Modern fields are designed to quickly infiltrate through the turf and drain into the washed drainage stone layer. I believe the rainfall volume would have to exceed the capacity of the drainage stone (and infiltation rates of the lower compacted earth) before the water would pond on the surface and start to flow towards the low points of the field. So I can see how the time of concentration would be much longer than 5 minutes.

 

[darthsoilsguy2]

you can't pond on the surface. The turf floats. Any buildup of water ruins the turf. the time of concentration i'm talking about is the subsurface drainage system. Concerned about the lowest points on the field becoming detention basins that lift the turf.

 

[cvg]

unless either the laterals get plugged or flow exceeds the capacity of the laterals, I would not expect water to build up and pond. assuming 40% voids, you would need approximately 4 inches of rainfall to fill up the 10 inch thick drainage layer. so for example, in Los Angeles, that would amount to a 500-year, 3-hour rainfall depth. The 100-year, 10-minute rainfall depth is just over 0.3 inches. I would make sure you fully understand how to construct the laterals and drainage layer so it continues to function properly.

 

[darthsoilsguy2]

Thank you both. i agree CVG, but the subsurface drainage is the problem i am asking about. The Tc i'm discussing is the time from 1hitting the turf, 2 draining down to the subgrade, 3 travelling across the soil subgrade, 4 travelling the lateral, 5 hitting the collector pipe. the installed collector for the laterals does not have capacity to drain a heavy short storm if the Tc is 5 minutes, but it does if the Tc is much longer like i heard from somebody else.

 

[cvg]

the point is that the laterals do not have to drain anything at all. the rock drainage layer could hold the entire 100-year storm rainfall without anything flowing through any laterals or collectors and without any floatation. so why knock yourself out trying to estimate a theoretical peak flow rate?

 

[darthsoilsguy2]

At a 1% slopes from center, the finished subgrade at the corners is over 2 feet below the center of the field. The laterals will drain regardless of what happens as they are flat drains. The laterals will take the water to the perimeter collector trench region, whether it is flooded or dry. Back to the OP, is there anybody out there who thinks the Tc for the system could be over 5 min or for that matter be close to an hour?

 

[beej67]

You could indeed use your rationale to claim the Tc is short. But if you do so, you really need to treat the thing as a storage reservoir and route it, and when you do so you'll find a pretty huge rate reduction, as well as a fairly large shift in the time to peak.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com