In-Channel Concrete Sediment Trap

[martin888888]

We have roadside concrete stromwater channels and are looking to put a sediment trap within the channel. Has anyone ever seen this done befoe? I would imagine it would be a concrete box structure with a grate that would just need regular maintence. Probably a 4" drain pipe in the bottom of it.

 

[gbam]

Interesting. Not sure how well that would work. I presume you would size the channel for a 10-year event or greater and the sediment traps for a smaller storm (1-2 year). I envision that once the vault fills up with water no more sediment would be collected; sediment would bypass the vault entrance with the discharge. One would have to size the vault system to collect the entire design storm flow to allow for sedimentation. How large would the vault have to be to settle out the sediment. When designing a settling basin the detention time is the key for settling out the sediment particles. These basins are rather large; 1/2-ac plus for the last one I designed. It will be interesting what other folks say.

 

[Twinkie]

How about some rock check dams in the channel? Or removing the concrete lining all together and letting nature do it's thing.

 

[puzzler77]

Rock check dams would slow down the flow but would not trap fine sediment. It takes days (not minutes) to get sediment to significantly be reduced. I have used 72 hours in the past but this does little towards a 48 hour drain time requirement. Storm water, I have been told, should not be retained longer than 48 hours for quantity measures but should be retained at least 72 hours for qualitative measures. It is impossible to do both.