Sediment screening for dry wells

[KaBone]

I have an asphalt paved area graded to a drywell for storm water infiltration. What are you folks doing to screen out sediments, leaves, and similar debris so the gravel doesn't get filled in with fines? Are you folks even worried about that? Low maintenance suggestions preferred.

 

[gbam]

KaBone you can grade a settling pond in front/around the inlet to help settle our the fines before they enter into the drywell. One can place trash rack around the inlet as well to trap floating debris. There are a;ll sorts of chambers on the market to collect trash.

 

[KaBone]

Definitely using a grated drop inlet. I can design a settling pond to remove fines. Aesthetically it's not the best with the dirt and staining. Every time some sees it, which will not be that often, they're going think something went wrong. Constuctibility wise it seems more challenging. Design wise I have a fairly significant slope (~10%) on one side and the run is kind of short so I'd have to check if there's enough settling time. Or maybe not. I'm guessing about 3 cu ft of sediment per year. The nil alternative means they'd have to clean out the drywell every 9 years or so.

Side question, are you folks completely filling your drywell with rock/stone/gravel, or just the bottom foot or so?

 

[gbam]

The other alternative would be to use a settling chamber/vault that can be vacuumed out periodically.

 

[beej67]

Depends a lot on where the project is, what the storms are like, and what the soils are like in particular. If you're in a clayey area, it could be a much bigger problem than if you're in a sandy area.

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

http://www.campbellcivil.com

 

[Twinkie]

Do you have room for a snout in the inlet design?

 

[KaBone]

Big mahalos for the replies - I'm not sure if I know what a snout is.

Dry, windy, sandy, open area. Ten year 1-hr design storm is 2.25".

I'm leaning towards doing nothing special to screen sediment, just letting the drywell fill. If it's filled with stone, they'll have to clean it every 8 years. If I only put stone in the bottom 2 feet, it might have to be cleaned in 25 years. Obviously the latter is cheaper and faster. I've just never designed one that way. If there's a reason for that I can't remember. That's why I was wondering if anyone's done it with stone only at the bottom.

 

[cvg]

time between cleaning will not vary regardless of how much stone you put in. the ability of the drywell to infiltrate will gradually deteriorate due to accumulation of a layer of silt or clay on the surface. you should not be allowing sand or gravel to go in at all. It doesn't take a very thick layer to effectively seal the surface and render the drywell ineffective. Maintenance will then need to remove rock and scarify to restore it to near previous condition. the number of years will just depend on your local conditions.

 

[Twinkie]

Snouts: Pretty easy and efficient

 

[KaBone]

Big mahalos all for the helpful responses. The snout looks promising.