Alternative to riprap in stormwater wet pond design

[Sparticus17]

I have looked at my local standards which state erosion protection must be placed around the perimeter of the stormwater wet pond to an elevation of a 1:5 year water level. Is there other less expensive options or products available than rip rap. Maybe for example a type of geo-fibre or grid. Thanks in advance.

 

[dicksewerrat]

I've used a geo-web with wllows planted in the holes for erosion control. It works well. but rip rap placed with dump trucks and backhoe may be cheaper.

 

[LHA]

Geotextiles (there are many out there, most have free design software) are a more attractive final product. And they may end up being cheaper, although the material cost is certainly higher. When costing them out, be sure to really think about labour involved in placing riprap on a steep slope several feet below where the dump trucks can get. Geotextiles are basically rolled down the hill and staked by hand. As sewerrat suggested, you can use what are called "live stakes" - green, freshly cut branches, which will then grow into plants and further strengthen the soil.

 

[Sparticus17]

The wet pond has a 7:1 sideslope where the riprap will be placed. The edge of the wet pond will be within 200m of the city's river edge. The proposed subdivision will be composed of executive townhouses and apartments. I am trying to make this pond look as natural as possible without breaking the budget. Stromwater quality is of number one importance. It may turn out to be a hybrid wetland/wetpond. Slope stability near the pond is not an issue.

 

[Xbxaddict]

Grass or jute matting can be considered erosion protection. I would call the soil/water conservation district in charge and see if they'd approve something as simple as grass since the slope is minor.

 

[dicksewerrat]

Then you may want to use a product I saw a few times. It is called 'Cable concrete'. Small pieces of concrete held together by steel cables. they have open space between the pieces for grass to grow thuogh. the grass does hide some of the concrete. We have used it for boat ramps and erosion control.

 

[LHA]

Cable concrete comes assembled in 4'x8' mats, so you will definitely need a machine to place cable concrete. If slope instability is not an issue, why bother with cable concrete?

I agree with xbx. If the ordinance only states "erosion protection", grass with some temp tackifier meets that. If the slope is only 15%, grass will permanently protect it. Ask the reviewer if that will work. You will need a water tolerant mix, not just a typical landscaping mix, or it will drown.

 

[layfieldman]

You can also try using a permanent turf reinforcement matting. It is similar to biodegradable straw or coconut except that it is composed of UV stable polypropylene. It allows grass to grow through it and will provide permanent root reinforcement up to 1:1 slopes. It is also available in green or tan so that from a distance it looks natural even before vegetation establishes itself.

 

[Sparticus17]

Thanks guys you have been a big help