Rill System for Stormwater Management??

[bushel3]

Has anyone heard of a "Rill" System for Stormwater Management before? I'm looking for information regarding the design of this system.

I recently inspected a storm water system for a subdivision that our client called a Rill System. My understanding after the inspection is the Rill System serves two purposes, beautification and storm water management. In this system all of the back yards of the homes are graded toward a small channel 6 inches to 1 foot deep and 1 to 2 feet wide. The channels have been lined with a sheet of plastic/visqueen to prevent the water from infiltrating the sand and gravel ground. The channels all flow to a system of interconnected detention ponds. Then there is a pump that pumps water from the detention pond back into the channels to keep water flowing through the channels. There is also a weir before the outlet structure to the detention pond to to mantain a the minimum depth of water in the small channels.

I'd like to find a text book or website describing the process with more detail so I can verify my observations.

Thanks for your help

 

[LHA]

I've never heard of Rill.

I can buy the "beautification" part, it sounds like a really expensive waterfall feature.

But "storm water management"? No infiltration, little if any peak flow attenuation, no filtration. Also, unless there is aeration, you will very soon (within months) end up with a stagnent pond.

What exactly does the developer claim is being "managed"?

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve

 

[bushel3]

The Homeowners association says they have to continually treat the water in the Rills kill to all the algee that grows in it during the summer. My understanding is that no infiltration occurs until the water gets to several interconnected large detention ponds. The community is built near a river and the soil is mainly granular. I believe that there isn't any liner in the detention pond so the water in the detention pond is level with the water in the river.

 

[bushel3]

I've since found a little more information regarding Rills. Rill System for Water Recirculation is in the fine print on the plans that I have. I think that the Rill System works hand in hand with the storm water system just to make water move through the subdivision. This appeals to people because flowing water looks good. I've found very little information on the internet, but it appears that the Rills system is a concept idea of some artists. I think there has also been a minimal amount of research done on the system but I've had a lot of trouble actually getting my hands on the documents that google has found.

 

[sam74]

I had a small part in a business park project we did where there were several wet ponds created that were interconnected with concrete channels with fake rocks that cascaded down the center of the business park.

The wet ponds were to maintain a minimum level of water at all times to keep the channels flowing while the bottom pond had water pumped from it back to the top. The storm drains were connected to the ponds and the pond at the bottom also had an overflow structure that connected to a dry pond that was out of sight.

Walking trails were created through this area over and along the channels. It actually turned out to be a very nice creation. The project was called Dowell Springs in Knoxville. If you do a google search you can see a few pictures at some of the contractors web sites. I can lead you to an aerial shot as well if your that interested. Can't really tell a great deal though.

 

[bushel3]

Sam74

The system that you are describing sounds very similar to the system that I have been looking at. We are going to critique someone else's design. Unfortunately I don't even have the complete set of plans to critique it. Right now there is a lot of algee (they have to treat them weekly in the summer) that is growing in the channels for what I suspect is two reasons. 1) Not enough flow and 2) Soil was placed on the bottom of the shallow channels to hold the liner down. I believe the algee is growing as a direct result of the soil which is promoting things to grow in it. I believe they should have used some sort of stone, or better yet built it out of concrete as you have described.

I was wondering what were some of the things that you considered while you were designing the channels? When you designed it how did you determine the amount of flow in the water ways?

Thanks for your help.

 

[sam74]

That was one of the first projects I ever worked on and I was just doing basic estimates for the drainage design and potable water usage working under someone else. I believe a LA did the detailed channel designs but I could be wrong.

I believe they had some vertical drops along the way in the channels to aide in aeration but I don't know if they require any chemical additives to add to the water. Since stormwater quality is becoming such a big issue I would assume not. Our city would probably make you discharge that water in the sanitary system.

Our main responsibility other than general civil/site was the pond modeling for which we used HEC 1. Shouldn't be any more difficult to do than an interconnected pond routine although I think I would use PondPack for that now.

You would figure out your channel flow by the depth of water in your pond and the elevation of your spillway (channel mouth). PondPack would give you a breakdown on what was flowing through the spillway or just use manning's equation to do it by hand. You could then design a minimum cross section for your channel at your least sloped location and use that as a guide for the rest of the site.

You would due this for numerous iterations for example a base flow run to see at a minimum what would be flowing and for various storm events to check for overtopping.

Base flow could be tricky since you would have to deal with evaportation. I believe on the project I worked on that this was automated with some sort of float valve so it was pretty much maintenance free.