Erosion and Sediment Control with Recycled Organic Waste - Berms

The following is very pertinent to the Top End of the NT today, as we experience a major 100mm per hour storm across the Dariwn region.

Where is your soil going today??

Erosion and sediment control, particularly on civil construction sites often seems to start and end with using a silt fence.

While silt fences can be effective, to be so, they require correct installation, and ongoing maintenance. While there are machines to install silt fencing [yes, they do exist!] rarely have I seen one in Australia, and especially on smaller civil works sites, they are, as they say, as rare as hen’s teeth!

Installing a silt fence is a tedious job, particularly the preparation of the footings, in which a lower area is buried, as well as refilling the trench. Mostly, and somewhat sadly, it is often done poorly, and the silt fence is often relatively ineffective.

In Australia with high summer storm rains, and especially so in the tropics, it is quite common to see a silt fence struggle with high rainfall intensity, and they sometimes breach. There are other options that can be simple and easy to install, and repair if necessary.

Top among the options is using a mulch or compost berm or contour bank. Many regions have mulched green waste available, and creating a berm is relatively simple using readily available on site equipment such as a bobcat or small backhoe. Accessing the greenwaste is often through the local council, or sometimes even using on site available cleared green materials can be useful too.
Ideally, pasteurised mulch is the preferred material, with coarse materials suitable. Ground woody waste, even small woody branches are usable. However, where pasteurised mulch is NOT available, unpasteurised mulch can do, although there will be a need to spray and kill any weeds that emerge within the berm – glyphosate is the normal option. Plants developing from the pasteurised mulch are very slow to almost none, although a few plants might be expected from blown in seeds, after a while.

There are some excellent resources on line, but the simple plan is to develop several berms across a slope, on the contour. They should be lightly keyed into the ground, often by building on a ripped base area or similar simple disturbance. Unlike an earth bank, they are supposed to be porous........just that all the water does not flow through at once, and sediment is collected and deposited along the way.

More information here:
http://www.caes.uga.edu/Publications/displayHTML.cfm?pk_id=6296 from Georgia in the US; a sub tropical region of the US

http://www.deq.state.or.us/wq/stormwater/docs/nwr/ephcompost04.pdf

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=119 - a very comprehensive overview of berm use and construction

http://www.creativeearth.net/stormwater.html - shows how to build a system


When the project is completed, the berm can then be used as part of the organic materials often used on site as part of the landscaping, or often left in place in small drainage lines to continue to function until there is improved cover on the nearby soil areas.

They work extremely well, are cheap to construct and maintain, and VERY environmentally friendly!

Compadre Zoysia for Roadsides and Median Strips

We have long advocated zoysia, especially seed sown versions such as Compadre, for use in transport corridors.

One of Australia's largest road organisations, the NSW RTA is now using zoysia for road corridor use, median strips and similar road applications.

They find the slower growth is a big advantage ........less mowing, maybe only one third as much mowing, as well as reduced intrusion into plants used in association with the grass. Previously, intrusion by faster growing species such as couch and kikuyu meant large maintenance budgets and regular spraying to eliminate ingress by the grass into adjacent plant communities such as Dianella spp, and similar lower growing species.

The use of seed sown Compadre zoysia offers significant cost advantages over turf sod in similar circumstances, and will achieve the same effect. There will be some added maintenance and management during the establishment phase of about 12 weeks, but by using hydroseeding on a weed free seed bed a first class result can be achieved. Zoysia's require less fertiliser in comparison to most other grasses, while still achieving adequate to good quality. Sometimes that fertiliser can be nil!!

It has been done in Darwin........and I am sure it can be done in your area too, if warm and wet in the summer.

One of the transport corridors done in Darwin was the nature strip around the bottom roundabout in McMinn street, near the Waterfront. And the roundabout was also done with another zoysia - Zoysia tenuifolia - also known as petting grass, which needs almost never being cut.

Contact us for more details. Compadre zoysia seed is also available.